tag:theconversation.com,2011:/us/topics/ultraviolet-radiation-18190/articlesUltraviolet radiation – The Conversation2023-12-19T19:01:49Ztag:theconversation.com,2011:article/2170972023-12-19T19:01:49Z2023-12-19T19:01:49ZWhat’s the difference between physical and chemical sunscreens? And which one should you choose?<figure><img src="https://images.theconversation.com/files/561796/original/file-20231127-29-cr1fq0.jpg?ixlib=rb-1.1.0&rect=42%2C21%2C7092%2C4557&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/attractive-woman-healthy-skin-applying-sunscreen-288608612">Shutterstock</a></span></figcaption></figure><p>Sun exposure can <a href="https://www.researchgate.net/publication/353329938_The_role_of_bacterial_cellulose_loaded_with_plant_phenolics_in_prevention_of_UV-induced_skin_damage">accelerate ageing</a>, <a href="https://pubmed.ncbi.nlm.nih.gov/33640513/">cause</a> skin burns, erythema (a skin reaction), skin cancer, melasmas (or sun spots) and other forms of hyperpigmentation – all triggered by <a href="https://pubmed.ncbi.nlm.nih.gov/29874551/">solar ultraviolet radiation</a>. </p>
<p>Approximately 80% of skin cancer cases in people engaged in outdoor activities are <a href="https://pubmed.ncbi.nlm.nih.gov/33197435/">preventable</a> by decreasing sun exposure. This can be done in lots of ways including wearing <a href="https://pubmed.ncbi.nlm.nih.gov/31978412/">protective clothing or sunscreens</a>.</p>
<p>But not all sunscreens work in the same way. You might have heard of “physical” and “chemical” sunscreens. What’s the difference and which one is right for you?</p>
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Read more:
<a href="https://theconversation.com/how-should-i-add-sunscreen-to-my-skincare-routine-now-its-getting-hotter-213453">How should I add sunscreen to my skincare routine now it's getting hotter?</a>
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<h2>How sunscreens are classified</h2>
<p>Sunscreens are <a href="https://pubmed.ncbi.nlm.nih.gov/33571844/">grouped</a> by their use of active <a href="https://pubmed.ncbi.nlm.nih.gov/35215026/">inorganic and organic ultraviolet (UV) filters</a>. Chemical sunscreens use organic filters such as <a href="https://www.science.org.au/curious/people-medicine/deciphering-label-your-sunscreen-bottle">cinnamates</a> (chemically related to cinnamon oil) and benzophenones. Physical sunscreens (sometimes called mineral sunscreens) use inorganic filters such as <a href="https://www.science.org.au/curious/people-medicine/deciphering-label-your-sunscreen-bottle">titanium and zinc oxide</a>.</p>
<p>These filters <a href="https://pubmed.ncbi.nlm.nih.gov/32335182/">prevent the effects of UV radiation</a> on the skin. </p>
<p>Organic UV filters are known as chemical filters because the molecules in them change to stop UV radiation reaching the skin. Inorganic UV filters are known as physical filters, because they work through physical means, such as <a href="https://pubmed.ncbi.nlm.nih.gov/35215026/">blocking, scattering and reflection</a> of UV radiation to prevent skin damage.</p>
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Read more:
<a href="https://theconversation.com/explainer-how-does-sunscreen-work-what-is-spf-and-can-i-still-tan-with-it-on-88869">Explainer: how does sunscreen work, what is SPF and can I still tan with it on?</a>
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<h2>Nano versus micro</h2>
<p>The effectiveness of the filters in physical sunscreen depends on factors including the size of the particle, how it’s mixed into the cream or lotion, the amount used and the <a href="https://www.ncbi.nlm.nih.gov/books/NBK592413/#:%7E:text=The%20index%20of%20refraction%20(n,the%20speed%20of%20light%20c.)">refraction index</a> (the speed light travels through a substance) of each filter. </p>
<p>When the particle size in physical sunscreens is large, it causes the light to be scattered and reflected more. That means physical <a href="https://www.researchgate.net/publication/363005590_Sunscreen_testing_A_critical_perspective_and_future_roadmap">sunscreens can be more obvious</a> on the skin, which can reduce their cosmetic appeal. </p>
<p>Nanoparticulate forms of physical sunscreens (with tiny particles smaller than 100 nanometers) can improve the cosmetic appearance of creams on the skin and UV protection, because the particles in this size range absorb more radiation than they reflect. These are sometimes labelled as “invisible” zinc or mineral formulations and are <a href="https://www.racgp.org.au/afp/2016/june/the-safety-of-nanoparticles-in-sunscreens-an-updat#ref-3">considered safe</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/561798/original/file-20231127-29-xpm7i4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Man puts zinc cream across nose" src="https://images.theconversation.com/files/561798/original/file-20231127-29-xpm7i4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/561798/original/file-20231127-29-xpm7i4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/561798/original/file-20231127-29-xpm7i4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/561798/original/file-20231127-29-xpm7i4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/561798/original/file-20231127-29-xpm7i4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/561798/original/file-20231127-29-xpm7i4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/561798/original/file-20231127-29-xpm7i4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Physical sunscreens may be more obvious on the skin.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/surfer-putting-face-sunscreen-lotion-before-1779554906">Shutterstock</a></span>
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<h2>So how do chemical sunscreens work?</h2>
<p>Chemical UV filters work by absorbing high-energy UV rays. This leads to the filter molecules interacting with sunlight and changing chemically. </p>
<p>When molecules return to their ground (or lower energy) state, they <a href="https://pubmed.ncbi.nlm.nih.gov/33640513/">release energy</a> as heat, distributed all over the skin. This may lead to uncomfortable reactions for people with skin sensitivity.</p>
<p>Generally, UV filters are meant to stay on the epidermis (the first skin layer) surface to protect it from UV radiation. When they enter into the dermis (the connective tissue layer) and bloodstream, this can lead to skin sensitivity and <a href="https://pubmed.ncbi.nlm.nih.gov/33571844/">increase the risk of toxicity</a>. The <a href="https://www.sciencedirect.com/science/article/pii/S0169409X20300077">safety profile</a> of chemical UV filters may depend on whether their small molecular size allows them to penetrate the skin. </p>
<p>Chemical sunscreens, compared to physical ones, cause more adverse reactions in the skin because of chemical changes in their molecules. In addition, some chemical filters, such as <a href="https://www.sciencedirect.com/topics/chemistry/dibenzoylmethane">dibenzoylmethane</a> tend to break down after UV exposure. These degraded products can no longer protect the skin against UV and, if they penetrate the skin, can <a href="https://pubmed.ncbi.nlm.nih.gov/32084432/">cause cell damage</a>.</p>
<p>Due to their stability – that is, how well they retain product integrity and effectiveness when exposed to sunlight – physical sunscreens may be <a href="https://pubmed.ncbi.nlm.nih.gov/21292345/">more suitable</a> for children and people with skin allergies.</p>
<p>Although sunscreen filter ingredients can rarely cause true allergic dermatitis, patients with photodermatoses (where the skin reacts to light) and eczema have <a href="https://pubmed.ncbi.nlm.nih.gov/21292345/">higher risk</a> and should take care and seek advice. </p>
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Read more:
<a href="https://theconversation.com/theres-a-serious-ethical-problem-with-some-sunscreen-testing-methods-and-youre-probably-not-aware-of-it-195359">There's a serious ethical problem with some sunscreen testing methods – and you're probably not aware of it</a>
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<a href="https://images.theconversation.com/files/561800/original/file-20231127-19-l879ck.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="woman compares sunscreen labels in pharmacy" src="https://images.theconversation.com/files/561800/original/file-20231127-19-l879ck.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/561800/original/file-20231127-19-l879ck.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/561800/original/file-20231127-19-l879ck.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/561800/original/file-20231127-19-l879ck.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/561800/original/file-20231127-19-l879ck.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/561800/original/file-20231127-19-l879ck.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/561800/original/file-20231127-19-l879ck.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">With lots of sunscreens on offer, it can be hard to decide which type is right for you.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/taking-sunscreen-lotion-shelves-pharmacy-store-1073742833">Shutterstock</a></span>
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<h2>What to look for</h2>
<p>The best way to check if you’ll have a reaction to a physical or chemical sunscreen is to <a href="https://www.medicalnewstoday.com/articles/patch-test-skincare">patch test</a> it on a small area of skin. </p>
<p>And the <a href="https://www.racgp.org.au/afp/2016/june/the-safety-of-nanoparticles-in-sunscreens-an-updat#ref-3">best sunscreen to choose</a> is one that provides broad-spectrum protection, is water and sweat-resistant, has a high sun protection factor (SPF), is easy to apply and has a low allergy risk.</p>
<p>Health authorities recommend sunscreen to prevent sun damage and cancer. Chemical sunscreens have the potential to penetrate the skin and may cause irritation for some people. Physical sunscreens are considered safe and effective and nanoparticulate formulations can increase their appeal and ease of use.</p><img src="https://counter.theconversation.com/content/217097/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Yousuf Mohammed receives funding from U.S FDA grants. This article reflects the views of the author and should not be construed to represent views or policies.</span></em></p><p class="fine-print"><em><span>Khanh Phan does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Not all sunscreens work the same way and some might irritate people with sensitive skin.Yousuf Mohammed, Dermatology researcher, The University of QueenslandKhanh Phan, Postdoctoral research associate, Frazer Institute, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2093712023-08-11T12:38:49Z2023-08-11T12:38:49ZSkin cancer screening guidelines can seem confusing – three skin cancer researchers explain when to consider getting checked<figure><img src="https://images.theconversation.com/files/539388/original/file-20230725-17-v7y631.jpg?ixlib=rb-1.1.0&rect=0%2C8%2C5454%2C3714&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A history of sunburns may put people at greater risk of developing skin cancer.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/young-womans-back-being-examined-at-a-royalty-free-image/166130792?phrase=skin+cancer+screening&adppopup=true">dnberty/iStock via Getty Images Plus</a></span></figcaption></figure><p><em>Protecting oneself from the summer sun and its damaging ultraviolet rays is often not straightforward. And public health messaging around when and how to be screened for skin cancer has become somewhat confusing.</em></p>
<p><em>In April 2023, the U.S. Preventive Services Task Force, an independent national panel of science experts, provided <a href="https://doi.org/10.1001/jama.2023.4342">updated recommendations on skin cancer</a> screening following a <a href="https://doi.org/10.1001/jama.2023.3262">systematic review of existing research</a>. The task force concluded that the evidence does not support annual widespread skin screening of adolescents and adults, but that catching cancers at the earliest stages reduces the risk of death from skin cancer.</em> </p>
<p><em>At first glance, these statements appear conflicting. So The Conversation asked dermatology experts <a href="https://som.cuanschutz.edu/Profiles/Faculty/Profile/7842">Enrique Torchia</a>, <a href="https://som.cuanschutz.edu/Profiles/Faculty/Profile/20820">Tamara Terzian</a> and <a href="https://coloradosph.cuanschutz.edu/resources/directory/directory-profile/Box-Neil-UCD4553">Neil Box</a> to help unravel the task force recommendations, what they mean for the public and how people can minimize their skin cancer risk.</em></p>
<h2>How common is skin cancer in the US?</h2>
<p>Skin cancer affects about 6 million Americans yearly, according to the Centers for Disease Control and Prevention. This number is <a href="https://www.cancer.org/research/cancer-facts-statistics/all-cancer-facts-figures/2023-cancer-facts-figures.html">more than all other types of cancers combined</a>. </p>
<p><a href="https://medschool.cuanschutz.edu/colorado-cancer-center/for-patients-families/cancers-we-treat/skin-cancer">Basal cell carcinoma and squamous cell carcinoma</a> – collectively known as keratinocyte cancers – account for more than <a href="https://doi.org/10.1016/j.jaad.2021.03.109">97% of skin cancer cases</a>, but invasive melanomas cause the most deaths. Keratinocyte cancers arise from basal cells and the more differentiated squamous cells in the epidermis – the top layer of skin – whereas melanoma comes from melanocytes found at the junction of the epidermis and the dermis, or middle layer. </p>
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<a href="https://images.theconversation.com/files/542208/original/file-20230810-21547-6nm4f8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram showing human skin layers." src="https://images.theconversation.com/files/542208/original/file-20230810-21547-6nm4f8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/542208/original/file-20230810-21547-6nm4f8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/542208/original/file-20230810-21547-6nm4f8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/542208/original/file-20230810-21547-6nm4f8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/542208/original/file-20230810-21547-6nm4f8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/542208/original/file-20230810-21547-6nm4f8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/542208/original/file-20230810-21547-6nm4f8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The majority of skin cancers arise from cells within the epidermis, or top layer, of the skin.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/human-skin-layers-royalty-free-illustration/1149397551?phrase=dermis+layers&adppopup=true">About time/ iStock via Getty Images Plus</a></span>
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<p>Unlike normal cells, skin cancer cells grow without constraints, acquiring the ability to invade down into the dermis.</p>
<p>Invasive melanomas are classified by stages 1 through 4. The higher the number, the more invasive the tumor is into the dermis and to other organs of the body in <a href="https://www.cancer.gov/publications/dictionaries/cancer-terms/def/metastasis">a process called metastasis</a>. </p>
<h2>What are the main causes of skin cancer?</h2>
<p>Overexposure to ultraviolet rays causes the majority of skin cancers. Both light- and dark-skinned people <a href="https://www.aad.org/media/stats-skin-cancer">can get skin cancer</a>, but light-skinned individuals have a greater risk. Those with light skin, light or red hair, or with numerous moles, are more susceptible to skin damage and severe burns by ultraviolet rays. Darker-skinned individuals produce more of the <a href="https://my.clevelandclinic.org/health/body/22615-melanin">protective pigment called melanin</a>. </p>
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<a href="https://images.theconversation.com/files/542237/original/file-20230810-23008-qfmzoe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Cartoon of a young female on the left before sunburn and on the right with a sunburned face, with sunrays hitting an illustration of the skin layers in the middle." src="https://images.theconversation.com/files/542237/original/file-20230810-23008-qfmzoe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/542237/original/file-20230810-23008-qfmzoe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/542237/original/file-20230810-23008-qfmzoe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/542237/original/file-20230810-23008-qfmzoe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/542237/original/file-20230810-23008-qfmzoe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/542237/original/file-20230810-23008-qfmzoe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/542237/original/file-20230810-23008-qfmzoe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Overexposure to UV light damages skin, causing sunburns and stimulating melanocytes to make melanin, the protective pigment that darkens skin during tanning. Sunscreen can protect skin from UV damage.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/care-before-after-image-royalty-free-illustration/609443652">chombosan/iStock via Getty Images Plus</a></span>
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<p>Tanning serves as the body’s protective response to skin damage from ultraviolet rays, stimulating melanocytes to <a href="https://doi.org/10.1111/exd.14260">produce melanin</a>. People who use tanning beds are at a higher risk of skin damage and skin cancers. This is why the American Academy of Dermatology and others <a href="https://www.aad.org/media/stats-indoor-tanning">recommend avoiding tanning beds</a>. Outdoor workers or those who spend time outdoors recreationally, especially at higher elevation, are exposed to more ultraviolet light. </p>
<p>A history of sunburns also puts people at greater risk of developing skin cancer. Because the damage from ultraviolet, or UV, exposure is cumulative, skin cancer is <a href="https://www.skincancer.org/skin-cancer-information/skin-cancer-facts/">more prevalent in people over 55 years old</a>. </p>
<p>Survivors of skin cancers are also <a href="https://doi.org/10.1111/jdv.12887">more likely to get another cancer</a> in their lifetime. Moreover, those who had a squamous cell carcinoma may be at <a href="https://doi.org/10.1007/s00403-017-1724-5">higher risk of dying from noncancer causes</a>. The reasons for these observations are not well understood but may be linked to inflammation or altered immunity, or both, in skin cancer survivors.</p>
<h2>What is the debate behind screening?</h2>
<p>The ongoing debate revolves around whether more screening reduces the death toll from melanoma. </p>
<p>Since the early 1990s, the incidence of melanoma has risen dramatically in the U.S. This increase may be due in part to more emphasis on early detection. <a href="https://doi.org/10.1056/NEJMsb2019760">More melanomas have been found</a>, particularly those identified at the earliest stage, also known as <a href="https://www.aimatmelanoma.org/stages-of-melanoma/">stage 0</a> or melanoma <em>in situ</em>. </p>
<p>Despite this, the rate of death per capita from melanoma has remained unchanged over the last 40 years. Researchers have <a href="https://doi.org/10.1056/NEJMsb2019760">attributed this fact to overdiagnosis</a>, in which suspicious lesions are diagnosed as early melanomas, even though they may not actually be melanomas or progress to be invasive melanomas, which have <a href="https://www.cancer.org/cancer/types/melanoma-skin-cancer/detection-diagnosis-staging/survival-rates-for-melanoma-skin-cancer-by-stage.html">the worst prognosis</a>. </p>
<p>This observation suggests that widespread screening may result in unnecessary surgical biopsies and increased psychological stress associated with a cancer diagnosis. </p>
<p>However, a recent study published after the task force recommendations showed that patients with melanoma <em>in situ</em> had a slight risk of death from melanoma, but <a href="https://doi.org/10.1001/jamadermatol.2023.1494">lived longer than the average person</a>. The authors speculated that the diagnosis of early stage melanoma resulted in a greater awareness of the patient’s overall health, leading to more health-conscious behavior. So, there may be additional benefits to screening the public. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/UnCUcFJJDSA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Regular self-exams help you catch skin cancer early, when it’s most treatable.</span></figcaption>
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<h2>What did the task force base its new recommendations on?</h2>
<p>The task force reviewed current and past data on the major types of skin cancers. The expert panel relied in part on the results of a large public <a href="https://doi.org/10.1016/j.jaad.2010.11.016">skin cancer screening program</a> in Germany. This program initially examined 20-year-olds from a single state and subsequently <a href="http://dx.doi.org/10.1136/bmjopen-2015-008158">expanded the program nationwide</a> to include people over 35. However, death rates from melanoma were unchanged compared to areas where skin exams were not offered. </p>
<p>The results of the German screening program did not provide strong confidence that annual widespread public screening of adults would reduce skin cancer deaths compared with current practices. However, the task force did conclude, based on numerous studies involving millions of patients, that detecting melanoma at early stages when tumors are less invasive <a href="https://doi.org/10.1001/jama.2023.3262">improved patient survival</a>. </p>
<h2>When should you get a skin exam?</h2>
<p>The American Academy of Dermatology, the <a href="https://www.skincancer.org/early-detection/self-exams/">Skin Cancer Foundation</a> and the <a href="https://www.cdc.gov/cancer/skin/basic_info/screening.htm">CDC recommend</a> <a href="https://www.aad.org/news/aad-statement-uspstf-cancer-screeening">monthly self-checks</a>. This requires familiarity with your skin or that of your family members. Luckily, there are many online guides on detecting suspicious skin lesions. </p>
<p>Whenever you have a concern about a spot on your skin, seek medical advice. Annual or more frequent exams are also <a href="https://www.aad.org/dw/dw-insights-and-inquiries/2019-archive/november/dwii-11-13-19-the-naked-truth-about-total-body-skin-examination-a-lesson-from-goldilocks-and-the-three-bears">recommended for high-risk groups</a>. This includes those who are older or susceptible to getting skin cancers, skin cancer survivors and immunocompromised people like organ transplant recipients. </p>
<p>Between 8% to 30% of the U.S. population <a href="https://doi.org/10.1016/j.jaad.2008.03.013">gets an annual skin exam</a>, but the numbers are imprecise because screening rates have not been well studied. Access to screening may also be challenging for some people. In response, nonprofits like the <a href="https://www.aad.org/public/public-health/skin-cancer-screenings/find-a-screening">American Academy of Dermatology</a>, <a href="https://www.skincancer.org/early-detection/destination-healthy-skin/">the Skin Cancer Foundation</a> and <a href="https://www.thesunbus.org/">The Sun Bus</a> provide resources for free exams. However, these opportunities are often few and far between. </p>
<p>Based on internal unpublished data from The Sun Bus, our mobile clinic operating in the central and southern U.S., a significant number of individuals seeking free exams were primarily motivated by concerns about a skin lesion and the cost of visiting a dermatologist.</p>
<p><iframe id="X7MiE" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/X7MiE/8/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>Our data suggests that screening programs attract individuals who are proactive and health-conscious.</p>
<h2>How can you minimize the risk of skin cancer?</h2>
<p>Strategies that limit UV exposure will <a href="https://www.cdc.gov/cancer/skin/basic_info/sun-safety.htm">reduce skin cancer risk</a>. This includes avoiding sunburns by: </p>
<ul>
<li>Finding shade</li>
<li>Covering exposed skin</li>
<li>Using a hat and sunglasses</li>
<li>Using and reapplying sunscreen routinely</li>
</ul>
<p>A broad-spectrum sunscreen and lip balm with a Sun Protection Factor (SPF) of at least 30 when applied correctly will <a href="https://www.aad.org/public/everyday-care/sun-protection/shade-clothing-sunscreen/how-to-select-sunscreen">block 97% of ultraviolet rays</a>. Apply these products 15-20 minutes before heading out into the sun and reapply every two hours. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/L7dH-I2qLU8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Don’t wait until you’re in the sun to apply sunscreen.</span></figcaption>
</figure>
<p>UV light is most intense between the hours of 10 a.m. to 4 p.m. It is a good idea to pay attention to the UV index – a forecast by zip code that <a href="https://www.epa.gov/sunsafety/uv-index-1">projects risk of UV exposure</a> on a scale of 0 to 11. A UV index below 2 is the safest, whereas 11 represents extreme danger. </p>
<p>Ideally, clothing should be rated with an Ultraviolet Protection Factor (UPF) of 50. Wearing regular long-sleeved clothing and pants will also <a href="https://www.skincancer.org/skin-cancer-prevention/sun-protection/sun-protective-clothing/">provide some protection</a>. </p>
<p>These measures can keep your skin healthy into your golden years by reducing skin aging and cancer caused by ultraviolet light.</p><img src="https://counter.theconversation.com/content/209371/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Enrique Torchia received funding from American Cancer Society and Dermatology Foundation. </span></em></p><p class="fine-print"><em><span>Neil Box receives funding from the National Institutes of Health and the American Skin Association. He is affiliated with Caris Life Sciences and the Colorado Melanoma Foundation. </span></em></p><p class="fine-print"><em><span>Tamara Terzian received funding from National Institutes of Health, Dermatology Foundation, Skin Cancer Foundation, American Skin Association, American Cancer Society, Cancer League of Colorado, and Colorado Clinical Translational Sciences Institute. She is affiliated with the Colorado Melanoma Foundation and the University of Colorado. </span></em></p>Widespread screening for skin cancer may not be necessary, but it is important to understand the risks behind UV overexposure and to get checked early if you have concerns.Enrique Torchia, Assistant Research Professor of Dermatology, University of Colorado Anschutz Medical CampusNeil Box, Associate Clinical Professor of Dermatology and Epidemiology, University of Colorado Anschutz Medical CampusTamara Terzian, Assistant Professor of Dermatology, University of Colorado Anschutz Medical CampusLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2029252023-04-03T15:21:53Z2023-04-03T15:21:53ZCountries agreed to ban ozone-depleting chemicals in the 1980s – but we found five CFCs increasing to record levels in the atmosphere<p>Despite a global ban in place since 2010, atmospheric concentrations of five ozone-depleting chemicals have reached a record high.</p>
<p>Chlorofluorocarbons, or CFCs, are entirely man-made gases used in a variety of applications, including refrigeration, air conditioning or as chemical solvents. They have been increasingly regulated by a series of international treaties since the 1980s. The 1987 <a href="https://www.unep.org/ozonaction/who-we-are/about-montreal-protocol">Montreal protocol</a>, which has been universally ratified, restricted the release of CFCs to the atmosphere where they contribute to the destruction of the ozone layer: a region high up in the stratosphere which absorbs harmful ultraviolet (UV) radiation and protects life below. </p>
<p>The goal of the Montreal protocol was to induce a decline in the atmospheric CFC concentration through controlling, and increasingly restricting, the production of these chemicals. This has worked well for many ozone-depleting substances, which is why the ozone layer is slowly recovering. And so the recent increase in atmospheric concentrations of five CFCs is quite surprising.</p>
<figure class="align-center ">
<img alt="Discarded aerosol canisters." src="https://images.theconversation.com/files/519030/original/file-20230403-16-q8yjf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/519030/original/file-20230403-16-q8yjf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/519030/original/file-20230403-16-q8yjf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/519030/original/file-20230403-16-q8yjf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/519030/original/file-20230403-16-q8yjf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/519030/original/file-20230403-16-q8yjf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/519030/original/file-20230403-16-q8yjf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Montreal protocol has succeeded in eliminating the biggest sources of CFCs.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/circa-1990-bucket-full-empty-aerosol-106925534">Joseph Sohm/Shutterstock</a></span>
</figcaption>
</figure>
<p><a href="https://www.nature.com/articles/s41561-023-01147-w">Our findings</a>, while worrying, should be considered an early warning. The impact of all five CFCs on the recovery of the ozone layer is still small. Nevertheless, we do not fully understand where they are coming from, so this could change in the future, and we should not ignore the cumulative effect of these emissions on human health and the environment.</p>
<h2>The global picture</h2>
<p>Our team has been analysing air samples from all over the world, focusing on so-called “background” sites that are far away from the sources of these CFCs, or in fact any industrial emissions. An example is the Cape Grim observatory on the remote west coast of Tasmania. This is the basis for our assessment of the threat these chemicals pose, as it reveals global trends in their atmospheric concentration.</p>
<p>Our main findings for the period 2010-2020 were twofold. First, concentrations of CFC-13 and CFC-113a continued their previously observed – and puzzling – increase. Rising concentrations of CFC-113a even accelerated around 2016. Second, concentrations of CFC-114a and CFC-115 were stable since the 2000s, while those of CFC-112a had even started to decrease. However, all of them began increasing around 2013-2014.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/519027/original/file-20230403-26-jnky50.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two line graphs side by side" src="https://images.theconversation.com/files/519027/original/file-20230403-26-jnky50.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/519027/original/file-20230403-26-jnky50.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=273&fit=crop&dpr=1 600w, https://images.theconversation.com/files/519027/original/file-20230403-26-jnky50.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=273&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/519027/original/file-20230403-26-jnky50.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=273&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/519027/original/file-20230403-26-jnky50.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=343&fit=crop&dpr=1 754w, https://images.theconversation.com/files/519027/original/file-20230403-26-jnky50.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=343&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/519027/original/file-20230403-26-jnky50.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=343&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Global emissions of the five CFCs weighted by their impact on ozone depletion (a) and the climate (b).</span>
<span class="attribution"><a class="source" href="https://www.nature.com/articles/s41561-023-01147-w">Western et al. (2023)/Nature Geoscience</a></span>
</figcaption>
</figure>
<p>These observations, combined with additional knowledge about atmospheric circulation and how CFCs are removed from the atmosphere through chemical reactions, allowed us to estimate the global emissions of these five gases. Their damage to the ozone layer can be expressed through their ozone depletion potential, which states how much ozone would be destroyed compared to the same quantity of CFC-11, which is different for each CFC. </p>
<p>The result is a relief. Emissions between 2010 and 2020 only resulted in a very small loss of around 0.002% of global stratospheric ozone. </p>
<p>There is no time to relax, though, for two reasons. All five CFCs are also potent greenhouse gases and, once emitted, will remain in the atmosphere for decades to centuries. Their warming effect in 2020 was already approximately that of Switzerland’s total CO₂ emissions. And if those emissions continue on their upwards trajectory, their contribution to climate change will expand too. The persistence of these gases in the atmosphere must be taken seriously: all emissions are a legacy for future generations to contend with.</p>
<h2>Tracking down the sources</h2>
<p>The first step towards avoiding future emissions is to find out where the current ones are coming from. There were already some hints in previous studies, which we gathered and combined with our own information, such as on the exact timing of when emissions started accelerating.</p>
<p>We found that three of the five CFCs (CFC-113a, CFC-114a and CFC-115) can be produced during the manufacture of other chemicals, which is allowed under the Montreal protocol, most notably hydrofluorocarbons or HFCs. HFCs have replaced CFCs for many applications as an ozone-friendly alternative. However, like CFCs, they are greenhouse gases and their production is now being reduced in <a href="https://treaties.un.org/Pages/ViewDetails.aspx?src=IND&mtdsg_no=XXVII-2-f&chapter=27&clang=_en">many countries</a> under the 2016 Kigali Amendment to the Montreal Protocol, which could reduce climate-related warming <a href="https://acp.copernicus.org/articles/22/6087/2022/">by 0.5°C</a>. </p>
<p>It’s likely that the CFCs are leaking out during the production process, where they are either used as a feedstock (a chemical ingredient to make another chemical) or as a result of incomplete conversion of the feedstock to the target chemical. The production of HFCs really took off in developing countries after CFCs were banned in 2010, which is around the same time as the increase in emissions of these five CFCs.</p>
<p>The production of HFCs is predicted to <a href="https://acp.copernicus.org/articles/22/6087/2022/">further increase</a> over the next few years, which could result in increasing emissions of these CFCs. CFC-113a is used to make at least one hydrofluoroolefin or HFO, which are alternatives to HFCs that don’t heat the climate and may be used long into the future. Despite HFCs and HFOs being more benign alternatives to CFCs, there may still be some cost to ozone during their production if CFCs continue to leak into the atmosphere.</p>
<p>We were unable to find a plausible source for the other two CFCs, CFC-13 and CFC-112a. The fact that their emissions are increasing and we don’t know why is a concern in itself.</p>
<h2>Time to revisit Montreal?</h2>
<p>The Montreal protocol has been a huge success in mitigating emissions of ozone-depleting substances. Total CFC emissions are now <a href="https://csl.noaa.gov/assessments/ozone/2022/">only around 5% of their peak</a> in the late 1980s. Yet an increase in the atmospheric abundance of some CFCs is still at odds with the treaty’s goals – and their elimination, by clogging leaks in industrial processes, could present an easy win to reduce these country-sized emissions of ozone-depleting and climate-warming gases. </p>
<p>It will take careful consideration by countries signed up to the protocol to find the necessary controls for quashing these trend-bucking emissions. In the meantime, we will continue to use our eyes in the sky to monitor the progress of a whole host of Earth-damaging gases.</p>
<hr>
<figure class="align-right ">
<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><strong><em>Don’t have time to read about climate change as much as you’d like?</em></strong>
<br><em><a href="https://theconversation.com/uk/newsletters/imagine-57?utm_source=TCUK&utm_medium=linkback&utm_campaign=Imagine&utm_content=DontHaveTimeTop">Get a weekly roundup in your inbox instead.</a> Every Wednesday, The Conversation’s environment editor writes Imagine, a short email that goes a little deeper into just one climate issue. <a href="https://theconversation.com/uk/newsletters/imagine-57?utm_source=TCUK&utm_medium=linkback&utm_campaign=Imagine&utm_content=DontHaveTimeBottom">Join the 10,000+ readers who’ve subscribed so far.</a></em></p>
<hr><img src="https://counter.theconversation.com/content/202925/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Luke Western receives funding from the European Commission under Horizon 2020. </span></em></p><p class="fine-print"><em><span>Johannes Laube received funding from the European Research Council. </span></em></p>Chlorofluorocarbons (CFCs) are also potent greenhouse gases which contribute to climate change.Luke Western, Research Associate in Atmospheric Science, University of BristolJohannes Laube, Honorary Lecturer, Centre for Ocean and Atmospheric Sciences, University of East AngliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1940652022-11-14T02:51:36Z2022-11-14T02:51:36ZTempted to buy a UV light disinfection gadget? Some can be dangerous – here’s what you need to know<figure><img src="https://images.theconversation.com/files/494987/original/file-20221114-12-tzfevs.jpg?ixlib=rb-1.1.0&rect=0%2C53%2C5443%2C3467&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">MBLifestyle/Shutterstock</span></span></figcaption></figure><p>The COVID-19 pandemic has fundamentally changed many of our behaviours and attitudes towards infection control.</p>
<p>Hand hygiene was one of the earliest and most adopted measures to counteract the spread of disease, but there have been more technology-based approaches, too.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/vodka-wont-protect-you-from-coronavirus-and-4-other-things-to-know-about-hand-sanitizer-133593">Vodka won't protect you from coronavirus, and 4 other things to know about hand sanitizer</a>
</strong>
</em>
</p>
<hr>
<p>One example is the booming industry of devices that use ultraviolet radiation (UV) to kill germs. While UV can successfully sanitise the air, or objects such as your smartphone, it can also come with cancer risk if the radiation is not behind a proper barrier.</p>
<p>Here’s what you need to know about UV sanitation devices.</p>
<h2>How does UV sanitation work?</h2>
<p>Ultraviolet light is light with wavelengths just short enough that most humans can’t see it under normal conditions. The most ubiquitous source of UV is the Sun, which radiates everything from vacuum UV to far UVC, UVC, UVB and UVA rays (see below).</p>
<p>The last two can pass the ozone layer in our atmosphere, while the first three are blocked – good news for life on Earth, since UVC in particular can be harmful to living things.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/494983/original/file-20221114-2672-jwwh8z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A chart showing the wavelengths of ultraviolet light" src="https://images.theconversation.com/files/494983/original/file-20221114-2672-jwwh8z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/494983/original/file-20221114-2672-jwwh8z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=204&fit=crop&dpr=1 600w, https://images.theconversation.com/files/494983/original/file-20221114-2672-jwwh8z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=204&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/494983/original/file-20221114-2672-jwwh8z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=204&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/494983/original/file-20221114-2672-jwwh8z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=256&fit=crop&dpr=1 754w, https://images.theconversation.com/files/494983/original/file-20221114-2672-jwwh8z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=256&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/494983/original/file-20221114-2672-jwwh8z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=256&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Ultraviolet light is invisible to the eye, and spans from 10 to 400 nanometres in wavelength.</span>
<span class="attribution"><span class="source">petrroudny43/Shutterstock</span></span>
</figcaption>
</figure>
<p>At a wavelength of 250–260 nanometres, energy generated by UVC rays can penetrate through microbes to break their DNA and RNA, disrupting their cell functions and killing them. </p>
<p>This is useful for germicidal (germ-killing) UVC radiation technology, although its efficacy depends on radiation intensity, the distance from light source to target, the type of surface being sanitised, and the wavelength at which the UVC is operating.</p>
<p>The blue light you often see on such devices is either decorative, or the visible light emitted by the chemicals used to produce UVC – remember, the UV light itself is invisible.</p>
<p>According to research, sanitation devices that emit high doses of germicidal UVC are an efficient means of killing fungi, viruses, bacteria and protozoa – single-celled organisms. They have been successfully used in treating <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/fsn3.1412">water</a>, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2789813/">air</a>, <a href="https://pubmed.ncbi.nlm.nih.gov/29124707/">sewage</a>, for <a href="https://www.sciencedirect.com/science/article/abs/pii/S1385894720342005">food safety</a>, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7644456/pdf/IJHS-14-52.pdf">medical settings</a>, <a href="https://visionasia.com.sg/uvc-disinfection-robots-in-public-transport/">public transport</a> and more. </p>
<p>The key is to have the UVC source fully enclosed and automatically stop if the device is open, so there’s no risk of exposing people to the radiation, which can cause severe burns and even increase the risk of cancer. </p>
<p>UV sanitation gadgets that operate without enclosure present serious health risks. Unfortunately, current lack of regulation means such devices are readily available for consumers to buy – and potentially be harmed by.</p>
<figure class="align-center ">
<img alt="A stock photograph of an electric toothbrush next to a white container with a blue light in the centre" src="https://images.theconversation.com/files/494985/original/file-20221114-18-gppq8f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/494985/original/file-20221114-18-gppq8f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/494985/original/file-20221114-18-gppq8f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/494985/original/file-20221114-18-gppq8f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/494985/original/file-20221114-18-gppq8f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/494985/original/file-20221114-18-gppq8f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/494985/original/file-20221114-18-gppq8f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An electric toothbrush head steriliser that’s fully enclosed should be perfectly safe to use.</span>
<span class="attribution"><span class="source">grandbrothers/Shutterstock</span></span>
</figcaption>
</figure>
<h2>A serious lack of regulation</h2>
<p>Numerous companies have researched and developed safe, efficient and fully enclosed UVC devices.</p>
<p>However, the market is unregulated, with serious concerns about the quality and safety of some dubious devices available for consumers. In 2020, the lighting industry body <a href="https://www.globallightingassociation.org/images/files/publications/GLA_UV-C_Safety_Position_Statement.pdf">Global Lighting Association</a> raised its concerns:</p>
<blockquote>
<p>“[I]n the midst of a global COVID-19 epidemic, GLA is concerned at the proliferation of UVC disinfecting devices – particularly being sold on the internet – with dubious safety features and inadequate safety instructions”.</p>
</blockquote>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/ultraviolet-light-can-make-indoor-spaces-safer-during-the-pandemic-if-its-used-the-right-way-141512">Ultraviolet light can make indoor spaces safer during the pandemic – if it's used the right way</a>
</strong>
</em>
</p>
<hr>
<p>UVC products without enclosure, such as the “<a href="https://www.fda.gov/medical-devices/safety-communications/do-not-use-ultraviolet-uv-wands-give-unsafe-levels-radiation-fda-safety-communication">disinfection wands</a>” you might see on the internet, <a href="https://www.cnet.com/home/smart-home/uvc-light-wands-kill-viruses-experts-warn-major-safety-issue-coronavirus-covid-19/">can be very unsafe</a>. They can affect exposed skin, eyes and mucous membranes.</p>
<p>Due to health risks, any non-enclosed UVC device should only be remote-controlled or automatic. It should also be equipped with safeguards, such as a sensor that turns it off if it detects anyone in the room.</p>
<p>To ensure the safety and efficacy of UVC devices available on the consumer market, we need watchdog bodies to urgently introduce rigorous global regulations.</p>
<h2>Is far UVC safer?</h2>
<p>Recently, <a href="https://www.nature.com/articles/s41598-022-08462-z">far UVC has been proposed as a possible solution</a> to this challenge. Radiating at a wavelength of 207–222 nanometres, far UVC has a <a href="https://www.nature.com/articles/s41598-020-67211-2">“shallow” skin entrance</a>. However, the research with far UVC is very recent and so far mostly focused on animals.</p>
<p>Very few human studies have been performed, and some have been funded by companies prototyping far UVC devices, which can introduce a bias. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7894148/">Literature search reviews</a> report different analytic parameters, which makes comparisons difficult to interpret.</p>
<p><a href="https://www.dundee.ac.uk/stories/research-investigates-safety-uv-technology-covid-19-inactivation">Some trials</a> have started, but there are few to date, and with small sample sizes.</p>
<p>We will need trials with rigorous ethical approvals to investigate the full far UVC impact on humans. There is a lack of understanding how far UVC might affect people with thinner outer skin layers, affected by cuts, light sensitivity, or various medical conditions.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/ultraviolet-radiation-is-a-strong-disinfectant-it-may-be-what-our-schools-hospitals-and-airports-need-142277">Ultraviolet radiation is a strong disinfectant. It may be what our schools, hospitals and airports need</a>
</strong>
</em>
</p>
<hr>
<h2>What to look out for if you still want a UV sanitation device</h2>
<p>When it comes to buying a UVC gadget, buyer beware. Never buy anything that claims you can disinfect hands, the body, or a whole room while people are around. Skin cancers like <a href="https://link.springer.com/article/10.1007/s42764-020-00009-8">basal cell carcinoma and squamous cell carcinoma</a> are attributed to UV exposure.</p>
<p>Check the documentation. Is there evidence the device is effective against microorganisms? What’s the length of exposure, and how far from the source is the target being sanitised?</p>
<p>You also need to be aware that the cost of efficient and safe new technology and efficient UVC-producing LEDs is very high. Therefore, you may need to question the effectiveness of a relatively “cheap” device.</p>
<p>In the absence of a global regulatory body within the UVC market, the rule of thumb is to purchase only a fully sealed, enclosed UVC device operating with strict safety and efficiency to harm microbes, not you.</p><img src="https://counter.theconversation.com/content/194065/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lotti Tajouri is affiliated with Dubai Police Scientist Council.</span></em></p><p class="fine-print"><em><span>Simon McKirdy has provided scientific advice to Glissner.</span></em></p><p class="fine-print"><em><span>Matthew Olsen and Rashed Alghafri do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Ultraviolet radiation at specific wavelengths is great at killing germs – but when used incorrectly, it can also cause health risks.Lotti Tajouri, Associate Professor, Genomics and Molecular Biology; Biomedical Sciences, Bond UniversityMatthew Olsen, Assistant researcher, Bond UniversityRashed Alghafri, Honorary Adjunct Associate Professor, Health Sciences and Medicine, Bond UniversitySimon McKirdy, Professor of Biosecurity, Murdoch UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1883442022-08-09T15:03:58Z2022-08-09T15:03:58ZDo chemicals in sunscreens threaten aquatic life? A new report says a thorough assessment is ‘urgently needed,’ while also calling sunscreens essential protection against skin cancer<figure><img src="https://images.theconversation.com/files/478144/original/file-20220808-4922-ds99rt.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3794%2C2514&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sunscreens for sale at a Walgreens drug store.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/shelves-of-suntan-lotion-for-sale-in-walgreens-news-photo/665553846">Jeff Greenberg/Universal Images Group via Getty Images</a></span></figcaption></figure><p><em>Studies have shown that the same active ingredients in sunscreens that protect people from cancer-causing ultraviolet rays can be toxic to a range of species in oceans, rivers and lakes. With both of these risks in mind, a <a href="https://nap.nationalacademies.org/catalog/26381/review-of-fate-exposure-and-effects-of-sunscreens-in-aquatic-environments-and-implications-for-sunscreen-usage-and-human-health">new report</a> from the National Academies of Sciences, Engineering and Medicine finds an urgent need for more information about whether these chemicals threaten aquatic life on a broad scale.</em> </p>
<p><em>The report calls on the U.S. Environmental Protection Agency to conduct a detailed review called an <a href="https://www.epa.gov/risk/ecological-risk-assessment">environmental risk assessment</a> of the likelihood that exposure to one or more of these chemicals, called <a href="https://ntp.niehs.nih.gov/whatwestudy/topics/uvfilters/index.html">UV filters</a>, may harm organisms in saltwater and freshwater ecosystems. The study recommends focusing on two types of settings – coral reefs in shallow waters near shore, and slow-moving freshwater bodies like ponds and marshes – that are heavily used for recreation and/or exposed to wastewater or urban runoff.</em> </p>
<p><em>The study recognizes that sunscreen with a Sun Protection Factor (SPF) of 30 or higher is an effective defense against sunburn and skin cancer, and that making it harder to buy broad-spectrum sunscreen that people will actually use could harm public health. Accordingly, it calls for research examining how changes in sunscreen usage could affect human health. Two members of the study committee explain how their group balanced these concerns.</em></p>
<h2>Many species are exposed to many stresses</h2>
<p><strong>Robert Richmond, Research Professor and Director, Kewalo Marine Laboratory, University of Hawaii at Manoa</strong></p>
<p>Studies to date have provided compelling laboratory evidence that some UV filters can have toxic effects on aquatic species, including <a href="http://dx.doi.org/10.1126/science.abo4627">corals</a>, <a href="http://dx.doi.org/10.1126/science.abn2600">anemones</a> and <a href="https://doi.org/10.1021/acs.est.8b02418">zebrafish</a>, that are exposed to the chemicals. These findings have raised concerns about sunscreens’ <a href="https://doi.org/10.1016/j.envpol.2020.115894">larger-scale impacts on biological communities and ecosystems</a>.</p>
<p>But outcomes in the environment will differ depending on what compounds, ecosystems and local environmental conditions are involved. That’s especially true for coral reefs. The committee highlighted reefs because they are <a href="https://coast.noaa.gov/states/fast-facts/coral-reefs.html">ecologically, economically and culturally valuable</a>, and attract large numbers of tourists who use sunscreens. </p>
<p>Coral reefs are <a href="https://doi.org/10.1016/j.oneear.2021.08.016">declining worldwide</a> due to multiple human-induced disturbances. Some of these disturbances are global, such as <a href="https://oceanservice.noaa.gov/facts/coralreef-climate.html">ocean warming and acidification driven by climate change</a>. Other stressors, such as coastal water quality, are more local. </p>
<p>Studying the effects of chemicals on corals and coral reefs is challenging because they are both complex systems. Reef-building corals are a combination of an animal, single-celled algae and rich populations of bacteria living and working together. Coral reefs are made up of thousands of interacting organisms. </p>
<p>Importantly, many stress responses in corals occur without causing outright death, but impair their health, growth, resilience and even ability to reproduce. Scientists need to know more about these responses to guide effective management responses and interventions.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/478146/original/file-20220808-14-54tuwr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Dozens of parrotfish swim over a reef of res, white and yellow corals." src="https://images.theconversation.com/files/478146/original/file-20220808-14-54tuwr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/478146/original/file-20220808-14-54tuwr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/478146/original/file-20220808-14-54tuwr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/478146/original/file-20220808-14-54tuwr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/478146/original/file-20220808-14-54tuwr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/478146/original/file-20220808-14-54tuwr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/478146/original/file-20220808-14-54tuwr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Healthy coral reefs like this one in American Samoa support such diverse communities of fish and other organisms that they often are called the rainforests of the sea.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1016/j.oneear.2021.08.016">Kevin Lino, NOAA/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>After in-depth reviews of the existing data, our study committee recommended that the U.S. Environmental Protection Agency should undertake an ecological risk assessment of the 17 UV filters used in sunscreens sold in the U.S. Such a study would include a comparison of toxicity findings to relevant concentrations and exposure conditions. </p>
<p>For example, what happens to organisms exposed to these chemicals occasionally versus those exposed regularly, in calm bays or along open, wave-swept coasts? How do UV filters differ in whether they break down in water, or accumulate in sediments or the tissues of living organisms? </p>
<p>In our view, an ecological risk assessment would provide EPA and others the basis for sound and effective policy development. The sooner this happens and the results are applied to the regulatory process, the better for everyone who is affected, including future generations.</p>
<h2>The challenge of understanding long-term effects on humans and the environment</h2>
<p><strong>Karen Glanz, George A. Weiss University Professor and Director, UPenn Prevention Research Center, University of Pennsylvania</strong></p>
<p>The question of whether UV filters pose harm to the environment while helping to reduce skin damage and prevent skin cancer is a conundrum. It seemingly pits human and environmental health against each other head-to-head and asks policymakers, medical experts and the public to choose between them. </p>
<p>Humans need sunlight to live, but overexposure to the sun’s damaging rays – ultraviolet radiation – causes sunburn and wrinkles and is a risk factor for the development of skin cancers, including the most deadly type, <a href="https://www.cancer.org/cancer/melanoma-skin-cancer/about/what-is-melanoma.html">melanoma</a>. Routine use of <a href="https://www.aad.org/public/diseases/skin-cancer/prevent/how">broad-spectrum sunscreen with SPF 30+</a> when outdoors has been found to prevent skin damage and skin cancer. But sunscreens are most effective as part of a <a href="https://www.cdc.gov/cancer/skin/basic_info/sun-safety.htm">set of behaviors</a> that also includes wearing hats and cover-up clothing and seeking shade. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"616291967698386944"}"></div></p>
<p>Most people in the U.S. don’t practice these behaviors frequently or thoroughly enough. So it’s important to weigh very carefully the potential effects of restricting the choice of available sunscreens. </p>
<p>Some jurisdictions already restrict the sale of certain sunscreens because concerned advocates believe doing so will be good for the environment. In the U.S., they include <a href="https://www.cntraveler.com/story/these-destinations-are-banning-certain-sunscreens">Hawaii, the U.S Virgin Islands and the city of Key West, Florida</a>. Our report doesn’t draw a definitive conclusion about whether these measures are scientifically justified or effective. Rather, it emphasizes analyzing whether and how they may affect human health as well as the
environment.</p>
<p>The study draws attention to the challenge of understanding risks from UV filters to aquatic environments under various conditions, and in the context of overarching environmental stressors such as rising sea temperatures. It’s important to understand that for both environmental and human health issues, laboratory studies don’t always match what happens in the environment. </p>
<p>Studies of model systems such as bacteria and yeast, and organisms such as fish embryos and insect larvae, can yield findings that do not hold up in studies of humans. For both the environment and humans, it may not be possible or ethical to conduct true experiments that test the long-term effects of chemicals in UV filters. </p>
<p>Members of our committee wrestled to interpret the available evidence, and also with the gaps in that evidence. Ultimately we concluded that the science is not settled, but that there is much to build on to advance understanding of this issue. Our conclusions are not a win/lose outcome for either the environment or humans. Rather, they point to a need to think both broadly and strategically for the benefit of people and the planet.</p><img src="https://counter.theconversation.com/content/188344/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert Richmond receives funding from the National Science Foundation, the National Oceanic and Atmospheric Administration, the U.S. Fish and Wildlife Service, the Pew Environmental Group, the National Fish and Wildlife Foundation, the H.W. Hoover Foundation and the Hawaii Division of Aquatic Resources.
He has been a Pew Fellow in Marine Conservation, and an Aldo Leopold Fellow in Environmental Leadership, and has served on the Board of Directors of the Palau International Coral Reef Center and as Science Advisor to the All Islands Committee of the US Coral Reef Task Force. He was a member of a previous study committee organized by the National Academies, on Interventions to Increase the Resilience of Coral Reefs.
</span></em></p><p class="fine-print"><em><span>Karen Glanz conducts research cancer prevention and control, theories of health behavior, and social and health policy. She has conducted descriptive, observational, methodological, intervention, and dissemination research in skin cancer prevention since 1993. She has worked on analyses of national surveys of UV exposure and sun protection; developed, analyzed and validated measures and methods of skin cancer prevention research; and led evidence reviews for skin cancer prevention. Her research has been funded by the U.S. Centers for Disease Control and Prevention, the National Institutes of Health, and the Skin Cancer Foundation. Dr. Glanz served on the US Task Force on Community Preventive Services for 10 years and co-led reviews of the effectiveness of skin cancer prevention programs. She is an elected member of the National Academy of Medicine. </span></em></p>Rising concern about possible environmental damage from the active ingredients in sunscreens could have ripple effects on public health if it causes people to use less of them.Robert Richmond, Professor of Biology and Director, Kewalo Marine Laboratory, University of HawaiiKaren Glanz, George A. Weiss University Professor and Director, UPenn Prevention Research Center, University of PennsylvaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1850742022-06-20T09:37:18Z2022-06-20T09:37:18ZBlue light: what we do and don’t know about the damage it causes our skin<figure><img src="https://images.theconversation.com/files/469485/original/file-20220617-25-ma9rqf.jpg?ixlib=rb-1.1.0&rect=44%2C44%2C5946%2C3943&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Is blue light harmful?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/disappointed-sad-woman-holding-mobile-phone-1129353881">Shutterstock</a></span></figcaption></figure><p>Take a wander down the skincare aisle of any health and beauty retailer and you’ll be met with a bewildering array of creams and sprays, promising to protect you from various threats to your skin.</p>
<p>You might have noticed skincare companies claiming their products can protect you from the effects of blue light. If you hadn’t thought about blue light before, you’d be forgiven for worrying about whether you should be concerned. </p>
<p>First you need to understand what blue light is. </p>
<p>Visible light accounts for 50% of the sunlight spectrum and, as the name suggests, it’s the only part of light that can be detected by the human eye. The blue band of this visible spectrum has a particularly high energy level.</p>
<p>The longer the wavelength, the less energy it transmits. Blue light has very short, high energy waves.</p>
<p>Blue light is all around you. The sun emits blue light. So do fluorescent and incandescent light bulbs, mobile phones, computer screens and flat screen televisions. </p>
<h2>What are the risks?</h2>
<p>There is mounting evidence that blue light can have a harmful effect on the skin and eyes and disrupt the circadian rhythm (your internal clock). Typically, studies investigating the impact of sun radiation on the skin have focused on ultraviolet radiation, particularly UVB, which is responsible for sunburn. The most frequently reported effect of blue light exposure is a <a href="https://pubmed.ncbi.nlm.nih.gov/26977040/">significant increase in reactive oxygen species (ROS)</a>, highly reactive chemicals formed from oxygen. Too much ROS can <a href="https://pubmed.ncbi.nlm.nih.gov/15797866/">damage your DNA</a> and <a href="https://aacrjournals.org/mcr/article/14/7/612/89680/Oxidative-Stress-Induced-Protein-Damage-Inhibits">key enzymes such as those responsible for DNA repair</a>, increasing your risk of cancer. </p>
<p><a href="https://www.sciencedirect.com/science/article/pii/S1011134421002517">Our research</a> showed blue light can induce pigmentation (tanning) across skin types. While many people consider a deep tan a desirable trait, it is a marker of skin damage and ROS. Others researchers found skin tans from visible light (which includes blue light) had <a href="https://www.sciencedirect.com/science/article/pii/S0022202X15349307">darker pigmentation that lasted longer</a> compared to ultraviolet radiation exposure. Our studies also showed blue light can <a href="https://www.nature.com/articles/s41598-018-30738-6">activate genes associated with inflammation and photoageing</a> (skin damge). Several studies have proved typical sunscreens do not prevent <a href="https://www.sciencedirect.com/science/article/pii/S1011134421002517">blue</a> and <a href="https://pubmed.ncbi.nlm.nih.gov/26977040/">visible</a> light damage. </p>
<p>While blue light appears to be less potent than ultraviolet radiation, this may be accounted for by the relatively larger amounts of blue light that reach the Earth. UVR accounts for around 5% of solar radiation in the UK at midday in the summer. Blue light makes up around <a href="https://onlinelibrary.wiley.com/doi/10.1111/php.12422">three times more at 15%</a>.</p>
<p><a href="https://onlinelibrary.wiley.com/doi/10.1111/jocd.13837">There are some beneficial effects</a> of blue light. It has been used to treat skin conditions including <a href="https://www.karger.com/Article/FullText/448000">eczema</a>, it is widely used in <a href="https://journals.lww.com/jdnaonline/Fulltext/2015/05000/Current_Evidence_and_Applications_of_Photodynamic.4.aspx">photodynamic therapy</a>, which is used to treat a range of skins conditions, from acne to cancer, and it boosts <a href="https://pubmed.ncbi.nlm.nih.gov/22081819/">wound healing</a>. But the harmful effects of blue light are likely to outweigh the positives for healthy people.</p>
<figure class="align-center ">
<img alt="Man in bed looks at laptop" src="https://images.theconversation.com/files/469486/original/file-20220617-17-pypzma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/469486/original/file-20220617-17-pypzma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/469486/original/file-20220617-17-pypzma.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/469486/original/file-20220617-17-pypzma.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/469486/original/file-20220617-17-pypzma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/469486/original/file-20220617-17-pypzma.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/469486/original/file-20220617-17-pypzma.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">We are all exposed to more blue light than ever before.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/man-home-front-laptop-watching-movies-1662226270">Shutterstock</a></span>
</figcaption>
</figure>
<p>Blue light can damage the skin but it’s less clear which sources of blue light are harmful to humans. The blue light from screens is responsible for a fraction of the blue light doses we get. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6280109/pdf/JBPE-8-447.pdf">Research</a> has shown screens from devices can increase ROS production. However, a <a href="https://www.beiersdorf.com/newsroom/press-releases/all-press-releases/2021/05/04-cell-phone-screens-do-not-damage-skin#:%7E:text=Artificial%20blue%20light%20has%20negligible,knowledge%20and%20of%20scientific%20studies.">study</a> by German skincare manufacturer Biersdorf found that an entire week’s worth exposure to blue light from a screen at a distance of 30cm is equivalent to just one minute of midday summer sun in Hamburg, Germany. <a href="https://www.sciencedirect.com/science/article/pii/S0190962219333249?via%3Dihub">Another study</a> found blue light from screens were 100 - 1,000 times less intense than blue light from the sun. It also failed to trigger melasma, which causes patches of skin discolouration, in patients who have the condition. It’s true we are spending more time in front of screens than ever before but while screens may cause some damage, it’s insignificant compared with sun exposure. </p>
<h2>Blue light skincare</h2>
<p>The cosmetics industry has started developing a wide range of skincare products that brands claim prevent blue light damage. However, there is <a href="https://onlinelibrary.wiley.com/doi/10.1111/jocd.13854">no regulated or standardised test</a> to assess a product’s ability to prevent blue light damage. Companies do carry out scientific tests on these products. But they can use any number of assessments in their work. This is very different from the regulations around sunscreen that claim to contain <a href="https://www.iso.org/standard/72250.html">Sun protection factor (SPF).</a>. SPF testing is closely regulated by the International Organization for Standardization (ISO). All products that claim to contain an SPF undergo an identical testing regime.</p>
<p>The lack of regulation for blue light claims makes it impossible for consumers to make informed choices about the level of protection offered and differences between products. This lack of regulation is unlikely to be dangerous for consumers, but the benefit from the products may be limited. Given the evidence around blue light emitted by screens, it’s worth applying scepticism to any claims that a product is needed to prevent damage from your computer screen or phone.</p>
<p>Traditional photoprotection products (such as sunscreens) don’t typically protect you from blue light damage. It’s encouraging the skincare industry is trying to address this need. But it is crucial that governments take the next step in the process and develop industry-wide, standardised testing. In the meantime, it is important to remember to limit any exposure to the sun. The use of sunscreens (or any product containing an SPF rating) have been proven to prevent skin cancer and photoageing, and products advertising blue light protection may give an additional benefit.</p><img src="https://counter.theconversation.com/content/185074/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Karl Lawrence has previously received funding from the sunscreen industry.</span></em></p>What you need to know about blue light protection lotions.Karl Lawrence, Post Doctoral Researcher, Photobiology, King's College LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1696022021-10-26T12:19:57Z2021-10-26T12:19:57ZType of ultraviolet light most effective at killing coronavirus is also the safest to use around people<figure><img src="https://images.theconversation.com/files/428067/original/file-20211022-9818-i87045.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5779%2C3752&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">UV light at most wavelengths can kill COVID–19. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/lamp-for-sterilization-covid-19-prevention-concept-royalty-free-image/1296016011?adppopup=true">andriano_cz/iStock via Getty Images</a></span></figcaption></figure><p>Scientists have long known that ultraviolet light can <a href="https://theconversation.com/ultraviolet-light-can-make-indoor-spaces-safer-during-the-pandemic-if-its-used-the-right-way-141512">kill pathogens on surfaces and in air and water</a>. <a href="https://www.nytimes.com/2020/03/28/travel/coronavirus-hotels-private-jets-virtual-spas.html">UV robots are used to disinfect</a> empty hospital rooms, buses and trains; UV bulbs in HVAC systems eliminate pathogens in building air; and <a href="https://www.nytimes.com/2008/03/02/business/02novel.html">UV lamps kill bugs in drinking water</a>.</p>
<p>Perhaps you have seen UV wands, UV LEDs and UV air purifiers advertised as silver bullets to protect against the coronavirus. While decades of research have looked at the ability of UV light to kill many pathogens, there are no set standards for UV disinfection products with regard to the coronavirus. These products may work to kill SARS-CoV-2, the virus that causes COVID-19, but they also may not. </p>
<p>I am an <a href="https://scholar.google.com/citations?user=uAS7KNUAAAAJ&hl=en&oi=ao">environmental engineer and expert in UV disinfection</a>. In May 2021, my colleagues and I set out to accurately test various UV systems and see <a href="https://doi.org/10.1128/AEM.01532-21">which was the most effective</a> at killing off – or inactivating – SARS-CoV-2.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/428307/original/file-20211025-27-12cylg0.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing UV light breaking down a strand of DNA." src="https://images.theconversation.com/files/428307/original/file-20211025-27-12cylg0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/428307/original/file-20211025-27-12cylg0.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=462&fit=crop&dpr=1 600w, https://images.theconversation.com/files/428307/original/file-20211025-27-12cylg0.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=462&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/428307/original/file-20211025-27-12cylg0.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=462&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/428307/original/file-20211025-27-12cylg0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=581&fit=crop&dpr=1 754w, https://images.theconversation.com/files/428307/original/file-20211025-27-12cylg0.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=581&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/428307/original/file-20211025-27-12cylg0.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=581&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">When UV light enters a cell, it breaks the bonds that hold DNA or RNA together.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:DNA_UV_mutation.svg#/media/File:DNA_UV_mutation.svg">NASA/David Herring via WikimediaCommons</a></span>
</figcaption>
</figure>
<h2>How does UV light kill a virus?</h2>
<p>Light is categorized by wavelength – the distance between peaks of a wave of light – and is measured in nanometers. UV wavelengths range from 100 to 400 nanometers – shorter in wavelength than the violet hues in visible light – and are invisible to the human eye. As wavelength shortens, photons of light contain higher amounts of energy.</p>
<p>Different wavelengths of UV light work better than others for inactivating viruses, and this depends on how well the wavelengths are absorbed by the virus’s DNA or RNA. When UV light gets absorbed, the photons of light transfer their energy to and <a href="https://doi.org/10.1038/s41598-021-93231-7">damage the chemical bonds of the genetic material</a>. The virus is then unable to replicate or cause an infection. Researchers have also shown the proteins that viruses use to attach to a host cell and initiate infection – like the spike proteins on a coronavirus – are also <a href="https://doi.org/10.1021/acs.est.7b04602">vulnerable to UV light</a>.</p>
<p>The dose of light matters too. Light can vary in intensity – bright light is more intense, and there is more energy in it than in dim light. Being exposed to a bright light for a short time can produce the same UV dose as being exposed to a dim light for a longer period. You need to know the right dose that can kill coronavirus particles at each UV wavelength.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/428069/original/file-20211022-17-63e9kd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A man with sunburned shoulders sitting on a beach." src="https://images.theconversation.com/files/428069/original/file-20211022-17-63e9kd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/428069/original/file-20211022-17-63e9kd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/428069/original/file-20211022-17-63e9kd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/428069/original/file-20211022-17-63e9kd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/428069/original/file-20211022-17-63e9kd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/428069/original/file-20211022-17-63e9kd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/428069/original/file-20211022-17-63e9kd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sunburns are caused by UV light damaging skin cells.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/man-with-sun-burnt-shoulders-sitting-on-beach-rear-royalty-free-image/85775471?adppopup=true">Ian Hooton/Science Photo Library via Getty Images</a></span>
</figcaption>
</figure>
<h2>Making ultraviolet lights safe for people</h2>
<p>Traditional UV systems use wavelengths at or around 254 nanometers. At these wavelengths the light is dangerous to human skin and eyes, <a href="https://doi.org/10.1111/php.13402">even at low doses</a>. Sunlight includes UV light near these wavelengths; anyone who has ever gotten a bad sunburn knows just how dangerous UV light can be. </p>
<p>However, recent research has shown that at certain UV wavelengths – specifically below 230 nanometers – the high-energy photons <a href="https://iuva.org/resources/covid-19/Far%20UV-C%20Radiation-%20Current%20State-of%20Knowledge.pdf">are absorbed by the top layers of dead skin cells</a> and don’t penetrate into the active skin layers where damage can occur. Similarly, the <a href="https://doi.org/10.1111/php.13402">tear layer around eyes also blocks out these germicidal UV rays</a>.</p>
<p>This means that at wavelengths of UV light below 230 nanometers, people can move around more freely while the air around them is being disinfected in real time.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/428310/original/file-20211025-19717-bfs99z.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing a lamp above a sample of water containing the coronavirus." src="https://images.theconversation.com/files/428310/original/file-20211025-19717-bfs99z.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/428310/original/file-20211025-19717-bfs99z.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=317&fit=crop&dpr=1 600w, https://images.theconversation.com/files/428310/original/file-20211025-19717-bfs99z.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=317&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/428310/original/file-20211025-19717-bfs99z.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=317&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/428310/original/file-20211025-19717-bfs99z.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=399&fit=crop&dpr=1 754w, https://images.theconversation.com/files/428310/original/file-20211025-19717-bfs99z.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=399&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/428310/original/file-20211025-19717-bfs99z.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=399&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Researchers used this setup to test multiple different UV lights at various doses to see what it took to kill SARS-CoV-2.</span>
<span class="attribution"><span class="source">Karl Linden</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Testing different wavelengths</h2>
<p>My colleagues and I tested five commonly used UV wavelengths to see which work best to inactivate SARS-CoV-2. Specifically, we tested how large a dose is needed to <a href="https://doi.org/10.1128/AEM.01532-21">kill 90% to 99.9% of the viral particles present</a>.</p>
<p>We ran these tests in a biosafety level three facility at the <a href="https://environmentalscience.cals.arizona.edu/person/charles-chuck-gerba">University of Arizona</a> that is built to handle lethal pathogens. There we tested numerous lights across the UV spectrum, including UV LEDs that emit light at 270 and 282 nanometers, traditional UV tube lamps at 254 nanometers and a newer technology called an <a href="https://www.ushio.eu/excimer-explained/">excited dimer, or excimer, UV source</a> at 222 nanometers. </p>
<p>To test each device we spiked a sample of water with millions of SARS-CoV-2 viruses and coated a petri dish with a thin layer of this mixture. We then shined UV light on the petri dish until we achieved a specific dose. Finally we examined the viral particles to see if they could still infect human cells in culture. If the viruses could infect the cells, the dose was not high enough. If the viruses did not cause an infection, the UV source at that dose had successfully killed the pathogen. We carefully repeated this process for a range of UV doses using the five different UV devices.</p>
<p>While all of the wavelengths we tested can inactivate SARS-CoV-2 at very low doses, the ones that required the lowest dose were the <a href="https://doi.org/10.1128/AEM.01532-21">systems that emit UV light at a wavelength of 222 nanometers</a>. In our experiment, it took a dose of less than 2 millijoules of energy per square centimeter to kill 99.9% of viral particles. This translates to needing about 20 seconds to disinfect a space receiving a low intensity of short wavelength UV light, similar to that used in our test.</p>
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<p>These 222-nanometer systems are almost twice as effective as conventional UV tube lamps, which are often used in ultraviolet disinfecting systems. But importantly, the winning lamp also happens to be the safest for humans, too. At the same UV light intensity it takes to kill 99.9% of SARS-CoV-2 in 20 seconds, a person could be safely exposed to 222-nanometer light for <a href="https://doi.org/10.1111/php.13402">up to one hour and 20 minutes</a>.</p>
<p>What this means is that <a href="https://edenpark.com/">widely available</a> types of <a href="https://www.ushio.com/product/care222-filtered-far-uv-c-excimer-lamp-module/">UV lamp</a> lights can be used to safely knock down levels of the coronavirus with people present.</p>
<h2>Better use of existing tech</h2>
<p>Many places or organizations – ranging from the <a href="https://www.defense.gov/News/Feature-Stories/Story/Article/2309289/air-guard-wing-receives-dods-first-uv-light-disinfectant-system/">U.S. Air Force</a> to the <a href="https://www.spaceneedle.com/elevatingclean">Space Needle in Seattle</a> to <a href="https://www.boeing.com/confident-travel/research/CAP-3_Disinfection_with_Far-UV.html">Boeing</a> – are already using or investigating ways to use UV light in the 222 nanometer range to protect public health. </p>
<p>I believe that our findings are important because they quantify the exact doses needed to achieve various levels of SARS-CoV-2 control, whether that be killing 90% or 99.9% of viral particles. </p>
<p>Imagine coffee shops, grocery stores, school classrooms, restaurants and concert venues now made safe by this technology. And this is not a solution for just SARS-CoV-2. These technologies could help protect human health in public spaces in future times of crisis, but also during times of relative normalcy, by reducing exposure to everyday viral and bacterial threats.</p><img src="https://counter.theconversation.com/content/169602/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Karl Linden advises various companies promoting the use of UV light for disinfection. He receives funding from federal agencies and industry to conduct research in his role as a professor at the University of Colorado Boulder. He is affiliated with the International Ultraviolet Association. </span></em></p>UV lights come in a variety of different wavelengths, but not all are equally effective at disinfection. Researchers tested a number of commercially available lights to find the best.Karl Linden, Professor of Environmental Engineering and the Mortenson Professor in Sustainable Development, University of Colorado BoulderLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1662162021-08-18T15:09:41Z2021-08-18T15:09:41ZRepairing ozone layer is also reducing CO₂ in the atmosphere – new study<figure><img src="https://images.theconversation.com/files/416734/original/file-20210818-23-19uzpwb.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5098%2C3548&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/view-earth-space-blue-planet-deep-296927024">Studio23/Shutterstock</a></span></figcaption></figure><p>Spring 2060. In dark glasses, a wide sunhat and with what little exposed skin left caked in sun cream, a child stares at the woodland across from their house. It looks scraggly and stunted, and with far fewer leaves than in the old photos she has seen. Still, no time to dwell on it: there’s a <a href="https://www.cancerresearchuk.org/about-cancer/causes-of-cancer/sun-uv-and-cancer/the-uv-index-and-sunburn-risk">UV index</a> of 20 and she’s already spent five minutes outside.</p>
<p>Thankfully, this is not our future. Due to steps the world took in the 1980s to protect the <a href="https://ozone.unep.org/20-questions-and-answers">ozone layer</a>, a region of the upper atmosphere that absorbs the Sun’s harmful ultraviolet (UV) radiation, we have one less environmental problem to worry about.</p>
<p>In the mid-1970s, scientists realised that the ozone layer was being depleted by the growing use of <a href="https://gml.noaa.gov/hats/publictn/elkins/cfcs.html">chlorofluorocarbons</a> (CFCs) as refrigerants and as propellants in aerosol cans, among other applications. With the 1987 signing of the <a href="https://theconversation.com/uk/topics/montreal-protocol-3788">Montreal Protocol</a>, which was later strengthened by numerous amendments and ratified by 197 countries, the world phased out CFCs. Today, CFC levels in the atmosphere are <a href="https://agage.mit.edu/data/agage-data">falling</a> and the ozone layer is <a href="https://csl.noaa.gov/assessments/ozone/2018/twentyquestions/#topics-5">beginning to recover</a>. </p>
<figure class="align-center ">
<img alt="A bin full of discarded aerosol cans." src="https://images.theconversation.com/files/416732/original/file-20210818-23-1f52akf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/416732/original/file-20210818-23-1f52akf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/416732/original/file-20210818-23-1f52akf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/416732/original/file-20210818-23-1f52akf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/416732/original/file-20210818-23-1f52akf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/416732/original/file-20210818-23-1f52akf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/416732/original/file-20210818-23-1f52akf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">CFCs are nontoxic and nonflammable, making them useful in everything from hair care to household cleaning.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/circa-1990-bucket-full-empty-aerosol-106925534">Joseph Sohm/Shutterstock</a></span>
</figcaption>
</figure>
<p>But what if the Montreal Protocol was never signed? What would the world we managed to avoid have looked like? This is the subject of <a href="https://www.nature.com/articles/s41586-021-03737-3">a new study</a> led by me with an international team of collaborators.</p>
<p>In earlier research, scientists showed there would have been thousands more <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1751-1097.2012.01223.x/full">skin cancer cases</a> in such a world, where the ozone layer is thinner and higher levels of UV radiation reach the planet’s surface. There would also have been <a href="https://www.pnas.org/content/104/12/4814">additional climate warming</a>, since CFCs, like carbon dioxide (CO₂), are also greenhouse gases, although far more potent. Our focus was on what could have happened to vegetation.</p>
<p>Like humans, plants are damaged when <a href="https://www.sciencedirect.com/science/article/abs/pii/000527289090156X">exposed to high UV levels</a>. Plants absorb CO₂ as they grow, but when UV radiation increases by 10%, <a href="https://pubs.rsc.org/en/content/articlelanding/2011/pp/c0pp90035d/">plants accrue 3% less biomass</a>. Without the Montreal Protocol, we estimated that UV levels would have been 4.5 times higher on average globally than today at the end of the century. We also estimated that by 2050, European, Asian and North American UV levels would be higher than they are in the present-day tropics. </p>
<p>Overall, this means that more of the CO₂ humans emit would have remained in the atmosphere, rather than being locked up in plants and the soil. And this extra CO₂ would have led to more global warming.</p>
<h2>A world without the Montreal Protocol</h2>
<p>Using computer models to represent the climate, the atmosphere’s chemistry, vegetation and the carbon cycle, we simulated two worlds. The first assumed that <a href="https://www.nature.com/articles/249810a0">the 1974 paper</a> alerting the world to the dangers of CFCs was never published and their use grows at <a href="http://www.pnas.org/cgi/doi/10.1073/pnas.0610328104">3% a year</a>. The second is a world where CFCs are controlled and the ozone layer recovers, the world we live in now and are on track to inhabit. </p>
<p>Apart from the CFCs, the two simulated worlds are identical. In both, CO₂ and other greenhouse gas emissions follow an <a href="https://ar5-syr.ipcc.ch/topic_futurechanges.php#box_2_2">intermediate scenario</a> for the 21st century, which is one of several used to inform the UN’s <a href="https://theconversation.com/ipcc-report-how-to-make-global-emissions-peak-and-fall-and-whats-stopping-us-165830">Intergovernmental Panel on Climate Change reports</a>. </p>
<p>The world in which CFCs were phased out looks like what we would expect from <a href="https://theconversation.com/this-is-the-most-sobering-report-card-yet-on-climate-change-and-earths-future-heres-what-you-need-to-know-165395">warmer future climates</a>. Global temperatures increase, with all their <a href="https://theconversation.com/3-dangers-of-rising-temperatures-that-could-affect-your-health-now-105028">negative consequences</a>, but – as we expect for the real world – the ozone layer recovers to its historic levels by the middle of the century. In the other world, the <a href="https://www.earthobservatory.nasa.gov/features/WorldWithoutOzone">ozone layer drastically thins</a> and by the end of the century ozone concentrations everywhere fall below levels seen in the <a href="https://earthobservatory.nasa.gov/world-of-change/Ozone">Antarctic ozone hole</a>.</p>
<figure class="align-center ">
<img alt="A satellite image of the southern hemisphere depicting relative ozone levels in the atmosphere." src="https://images.theconversation.com/files/416580/original/file-20210817-15-pzobqj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/416580/original/file-20210817-15-pzobqj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/416580/original/file-20210817-15-pzobqj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/416580/original/file-20210817-15-pzobqj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/416580/original/file-20210817-15-pzobqj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/416580/original/file-20210817-15-pzobqj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/416580/original/file-20210817-15-pzobqj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Antarctic ozone hole recorded at its greatest extent in September 2006.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Montreal_Protocol#/media/File:NASA_and_NOAA_Announce_Ozone_Hole_is_a_Double_Record_Breaker.png">NASA</a></span>
</figcaption>
</figure>
<p>By the 2050s, because of UV damage, plants in the world where CFC use continues unabated absorb half the carbon they do in the world where CFCs were phased out. By the end of the century, plants in this high-CFC world absorb less than 15% of the carbon they do in the other world, resulting in 30% less carbon stored in plants and soils. This means 30% more CO₂ in the atmosphere by the end of the century, which adds 0.8°C more warming to the climate.</p>
<p>By itself, this 0.8°C would be enough to take current global temperatures (just over 1°C above the <a href="https://climate.nasa.gov/vital-signs/global-temperature/">pre-industrial average</a>) to beyond the 1.5°C level that represents the most ambitious target of the <a href="https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement">Paris Agreement</a>. Adding the 1.7°C that would have resulted from the greenhouse effect of CFCs themselves means that an extra 2.5°C of warming was prevented by the Montreal Protocol.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/416738/original/file-20210818-13-7c7vgh.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Four different world maps depicting declines in carbon uptake by plants across the 21st century." src="https://images.theconversation.com/files/416738/original/file-20210818-13-7c7vgh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/416738/original/file-20210818-13-7c7vgh.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/416738/original/file-20210818-13-7c7vgh.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/416738/original/file-20210818-13-7c7vgh.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/416738/original/file-20210818-13-7c7vgh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=473&fit=crop&dpr=1 754w, https://images.theconversation.com/files/416738/original/file-20210818-13-7c7vgh.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=473&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/416738/original/file-20210818-13-7c7vgh.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=473&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Plants would take up much less carbon worldwide by the late 21st century if CFC use continued unabated.</span>
<span class="attribution"><a class="source" href="https://www.nature.com/articles/s41586-021-03737-3">Young et al. (2021)/Nature</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>While we have avoided the world from our simulations, threats to the ozone layer still exist. Some scientists favour counteracting climate change by emulating the global cooling effects of <a href="https://www.usgs.gov/natural-hazards/volcano-hazards/volcanoes-can-affect-climate">large volcanic eruptions</a> – injecting particles into the upper atmosphere in a process known as <a href="https://theconversation.com/should-we-engineer-the-climate-a-social-scientist-and-natural-scientist-discuss-104516">stratospheric sulphate geoengineering</a>. </p>
<p>But this could <a href="https://science.sciencemag.org/content/320/5880/1201.abstract">deplete the ozone layer</a>. Our study shows that the knock-on effect on the biosphere must be considered in any impact assessment of such actions. </p>
<p>For its effectiveness in acting on dire scientific warnings, it’s tempting to think of the Montreal Protocol as a model for <a href="https://ukcop26.org/">climate negotiations</a>. Yet with just a handful of companies making CFCs and alternative chemicals readily available, the ozone issue was far more straightforward than reducing emissions from fossil fuels.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/shrinking-hole-in-the-ozone-layer-shows-what-collective-action-can-achieve-62007">Shrinking hole in the ozone layer shows what collective action can achieve</a>
</strong>
</em>
</p>
<hr>
<p>Nevertheless, as well as protecting the ozone layer, the Montreal Protocol has itself been a phenomenally successful climate treaty. It has controlled not only the emissions of highly potent greenhouse gases like CFCs, but, as we have shown, it has avoided additional CO₂ levels through protecting the world’s plant life.</p><img src="https://counter.theconversation.com/content/166216/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paul Young receives funding from the Engineering and Physical Sciences Research Council. </span></em></p>New research shows how the Montreal Protocol protected vegetation, helping keep carbon out of the atmosphere.Paul Young, Senior Lecturer in Atmospheric and Climate Science, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1599912021-05-03T12:03:31Z2021-05-03T12:03:31ZMassive flare seen on the closest star to the solar system: What it means for chances of alien neighbors<figure><img src="https://images.theconversation.com/files/397916/original/file-20210429-21-qm3fki.jpg?ixlib=rb-1.1.0&rect=32%2C70%2C1230%2C1153&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Proxima Centauri is the closest star to the solar system and is home to a potentially habitable planet.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:New_shot_of_Proxima_Centauri,_our_nearest_neighbour_(10581847073).jpg#/media/File:New_shot_of_Proxima_Centauri,_our_nearest_neighbour_(10581847073).jpg">Hubble/European Space Agency/WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p><em>The Sun isn’t the only star to produce stellar flares. On April 21, 2021, a team of astronomers published new research describing the <a href="https://doi.org/10.3847/2041-8213/abf14c">brightest flare ever measured from Proxima Centauri in ultraviolet light</a>. To learn about this extraordinary event – and what it might mean for any life on the planets orbiting Earth’s closest neighboring star – The Conversation spoke with <a href="https://scholar.google.com/citations?user=I-dkA7UAAAAJ&hl=en&oi=ao">Parke Loyd, an astrophysicist at Arizona State University</a> and co-author of the paper. Excerpts from our conversation are below and have been edited for length and clarity.</em></p>
<h2>Why were you looking at Proxima Centauri?</h2>
<p>Proxima Centauri is the closest star to this solar system. A couple of years ago, <a href="https://doi.org/10.1038/nature19106">a team discovered</a> that there is a <a href="https://exoplanets.nasa.gov/exoplanet-catalog/7167/proxima-centauri-b/">planet – called Proxima b – orbiting the star</a>. It’s just a little bit bigger than Earth, <a href="https://doi.org/10.1038/nature19106">it’s probably rocky</a> and it is in what is called the habitable zone, or the Goldilocks zone. This means that Proxima b is about the right distance from the star so that it could have liquid water on its surface.</p>
<p>But this star system differs from the Sun in a pretty key way. Proxima Centauri is a small star called a <a href="https://www.space.com/23772-red-dwarf-stars.html">red dwarf</a> – it’s around 15% of the radius of our Sun, and it’s substantially cooler. So Proxima b, in order for it to be in that Goldilocks zone, actually is a lot closer to Proxima Centauri than Earth is to the Sun. </p>
<p>You might think that a smaller star would be a tamer star, but that’s actually not the case at all – red dwarfs produce stellar flares <a href="https://ui.adsabs.harvard.edu/abs/1989MmSAI..60..263G/abstract">a lot more frequently than the Sun does</a>. So Proxima b, the closest planet in another solar system with a chance for having life, is subject to space weather that is a lot more violent than the space weather in Earth’s solar system.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/397919/original/file-20210429-15-1b7x9r9.gif?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photo of the surface of the Sun with a towering explosion of plasma." src="https://images.theconversation.com/files/397919/original/file-20210429-15-1b7x9r9.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/397919/original/file-20210429-15-1b7x9r9.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=601&fit=crop&dpr=1 600w, https://images.theconversation.com/files/397919/original/file-20210429-15-1b7x9r9.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=601&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/397919/original/file-20210429-15-1b7x9r9.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=601&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/397919/original/file-20210429-15-1b7x9r9.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=756&fit=crop&dpr=1 754w, https://images.theconversation.com/files/397919/original/file-20210429-15-1b7x9r9.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=756&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/397919/original/file-20210429-15-1b7x9r9.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=756&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Solar flares – like this one captured by a NASA satellite orbiting the Sun – eject huge amounts of radiation.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Solar_flare_(TRACE).gif#/media/File:Solar_flare_(TRACE).gif">NASA/Wikimedia Commons</a></span>
</figcaption>
</figure>
<h2>What did you find?</h2>
<p>In 2018, my colleague Meredith MacGregor discovered flashes of light coming from Proxima Centauri that <a href="https://doi.org/10.3847/2041-8213/aaad6b">looked very different from solar flares</a>. She was using a telescope that detects light at millimeter wavelengths to monitor Proxima Centauri and saw a big of flash of light in this wavelength. Astronomers had never seen a stellar flare in millimeter wavelengths of light.</p>
<p>My colleagues and I wanted to learn more about these unusual brightenings in the millimeter light coming from the star and see whether they were actually flares or some other phenomenon. We used nine telescopes on Earth, as well as a satellite observatory, to get the longest set of observations – about two days’ worth – of Proxima Centauri with the most wavelength coverage that had ever been obtained.</p>
<p>Immediately we <a href="https://doi.org/10.3847/2041-8213/abf14c">discovered a really strong flare</a>. The ultraviolet light of the star increased by over 10,000 times in just a fraction of a second. If humans could see ultraviolet light, it would be like being blinded by the flash of a camera. Proxima Centauri got bright really fast. This increase lasted for only a couple of seconds, and then there was a gradual decline.</p>
<p>This discovery confirmed that indeed, these weird millimeter emissions are flares.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/397922/original/file-20210429-19-9tx3mg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A gray rocky planet with a pale star behind it." src="https://images.theconversation.com/files/397922/original/file-20210429-19-9tx3mg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/397922/original/file-20210429-19-9tx3mg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/397922/original/file-20210429-19-9tx3mg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/397922/original/file-20210429-19-9tx3mg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/397922/original/file-20210429-19-9tx3mg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/397922/original/file-20210429-19-9tx3mg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/397922/original/file-20210429-19-9tx3mg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Proxima b – shown here in an artist’s rendering – is rocky and might support water or even life if the atmosphere is still intact.</span>
<span class="attribution"><a class="source" href="https://www.eso.org/public/images/ann16056a/">European Southern Observatory/M. Kornmesser</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>What does that mean for chances of life on the planet?</h2>
<p>Astronomers are actively exploring this question at the moment because it can kind of go in either direction. When you hear ultraviolet radiation, you’re probably thinking about the fact that people wear sunscreen to try to protect ourselves from ultraviolet radiation here on Earth. Ultraviolet radiation can <a href="https://www.livescience.com/38039-what-causes-sunburns.html">damage proteins and DNA</a> in human cells, and this results in sunburns and can cause cancer. That would potentially be true for life on another planet as well. </p>
<p>On the flip side, messing with the chemistry of biological molecules can have its advantages – it <a href="https://doi.org/10.1023/A:1006596718708">could help spark life on another planet</a>. Even though it might be a more challenging environment for life to sustain itself, it might be a better environment for life to be generated to begin with.</p>
<p>[<em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>.]</p>
<p>But the thing that astronomers and astrobiologists are most concerned about is that every time one of these huge flares occurs, it basically <a href="https://doi.org/10.1089/ast.2017.1794">erodes away a bit of the atmosphere</a> of any planets orbiting that star – including this potentially Earth-like planet. And if you don’t have an atmosphere left on your planet, then you definitely have a pretty hostile environment to life – there would be huge amounts of radiation, massive temperature fluctuations and little or no air to breathe. It’s not that life would be impossible, but having the surface of a planet basically directly exposed to space would be an environment totally different than anything on Earth.</p>
<h2>Is there any atmosphere left on Proxima b?</h2>
<p>That’s anybody’s guess at the moment. The fact that these flares are happening doesn’t bode well for that atmosphere being intact – especially if they’re associated with <a href="https://doi.org/10.1146/annurev.aa.07.090169.001053">explosions of plasma</a> like what happens on the Sun. But that’s why we’re doing this work. We hope the folks who build models of planetary atmospheres can take what our team has learned about these flares and try to figure out the odds for an atmosphere being sustained on this planet.</p><img src="https://counter.theconversation.com/content/159991/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>R. O. Parke Loyd receives funding from NASA. </span></em></p>Astronomers just measured the largest flare ever from Proxima Centauri, humanity’s closest neighboring star. These flares could be bad news for life trying to develop on a planet orbiting the star.R. O. Parke Loyd, Post-Doctoral Researcher in Astrophysics, Arizona State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1446542021-04-12T15:39:24Z2021-04-12T15:39:24ZWill summer slow the spread of COVID-19? New research sheds light<figure><img src="https://images.theconversation.com/files/394523/original/file-20210412-13-yn1tx3.jpg?ixlib=rb-1.1.0&rect=90%2C49%2C5159%2C3417&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/chicago-192702896">MaxyM/Shutterstock</a></span></figcaption></figure><p>At face value, it seems highly plausible that SARS-CoV-2 – the virus that causes COVID-19 – could behave seasonally, being more prevalent in winter and less so in summer. The four other coronaviruses that commonly circulate in humans <a href="https://doi.org/10.1093/infdis/jiaa161">behave in this way</a>. We’ve also seen COVID-19 cases, hospitalisations and deaths <a href="https://coronavirus.data.gov.uk/">spike over winter</a> in the UK and other countries, which is suggestive of a seasonal effect. </p>
<p>Some association between viral transmission and the seasons is to be expected. Many human behaviours are seasonal. In summer, we spend more time outdoors, where risk of infection is <a href="https://medicalxpress.com/news/2020-10-coronavirus-rare-impossible.html">much lower</a>, and we are likely to lead more active lifestyles, which can <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7261095/">raise the body’s ability</a> to resist infection. We’re also likely to benefit from increased exposure to sunlight, which <a href="https://www.sciencedirect.com/science/article/abs/pii/S0031302516326927">raises vitamin D levels</a> and so can boost our immune systems.</p>
<p>There’s also evidence that the ultraviolet (UV) radiation in sunlight <a href="https://doi.org/10.1093/infdis/jiaa274">reduces how long</a> the virus can survive on surfaces. It’s also possible that humidity and temperature may influence transmission. When combined together, these factors will likely have an effect on the virus’s spread.</p>
<p>But how significant is this effect? And what are the implications for controlling COVID-19 as we begin to approach the warmer months, as well as for the potential of another winter resurgence? As existing research had produced inconclusive results on whether and how the seasons affect SARS-CoV-2, my colleagues and I set out to see if we could find some more conclusive answers to these questions.</p>
<h2>Assessing the impact of climate</h2>
<p>Epidemiologists use something called the <a href="https://www.bbc.co.uk/news/health-52473523">reproductive number, or R,</a> to describe the growth of an epidemic – the higher the R number, the faster the spread. At the start of an epidemic, its growth won’t be affected by anyone having been exposed to the disease and developing immunity and so it will spread exponentially. At this point the R number that describes this spread is referred to as R₀.</p>
<p>Using data from outbreaks around the world, <a href="https://doi.org/10.1016/j.onehlt.2021.100221">our new research</a> determined R₀ for COVID-19 in 359 large cities. Each city included in our study had over 500,000 inhabitants and had experienced a significant COVID-19 outbreak in 2020.</p>
<p>We focused on large cities (rather than on countries or on smaller populations) because these allowed us to look at outbreaks that were big enough and sufficiently geographically varied to allow for useful comparisons. By comparing cities’ outbreak data against information on their demographics, climate and infection control measures, we could then determine whether any of these factors explained the rate of spread of the virus.</p>
<figure class="align-center ">
<img alt="A couple enjoying a walk in the sunshine" src="https://images.theconversation.com/files/394525/original/file-20210412-13-1hpcvwr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/394525/original/file-20210412-13-1hpcvwr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/394525/original/file-20210412-13-1hpcvwr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/394525/original/file-20210412-13-1hpcvwr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/394525/original/file-20210412-13-1hpcvwr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/394525/original/file-20210412-13-1hpcvwr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/394525/original/file-20210412-13-1hpcvwr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">While there does appear to be a seasonal effect on transmission, we still can’t pinpoint the exact cause of it.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/beautiful-senior-couple-walking-their-bike-1636441447">Fit Ztudio/Shutterstock</a></span>
</figcaption>
</figure>
<p>We found that increased UV radiation corresponded with a reduction in how rapidly the virus spread. On average, R₀ decreased by 0.05 for every ten kilojoules per square metre (kJ/m²) increase in daily UV radiation (cities in our dataset ranged from receiving 30kJ/m² to around 130kJ/m² of UV each day). </p>
<p>As UV radiation levels are higher in summer, our findings suggest there is indeed some seasonal effect on transmission. However, it’s important to note that this correlation doesn’t necessarily mean that UV radiation is the cause of this decrease in transmission, since UV radiation may correlate with other causal factors.</p>
<p>For example, the higher the UV radiation in a city, the hotter it tends to be. We didn’t find a separate statistically significant link between R₀ and temperature or humidity on a global level, but we can’t rule out such relationships. </p>
<p>Association between viral spread and temperature or humidity may have been masked by many other factors that affect R₀, as well as the strong correlation between UV radiation and temperature. Indeed, there’s some <a href="https://doi.org/10.1371/journal.pone.0238339">weak evidence</a> of an association between viral spread and temperature in other studies.</p>
<h2>So what does this mean?</h2>
<p>While the effect of UV radiation that we observed was statistically significant, it was relatively small in comparison to other factors. The demographic features of cities, such as their size and amount of air pollution (a potential measure of industrialisation and population congestion), together with public health measures accounted for more of the observed variation we saw in R₀ values.</p>
<figure class="align-center ">
<img alt="A sign on a supermarket floor promoting social distancing" src="https://images.theconversation.com/files/394526/original/file-20210412-21-485rsq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/394526/original/file-20210412-21-485rsq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/394526/original/file-20210412-21-485rsq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/394526/original/file-20210412-21-485rsq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/394526/original/file-20210412-21-485rsq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/394526/original/file-20210412-21-485rsq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/394526/original/file-20210412-21-485rsq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Interventions to limit the spread of the virus, such as social distancing, have had a far greater impact than the seasons.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/red-round-sign-printed-on-ground-1701116239">Cryptographer/Shutterstock</a></span>
</figcaption>
</figure>
<p>Government interventions accounted for about four times the explainable variation in R₀ compared to UV. Importantly, this is in our control. In the immediate future, potential further waves of the pandemic will be predominantly determined by controls that governments dictate, rather than the weather. Added to this are the effects of the COVID-19 vaccines that are now being rolled out.</p>
<p>In the longer term, questions still remain about whether COVID-19 will become a seasonal endemic infection similar to influenza and other coronaviruses. Our research has identified evidence for small seasonal drivers that may induce this type of variation when COVID-19 likely stabilises as an endemic infectious disease. </p>
<p>But predicting this behaviour for such a complex system as the world is difficult, and as we move out of the initial epidemic phase, the longer-term behaviour of COVID-19 transmission will probably depend on many other factors. These will likely include the level and duration of immunity acquired by infected individuals, as well as the efficacy and length of protection provided by current and future vaccines, and the evolution of new variants of the virus.</p><img src="https://counter.theconversation.com/content/144654/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kieran Sharkey receives funding from the UK's Engineering and Physical Sciences Research Council (EPSRC). </span></em></p>The seasons can affect transmission of the virus – but this will likely be dwarfed by the impact of public health measures.Kieran Sharkey, Reader in Mathematical Sciences, University of LiverpoolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1330402020-09-24T12:21:12Z2020-09-24T12:21:12ZDynamic tattoos promise to warn wearers of health threats<figure><img src="https://images.theconversation.com/files/359680/original/file-20200923-17-1hotilu.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6357%2C4902&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">In the not-too-distant future, tattoos could become medical diagnostic devices as well as body art.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/cropped-view-of-female-doctor-in-white-coat-with-royalty-free-image/918494936?adppopup=true">LightFieldStudios/iStock via Getty Images </a></span></figcaption></figure><p>In the sci-fi novel <a href="https://www.nealstephenson.com/the-diamond-age.html">“The Diamond Age”</a> by Neal Stephenson, body art has evolved into “constantly shifting mediatronic tattoos” – in-skin displays powered by nanotech robopigments. In the 25 years since the novel was published, nanotechnology has had time to catch up, and the sci-fi vision of dynamic tattoos is starting to become a reality. </p>
<p>The first examples of color-changing nanotech tattoos have been developed over the past few years, and they’re not just for body art. They have a biomedical purpose. Imagine a tattoo that alerts you to a health problem signaled by a change in your biochemistry, or to radiation exposure that could be dangerous to your health.</p>
<p>You can’t walk into a doctor’s office and get a dynamic tattoo yet, but they are on the way. Early proof-of-concept studies provide convincing evidence that tattoos can be engineered, not only to change color, but to sense and convey biomedical information, including the onset of cancer. </p>
<h2>Signaling biochemical changes</h2>
<p>In 2017, researchers tattooed pigskin, which had been removed from the pig, with <a href="http://doi.org/10.1145/3123021.3123039">molecular biosensors that use color</a> to indicate sodium, glucose or pH levels in the skin’s fluids.</p>
<p>In 2019, a team of researchers expanded on that study to include <a href="http://doi.org/10.1002/anie.201904416">protein sensing and developed smartphone readouts for the tattoos</a>. This year, they also showed that <a href="http://doi.org/10.1016/j.snb.2020.128378">electrolyte levels could be detected with fluorescent tattoo sensors</a>. </p>
<p>In 2018, a team of biologists developed a <a href="http://doi.org/10.1126/scitranslmed.aap8562">tattoo made of engineered skin cells</a> that darken when they sense an imbalance of calcium caused by certain cancers. They demonstrated the cancer-detecting tattoo in living mice. </p>
<h2>UV radiation sensors</h2>
<p><a href="https://www.emergentnanomaterials.com/">My lab</a> is <a href="https://go.ted.com/carsonbruns">looking at tech tattoos from a different angle</a>. We are interested in sensing external harms, such as ultraviolet radiation. UV exposure in sunlight and tanning beds is the main risk factor for all types of skin cancer. Nonmelanoma skin cancers are the most common malignancies in the U.S., Australia and Europe. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/358923/original/file-20200920-20-5f64p7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A four-panel series shows a UV-activated tattoo appearing in a star pattern, erased and then appearing in a dot pattern" src="https://images.theconversation.com/files/358923/original/file-20200920-20-5f64p7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358923/original/file-20200920-20-5f64p7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=151&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358923/original/file-20200920-20-5f64p7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=151&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358923/original/file-20200920-20-5f64p7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=151&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358923/original/file-20200920-20-5f64p7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=190&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358923/original/file-20200920-20-5f64p7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=190&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358923/original/file-20200920-20-5f64p7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=190&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">UV-activated tattoo ink is invisible until exposed to UV light.</span>
<span class="attribution"><span class="source">Jesse Butterfield/The Laboratory for Emergent Nanomaterials, University of Colorado Boulder</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>To help address this problem, we developed <a href="https://doi.org/10.1021/acsnano.0c05723">an invisible tattoo ink that turns blue only in UV light</a>, alerting you when your skin needs protection. The tattoo ink contains a UV-activated dye inside of a plastic nanocapsule less than a micron in diameter – or thousandth of a millimeter – about the same size as an ordinary tattoo pigment.</p>
<p>The nanocapsule is needed to make the color-changing tattoo particles large enough. If tattoo pigments are too small, the immune system rapidly clears them from the skin and the tattoo disappears. They are implanted using tattoo machines in the same way as regular tattoos, but they last for only several months before they start to degrade from UV exposure and other natural processes and fade, requiring a “booster” tattoo. </p>
<p>I served as the first human test subject for these tattoos. I created “solar freckles” on my forearm – invisible spots that turned blue under UV exposure and reminded me when to wear sunscreen. My lab is also working on invisible UV-protective tattoos that would absorb UV light penetrating through the skin, like a long-lasting sunscreen just below the surface. We’re also working on “thermometer” tattoos using temperature-sensitive inks. Ultimately, we believe tattoo inks could be used to prevent and diagnose disease.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/4CGFPbFqdJ4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">In this TEDx talk, the author demonstrates the UV-detecting tattoo.</span></figcaption>
</figure>
<h2>Temporary high-tech tattoos</h2>
<p>Temporary transfer tattoos are also undergoing a high-tech revolution. <a href="http://doi.org/10.1126/science.1206157">Wearable electronic tattoos</a> that can sense electrophysiological signals like heart rate and brain activity or monitor hydration and glucose levels from sweat are under development. They can even be used for <a href="https://duoskin.media.mit.edu/">controlling mobile devices</a>, for example shuffling a music playlist at the touch of a tattoo, or for <a href="http://www.hybrid-ecologies.org/projects/12-skintillates">luminescent body art</a> that lights up the skin. </p>
<p>The advantage of these wearable tattoos is that they can use battery-powered electronics. The disadvantage is that they are much less permanent and comfortable than traditional tattoos. Likewise, electronic devices that go underneath the skin are being developed by <a href="https://doi.org/10.1063/1.3238552">scientists</a>, <a href="https://doi.org/10.1145/2207676.2207745">designers</a> and <a href="https://wiki.biohack.me/wiki/index.php?title=Modifications_-_Implantable_Mods">biohackers</a> alike, but they require invasive surgical procedures for implantation. </p>
<p>Tattoos injected into the skin offer the best of both worlds: minimally invasive, yet permanent and comfortable. New <a href="http://doi.org/10.1063/1.5074176">needle-free tattooing methods</a> that fire microscopic ink droplets into the skin are now in development. Once perfected they will make tattooing quicker and less painful. </p>
<h2>Ready for everyday use?</h2>
<p>The color-changing tattoos in development are also going to open the door to a new kind of dynamic body art. Now that tattoo colors can be changed by an electromagnetic signal, you’ll soon be able to “program” your tattoo’s design, or switch it on and off. You can proudly display your neck tattoo at the motorcycle rally and still have clear skin in the courtroom. </p>
<p>As researchers develop dynamic tattoos, they’ll need to study the safety of the high-tech inks. As it is, little is known about the safety of the more than 100 different pigments used in normal tattoo inks. The <a href="https://www.fda.gov/cosmetics/cosmetic-products/tattoos-permanent-makeup-fact-sheet">U.S. Food and Drug Administration</a> has not exercised regulatory authority over tattoo pigments, citing other competing public health priorities and a lack of evidence of safety problems with the pigments. So U.S. manufacturers can put whatever they want in tattoo inks and sell them without FDA approval. </p>
<p>So far, there is <a href="http://doi.org/10.1586/edm.09.28">no evidence that tattoos cause cancer</a>, and <a href="http://doi.org/10.1111/phpp.12181">one study even found that black tattoos protect against UV-induced skin cancer</a>. Still, many tattoo inks <a href="http://doi.org/10.1111/j.1600-0536.2007.01301.x">contain or degrade into substances that are known to be hazardous</a>, and health complications including infection, allergy and granuloma have been <a href="https://doi.org/10.1016/j.clindermatol.2007.05.012">found in about 2% of tattoos</a>. More research is needed to understand the long-term effects of nano- and microimplants in the skin in general. </p>
<p>A wave of high-tech tattoos is slowly upwelling, and it will probably keep rising for the foreseeable future. When it arrives, you can decide to surf or watch from the beach. If you do climb on board, you’ll be able to check your body temperature or UV exposure by simply glancing at one of your tattoos.</p><img src="https://counter.theconversation.com/content/133040/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Carson J. Bruns does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Researchers are developing tattoo inks that do more than make pretty colors. Some can sense chemicals, temperature and UV radiation, setting the stage for tattoos that diagnose health problems.Carson J. Bruns, Assistant Professor, University of Colorado BoulderLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1368902020-05-11T14:13:30Z2020-05-11T14:13:30ZWe found high UV doses at high-altitude hiking trails in Reunion and Cape Town<figure><img src="https://images.theconversation.com/files/332715/original/file-20200505-83725-1pq0shf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A couple taking in the view from Table Mountain, Cape Town.</span> <span class="attribution"><span class="source">Getty Images</span></span></figcaption></figure><p>Ultraviolet (UV) radiation from the sun is important for life on earth and especially for humans. </p>
<p>In <a href="http://www.scielo.org.mx/pdf/rmcp/v10n2/2448-6698-rmcp-10-02-416-en.pdf">animals</a> UV radiation is essential for biological functions like calcium metabolism. In <a href="https://books.google.com/books?id=Rq3SBAAAQBAJ&lpg=PA131&ots=BpvaX092Oa&dq=Caldwell%2C%20M.%20M.%20%3A%20Solar%20UV%20irradiation%20and%20the%20growth%20and%20development%20of%20higher%20plants%2CPhotophysiology%2C%206%2C%20131%E2%80%93177%2C%201971.&lr&hl=fr&pg=PA131#v=onepage&q&f=false">vegetation</a> it’s necessary for photosynthesis. And in humans, UV plays an <a href="https://www.mdpi.com/52688">important</a> role in synthesis of <a href="https://www.who.int/uv/resources/FAQ/uvhealtfac/en/index1.html">vitamin D</a>, which makes for strong bones, joints and muscles. </p>
<p>But too much UV radiation is also very dangerous for human health. Excessive exposure can cause skin ageing and sunburn and can induce skin cancer such as <a href="https://www.ncbi.nlm.nih.gov/books/NBK481848/">melanoma</a>, cataracts, ocular melanoma, and immunodeficiency. </p>
<p>The sun is the main natural source of <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-4632.2010.04474.x">ultraviolet radiation</a>. The risk for human health also depends on <a href="https://www.who.int/uv/publications/en/UVIGuide.pdf">UV intensity</a>. The UV level is affected by several atmospheric factors, such as ozone, aerosol, cloud cover or altitude. This is one reason why changes to the <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/91GL02786">ozone layer</a> as a result of global pollutant emissions make a difference to human health. The UV intensity is higher at <a href="https://www.who.int/uv/publications/en/UVIGuide.pdf">high altitudes</a> because there is less atmosphere to absorb it. Tropical regions also experience high UV exposure because the sun shines there a lot of the time.</p>
<p>We tested the <a href="https://www.mdpi.com/2073-4433/10/10/589">UV exposure</a> in high-altitude sites in Cape Town and Reunion Island. We assessed human exposure for hiking activities at two popular high-altitude hiking trails on the Maïdo–Grand Bénare (Reunion) and Table Mountain (Cape Town) with a handheld radiometer. We recorded extreme exposure doses. </p>
<p>These high exposure doses highlight the importance of raising public awareness on the risk related to excess UVR exposure at tourist sites, especially those at high altitude. Our findings suggest a need for strong public awareness campaigns among visitors to sites like these to prevent skin diseases and cancers that could result from overexposure to UV radiation.</p>
<h2>Our study</h2>
<p>We chose our testing sites – Table Mountain (altitude of 1,035 metres) in Cape Town and Maïdo-Grand Bénare (2,898 metres) on Reunion Island – because they are popular tourist destinations for outdoor activities for most of the year. Yet their high risk for UV is not necessarily well known. Tourists, hikers and employees of the local national parks may be exposed to high UV levels. Every year, <a href="https://www.tablemountain.net/annual_report_2019/">1,000,000 people</a> visit Table Mountain and <a href="http://www.ipreunion.com/photo-du-jour/reportage/2016/05/21/observatoire-regional-du-tourisme-le-tourisme-a-la-reunion-grimpe-de-1-pour-le-premier-trimestre-2016,44240.html">180,000 hike</a> on Réunion Island mountain.</p>
<p>Two markers were used to quantify the UV exposure. One was the UV index, <a href="https://www.who.int/uv/intersunprogramme/activities/uv_index/en/">defined</a> by the World Health Organisation (WHO) as a simple number for public awareness. UV index categories are low (1-2), moderate (3-5), high (6-7), very high (9-10), and extreme (11+). </p>
<p>The maximum UV index numbers recorded were 14 at Table Mountain and 20 at Maïdo-Grand Bénare, which is close to double the extreme UV index threshold <a href="https://www.who.int/uv/intersunprogramme/activities/en/uvcodes.jpg">defined</a> by the WHO. </p>
<p>The study also measured cumulative standard erythemal dose (SED), a measure of UV exposure in terms of joules per square metre.</p>
<p>The field measurement indicated that people were exposed to 40 SED when hiking Table Mountain and 64 when hiking Maïdo-Grand Bénare. These doses correspond to 3 to 25 times the minimal dose required to elicit a sunburn response depending on skin type (lighter skin requires a smaller dose while darker skin requires a larger dose).</p>
<p>Information about the <a href="https://www.mdpi.com/545770">climate</a> of the two sites shows that the total daily dose is extremely high during summer in Cape Town, and all year around in Reunion Island. Total daily dose is above the level where all skin types will experience sunburn, although people with deeply pigmented skin are less affected. These extreme exposures increase <a href="https://www.sciencedirect.com/science/article/pii/S0079610706000137">the risk</a> of cataracts, immunodeficiency and melanoma – at least for people with white skin. The link between sunburn and these health risks is not known for people with dark skin.</p>
<p>Melanoma is a type of skin cancer. The mean melanoma rate worldwide in <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5575560/">2015</a> (male and female mixed) was five per 100,000. In South Africa, <a href="http://www.samj.org.za/index.php/samj/article/view/12576">the melanoma rate</a> for the total population, regardless of skin type, is five per 100,000 people for men and three per 100,000 for women. Among white South Africans, the melanoma rate is about 20 per 100,000 for men and 16 per 100,000 for women, which is similar to some of the rates recorded in Australia. </p>
<p><a href="https://www.em-consulte.com/es/article/1095782/donnees-epidemiologiques-des-melanomes-cutanes-a-l">From 2006 to 2015</a>, the male population of Reunion Island saw an increase in skin diseases from 2.7 to 7.1 cases per 100,000 people while cases in the female population surged from 3.0 to 6.1 per 100,000. These increasing rates may be due to an <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2697050/">atmospheric change</a> and a human behaviour change (such as the popularity of <a href="https://www.sciencedirect.com/science/article/abs/pii/S0190962203000215">suntanning</a> for aesthetic reasons). </p>
<h2>Cover up</h2>
<p>The results of our tests highlight the importance of public awareness and prevention of the <a href="https://www.who.int/uv/publications/en/UVIGuide.pdf">risks related to UV</a>, especially at exposed sites like Table Mountain and Maïdo-Grand Bénare. The <a href="https://www.who.int/uv/intersunprogramme/activities/uv_index/en/index1.html">WHO</a> recommends that people avoid being outside in the middle of the day and wear long-sleeved shirts, hats, sunglasses and sunscreen.</p>
<p>This is particularly important in <a href="https://www.atmos-chem-phys.net/19/10087/2019/">tropical regions</a>, where there are several factors that can increase UV radiation: being relatively close to the Equator, low ozone, low aerosols, low solar zenith angle and clouds.</p><img src="https://counter.theconversation.com/content/136890/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>This research was funded jointly by the CNRS (Centre National de la Recherche Scientifique) and the NRF (National Research Foundation) in the framework of the International Research Project ARSAIO and by the South Africa - France PHC-Protea Program (project No 42470VA).</span></em></p><p class="fine-print"><em><span>Caradee Yael Wright receives funding from the South African Medical Research Council and the National Research Foundation of South Africa. </span></em></p><p class="fine-print"><em><span>This research was funded jointly by the CNRS (Centre National de la Recherche Scientifique) and the NRF (National Research Foundation) in the framework of the International Research Project ARSAIO and by the South Africa - France PHC-Protea Program (project No 42470VA)</span></em></p>Too much ultraviolet radiation is dangerous for human health. Excessive exposure can cause skin ageing and sunburn and can induce melanoma, cataracts, ocular melanoma, and immunodeficiency.Jean-Maurice Cadet, PhD Candidate, Université de la RéunionCaradee Yael Wright, Specialist Scientist (Public Health), South African Medical Research CouncilHassan Bencherif, Professor, Université de la RéunionLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1164982019-06-18T23:49:20Z2019-06-18T23:49:20ZSummer is here! Why you need to protect your children’s eyes<figure><img src="https://images.theconversation.com/files/272898/original/file-20190506-103063-n27j3r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Climate change and especially variations in the ozone layer have increased the danger from the sun's harmful rays during the last 25 years. Children are particularly at risk.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/">Shutterstock</a></span></figcaption></figure><p>Should we buy sunglasses for children? And if so, how do we choose a quality product?</p>
<p>It’s a question that I get a lot in clinics. I reply that it is good to remember what the sun’s effects on eye health are, and how they often act without us even realizing. Exposure to harmful sunlight has increased during the past 25 years, especially with climate change and the variations in the ozone layer.</p>
<p>In considering this, we must first differentiate between the types of radiation — in other words the rays the sun emits and that touch us, the intensity of the light and the brightness associated with glare.</p>
<p>Emitted rays can be perceived as visible light or remain unseen, as light which is invisible to the human eye. It is the latter that are harmful to eye health. These include short rays — ultraviolet rays (UV-0 to 400 nanometers of wavelength) and the <a href="https://www.livescience.com/50260-infrared-radiation.html">longest infrared rays</a>, which are more associated with heat and burns. Each of these rays is subdivided into three families: A, B and C.</p>
<p>UVA rays, which are 315 to 400 nanometres, are known for their harmful effects associated with the development of skin cancer. UVB (280-315 nm) are the most damaging to the structures of the human eye. UVC (0-280 nm) have negligible effects because they are mostly blocked by the ozone layer when it is in good condition. </p>
<p>Infrared rays, on the other hand, <a href="https://www.ncbi.nlm.nih.gov/pubmed/?term=Biohazards+of+ultraviolet%2C+visible+and+infrared+radiation">pose a risk to the retina</a>.</p>
<h2>Children at risk</h2>
<p>The damage to our body tissues is also proportional to the amount of time we spend in the sun throughout our lives. Children are, in theory, the ones who spend the most time outdoors and the cumulative dose of sun exposure is therefore maximum between birth and 16 years of age. That means they are the most at risk today. </p>
<p>The amount of sunlight absorbed also depends on where you live and the time of day you are exposed. We receive more sunlight near the Equator than further north or south. The radiation is also more direct. </p>
<p>The same principle applies to the time of day. One might think that the maximum radiation occurs at noon, when the sun is at its zenith. But solar damage, at least to the eyes, actually occurs more in the morning and afternoon, when the sun is at an angle of about <a href="https://doi.org/10.1080/15459624.2012.737700">30 degrees to 40 degrees</a> to the horizon. For example, in Québec, the risk is therefore greatest between 9 a.m. and 10 a.m., then between 3:30 p.m. and 5 p.m. in the evening, during the summer. </p>
<h2>Harmful reflection</h2>
<p>Reflection can significantly increase harmful radiation. A surface of water such as a lake or river, sand, something white like snow, a wall covering or metal are all mirrors that increase and concentrate solar rays. </p>
<p><a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5820813/">Snow blindness</a>, which occurs when the eye is exposed to radiation on a snowy or icy surface for too long, is an example. <a href="https://www.who.int/uv/faq/uvhealtfac/en/">UVA rays that accumulate in the lens promote the development of cataracts</a>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/270829/original/file-20190424-121228-17y9c32.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/270829/original/file-20190424-121228-17y9c32.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/270829/original/file-20190424-121228-17y9c32.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/270829/original/file-20190424-121228-17y9c32.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/270829/original/file-20190424-121228-17y9c32.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/270829/original/file-20190424-121228-17y9c32.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/270829/original/file-20190424-121228-17y9c32.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Harmful radiation can be significantly increased by reflection, such as with snow.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Minor deformities of the bulbar conjunctiva — the white of the eye — are also possible. <a href="https://www.aao.org/eye-health/diseases/pinguecula-pterygium">Pingueculas are benign but obvious as small bumps</a>, sometimes vascularized, making the eyes chronically red. Pterygium is more damaging. It is a membrane that invades and pulls on the cornea, which can reduce vision. In advanced cases, this requires surgery. </p>
<p>If UV rays reach the retina, they will create a damage that can <a href="https://www.ncbi.nlm.nih.gov/pubmed/21646979">contribute to the development of macular degeneration</a>. The effects of the solar eclipse are well known — if you look at it without protection, <a href="https://www.ncbi.nlm.nih.gov/pubmed/3998365">infrared rays can then burn the retina</a>, often irreparably.</p>
<p>Don’t let your guard down on cloudy, humid days, however. They also pose an increased risk. Clouds don’t block the harmful rays and water particles also act as a mirror. As a result, radiation and the risk of glare is increased.</p>
<p>Glare is the intensity of light perceived by the eye and tolerance to brightness varies from one person to another. It depends on the amount of retinal pigments they have inherited. People with dark eyes and skin will have more pigments than people with blond hair and blue eyes. The latter will wrinkle their eyes more in front of medium intensity light and will need the protection of a darker coloured filter.</p>
<p>To sum up, <a href="https://www.arpansa.gov.au/understanding-radiation/radiation-sources/more-radiation-sources/sun-exposure">the sun emits harmful rays 365 days a year</a>, no matter if it is cloudy or rainy. The damage suffered is proportional to the amount of exposure and children absolutely must be protected. If they are highly exposed and unprotected, they will be among those who will develop cataracts at an earlier age, between 55 and 65 years of age, and run the risk of skin cancer of the eyelids, which are more fragile than the rest of the dermis.</p>
<h2>How do we protect ourselves?</h2>
<p>There are ways to protect yourself. Wearing a cap or hat helps to limit exposure. Because that is not completely effective, it is also necessary to use sun lenses, which are available in glasses and contact lenses. It is even better to have a combination of both.</p>
<p>Sunglasses must be ophthalmic quality. In other words, the lenses, which are often molded, do not have an effective power and do not create distortion. </p>
<p>Maximum protection is key and the 100 per cent UV or UV 400 label is the standard. Avoid UV 100 — without the percentage at the end — or other denominations. It is important to note that UV filters are invisible and the quality of protection has nothing to do with the colour. They can also be added to prescription lenses for those who have to wear glasses on a daily basis. </p>
<p>Finally, the frame must be curved and not leave any space between the bezel and the eye. Otherwise, the window protects against direct radiation, but all the rays that arrive from the side and even from the back will reach the eye. The damage can then be even greater. That is because the pupil is dilated since it is under a sunscreen reducing the brightness, so more harmful rays enter the eye. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/270832/original/file-20190424-121241-eynheo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/270832/original/file-20190424-121241-eynheo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/270832/original/file-20190424-121241-eynheo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/270832/original/file-20190424-121241-eynheo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/270832/original/file-20190424-121241-eynheo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/270832/original/file-20190424-121241-eynheo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/270832/original/file-20190424-121241-eynheo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Hat, sunglasses and protective cream. Now, you’re ready for summer!</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>The shade is chosen according to activity and visual needs. Grey or green are common and neutral in terms of colour perception. Brown and amber are ideal for driving. Pink/violet increases the contrast on golf greens. Options can also be added, such as polarization, which can reduce glare by at least 50 per cent, making it ideal for those working in water, snow or reflective surfaces. </p>
<p>The quality of the lens is not proportional to the price paid. However, in general, a good quality, break-resistant frame, which is especially good for children, and with adequate ophthalmic lenses will not be cheap. </p>
<p>Opticians and optometrists should be consulted if protective contact lenses are to be used. For active wearers, there are several lens brands that already offer adequate UV protection. A well-known company has also just launched the first photochromic contact lens, which tints when exposed to the sun. </p>
<p>The combination of contact lenses and sunglasses is optimal and ideal. The lens covers the entire cornea and pupil, as well as part of the white of the eye, blocking the sun’s rays. Besides cutting the sun that reaches the eyes directly, the lens also protects the sides. The sunglasses also provide total UV protection, reduce glare and the choice of shade ensures adequate patient comfort. </p>
<p>Anyone who is exposed to or works in the sun should also consider applying sunscreen — and then you’re ready for summer!</p><img src="https://counter.theconversation.com/content/116498/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Langis Michaud ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'a déclaré aucune autre affiliation que son organisme de recherche.</span></em></p>The sun emits harmful rays 365 days a year, even when cloudy or rainy. Children must be protected or they may develop cataracts at an earlier age and run the risk of skin cancer of the eyelids.Langis Michaud, Professeur Titulaire. École d'optométrie. Expertise en santé oculaire et usage des lentilles cornéennes spécialisées, Université de MontréalLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/818032017-09-15T10:21:37Z2017-09-15T10:21:37ZSeeds in space – how well can they survive harsh, non-Earth conditions?<figure><img src="https://images.theconversation.com/files/185909/original/file-20170913-18075-165yqah.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Spend many months attached to the ISS and see how well you grow.</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/mission_pages/station/research/experiments/1674.html">NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Will we someday colonize space? Will our children visit other planets? To achieve goals like these, we’ll need to crack one crucial challenge: how to feed ourselves for long periods away from Earth.</p>
<p>A <a href="http://www.mars-one.com/faq/mission-to-mars/how-long-does-it-take-to-travel-to-mars">trip to Mars would take months</a>, and exploring the depths of the galaxy would take even longer. Provision of nutritious food for travelers is a significant obstacle. While stockpiling food is an option, storing enough to last many months strains weight and space limitations in spacecraft – and missions could easily outlast food shelf life. Growing food in space will be essential.</p>
<p>Essential – and not necessarily easy. The conditions in the vacuum of space are quite harsh compared to Earth. Seeds in space must be able to withstand large doses of ultraviolet and cosmic radiation, low pressure and microgravity. </p>
<p>Believe it or not, the first space travelers were seeds. In 1946, <a href="https://www.nasa.gov/pdf/449089main_White_Sands_Missile_Range_Fact_Sheet.pdf">NASA launched a V-2 rocket carrying maize</a> seeds to observe how they’d be affected by radiation. Since then, the scientific community has learned <a href="https://doi.org/10.1079/SSR200193">a great deal</a> about the effects of the space environment on seed <a href="https://doi.org/10.1016/j.asr.2011.05.017">germination</a>, <a href="https://doi.org/10.1016/0273-1177(86)90076-1">metabolism</a>, <a href="https://doi.org/10.1016/j.asr.2005.06.043">genetics</a>, <a href="http://journal.ashspublications.org/content/130/6/848.short">biochemistry</a> and even <a href="https://doi.org/10.1016/S0273-1177(03)00250-3">seed</a> <a href="https://doi.org/10.1016/j.actaastro.2006.09.009">production</a>. </p>
<p>Astrobiologists David Tepfer and Sydney Leach recently investigated <a href="https://doi.org/10.1089/ast.2015.1457">how seeds would do back on Earth</a> after spending extended periods on the International Space Station. The experiments they conducted on the <a href="https://www.nasa.gov/mission_pages/station/research/experiments/696.html">EXPOSE</a> <a href="https://www.nasa.gov/mission_pages/station/research/experiments/211.html">missions</a> were much longer than many other ISS seed experiments, and placed the seeds on the outside of the station, in the dead of space, rather than inside. The goal was to understand not only the effects of long-term radiation exposure, but a bit about the molecular mechanisms of those effects.</p>
<h2>Seeds have some defenses</h2>
<p>Seeds possess a couple of remarkable traits that Tepfer and Leach hypothesized would give these “model space travelers” a fighting chance.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/185911/original/file-20170913-20280-41e1zd.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/185911/original/file-20170913-20280-41e1zd.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/185911/original/file-20170913-20280-41e1zd.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=575&fit=crop&dpr=1 600w, https://images.theconversation.com/files/185911/original/file-20170913-20280-41e1zd.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=575&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/185911/original/file-20170913-20280-41e1zd.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=575&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/185911/original/file-20170913-20280-41e1zd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=722&fit=crop&dpr=1 754w, https://images.theconversation.com/files/185911/original/file-20170913-20280-41e1zd.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=722&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/185911/original/file-20170913-20280-41e1zd.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=722&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Seeds protect their important insides with a strong external seed coat.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Dycotyledon_seed_diagram-en.svg">LadyofHats</a></span>
</figcaption>
</figure>
<p>First, they contain multiple copies of important genes – what scientists call redundancy. Genetic redundancy is common in flowering plants, especially food products such as <a href="https://www.sciencedaily.com/releases/2014/09/140930090636.htm">seedless watermelon and strawberries</a>. If one genetic copy is damaged, there’s still another available to do the job.</p>
<p>Secondly, seed coats contain chemicals called flavonoids that act as sunscreens, protecting the seed’s DNA from damage by ultraviolet (UV) light. On Earth, our planet’s atmosphere filters out some harmful UV light before it can reach us. But in space, there is no protective atmosphere.</p>
<p>Would these special features be enough to let the seeds survive or even thrive? To find out, Tepfer and Leach conducted a series of experiments – both outside the International Space Station and back on Earth – with tobacco, <em>Arabidopsis</em> (a flowering plant commonly used in research) and morning glory seeds. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/185905/original/file-20170913-20310-w6bmrn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/185905/original/file-20170913-20310-w6bmrn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/185905/original/file-20170913-20310-w6bmrn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=440&fit=crop&dpr=1 600w, https://images.theconversation.com/files/185905/original/file-20170913-20310-w6bmrn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=440&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/185905/original/file-20170913-20310-w6bmrn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=440&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/185905/original/file-20170913-20310-w6bmrn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=553&fit=crop&dpr=1 754w, https://images.theconversation.com/files/185905/original/file-20170913-20310-w6bmrn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=553&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/185905/original/file-20170913-20310-w6bmrn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=553&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The EXPOSE-R experiment attached to the exterior of the International Space Station.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/mission_pages/station/expeditions/expedition26/russian_eva27.html">NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Bombarded with energy</h2>
<p>Their EXPOSE-E experiment flew to the International Space Station (ISS) in 2008 and lasted 558 days – so just under two years.</p>
<p>They stored the seeds in a single layer on the outside of the ISS behind a special kind of glass that let in ultraviolet radiation only at wavelengths between 110 and 400 nanometers. DNA readily absorbs UV radiation in this wavelength range. A second, identical set of seeds was on the ISS, but shielded completely from UV radiation. The purpose of this experimental design was to observe the effects of UV radiation separately from other types of radiation <a href="https://www.space.com/32644-cosmic-rays.html">like cosmic rays</a> that are everywhere in space.</p>
<p>Tepfer and Leach chose tobacco and <em>Arabidopsis</em> seeds for EXPOSE-E because both have a redundant genome and therefore good odds for survival. They also included a genetically engineered variety of tobacco with an antibiotic resistance gene added; the plan was to later test this gene in bacteria and determine if there was any damage. In addition to normal <em>Arapidopsis</em>, they sent up two genetically modified strains of the plant that contained low and absent UV-protective chemicals in their seed coat. They also sent purified DNA and purified flavonoids. This gave the researchers a wide range of scenarios by which to understand the effects of space on the seeds.</p>
<p>A second ISS mission called EXPOSE-R included only the three types of <em>Arabidopsis</em> seeds. These received a little over double the dose of ultraviolet light because of the longer experiment time, 682 days. Lastly, researchers performed a ground experiment back in the lab that exposed <em>Arabidopsis</em>, tobacco and morning glory seeds to very high doses of UV light for only a month.</p>
<p>After all these various exposure conditions, it was time to see how well the seeds could grow.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/185907/original/file-20170913-20270-l4me1j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/185907/original/file-20170913-20270-l4me1j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/185907/original/file-20170913-20270-l4me1j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=410&fit=crop&dpr=1 600w, https://images.theconversation.com/files/185907/original/file-20170913-20270-l4me1j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=410&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/185907/original/file-20170913-20270-l4me1j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=410&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/185907/original/file-20170913-20270-l4me1j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=515&fit=crop&dpr=1 754w, https://images.theconversation.com/files/185907/original/file-20170913-20270-l4me1j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=515&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/185907/original/file-20170913-20270-l4me1j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=515&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Expose-R experiment was equipped with three trays containing a variety of biological samples – including seeds.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/mission_pages/station/multimedia/exp18_eva2.html">NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>What would researchers reap?</h2>
<p><a href="https://doi.org/10.1089/ast.2015.1457">When the seeds returned to Earth</a>, the researchers measured their germination rates – that is, how quickly the root emerged from the seed coat.</p>
<p>The seeds that had been shielded in the lab did the best, with more than 90 percent of them germinating. Next came the seeds that had been exposed to UV radiation for one month in the laboratory, with better than 80 percent germinating. </p>
<p>For the space-traveling seeds, more than 60 percent of the shielded seeds germinated. A mere 3 percent of space UV-exposed seeds did.</p>
<p>The 11 <em>Arabidopsis</em> plants that did grow from both the wild type and genetically engineered seeds did not survive once planted in soil. Tobacco plants, however, showed reduced growth but that growth rate recovered in subsequent generations. Tobacco has a much heartier seed coat and a more redundant genome, which may explain its apparent survival advantage.</p>
<p>When the researchers plugged the antibiotic resistance gene into bacteria, they found it was still functional after its trip to space. That finding suggests it’s not genetic damage that’s making these seeds less viable. Tepfer and Leach attributed the reduced germination rate to damage to other molecules in the seed besides DNA – such as proteins. A redundant genome or built-in DNA repair mechanisms weren’t going to overcome that damage, further explaining why the <em>Arabidopsis</em> plants didn’t survive transplanting.</p>
<p>In the ground experiments, the researchers found that radiation damage is dose-dependent – the more radiation the seeds received, the worse their germination rate.</p>
<p>These discoveries could inform future directions for research in space agriculture. Scientists may consider genetically engineering seeds to have added protection for the cellular machinery critical for protein synthesis, such as ribosomes. Future research will also need to explore further how seeds stored in space germinate in microgravity, rather than on Earth.</p>
<p>As researchers add to the knowledge of how space affects plants and their seeds, we can continue to make the strides necessary toward producing food in space. It will be a crucial step toward sustainable colonies that can survive beyond the comfortable confines of Earth’s biosphere.</p><img src="https://counter.theconversation.com/content/81803/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gina Riggio is affiliated with Blue Marble Space.</span></em></p>If you want to live on Mars, you’re going to need to grow food. Seeds are naturally equipped to handle challenging Earth environments, but how well can they survive what they’ll encounter off-planet?Gina Misra, Ph.D. Student in Cell and Molecular Biology, University of ArkansasLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/811222017-07-24T08:06:31Z2017-07-24T08:06:31ZBooze in space: how the universe is absolutely drowning in the hard stuff<figure><img src="https://images.theconversation.com/files/179195/original/file-20170721-18128-14pw7he.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Mine's a Star-opramen. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/retro-astronaut-mug-beer-pop-art-486571996?src=GRArIRYoATk-qqeZn7VeGg-1-7">Studioloks</a></span></figcaption></figure><p>A cold beer on a hot day or a whisky nightcap beside a coal fire. A well earned glass can loosen your thinking until you feel able to pierce the mysteries of life, death, love and identity. In moments like these, alcohol and the cosmic can seem intimately entwined. </p>
<p>So perhaps it should come as no surprise that the universe is awash with alcohol. In the gas that occupies the space between the stars, the hard stuff is almost all-pervasive. What is it doing there? Is it time to send out some big rockets to start collecting it?</p>
<p>The chemical elements around us reflect the history of the universe and the stars within it. Shortly after the Big Bang, protons were formed throughout the expanding, cooling universe. Protons are the nuclei of hydrogen atoms and building blocks for the nuclei of all the other elements. </p>
<p>These have mostly been manufactured since the Big Bang through nuclear reactions in the hot dense cores of stars. Heavier elements such as lead or gold are only fabricated in rare massive stars or incredibly explosive events. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/179175/original/file-20170721-18110-oqdban.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/179175/original/file-20170721-18110-oqdban.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/179175/original/file-20170721-18110-oqdban.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=835&fit=crop&dpr=1 600w, https://images.theconversation.com/files/179175/original/file-20170721-18110-oqdban.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=835&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/179175/original/file-20170721-18110-oqdban.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=835&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/179175/original/file-20170721-18110-oqdban.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1050&fit=crop&dpr=1 754w, https://images.theconversation.com/files/179175/original/file-20170721-18110-oqdban.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1050&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/179175/original/file-20170721-18110-oqdban.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1050&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Ethanol molecule.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Ethanol-3D-balls.png#/media/File:Ethanol-3D-balls.png">Wikimedia</a></span>
</figcaption>
</figure>
<p>Lighter ones such as carbon and oxygen are synthesised in the life cycles of very many ordinary stars – including our own sun eventually. Like hydrogen, they are among the most common in the universe. In the vast spaces between the stars, <a href="https://ay201b.wordpress.com/2011/04/12/course-notes/">typically</a> 88% of atoms are hydrogen, 10% are helium and the remaining 2% are chiefly carbon and oxygen.</p>
<p>Which is great news for booze enthusiasts. Each molecule of ethanol, the alcohol that gives us so much pleasure, includes nine atoms: two carbon, one oxygen and six hydrogen. Hence the chemical symbol C₂H₆O. It’s as if the universe turned itself into a monumental distillery on purpose. </p>
<h2>Interstellar intoxication</h2>
<p>The spaces between stars are known as the interstellar medium. The famous Orion Nebula is perhaps the best known example. It is the closest region of star formation to Earth and visible to the naked eye – albeit still more than 1,300 light years away. </p>
<p>Yet while we tend to focus on the colourful parts of nebulae like Orion where stars are emerging, this is not where the alcohol is coming from. Emerging stars produce intense ultraviolet radiation, which destroys nearby molecules and makes it harder for new substances to form. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/179190/original/file-20170721-18113-gcen2i.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/179190/original/file-20170721-18113-gcen2i.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/179190/original/file-20170721-18113-gcen2i.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=587&fit=crop&dpr=1 600w, https://images.theconversation.com/files/179190/original/file-20170721-18113-gcen2i.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=587&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/179190/original/file-20170721-18113-gcen2i.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=587&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/179190/original/file-20170721-18113-gcen2i.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=737&fit=crop&dpr=1 754w, https://images.theconversation.com/files/179190/original/file-20170721-18113-gcen2i.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=737&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/179190/original/file-20170721-18113-gcen2i.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=737&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Orion Nebula.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Orion_Nebula#/media/File:Orion_Nebula_-_Hubble_2006_mosaic_18000.jpg">Wikimedia</a></span>
</figcaption>
</figure>
<p>Instead you need to look to the parts of the interstellar medium that appear to astronomers as dark and cloudy, and only dimly illuminated by distant stars. The gas in these spaces is <a href="http://casswww.ucsd.edu/archive/public/tutorial/ISM.html">extremely cold</a>, slightly less than -260°C, or about 10°C above absolute zero. This makes it very sluggish. </p>
<p>It is also fantastically widely dispersed. At sea level on Earth, by my calculations there are roughly 3x10<sup>25</sup> molecules per cubic metre of air – that’s a three followed by 25 zeros, an enormously huge number. At passenger jet altitude, circa 36,000ft, the density of molecules is about a third of this value – say 1x10<sup>25</sup>. We would struggle to breathe outside the aircraft, but that’s still quite a lot of gas in absolute terms. </p>
<p>Now compare this to the dark parts of the interstellar medium, where there are typically 100,000,000,000 particles per cubic metre, or 1x10<sup>11</sup>, and often much less than even that. These atoms seldom come close enough to interact. Yet when they do, they can form molecules less prone to being blown apart by further high-speed collisions than when the same thing happens on Earth. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/179196/original/file-20170721-18165-1tl87lr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/179196/original/file-20170721-18165-1tl87lr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/179196/original/file-20170721-18165-1tl87lr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/179196/original/file-20170721-18165-1tl87lr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/179196/original/file-20170721-18165-1tl87lr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/179196/original/file-20170721-18165-1tl87lr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/179196/original/file-20170721-18165-1tl87lr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/179196/original/file-20170721-18165-1tl87lr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The proof is out there.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/very-bright-white-star-named-procyon-412689028?src=sMN_naWxfUHYuErfk0iKOQ-2-44">Tragoolchitr Jittasaiyapan</a></span>
</figcaption>
</figure>
<p>If an atom of carbon meets an atom of hydrogen, for instance, they can stick together as a molecule called <a href="https://link.springer.com/referenceworkentry/10.1007%2F978-3-642-11274-4_1807">methylidyne</a> (chemical symbol CH). Methylidyne is highly reactive and so is quickly destroyed on Earth, but it is common in the interstellar medium. </p>
<p>Simple molecules like these are more free to encounter other molecules and atoms and slowly build up more complex substances. Sometimes molecules will be destroyed by ultraviolet light from distant stars, but this light can also turn particles into slightly different versions of themselves called <a href="http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/bonding/ionic_bondingrev1.shtml">ions</a>, thereby slowly expanding the range of molecules that can form. </p>
<h2>Soot and fire water</h2>
<p>To make a nine-atom molecule such as ethanol in these cool and tenuous conditions might still take an extremely long time – certainly much longer than the seven days you might ferment home brew in the attic, let alone the time it takes to walk to the liquor store. </p>
<p>But there is help at hand from other simple organic molecules, which start sticking together to form grains of dust, something like soot. On the surfaces of these grains, chemical reactions take place much more rapidly because the molecules get held in proximity to them. </p>
<p>It is therefore cool sooty regions, the potential stellar birthplaces of the future, that encourage complex molecules to appear more quickly. We can tell from the distinctive spectrum lines of different particles in these regions that there is water, carbon dioxide, methane and ammonia – but also plenty of ethanol. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/179199/original/file-20170721-18148-1xqq9en.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/179199/original/file-20170721-18148-1xqq9en.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/179199/original/file-20170721-18148-1xqq9en.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=693&fit=crop&dpr=1 600w, https://images.theconversation.com/files/179199/original/file-20170721-18148-1xqq9en.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=693&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/179199/original/file-20170721-18148-1xqq9en.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=693&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/179199/original/file-20170721-18148-1xqq9en.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=871&fit=crop&dpr=1 754w, https://images.theconversation.com/files/179199/original/file-20170721-18148-1xqq9en.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=871&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/179199/original/file-20170721-18148-1xqq9en.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=871&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Room for more!</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/almost-empty-beer-glass-isolated-on-453410167?src=zWSyEpcHcissj_TKI0sNcA-1-76">Africa Studio</a></span>
</figcaption>
</figure>
<p>Now when I say plenty, you have to bear in mind the vastness of the universe. And we are still only <a href="http://adsabs.harvard.edu/doi/10.1086/168830">talking about</a> roughly one in every 10m atoms and molecules. Suppose you could travel through interstellar space holding a pint glass, scooping up only alcohol as you moved. To collect enough for a pint of beer you would have to travel about half a million light years – much further than the size of our Milky Way. </p>
<p>In short, there are mind-bogglingly vast quantities of alcohol in outer space. But since it is dispersed over truly enormous distances, the drinks companies can rest easy. It will be a cold day on the sun before we figure out how to collect any of it, I’m sorry to say.</p><img src="https://counter.theconversation.com/content/81122/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alexander MacKinnon does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>It’s like one great big distillery up there.Alexander MacKinnon, Senior Lecturer, Astrophysics, University of GlasgowLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/743552017-05-26T01:32:59Z2017-05-26T01:32:59ZHow do the chemicals in sunscreen protect our skin from damage?<figure><img src="https://images.theconversation.com/files/171062/original/file-20170525-23230-m46xg5.jpg?ixlib=rb-1.1.0&rect=0%2C98%2C2000%2C1419&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Don't skimp on the SPF.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/toned-photo-kid-beach-smooth-skin-381581356">Sabphoto via Shutterstock.com</a></span></figcaption></figure><p>Not so long ago, people like my Aunt Muriel thought of sunburn as a necessary evil on the way to a “good base tan.” She used to slather on the baby oil while using a large reflector to bake away. Aunt Muriel’s mantra when the inevitable burn and peel appeared: Beauty has its price.</p>
<p>Was she ever right about that price – but it was a lot higher than any of us at the time recognized. What sun addicts didn’t know then was that we were setting our skin up for damage to its structural proteins and DNA. Hello, wrinkles, liver spots and cancers. No matter <a href="https://doi.org/10.1001/archderm.1988.01670060015008">where your complexion falls</a> on the <a href="http://www.skincancer.org/prevention/are-you-at-risk/fitzpatrick-skin-quiz">Fitzpatrick Skin Type</a> scale, ultraviolet radiation (UV) from the sun or tanning beds will damage your skin.</p>
<p>Today, recognition of the risks posed by UV rays has motivated scientists, myself included, to study what’s going on in our cells when they’re in the sun – and devise modern ways to ward off that damage.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/170967/original/file-20170525-23279-110s6q8.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/170967/original/file-20170525-23279-110s6q8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/170967/original/file-20170525-23279-110s6q8.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=236&fit=crop&dpr=1 600w, https://images.theconversation.com/files/170967/original/file-20170525-23279-110s6q8.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=236&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/170967/original/file-20170525-23279-110s6q8.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=236&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/170967/original/file-20170525-23279-110s6q8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=297&fit=crop&dpr=1 754w, https://images.theconversation.com/files/170967/original/file-20170525-23279-110s6q8.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=297&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/170967/original/file-20170525-23279-110s6q8.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=297&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">UV light that affects our skin has a shorter wavelength than the parts of the electromagnetic spectrum we can see.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:EM_Spectrum_Properties_edit.svg">Inductiveload, NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>What happens when sun hits skin</h2>
<p>Sunlight is composed of packets of energy called photons. The visible colors we can see by eye are relatively harmless to our skin; it’s the sun’s ultraviolet (UV) light photons that can cause skin damage. UV light can be broken down into two categories: UVA (in the wavelength range 320-400 nanometers) and UVB (in the wavelength range 280–320 nm). </p>
<p><iframe id="Niww2" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/Niww2/8/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>Our skin contains molecules that are perfectly structured to absorb the energy of UVA and UVB photons. This puts the molecule into an energetically excited state. And as the saying goes, what goes up must come down. In order to release their acquired energy, these molecules undergo chemical reactions – and in the skin that means there are biological consequences.</p>
<p>Interestingly, some of these effects used to be considered helpful adaptations – though we now recognize them as forms of damage. Tanning is due to the production of <a href="https://www.derm101.com/inflammatory/embryologic-histologic-and-anatomic-aspects/melanocytes/">extra melanin pigment induced by UVA rays</a>. Exposure to the sun also turns on the skin’s natural antioxidant network, which <a href="http://www.nature.com/nchembio/journal/v10/n7/pdf/nchembio.1548.pdf">deactivates highly destructive reactive oxygen species (ROS) and free radicals</a>; if left unchecked, these can cause cellular damage and oxidative stress within the skin.</p>
<p>We also know that UVA light penetrates deeper into the skin than UVB, destroying a structural protein called collagen. As collagen degrades, our skin loses its elasticity and smoothness, leading to wrinkles. UVA is responsible for many of the visible signs of aging, while UVB light is considered the primary source of sunburn. Think “A” for aging and “B” for burning.</p>
<p>DNA itself can absorb both <a href="http://www.pnas.org/content/103/37/13765.short">UVA and UVB rays, causing mutations</a> which, if unrepaired, can lead to non-melanoma (basal cell carcinoma, squamous cell carcinoma) or <a href="https://doi.org/10.1126/science.1253735">melanoma skin cancers</a>. Other skin molecules pass absorbed UV energy on to those highly reactive ROS and free radicals. The resulting oxidative stress can overload the skin’s built-in antioxidant network and cause cellular damage. ROS can react with DNA, forming mutations, and with collagen, leading to wrinkles. They can also interrupt cell signaling pathways and gene expression.</p>
<p>The end result of all of these photoreactions is photodamage that accumulates over the course of a lifetime from repeated exposure. And – this cannot be emphasized enough — this applies to all skin types, from Type I (like Nicole Kidman) to Type VI (like Jennifer Hudson). <a href="http://www.skincancer.org/skin-cancer-information/skin-cancer-facts">Regardless of how much melanin we have in our skin</a>, we can develop UV-induced skin cancers and we will all eventually see the signs of photo-induced aging in the mirror.</p>
<h2>Filtering photons before the damage is done</h2>
<p>The good news, of course, is that the risk of skin cancer and the visible signs of aging can be minimized by preventing overexposure to UV radiation. When you can’t avoid the sun altogether, today’s sunscreens have got your back (and all the rest of your skin too).</p>
<p>Sunscreens employ UV filters: molecules specifically designed to help reduce the amount of UV rays that reach through the skin surface. A film of these molecules forms a protective barrier either absorbing (chemical filters) or reflecting (physical blockers) UV photons before they can be absorbed by our DNA and other reactive molecules deeper in the skin. </p>
<p><iframe id="kJPnc" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/kJPnc/2/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>In the United States, the Food and Drug Administration regulates sunscreens as drugs. Because we were historically most concerned with protecting against sunburn, <a href="http://dx.doi.org/10.1016/j.jaad.2010.01.005">14 molecules that block sunburn-inducing UVB rays</a> are approved for use. That we have just two UVA-blocking molecules available in the United States – avobenzone, a chemical filter; and zinc oxide, a physical blocker – is a testament to our more recent understanding that UVA causes trouble, not just tans.</p>
<p>The FDA also has enacted <a href="https://www.federalregister.gov/documents/2011/06/17/2011-14766/labeling-and-effectiveness-testing-sunscreen-drug-products-for-over-the-counter-human-use">strict labeling requirements</a> – most obviously about SPF (sun protection factor). On labels since 1971, SPF represents the relative time it takes for an individual to get sunburned by UVB radiation. For example, if it takes 10 minutes typically to burn, then, if used correctly, an SPF 30 sunscreen should provide 30 times that – 300 minutes of protection before sunburn. </p>
<p>“Used correctly” is the key phrase. Research shows that it takes about one ounce, or basically a <a href="https://www.aad.org/media/stats/prevention-and-care/sunscreen-faqs">shot glass-sized amount of sunscreen</a>, to cover the exposed areas of the average adult body, and a nickel-sized amount for the face and neck (more or less, depending on your body size). The majority of people apply between a <a href="https://www.ncbi.nlm.nih.gov/pubmed/12374537">quarter to a half of the recommended amounts</a>, placing their skin at risk for sunburn and photodamage.</p>
<p>In addition, sunscreen efficacy decreases in the water or with sweating. To help consumers, FDA now requires sunscreens labeled <a href="https://www.federalregister.gov/documents/2011/06/17/2011-14766/labeling-and-effectiveness-testing-sunscreen-drug-products-for-over-the-counter-human-use">“water-resistant” or “very water-resistant”</a> to last up to 40 minutes or 80 minutes, respectively, in the water, and the <a href="https://www.aad.org/media/stats/prevention-and-care/sunscreen-faqs">American Academy of Dermatology</a> and other medical professional groups <a href="https://www.cancer.org/cancer/skin-cancer/prevention-and-early-detection/uv-protection.html">recommend reapplication immediately after any water sports</a>. The general <a href="https://www.aad.org/media/stats/prevention-and-care/sunscreen-faqs">rule of thumb</a> is to reapply about every two hours and certainly after water sports or sweating.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/171063/original/file-20170525-23234-v4lxdi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/171063/original/file-20170525-23234-v4lxdi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/171063/original/file-20170525-23234-v4lxdi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/171063/original/file-20170525-23234-v4lxdi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/171063/original/file-20170525-23234-v4lxdi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/171063/original/file-20170525-23234-v4lxdi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/171063/original/file-20170525-23234-v4lxdi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/171063/original/file-20170525-23234-v4lxdi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">In the U.S., the FDA regulates sunscreens available to consumers.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/alameda-ca-june-05-2016-store-433399849">Sheila Fitzgerald via Shutterstock.com</a></span>
</figcaption>
</figure>
<p>To get high SPF values, multiple UVB UV filters are combined into a formulation based upon <a href="https://www.federalregister.gov/documents/2011/06/17/2011-14766/labeling-and-effectiveness-testing-sunscreen-drug-products-for-over-the-counter-human-use">safety standards set by the FDA</a>. However, the SPF doesn’t account for UVA protection. For a sunscreen to make a claim as having UVA and UVB protection and be labeled “Broad Spectrum,” it must pass <a href="https://www.fda.gov/drugs/guidancecomplianceregulatoryinformation/guidances/ucm330694.htm">FDA’s Broad Spectrum Test</a>, where the sunscreen is hit with a large dose of UVB and UVA light before its effectiveness is tested. </p>
<p>This pre-irradiation step was established in <a href="https://www.fda.gov/drugs/guidancecomplianceregulatoryinformation/guidances/ucm330694.htm">FDA’s 2012 sunscreen labeling rules</a> and acknowledges something significant about UV-filters: some can be photolabile, meaning they can degrade under UV irradiation. The most famous example may be <a href="http://onlinelibrary.wiley.com/doi/10.1046/j.1440-0960.1999.00319.x/full">PABA</a>. This UVB-absorbing molecule is rarely used in sunscreens today because it forms photoproducts that elicit an allergic reaction in some people.</p>
<p>But the Broad Spectrum Test really came into effect only once the UVA-absorbing molecule avobenzone came onto the market. Avobenzone can interact with octinoxate, a strong and widely used UVB absorber, in a way that makes avobenzone less effective against UVA photons. The UVB filter octocrylene, on the other hand, helps stabilize avobenzone so it lasts longer in its UVA-absorbing form. Additionally, you may notice on some sunscreen labels the molecule ethylhexyl methoxycrylene. It helps stabilize avobenzone even in the presence of octinoxate, and provides us with longer-lasting protection against UVA rays.</p>
<p>Next up in sunscreen innovation is the broadening of their mission. Because even the highest SPF sunscreens don’t block 100 percent of UV rays, the addition of antioxidants can supply a second line of protection when the skin’s natural antioxidant defenses are overloaded. Some antioxidant ingredients my colleagues and I have worked with include <a href="http://www.springer.com/us/book/9783319293813">tocopheral acetate (Vitamin E), sodium ascorbyl phosophate (Vitamin C), and DESM</a>. And sunscreen researchers are beginning to investigate if the <a href="http://www.springer.com/us/book/9783319293813">absorption of other colors of light</a>, like infrared, by skin molecules has a role to play in photodamage.</p>
<p>As research continues, one thing we know for certain is that protecting our DNA from UV damage, for people of every color, is synonymous with preventing skin cancers. The Skin Cancer Foundation, American Cancer Society and the American Academy of Dermatology all stress that research shows regular use of an SPF 15 or higher sunscreen prevents sunburn and reduces the risk of <a href="http://dx.doi.org/10.1016/S0140-6736(98)12168-2">non-melanoma cancers by 40 percent</a> and <a href="https://doi.org//10.1200/jco.2010.28.7078">melanoma by 50 percent</a>.</p>
<p>We can still enjoy being in the sun. Unlike my Aunt Muriel and us kids in the 1980s, we just need to use the resources available to us, from long sleeves to shade to sunscreens, in order to protect the molecules in our skin, especially our DNA, from UV damage.</p><img src="https://counter.theconversation.com/content/74355/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kerry Hanson has consulted for Bayer, J&J/Neutrogena, and P&G. Her academic work has been funded by Hallstar and through a joint University of California Discovery Grant with Merck. She is a member of the American Chemical Society. </span></em></p>Energy from the sun’s rays can cause skin damage and cancers. Sunscreens can absorb or reflect the dangerous UV light. Here’s how it works.Kerry Hanson, Research Chemist, University of California, RiversideLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/438622015-07-01T04:22:33Z2015-07-01T04:22:33ZThe best time for marathon runners to get on the road<figure><img src="https://images.theconversation.com/files/86687/original/image-20150629-9059-1ufcpk6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Intensive sun exposure for marathon runners in the middle of the day could lead to sunburn, skin cancer and cataracts. </span> <span class="attribution"><span class="source">Rogan Ward/Reuters</span></span></figcaption></figure><p>Running has been a popular recreational activity for many years. But for marathon runners who train outdoors, the significant proportion of time they spend in the sun means they are potentially exposed to harmful rays.</p>
<p>Solar ultraviolet radiation can lead to sunburn, fatal skin cancers and cataracts – particularly when the exposure to the sun is for a long time or during the hottest time of the day.</p>
<p>For runners, timing their sun exposure and protecting themselves from excess solar ultraviolet radiation are important in preventing the harmful effects of sun rays.</p>
<h2>Putting skin cancer into perspective</h2>
<p>Across the world, <a href="http://www.cdc.gov/mmwr/preview/mmwrhtml/mm64e0602a1.htm">skin cancer</a> has become the fifth most common cancer for men and seventh for women. Australia and New Zealand have seen large increases in <a href="http://sciencelearn.org.nz/Contexts/You-Me-and-UV/Looking-Closer/NZ-skin-cancer-statistics">skin cancer</a>. In South Africa, skin cancer forms about 30% of all histologically diagnosed cases of <a href="http://www.cansa.org.za/files/2012/05/SKIN_CANCER_Leaflet-2010.pdf">cancer</a>.</p>
<p>Ultraviolet rays are at their strongest in places that are: </p>
<ul>
<li><p>closer to the equator;</p></li>
<li><p>at a high altitude;</p></li>
<li><p>have snow, or other highly reflective (e.g. water) surfaces;</p></li>
<li><p>have low stratospheric ozone levels (a protective layer up in the atmosphere); and</p></li>
<li><p>have skies free of clouds and particles.</p></li>
</ul>
<p>South Africa, Australia, New Zealand and South American countries face a particular risk of skin cancer because of their locations. South Africa, like Australia, is relatively close to the equator. New Zealand has clear skies, and parts of the country are at a high altitude and has several snow surfaces. In spring and early summer, all these countries experience the effects of <a href="http://www.wmo.int/pages/prog/arep/gaw/ozone/">ozone depletion</a>.</p>
<h2>Timing South Africa’s sun rays</h2>
<p><a href="http://onlinelibrary.wiley.com/doi/10.1111/php.12461/abstract">Our study</a> is the first to measure the exact time that sun exposure is most harmful. We did this by monitoring a sample of four marathon runners during marathons and training. A high-tech instrument that measures sun exposure was attached to an arm of each of the runners.</p>
<p>What made our study unique was that the instrument measured sun exposure every minute and instantly linked it to a specific time. This enabled us to track the exact movement and location of runners, including when they were likely running in shade.</p>
<p>The results show solar ultraviolet radiation levels at their highest between 10AM and 2PM.</p>
<h2>Tips for marathon runners</h2>
<p>Runners can experience excess sun exposure acutely in the form of sunburn after running for a short-to-medium time during peak solar ultraviolet radiation hours. Years of regular sun exposure can lead to more chronic health effects such as skin cancer and cataracts in adulthood or old age. </p>
<p>Running early in the morning or late afternoon, wearing protective and cool clothing, a hat and sunglasses, and applying sunscreen to exposed skin, will offer protection. Runners should use extra protection or regularly re-apply sunscreen in marathons that span midday hours.</p>
<p>Studies in <a href="https://www.researchgate.net/profile/Michael_Kimlin/publication/27468775_Evaluation_of_differences_in_ultraviolet_exposure_during_weekend_and_occupational_activities/links/00b7d53af72806c273000000.pdf">Australia</a> and <a href="http://www.ncbi.nlm.nih.gov/pubmed/17576384">New Zealand</a> has provided important data about the levels of sun exposure from different activities. This has been used to guide interventions for groups at risk. For example, the government has produced a vitamin D guideline for <a href="http://www.health.govt.nz/publication/consensus-statement-vitamin-d-and-sun-exposure-new-zealand">New Zealand</a>.</p>
<p>It is hoped that detailed data on different areas of activity in South Africa will lead to targeted interventions and education awareness campaigns.</p><img src="https://counter.theconversation.com/content/43862/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Caradee Yael Wright does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Runners have a greater risk of developing skin cancer because they are more likely have sun damage on their skin as a result of chronic sun exposure.Caradee Yael Wright, Specialist Scientist (Public Health), South African Medical Research CouncilLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/437882015-06-29T04:20:31Z2015-06-29T04:20:31ZWhen it’s not good for the sun to shine on you<figure><img src="https://images.theconversation.com/files/86381/original/image-20150625-13016-1fiuveb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Employers have a duty to keep their employees safe from the sun. </span> <span class="attribution"><span class="source">Reuters/Mike Blake</span></span></figcaption></figure><p>A real-time <a href="http://www.sajs.co.za/real-time-measurement-outdoor-worker%E2%80%99s-exposure-solar-ultraviolet-radiation-pretoria-south-africa/mmathapelo-makgabutlane-caradee-y-wright">study</a> using a hand-held device to measure solar ultraviolet radiation value has found that outdoor workers may be heavily exposed to up to 80% of sun rays. </p>
<p>The study was done in South Africa, which has a large number of people who spend the majority of their lives working outdoors. The location was Pretoria, a city north of Johannesburg that gets considerable solar <a href="http://www.cancer.org/cancer/cancercauses/sunanduvexposure/index">ultraviolet</a> radiation because of its low latitude (22–35°S) and relatively clear skies. </p>
<p>A previous <a href="http://www.scielo.org.za/scielo.php?pid=S0256-95742014000800033&script=sci_arttext">investigation</a> found a direct link between poor health and people working in extreme heat. There were risks of exposure to heat in mining and in particular for outdoor workers in agriculture, quarries and construction industries in hot regions.</p>
<p>Since this was the first <a href="http://www.nova.edu/ssss/QR/QR13-4/baxter.pdf">case study</a> of its kind in South Africa, our approach was to test the instrument available for measuring sun exposure. We then collected preliminary data on an outdoor worker’s sun exposure patterns. The broader implications of the case study were supported by previous studies into how the sun affects people working outdoors. </p>
<p>There were issues around reliability of the device, which is why a larger study using more better quality, real-time instruments would advance the work further. Such large studies have been done in the US, Europe and Australia, and have led to improvements in occupational health policy with respect to sun protection guidelines. In some cases, such data has helped make skin cancer a notifiable or reportable occupational disease.</p>
<h2>Real-time measurement of the sun</h2>
<p>The study sought to estimate the amount of solar ultraviolet radiation that outdoor workers are exposed to on a daily basis during work. Although <a href="http://www.scielo.org.za/scielo.php?pid=S0038-23532012000600014&script=sci_arttext">previous</a> studies of this nature have been conducted, it was the first of its kind in South Africa where the estimation was calculated using real-time measurements of solar ultraviolet radiation.</p>
<p>As part of this research a school groundsman was monitored for the duration of the study. Half-hourly solar ultraviolet radiation readings were taken with the hand-held instrument while he was on duty, whether in the sun or shade.</p>
<p>These solar ultraviolet radiation readings were then compared to the solar ultraviolet radiation readings recorded by the research-grade solar ultraviolet radiation <a href="http://www.scielo.org.za/scielo.php?pid=S0038-23532013000100019&script=sci_arttext">recorder</a> at the South African Weather Service in Pretoria. </p>
<p>The amount of solar ultraviolet radiation measured for the outdoor worker was compared to the amount of solar ultraviolet radiation measured by the recorder at the Weather Service. It gave an indication of the amount of solar ultraviolet radiation to which the outdoor worker was potentially exposed. This figure was used to determine whether or not the level of exposure to solar ultraviolet radiation posed a risk of sunburn.</p>
<p>Based on the readings, combined with the findings of previous research, it was found that outdoor workers in Pretoria are potentially exposed to more than 80% of the solar ultraviolet radiation that reaches the ground. This amount of exposure is likely to lead to a high risk of sunburn depending on the time of the year. </p>
<p>With this amount of exposure people of all skin types are at risk of over-exposure to solar ultraviolet radiation and therefore <a href="https://sciencequestionswithchris.wordpress.com/2013/08/19/why-dont-dark-skinned-people-get-sunburns/">sunburn</a> on at least some days of the year.</p>
<h2>Exposure to sun causes skin cancer</h2>
<p>A large number of skin ailments in South Africa are linked to the harmful effects of exposure to the sun. The nature of outdoor work dictates that the sun cannot be avoided. This includes farm workers, construction workers, policemen directing, labourers carrying out repairs to roads or collecting refuse. </p>
<p>But they are among the least protected workers in most developing countries. Sunburn, cataracts and skin cancer are the main adverse health effects of excess sun exposure.</p>
<p>The rise of skin cancers and other illnesses associated with ultraviolet rays makes it necessary for employers to take steps to safeguard their employees.
The International Labour Organisation has set <a href="http://www.ilo.org/wcmsp5/groups/public/@ed_protect/@protrav/@safework/documents/normativeinstrument/wcms_107729.pdf">standards</a> which includes that employers should take safety precautions to reduce risks faced by workers. South Africa is a <a href="http://www.ilo.org/global/standards/information-resources-and-publications/news/WCMS_216613/lang--en/index.htm">signatory</a> to the convention.</p>
<p>Employers should encourage the use of protective gear. The use of clothing, including hats, to shield people from the sun, sunglasses and sunscreen are simple recommendations. Devices that measure the impact of the sun on workers should also be considered. </p>
<hr>
<p><em>This piece is based on an <a href="http://www.sajs.co.za/real-time-measurement-outdoor-worker%E2%80%99s-exposure-solar-ultraviolet-radiation-pretoria-south-africa/mmathapelo-makgabutlane-caradee-y-wright">article</a> in the South African Journal of Science.</em></p><img src="https://counter.theconversation.com/content/43788/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Caradee Yael Wright receives funding from the South African Medical Research Council and the National Research Foundation. She is affiliated with the University of Pretoria as an Extraordinary Lecturer.</span></em></p><p class="fine-print"><em><span>Mmathapelo Makgabutlane does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A real-time hand-held device can help employers measure the impact of the sun on workers.Mmathapelo Makgabutlane, Researcher, University of PretoriaCaradee Yael Wright, Specialist Scientist (Public Health), South African Medical Research CouncilLicensed as Creative Commons – attribution, no derivatives.