tag:theconversation.com,2011:/ca/topics/ultraviolet-light-27706/articlesUltraviolet light – The Conversation2024-01-25T16:08:19Ztag:theconversation.com,2011:article/2217862024-01-25T16:08:19Z2024-01-25T16:08:19ZAnimals see the world in different colours than humans – new camera reveals what this looks like<figure><img src="https://images.theconversation.com/files/571226/original/file-20240124-17-mpvmh4.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C644%2C644&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Visualising the colours birds perceive reveals the ultraviolet patterns that are usually hidden from us.</span> <span class="attribution"><a class="source" href="https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3002444#sec014">Vasas et al. (2024) PLOS Biology</a>, <span class="license">Author provided</span></span></figcaption></figure><p>If you’ve ever wished you could see the world though the eyes of another animal, we have good news for you. We also wondered about that and, being scientists who specialise in colour vision, have created a solution: a camera system and software package that allows you to record videos <a href="http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3002444">in animal-view colours</a>.</p>
<p>Many animals, including bees, birds and <a href="https://www.sciencefriday.com/articles/ultraviolet-light-animals/#:%7E:text=Okay%2C%20fine%2C%20mammals%20can%20have,with%20their%20short%20blue%20cones.">even mammals</a> like reindeer and mice can perceive ultraviolet light. Indeed, the lack of UV-sensitivity in humans is more of an exception than the rule. At the other end of the visible light spectrum, human eyes have receptors that are sensitive to red while many animals – including bees, mice and dogs – are just as blind to red as we are to ultraviolet light. </p>
<p>Even when it comes to blues and greens, colours perceived across the animal kingdom, the precise wavelength of the light an animal would experience as “pure blue” or “pure green” is specific to the species. As a result, no two species see the world in the same colours.</p>
<p>We invite you to stare at the sky and appreciate that its blueness is the joint product of the sunlight being scattered in the atmosphere and your own sensory system. The colour you see is specific to you – in fact, for many animals, the sky is ultraviolet-coloured.</p>
<p>Now, slowly lower your eyes and try to imagine how the rest of the landscape could appear for other species. With our new camera system, we took one step closer to understanding this wonderful, strange world that other animals live in.</p>
<h2>Capturing the world in motion</h2>
<p>While we cannot possibly imagine how ultraviolet appears to the animals who can perceive it, we can visualise it using false colour imagery. For example, for honeybees that are sensitive to three types of light (ultraviolet, blue and green), we can shift their perceivable colours into the human visible range such that ultraviolet is represented as blue, blue becomes green, and green becomes red.</p>
<p>Up until now, we could only apply this process to immobile objects. False colour photography relies on taking a series of photos through a succession of optic filters and subsequently overlaying them, and this sequential method means that everything must be in the exact same position in all the photos.</p>
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<a href="https://images.theconversation.com/files/571229/original/file-20240124-23-rt4qn2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A large butterfly in fluorescent orange and purple hues contrasted with a smaller yellow version of the same image." src="https://images.theconversation.com/files/571229/original/file-20240124-23-rt4qn2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/571229/original/file-20240124-23-rt4qn2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/571229/original/file-20240124-23-rt4qn2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/571229/original/file-20240124-23-rt4qn2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/571229/original/file-20240124-23-rt4qn2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/571229/original/file-20240124-23-rt4qn2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/571229/original/file-20240124-23-rt4qn2.jpg?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"></a>
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<span class="caption">A museum specimen of <em>Phoebis philea</em> seen using false colour imaging.</span>
<span class="attribution"><a class="source" href="https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3002444#sec014">Vasas et al. (2024) PLOS Biology</a></span>
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<p>This is a serious drawback. It makes for a laborious process which sets the limit on the number of objects that can be realistically imaged. For example, taking photos of an iridescent peacock feather from a hundred different angles would require screwing on and off each filter a hundred times.</p>
<p>Even worse, all movement-related information is discarded. Yet the living world is in constant motion: trees sway in the wind, leaves flutter, birds hop along branches looking for insects that scutter in the undergrowth. We needed a way to be able to visualise all this movement.</p>
<p>The first challenge was to devise a camera that records in ultraviolet and visible light simultaneously. The solution turned out to be a beam splitter. This specialised piece of optical equipment reflects ultraviolet light as if it was a mirror, but allows visible light to pass through, just like clear glass. </p>
<p>We positioned two cameras (nothing too fancy, the same kind you can buy in shops and online, but with one modified to record in ultraviolet) in a 3D-printed casing, such that the modified camera received reflected ultraviolet light while a stock camera received transmitted visible light. We overlayed and synchronised the recordings of these two cameras, and a series of conversion steps allowed us to calculate the amount of light that had reached each camera’s sensors. </p>
<p>From this, we could estimate the amount of light that would have been captured by an animal’s eye if it were seeing the scene from the vantage point of our camera.</p>
<iframe src="https://widgets.figshare.com/articles/25049583/embed?show_title=1" width="100%" height="351" allowfullscreen="" frameborder="0"></iframe>
<h2>Try it yourself</h2>
<p>We have made all <a href="https://github.com/hanleycolorlab/video2vision">codes</a> necessary for implementing the video conversions and the <a href="https://gitlab.com/multispectrum-beamsplitter">plans</a> of the camera system freely available online, along with our best attempt to explain how to build the camera from scratch. </p>
<p>Our goal is for other researchers to build their own cameras and to use them to answer their own questions about how other species see the world. There are so many possibilities. </p>
<p>We can record the dances of peacocks and see how dazzling their feathers appear to peahens. The iridescence of these feathers extends into the ultraviolet – our recordings show the feathers appear even more colourful for their target audience than to us.</p>
<p>We can accurately describe how the startle displays of caterpillars appear to their bird predators, and understand why the unexpected flash of colourful patterns scares them away. We can ask questions about how animals move between spots on the forest floor to show off or hide their colours. </p>
<p>We can also create image records of butterflies and other insects held in museum collections and offer animal-view conversions as part of a digital library. And we can ensure glass facades are sufficiently visible to birds who might <a href="https://theconversation.com/billions-of-birds-collide-with-glass-buildings-but-architecture-has-solutions-215419">otherwise collide with them</a>.</p>
<p>But the most exciting questions will be those we have yet to consider. Only now that we have started taking videos of the natural world in colours that animals see are we beginning to notice how much information is out there. Discoveries await you in your own backyard.</p>
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<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">
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<p class="fine-print"><em><span>Daniel Hanley received funding from the National Geographic Society.</span></em></p><p class="fine-print"><em><span>Vera Vasas 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>Humans can’t see ultraviolet light – but lots of other animals can.Vera Vasas, Research Fellow in Ecology and Evolution, University of SussexDaniel Hanley, Assistant Professor, George Mason UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2145842023-10-03T23:06:07Z2023-10-03T23:06:07ZFrom glowing cats to wombats, fluorescent mammals are much more common than you’d think<p>Recently, several mammals have been reported to “glow” under ultraviolet (UV) light, including our beloved platypus. But no one knew how common it was among mammals until now.</p>
<p>Our research, published <a href="https://royalsocietypublishing.org/doi/10.1098/rsos.230325">in Royal Society Open Science today</a>, found this glow – known as fluorescence – is extremely common. Almost every mammal we studied showed some form of fluorescence.</p>
<p>We also examined the glow to determine if it was really fluorescence and not some other phenomenon. Then, we tested if the fluorescence we observed in museum specimens was natural and not caused by preservation methods.</p>
<p>We also searched for links between the type and degree of fluorescence and the lifestyle of each species, to gain insights on whether there are any benefits to glowing under UV if you’re a mammal.</p>
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<h2>Nightclub lights</h2>
<p>Nightclub visitors will be familiar with white clothes, or perhaps their gin and tonic, glowing blue under UV light. This is a great example of fluorescence – when the energy from UV light, which is a form of electromagnetic radiation invisible to humans, is absorbed by certain chemicals. </p>
<p>These chemicals then emit visible light, which is lower-energy electromagnetic radiation. In the case of gin and tonic, this is due to the presence of the quinine molecule in the tonic water. </p>
<p>In the case of animals, this can be due to proteins or pigments in their scales, skin or fur. Fluorescence is quite common among animals. It <a href="https://royalsocietypublishing.org/doi/full/10.1098/rstb.2016.0335?rss=1">has been reported</a> for birds, reptiles, amphibians, fish, corals, molluscs and most famously scorpions and other arthropods.</p>
<p>However, it has been described less frequently in mammals, although recent studies have provided several examples. We already knew that bones and teeth glow with fluorescence, as do white human hair and nails. Some rodents have a pink glow under UV light and platypuses <a href="https://www.degruyter.com/document/doi/10.1515/mammalia-2020-0027/html">glow blue-green</a>. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-is-the-electromagnetic-spectrum-8046">Explainer: what is the electromagnetic spectrum?</a>
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<a href="https://images.theconversation.com/files/551604/original/file-20231003-19-ee6wee.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A glowing blue drink on a table in a dark restaurant" src="https://images.theconversation.com/files/551604/original/file-20231003-19-ee6wee.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/551604/original/file-20231003-19-ee6wee.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/551604/original/file-20231003-19-ee6wee.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/551604/original/file-20231003-19-ee6wee.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/551604/original/file-20231003-19-ee6wee.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/551604/original/file-20231003-19-ee6wee.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/551604/original/file-20231003-19-ee6wee.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&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 reason a gin and tonic looks fluorescent under UV lighting is thanks to the quinine in the tonic.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Glowing_cocktail.jpg">Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<h2>How often do mammals glow?</h2>
<p>Our team came together because we were curious about fluorescence in mammals. We wanted to know if the glow reported recently for various species was really fluorescence, and how widespread this phenomenon was. We obtained preserved and frozen specimens from museums and wildlife parks to study.</p>
<p>We started with the platypus to see if we could replicate the previously reported fluorescence. We photographed preserved and frozen platypus specimens under UV light and observed a fluorescent (although rather faint) glow.</p>
<p>To make sure it was fluorescence and not some other effect that looked like it, we used a technique called fluorescence spectroscopy. </p>
<p>This involved shining various sources of light at the samples and recording the specific “fingerprints” of the resulting glow, known as an <a href="https://www.britannica.com/science/spectrum#ref11393">emission spectrum</a>. This way, we could confirm what we saw was indeed fluorescence.</p>
<p>We repeated this process for other mammals and found clear evidence of fluorescence in the white fur, spines and even skin and nails of koalas, Tasmanian devils, short-beaked echidnas, southern hairy-nosed wombats, quendas (bandicoots), greater bilbies and even cats.</p>
<p>Both fresh-frozen and chemically treated museum specimens were fluorescent. This meant it wasn’t preservation chemicals such as borax or arsenic causing the fluorescence. So, we concluded this was a real biological phenomenon. </p>
<h2>Mammals in dazzling lights</h2>
<p>Using specimens from the Western Australian Museum’s collection, we took the experiment to the next stage. We recorded every species of mammal that was fluorescent when we exposed the specimens to UV light.</p>
<p>As a result, we found 125 fluorescent species of mammal, representing all known orders. Fluorescence is clearly common and widely distributed among mammals.</p>
<p>In particular, we noticed that white and light-coloured fur is fluorescent, with dark pigmentation preventing fluorescence. For example, a zebra’s white stripes fluoresced while the dark stripes didn’t.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/zebras-stripes-are-a-no-fly-zone-for-flies-111888">Zebra's stripes are a no fly zone for flies</a>
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</em>
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<hr>
<p>We then used our dataset to test if fluorescence might be more common in nocturnal species. To do this, we correlated the total area of fluorescence with ecological traits such as nocturnality, diet and locomotion.</p>
<p>Nocturnal mammals were indeed more fluorescent, while aquatic species were less fluorescent than those that burrowed, lived in trees, or on land. </p>
<p>Based on our results, we think fluorescence is very common in mammals. In fact, it is likely the default status of hair unless it is heavily pigmented. This doesn’t mean fluorescence has a biological function – it may just be an artefact of the structural properties of unpigmented hair.</p>
<p>However, we suggest florescence may be important for brightening pale-coloured parts of animals that are used as visual signals. This could improve their visibility, especially in poor light – just like the fluorescent optical brighteners that are added to white paper and clothing.</p><img src="https://counter.theconversation.com/content/214584/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kenny Travouillon received funding from the Australian Biological Resources Study and is an adjunct at Curtin University. </span></em></p><p class="fine-print"><em><span>Christine Elizabeth Cooper receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Jemmy Bouzin receives funding from the Government of Seychelles. </span></em></p><p class="fine-print"><em><span>Linette Umbrello receives funding from the Australian Biological Resources Study and is a Research Associate at the Western Australian Museum. </span></em></p><p class="fine-print"><em><span>Simon Lewis 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>After combing through museum collections, our team of researchers found a whopping 125 fluorescent mammal species – from polar bears and dolphins, to leopards, zebras and wombats.Kenny Travouillon, Curator of Mammals, Western Australian MuseumChristine Elizabeth Cooper, Senior Lecturer, Curtin UniversityJemmy Bouzin, PhD candidate, Curtin UniversityLinette Umbrello, Postdoctoral research associate, Queensland University of TechnologySimon Lewis, Professor of Forensic and Analytical Chemistry, Curtin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2124202023-09-04T17:37:53Z2023-09-04T17:37:53ZDogs don’t see life through rose-coloured glasses, nor in black and white<p>For a few months now, I’ve been treating six-year-old Samuel, who has the beginnings of myopia. He’s very quick for his age and often asks me questions about tests I give him, and about what I see inside his eyes. </p>
<p>But the last question surprised me. </p>
<p>Samuel knows that some people, like his father, don’t see colours well. But what about his little poodle, Scotch, he asked?</p>
<p>I’m not a veterinarian and don’t want to intrude on their domain of expertise. However, as an optometrist, I can offer some insights that might help answer Samuel’s question. </p>
<h2>Cones and rods</h2>
<p>Ambient light is composed of <a href="https://www.britannica.com/science/photon">particles (photons)</a>, which line up in rays. Light rays travel and strike objects. Some rays are absorbed, while others are reflected, depending on the characteristics of their surfaces and the composition of their materials. The wavelengths of the reflected rays determine the colour of the object as it is perceived by the eye. </p>
<p>Like everything about human vision, colour perception is complex. The retina, the sensitive part that lines the back of the eye, has two types of photon receptors: cones and rods. The cones, in the centre of the retina (fovea), perceive bright light and are <a href="https://askabiologist.asu.edu/rods-and-cones">responsible for colour perception</a>.</p>
<p>There are three types of cones. Each type contains a specific photo-pigment called opsin, which defines its nature. The opsin is produced under the influence of specific genes. The shortest opsin (“Cone S” for <em>short</em>) reacts mainly to blue light (420 nm). The longer one (“Cone L”) is more sensitive to orange-red light (560 nm) and the one in between (“Cone M” for <em>middle</em>) <a href="https://opentextbc.ca/biology/chapter/17-5-vision/">is activated in the presence of green (530 nm)</a>.</p>
<p>However, each cone reacts to each of the rays entering the eye. For example, a red ball will produce a weak response from the S cone (3/10), a slightly stronger response from the M cone (5/10) and a <a href="https://opentextbc.ca/biology/chapter/17-5-vision/">strong response from the L cone</a> (8/10). </p>
<p>The brain combines the signals emitted by each of these cones to form the colour it perceives. So, in the previous example, the perceived colour would be coded 3-5-8, corresponding to what we know as red. A pink colour might have the code 4-6-6, and blue, 8-6-3. Each combination of the 3-cone signals is unique, which allows us to appreciate different hues in all their variations. </p>
<p>That is, as long as the genetic code is intact. </p>
<p>The genes associated with colour vision can be mutated or defective, in which case the person will be partially or completely impaired. The best known of these anomalies is colour blindness (red-green deficiency or daltonism).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/544341/original/file-20230823-249-j6j8jf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="perception of a plant according to a colour-blind person" src="https://images.theconversation.com/files/544341/original/file-20230823-249-j6j8jf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/544341/original/file-20230823-249-j6j8jf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=331&fit=crop&dpr=1 600w, https://images.theconversation.com/files/544341/original/file-20230823-249-j6j8jf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=331&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/544341/original/file-20230823-249-j6j8jf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=331&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/544341/original/file-20230823-249-j6j8jf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=415&fit=crop&dpr=1 754w, https://images.theconversation.com/files/544341/original/file-20230823-249-j6j8jf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=415&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/544341/original/file-20230823-249-j6j8jf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=415&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Colour blindness is associated with difficulty in perceiving red and green.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
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<h2>And what about animals?</h2>
<p>Colour vision, in humans as in animals, <a href="https://www.discoverwildlife.com/animal-facts/animal-vision-how-do-animals-see/">has developed throughout evolution</a> and results from the needs of each species according to their environment, the prey they hunt and the threats they need to avoid.</p>
<p>For example, birds have a fourth opsin that allows them to see ultraviolet (UV) light. Humans cannot perceive this light because our crystalline (internal) lens <a href="https://www.nwf.org/Magazines/National-Wildlife/2012/AugSept/Animals/Bird-Vision">filters UV rays</a>. UV rays influence birds’ behavioural decisions, including foraging and <a href="https://www.sciencedirect.com/science/article/abs/pii/S0065345408601059#:%7E:text=Publisher%20%20Summary,light%2C%20depending%20on%20the%20species.">their choice of a mate</a>.</p>
<p>So the colour vision of birds is more complex, with the result that the pigeon, which can perceive a myriad of colours, wins the <a href="https://nuscimagazine.com/the-world-through-the-eyes-of-a-pigeon/#:%7E:text=Though%20this%20range%20of%20vision,is%20one%20of%20these%20animal">award for best color vision among all species</a>.</p>
<p>Insects also perceive UV light. This function is essential for them to spot pollen, although their colour vision is very poor. Their eyes are made up of multiple lenses (ommatidia) that perceive <a href="https://www.mpg.de/14337047/how-flies-see-the-world">more movement than colour</a>. That’s much more practical while in fast flight.</p>
<p>Most forest-dwelling mammals have only two opsins. That’s because they lost the one associated with orange-red over the course of evolution. This explains why, unlike humans, these animals don’t perceive the orange bibs of hunters. </p>
<p>Snakes, on the other hand, are more sensitive to red and infrared light, thanks to their infrared receptors. This is an advantage when it comes to spotting prey, as <a href="https://phys.org/news/2006-08-snakes-vision-enables-accurate-prey.html">they can distinguish their heat even at night</a>. </p>
<p>Unsurprisingly, it’s the monkey that’s closest to the human, with its three opsins. It is said to be trichromatic. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/544344/original/file-20230823-19-pd8rjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="close-up of a black dog's eyes" src="https://images.theconversation.com/files/544344/original/file-20230823-19-pd8rjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/544344/original/file-20230823-19-pd8rjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/544344/original/file-20230823-19-pd8rjz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/544344/original/file-20230823-19-pd8rjz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/544344/original/file-20230823-19-pd8rjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/544344/original/file-20230823-19-pd8rjz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/544344/original/file-20230823-19-pd8rjz.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">Dogs only perceive yellow-green and violet-blue. Colours are perceived as paler, like pastels.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<h2>Back to Scotch</h2>
<p>The vision of dogs — such as our friend Scotch — is <a href="https://ophtalmoveterinaire.com/maladies_oculaires/vision-comment-voit-mon-chien/#:%7E:text=For%20r%C3%A9sumer%2C%20the%20vision%20of,for%20his%20life%20of%20dog.">quite different</a>. </p>
<p>Unlike humans, dogs’ eyes are located on the side of the skull. As a result, dogs have a wider field of vision (250 to 280 degrees), but less simultaneous vision. </p>
<p>So Scotch’s vision of movement is well developed throughout his visual field. But his central vision is actually six times weaker than ours. This is equivalent to the vision of a very myopic person not wearing glasses. Why? Because the dog’s retina contains no fovea, and therefore fewer cones. </p>
<p>But while dogs eyes have fewer cones, they have more rods. And as an added bonus, they have an extra layer of the retina, called the tapetum lucidum — or carpet. When combined, these ingredients mean dogs see better in dim light and at night. This layer receives light and reflects it back onto the retina for a second exposure. This explains why your dog’s eyes seem to glow at night.</p>
<p>When it comes to colours, dogs are dichromats. They perceive only yellow-green and violet-blue. Colours are perceived paler, like pastels. And some colours don’t contrast: that’s why a red ball on green grass will appear to them as pale yellow on a grey background, with little contrast.</p>
<p>So it’s possible, depending on the colour of the ball, that Scotch will not see it, and as a result, will gaze up at Samuel with a lost look. As for the infrared, he perceives heat through his nose, not through his eyes.</p>
<p>Cats are also dichromats. Their vision is therefore similar to that of dogs, but their colour palette is different — more oriented towards violet and green. Having no perception of red-green, they are essentially colour-blind. They are also very short-sighted. Their clear vision is limited to a few meters in front of them.</p>
<p>Throughout cats’ evolution, other senses came to compensate for this. Among other things, although they only perceive certain contrasts, they are <a href="https://www.wired.com/2013/10/cats-eye-view/">formidable at perceiving movement</a>. Mice move quickly! </p>
<p>Every species adapts to its environment, and humans are no exception. Who knows what our colour vision will be like 500 years from now, after we’ve been exposed to more and more electronic devices and artificial colours? </p>
<p>But that’s a question for Samuel to answer when he’s older.</p><img src="https://counter.theconversation.com/content/212420/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>Your faithful companion sees the world differently than you do, but it’s a mistake to assume dogs only see black, white and shades of grey.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/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>
<figure class="align-center zoomable">
<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>
<figcaption>
<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>
</figcaption>
</figure>
<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>
<figure class="align-center zoomable">
<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>
<figcaption>
<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>
</figcaption>
</figure>
<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>
<figure>
<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>
</figure>
<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/1989802023-02-02T02:43:56Z2023-02-02T02:43:56ZThis strange donkey orchid uses UV light to trick bees into thinking it has food<figure><img src="https://images.theconversation.com/files/507764/original/file-20230202-1153-nnxcj.jpeg?ixlib=rb-1.1.0&rect=119%2C12%2C1867%2C1278&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://inaturalist.ala.org.au/observations/86142077">Stephen Buckle/iNaturalist</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>If you’ve ever compared a frozen pizza to the photo on the box, you know the feeling of being duped by appetising looks.</p>
<p>In <a href="https://onlinelibrary.wiley.com/doi/10.1002/ece3.9759">our latest study</a> we show that animals – in this case, bees – are also prone to being tricked into making poor decisions, which explains a lot about how gaps in perception are exploited in nature.</p>
<p>When Charles Darwin was testing the theory of evolution 150 years ago, he looked at the interaction between flowering plants and the animals that forage to collect nectar.</p>
<p>This helped establish that flowers have adaptations to promote easier pollinator access, making it beneficial for the animal who gets a food “reward” from them. At the same time, it means the <a href="https://en.wikipedia.org/wiki/Fertilisation_of_Orchids">plants get pollinated and can reproduce</a>. </p>
<p>One perplexing problem is some flowering plants that reproduce by pollination are non-rewarding – the animal doesn’t get nectar from visiting the flower. This is true of <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/plb.13113">certain orchids</a>, yet these flowers are still visited by pollinators and survive well in nature.</p>
<h2>A mistaken identity</h2>
<p>With the benefit of modern scientific tools like a spectrophotometer that measures the amount of colour, <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0096646">digital ultraviolet (UV) photography</a> and computer modelling of how bees see the world, our international team set out to understand how some orchids have evolved dazzling floral displays.</p>
<p>Our chosen species was the winter donkey orchid (<em>Diuris brumalis</em>), <a href="https://florabase.dpaw.wa.gov.au/browse/profile/12943">endemic to Western Australia</a>. This non-rewarding, food deceptive plant blooms at the same time as rewarding native pea plants (<em>Daviesia</em>). </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/507769/original/file-20230202-17-45084q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A yellow flower with two large petals on top and a similar orange flower next to it" src="https://images.theconversation.com/files/507769/original/file-20230202-17-45084q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507769/original/file-20230202-17-45084q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507769/original/file-20230202-17-45084q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507769/original/file-20230202-17-45084q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507769/original/file-20230202-17-45084q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507769/original/file-20230202-17-45084q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507769/original/file-20230202-17-45084q.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">A winter donkey orchid (left) and a prickly bitter-pea.</span>
<span class="attribution"><span class="source">Cal Wood/iNaturalist;
caitlind164/iNaturalist</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>As a result, native <em>Trichocolletes</em> bees appear to mistake the orchid for legume plants <a href="https://academic.oup.com/aob/article/122/6/1061/5088838">frequently enough</a> that the orchid gets pollinated.</p>
<p>We quantified the flower colour signals from both plants, revealing the main component of the visual information perceived by a bee was in the short wavelength UV region of the spectrum.</p>
<p>This made sense – while our vision sees blue, green and red wavelengths of light as primary colours, bees can see UV reflected light <a href="https://theconversation.com/our-bee-eye-camera-helps-us-support-bees-grow-food-and-protect-the-environment-110022">but lack a channel for perceiving primary red</a>.</p>
<p>By using computer models of bee pollinator perception, we observed the orchid mimic species and the native pea plant species did actually look similar in colour to bees.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/507759/original/file-20230202-3738-nxfh9e.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A chart showing two images of flowers, a larger yellow one and a smaller one, with graphs next to them" src="https://images.theconversation.com/files/507759/original/file-20230202-3738-nxfh9e.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507759/original/file-20230202-3738-nxfh9e.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=362&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507759/original/file-20230202-3738-nxfh9e.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=362&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507759/original/file-20230202-3738-nxfh9e.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=362&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507759/original/file-20230202-3738-nxfh9e.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=455&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507759/original/file-20230202-3738-nxfh9e.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=455&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507759/original/file-20230202-3738-nxfh9e.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=455&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Flower shape and colour properties of an orchid (upper row) and a native pea flower (lower row) shown in the field, as individual flowers, and with spectral measurements.</span>
<span class="attribution"><a class="source" href="https://onlinelibrary.wiley.com/doi/10.1002/ece3.9759">Scaccabarozzi et al., 2023</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Putting a UV block on flowers</h2>
<p>What was surprising, however, was the non-rewarding orchid flowers – pollinated by deception – actually have more conspicuous advertising for bee vision.</p>
<p>For example, the main display outer flower petals were significantly larger on the orchid plants, and also produced a stronger UV colour signal.</p>
<p>To understand if such signalling was biologically relevant, we next conducted field experiments with the plants. We used a special UV sun-blocking solution to remove the strong UV signals in half of the orchid species, whilst the other half retained their natural appearance.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/507760/original/file-20230202-1411-nxfh9e.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A row of colourful and greyscale images showing flowers next to a hexagonal chart" src="https://images.theconversation.com/files/507760/original/file-20230202-1411-nxfh9e.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/507760/original/file-20230202-1411-nxfh9e.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=235&fit=crop&dpr=1 600w, https://images.theconversation.com/files/507760/original/file-20230202-1411-nxfh9e.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=235&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/507760/original/file-20230202-1411-nxfh9e.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=235&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/507760/original/file-20230202-1411-nxfh9e.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=296&fit=crop&dpr=1 754w, https://images.theconversation.com/files/507760/original/file-20230202-1411-nxfh9e.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=296&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/507760/original/file-20230202-1411-nxfh9e.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=296&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 photographs of orchid flowers (upper left panel) in natural state and also with applied UV blocking screen. Middle panels show false-colour photographs of flower appearance for a bee, and right hand panel a computer model of how bee vision perceives flower colours.</span>
<span class="attribution"><a class="source" href="https://onlinelibrary.wiley.com/doi/10.1002/ece3.9759">Scaccabarozzi et al., 2023</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>At the completion of the field season, several months latter, we could measure which plants were more successfully pollinated by bees, revealing the strong UV signals had a significant role in promoting pollination in the orchids.</p>
<p>A second interesting finding of the field experiments was the distance between the pea flowers and their copycat orchids was a major factor in the success of the orchids’ deception strategy.</p>
<p>If the orchids with strong UV signals were within close proximity – a meter or two – to the rewarding native pea flowers, the deception was less successful and few orchid flowers were pollinated. However, if the deceptive orchids were about eight meters away from the rewarding model species, this produced the highest success rate in pollination.</p>
<h2>Why deception works</h2>
<p>It turns out a distance of about eight meters is important because of the way bee brains process colour. When bees see a pair of colours in close proximity, they can evaluate them at the same time. This leads to <a href="https://link.springer.com/article/10.1007/s00359-005-0622-z">very precise colour matching</a>. A similar process happens in human brains – we also have <a href="https://opg.optica.org/josa/abstract.cfm?uri=josa-47-1-43">to see colours at the same time</a>. </p>
<p>However, seeing colour stimuli with a time interval in between means the brain has to remember the first colour, inspect the second colour, and make a mental calculation about whether the two samples are indeed the same. </p>
<p>Neither bee brains, nor our own, are good at successive colour comparisons. This is why when we purchase paint for a repair job we take a sample to get a precise match, rather than try and remember what we thought the colour should look like.</p>
<p>Deceptive flowers are successful by exploiting this perceptual gap in how brains have to code information when bees need to fly several meters in search of more food.</p>
<p>By using a “look at me” strategy (essentially, better advertising than other plants) it is possible to survive in nature without actually offering a food reward to the pollinators. To do this, the plants need to be at an optimal distance from the plants they are mimicking. Not too close and not too far, and success is assured.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/like-finding-life-on-mars-why-the-underground-orchid-is-australias-strangest-most-mysterious-flower-144727">'Like finding life on Mars': why the underground orchid is Australia's strangest, most mysterious flower</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/198980/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Adrian Dyer receives funding from The Australian Research Council.</span></em></p><p class="fine-print"><em><span>Endeavor Fellowship Program grant ID 5117_2016 (Daniela Scaccabarozzi)
Templeton World Charity Foundation grant TWCF0541 (Monica Gagliano)</span></em></p>Orchids give nothing in return to pollinators, so how come they get visited by bees anyway? The answer is trickery and deceit.Adrian Dyer, Associate Professor, Monash UniversityDaniela Scaccabarozzi, Uppsala UniversityLicensed 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/1875592022-09-06T12:37:31Z2022-09-06T12:37:31ZHuman skin stood up better to the sun before there were sunscreens and parasols – an anthropologist explains why<figure><img src="https://images.theconversation.com/files/480836/original/file-20220824-4026-m7s9pf.jpg?ixlib=rb-1.1.0&rect=663%2C34%2C5087%2C3794&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The sun’s rays often feel good on your skin, but can cause serious damage.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/close-up-of-woman-against-sky-during-sunset-royalty-free-image/1340270649">Maksim Chernyshev/EyeEm via Getty Images</a></span></figcaption></figure><p>Human beings have a conflicted relationship with the sun. People love sunshine, but then get hot. Sweat gets in your eyes. Then there are all the protective rituals: the sunscreen, the hats, the sunglasses. If you stay out too long or haven’t taken sufficient precautions, your skin lets us you know with an angry sunburn. First the heat, then the pain, then the remorse.</p>
<p>Were people always this obsessed with what the sun would do to their bodies? <a href="https://scholar.google.com/citations?user=NIAvKr8AAAAJ&hl=en&oi=ao">As a biological anthropologist</a> who has studied primates’ adaptations to the environment, I can tell you the short answer is “no,” and they didn’t need to be. For eons, skin stood up to the sun.</p>
<h2>Skin, between you and the world</h2>
<p>Human beings evolved under the sun. Sunlight was a constant in people’s lives, warming and guiding them through the days and seasons. <em>Homo sapiens</em> spent the bulk of our prehistory and history outside, mostly naked. Skin was the primary interface between our ancestors’ bodies and the world.</p>
<p>Human skin was adapted to whatever conditions it found itself in. People took shelter, when they could find it, in caves and rock shelters, and got pretty good at making portable shelters from wood, animal skins and other gathered materials. At night, they huddled together and probably covered themselves with fur “blankets.” But during the active daylight hours, people were outdoors and their mostly bare skin was what they had.</p>
<p>During a person’s lifetime, <a href="https://medlineplus.gov/ency/anatomyvideos/000125.htm">skin responds to routine exposure to the sun</a> in many ways. The surface layer of the skin – the epidermis – <a href="https://newsinhealth.nih.gov/2014/07/sun-skin">becomes thicker by adding more layers of cells</a>. For most people, the skin becomes gradually darker as specialized cells kick into action to produce a <a href="https://my.clevelandclinic.org/health/body/22615-melanin">protective pigment called eumelanin</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/480838/original/file-20220824-12-e8zgi6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="cross-sectional diagram of skin's layers with sunlight hitting the surface and showing increased production of melanin" src="https://images.theconversation.com/files/480838/original/file-20220824-12-e8zgi6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/480838/original/file-20220824-12-e8zgi6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/480838/original/file-20220824-12-e8zgi6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/480838/original/file-20220824-12-e8zgi6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/480838/original/file-20220824-12-e8zgi6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/480838/original/file-20220824-12-e8zgi6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/480838/original/file-20220824-12-e8zgi6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Exposure to the sun’s rays triggers production of more protective eumelanin, which also darkens the skin’s appearance.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/tanning-process-skin-human-anatomy-royalty-free-illustration/645165034">ttsz/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<p>This remarkable molecule absorbs most visible light, causing it to look very dark brown, almost black. Eumelanin also absorbs damaging ultraviolet radiation. Depending on their genetics, people produce different amounts of eumelanin. Some have a lot and are able to produce a lot more when their skin is exposed to sun; others have less to start out with and produce less when their skin is exposed.</p>
<p><a href="https://scholar.google.com/citations?user=NIAvKr8AAAAJ&hl=en&oi=ao">My research on</a> <a href="https://doi.org/10.1111/pcmr.12976">the evolution of human skin pigmentation</a> has shown that the skin color of people in prehistory was tuned to local environmental conditions, primarily to local levels of ultraviolet light. People who lived under strong UV light – like you’d find near the equator – year in and year out had darkly pigmented and highly tannable skin capable of making a lot of eumelanin. People who lived under weaker and more seasonal UV levels – like you’d find in much of northern Europe and northern Asia – had lighter skin that had only limited abilities to produce protective pigment.</p>
<p>With only their feet to carry them, our distant ancestors didn’t move around much during their lives. Their skin adapted to subtle, seasonal changes in sunlight and UV conditions by producing more eumelanin and becoming darker in the summer and then losing some pigment in the fall and winter when the sun wasn’t so strong. Even for people with lightly pigmented skin, painful sunburns would have been exceedingly rare because there was never a sudden shock of strong sun exposure. Rather, as the sun strengthened during spring, the top layer of their skin would have gotten <a href="https://doi.org/10.1007/978-3-540-89656-2_60">gradually thicker over weeks and months of sun exposure</a>.</p>
<p>This is not to say that the skin would have been undamaged by today’s standards: Dermatologists would be appalled by the leathery and wrinkled appearance of the sun-exposed skin of our ancestors. Skin color, like the levels of sun itself, changed with the seasons and skin quickly showed its age. This is still the case for people who live traditional, mostly outdoor, lives in many parts of the world.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/479980/original/file-20220818-27-79ac87.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a squatting old man with weathered skin" src="https://images.theconversation.com/files/479980/original/file-20220818-27-79ac87.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/479980/original/file-20220818-27-79ac87.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/479980/original/file-20220818-27-79ac87.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/479980/original/file-20220818-27-79ac87.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/479980/original/file-20220818-27-79ac87.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/479980/original/file-20220818-27-79ac87.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/479980/original/file-20220818-27-79ac87.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">Chronic unprotected sun exposure can damage skin, with effects that look like those on this farmer in India.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:2020_Indian_farmers%27_protest_-_old_man_sitting.jpg">Randeep Maddoke/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>There is no preserved skin from thousands of years ago for scientists to study, but we can infer from the effects of sun exposure on modern people that the damage was similar. <a href="https://doi.org/10.1111/j.1365-2133.2009.09565.x">Chronic sun exposure</a> <a href="https://doi.org/10.1016/S1011-1344(01)00198-1">can lead to skin cancer</a>, but rarely of the variety – <a href="https://doi.org/10.1016/j.bjps.2006.05.008">melanoma</a> – that would cause death during reproductive age.</p>
<h2>Indoor living changed skin</h2>
<p>Until around 10,000 years ago – a drop in the bucket of evolutionary history – human beings made their living by <a href="https://www.history.com/topics/pre-history/hunter-gatherers">gathering foods, hunting and fishing</a>. Humanity’s relationship with the sun and sunlight changed a lot after people started to settle down and live in permanent settlements. <a href="https://www.smithsonianmag.com/history/the-seeds-of-civilization-78015429/">Farming and food storage</a> were associated with the development of immovable buildings. By around 6000 B.C. many people throughout the world were spending more time in walled settlements, and more time indoors.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/480840/original/file-20220824-4729-j9lpxl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="line drawing of royal bearded man followed by two smaller men with parasol and fly whisk" src="https://images.theconversation.com/files/480840/original/file-20220824-4729-j9lpxl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/480840/original/file-20220824-4729-j9lpxl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1019&fit=crop&dpr=1 600w, https://images.theconversation.com/files/480840/original/file-20220824-4729-j9lpxl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1019&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/480840/original/file-20220824-4729-j9lpxl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1019&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/480840/original/file-20220824-4729-j9lpxl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1281&fit=crop&dpr=1 754w, https://images.theconversation.com/files/480840/original/file-20220824-4729-j9lpxl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1281&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/480840/original/file-20220824-4729-j9lpxl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1281&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Persian King Darius the Great, who lived more than 2,500 years ago, is portrayed being shielded from the sun.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/king-darius-the-great-followed-by-his-royalty-free-illustration/1367186124">Luisa Vallon Fumi/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<p>While most people still spent most of their time outside, some stayed indoors if they could. Many of them <a href="https://www.folkwear.com/blogs/news/historyoftheparasol">started protecting themselves from the sun</a> when they did go out. By at least 3000 B.C., a whole industry of sun protection grew up to create gear of all sorts – parasols, umbrellas, hats, tents and clothing – that would protect people from the discomfort and inevitable darkening of the skin associated with lengthy sun exposure. While some of these were originally reserved for nobility – like the parasols and umbrellas of ancient Egypt and China – these luxury items <a href="https://doi.org/10.1007/s11199-017-0785-4">began to be made</a> and <a href="https://doi.org/10.1080/17532523.2016.1281875">used more widely</a>.</p>
<p>In some places, people even developed <a href="https://doi.org/10.1371/journal.pone.0136090">protective pastes made out of minerals</a> and plant residues – <a href="https://doi.org/10.1111/jocd.14004">early versions of modern sunscreens</a> – to protect their exposed skin. Some, like the <a href="https://www.scmp.com/lifestyle/fashion-beauty/article/3100999/all-natural-sunscreen-and-beauty-product-thanaka-paste-has">thanaka paste used by people in Myanmar</a>, still persists today.</p>
<p>An important consequence of these practices in traditional agricultural societies was that people who spent most of their time indoors considered themselves privileged, and their lighter skin announced their status. A “farmer’s tan” was not glamorous: <a href="https://www.ucpress.edu/book/9780520283862/living-color">Sun-darkened skin was a penalty associated with hard outdoor work</a>, not the <a href="https://doi.org/10.2105/AJPH.2008.144352">badge of a leisurely vacation</a>. From Great Britain to China, Japan and India, suntanned skin became associated with a life of toil.</p>
<p>As people have moved around more and faster over longer distances in recent centuries, and spend more time indoors, their skin hasn’t caught up with their locations and lifestyles. Your levels of eumelanin probably aren’t perfectly adapted to the sun conditions where you live and so aren’t able to protect you the same way they might have your ancient ancestors.</p>
<p>Even if you’re naturally darkly pigmented or capable of tanning, everyone is susceptible to <a href="https://doi.org/10.1001/jamadermatol.2017.4201">damage caused by episodes of sun exposure</a>, especially after long breaks spent completely out of the sun. The “vacation effect” of sudden strong UV exposure is really bad because a sunburn signals damage to the skin that is never completely repaired. It’s like a bad debt that presents itself as prematurely aged or precancerous skin many years later. There is no healthy tan – a tan doesn’t protect you from further sun damage, it’s the sign of damage itself.</p>
<p>People may love the sun, but we’re not our ancestors. Humanity’s relationship with the sun has changed, and this means changing your behavior to save your skin.</p><img src="https://counter.theconversation.com/content/187559/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nina G. Jablonski consults for L'Oreal and has received funding from the National Science Foundation, The Leakey Foundation, The Wenner-Gren Foundation, The Robert Wood Johnson Foundation, and The Rockefeller Foundation.</span></em></p>Our ancient ancestors didn’t have clothes or houses – but that constant exposure to the sun helped their skin protect itself from the worst sun damage.Nina G. Jablonski, Evan Pugh University Professor of Anthropology, Penn StateLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1865392022-07-20T12:21:28Z2022-07-20T12:21:28ZIt’s a myth that sunscreen prevents melanoma in people of color – a dermatologist explains<p>Melanoma is a potentially deadly form of skin cancer that effects people of every racial and ethnic group. The risk factor most closely linked to developing melanoma is exposure to ultraviolet, or UV, rays from the sun. In fact, sunburns have been associated with <a href="https://doi.org/10.1016/j.ejca.2004.10.016">doubling one’s risk of melanoma</a>. </p>
<p>Sunscreen can block UV rays and therefore reduce the risk of sunburns, which ultimately may reduce the risk of developing melanoma. Thus, the promotion of sunscreen as an effective melanoma prevention strategy is a <a href="https://doi.org/10.1111/ijd.12606">reasonable public health message</a>. </p>
<p>But while this may be true for light-skinned people, such as <a href="https://doi.org/10.1200/JCO.2010.28.7078">individuals of European descent</a>, this is not the case for darker-skinned people, such as individuals of African or Asian descent.</p>
<p>The public health messages <a href="https://doi.org/10.1016/j.jaad.2013.11.038">promoted by many clinicians</a> and <a href="https://www.skincancer.org/prevention/skin-cancer-and-skin-of-color">public health groups</a> regarding sunscreen recommendations for dark-skinned people is not supported by the available evidence. <a href="https://www.npr.org/sections/codeswitch/2018/07/05/559883985/will-your-melanin-protect-you-from-the-sun">Media messaging</a> exacerbates the problem with <a href="https://www.usatoday.com/story/life/health-wellness/2022/06/14/dermatologists-poc-sunscreen/7609507001/">headline</a> after <a href="https://news.yahoo.com/black-does-crack-expert-approved-201834873.html">headline</a> warning that Black people <a href="https://www.bbc.com/news/health-62155509">can also develop melanoma</a> and that Black people are not immune. </p>
<p>To be sure, they can get melanoma, but the risk is very low. In the same way, <a href="https://seer.cancer.gov/statistics-network/explorer/application.html?site=55&data_type=1&graph_type=2&compareBy=sex&chk_sex_3=3&chk_sex_2=2&rate_type=1&race=1&age_range=1&stage=101&advopt_precision=1&advopt_show_ci=on&advopt_display=1">men can develop breast cancer</a>, however, we do not promote mammography as a strategy to fight breast cancer in men.</p>
<p>This message is important to me <a href="https://dellmed.utexas.edu/directory/ade-adamson">as a Black board-certified dermatologist and health services researcher</a> at Dell Medical School at the University of Texas at Austin, where I am director of the pigmented lesion clinic. In this capacity I take care of patients at high risk for melanoma.</p>
<h2>Melanoma in Black people is not associated with UV exposure</h2>
<p>In the U.S., melanoma is <a href="https://seer.cancer.gov/statistics-network/explorer/application.html?site=53&data_type=1&graph_type=2&compareBy=race&chk_race_9=9&chk_race_8=8&rate_type=2&sex=1&age_range=1&stage=101&advopt_precision=1&advopt_show_ci=on&hdn_view=1&advopt_display=1">30 times more common</a> among white people than Black people. </p>
<p>In Black people, melanoma usually develops in parts of the body that are not exposed to the sun, such as the palms of the hands and soles of the feet. These cancers are called “acral melanomas,” and sunscreen will do nothing to reduce the risk of these cancers.</p>
<p>When was the last time you had a sunburn on the palms or soles? Even among white people, <a href="https://doi.org/10.1111/j.1365-2133.2006.07368.x">there is no relationship</a> between sun exposure and the risk of acral melanomas. Famously, <a href="http://dx.doi.org/10.1111/pcmr.12279">Bob Marley died from an acral melanoma</a> on his big toe, but sunscreen would not have helped. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/P7ORgp8007U?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The rare form of skin cancer that killed Bob Marley is thought to be caused by an injury or trauma.</span></figcaption>
</figure>
<p>Last year my research group <a href="https://doi.org/10.1001/jamadermatol.2020.4616">conducted a systematic review</a> in which we analyzed all of the published medical literature related to UV exposure and melanoma in people of color. This includes those of African, Asian, Pacific Islander, Indigenous and Hispanic descent. Of the 13 studies that met our criteria for inclusion, 11 showed no association between UV exposure and melanoma. </p>
<p>Among the two studies that showed an association, one study showed a positive <a href="https://doi.org/10.1001/archderm.140.7.819">association between melanoma and UV exposure in Black men</a>. But that same study also examined UV exposure and melanoma in other groups, including Black women, white men and women and Hispanic men and women. In these other groups the researchers found no association between UV exposure and melanoma. This is a surprising result, given that white people are the group in which the association between UV exposure and melanoma has been consistently demonstrated, calling into question the validity of the study results. </p>
<p>The other study showing an association between UV and melanoma <a href="https://doi.org/10.3892/or.2011.1164">was among Hispanic men in Chile</a> based on latitude within the country. A major caveat to this study is that the city with the highest number of melanomas is also home to a large population of Chileans of Croatian descent, who would not be considered people of color.</p>
<p>Unfortunately, none of these studies measured melanin concentrations of individuals, so it is not possible to know whether theoretically lighter-skinned people of color may be at risk for UV-associated melanoma. However, even in light-skinned East Asian individuals, there is no evidence that UV exposure is linked to melanoma.</p>
<p>The bottom line is that the link between UV exposure and melanoma in people of color has been studied many times over and has yielded little to no evidence of a connection.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/274103/original/file-20190513-183089-143tn1g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/274103/original/file-20190513-183089-143tn1g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/274103/original/file-20190513-183089-143tn1g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/274103/original/file-20190513-183089-143tn1g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/274103/original/file-20190513-183089-143tn1g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/274103/original/file-20190513-183089-143tn1g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/274103/original/file-20190513-183089-143tn1g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Darker skin provides more protection from damage by the ultraviolet rays of the sun.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/happy-african-american-family-father-son-116979724?src=8lZJLe5GKU-Gie1opBfdOA-1-17">Spotmatik/Shutterstock.com</a></span>
</figcaption>
</figure>
<h2>Racial disparities in melanoma outcomes are not related to UV exposure</h2>
<p>Many dermatologists often point out that Black patients tend to show up to the doctor <a href="https://doi.org/10.1016/j.jaad.2016.06.006">with later-stage melanoma</a>, which is true. However, this is an issue of access and awareness and has nothing to do with sunscreen application or protection from the sun. Black people should be aware of growths on their skin and seek medical attention if they have any changing, bleeding, painful or otherwise concerning spots, particularly on the hands and feet. </p>
<p>However, the notion that regular application of daily sunscreen will reduce an already extremely rare occurrence is nonsensical. </p>
<p>UV radiation does affect dark skin and can cause DNA damage; however, the damage <a href="https://doi.org/10.1096/fj.02-0865fje">is seven to eight times lower</a> than the damage done to white skin, given the natural sun-protective effect of increased melanin in darker skin. </p>
<p>To be clear, using regular sunscreen may help with reducing other effects of the sun’s rays such as sunburns, wrinkling, photoaging and freckling, which are all positive. But for the average Black person, sunscreen is unlikely to reduce their low risk of melanoma any further.</p>
<p>If sunscreen were important in the prevention of melanoma in dark-skinned patients, then why have we never heard of an epidemic of melanoma in sub-Saharan Africa, a region with intense sun, a lot of Black people and little sunscreen? </p>
<p>In certain subpopulations of Black people, such as those with disorders causing sun sensitivity, or patients with albinism – a condition in which people produce little or no melanin – or those with suppressed immune systems, sunscreen use may reduce risk of melanoma. But if you don’t fall into one of these categories, any meaningful risk reduction from the application of sunscreen is unlikely.</p>
<h2>One-size-fits-all public health messaging misses the mark</h2>
<p>Many dermatology and skin cancer-focused organizations – a few of which I belong to – promote the public health message of sunscreen use to reduce melanoma risk among Black patients. However, this message is not supported by evidence. There exists no study that demonstrates sunscreen reduces skin cancer risk in Black people. Period.</p>
<p>This issue of regular sunscreen use in Black people was made even more pressing after the release of two recent studies on <a href="https://doi.org/10.1001/jamadermatol.2022.0263">sunscreen absorption</a> in the <a href="https://doi.org/10.1001/jama.2019.20747">Journal of the American Medical Association</a>. This study showed that significant amounts of certain chemical sunscreen ingredients can get in the blood when used at <a href="https://twitter.com/AdeAdamson/status/1125522416837517312">maximal conditions</a>, with unknown impacts on human health. </p>
<p>To me, the most shocking part of the studies were that most of the participants were Black, the group least likely to derive any meaningful associated health benefits from sunscreen, while being exposed to potentially harmful levels of chemicals.</p>
<p>As dermatologists and public health advocates, we can improve how we educate patients and the public about melanoma prevention without promoting public health messages that are <a href="https://www.instagram.com/tv/BxPUuGUFR6X/?utm_source=ig_share_sheet&igshid=1jqzljkns187e">grounded in fear</a> and lack evidence. Black people should be informed that they are at risk of developing melanoma, but that <a href="https://doi.org/10.1001/jamadermatol.2021.2215">risk is low</a>.</p>
<p>Any dark-skinned person who develops a new, changing or symptomatic mole should see a doctor, particularly if the mole is on the palms or soles. We don’t know what the risk factors are for melanoma in Black or dark-skinned people, but they certainly are not UV rays. </p>
<p><em>This is an updated version of a piece that was <a href="https://theconversation.com/sunscreen-wouldnt-have-saved-bob-marley-from-melanoma-and-it-wont-help-other-dark-skinned-people-116979?notice=Article+has+been+updated">published on May 14, 2019</a>.</em></p><img src="https://counter.theconversation.com/content/186539/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Adewole S. Adamson receives grant funding for his research from the American Cancer Society, Dermatology Foundation, and Robert Wood Johnson Foundation.</span></em></p>While sunscreen has the potential to reduce skin cancer for light-skinned people, it has never been shown to do the same for Black people. Yet that distinction is lacking in public health messaging.Adewole S. Adamson, Assistant Professor of Internal Medicine (Division of Dermatology), The University of Texas at AustinLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1757232022-02-21T12:19:21Z2022-02-21T12:19:21ZThe secret ultraviolet colours of sunflowers attract pollinators and preserve water<figure><img src="https://images.theconversation.com/files/447129/original/file-20220217-6550-1my6qii.jpg?ixlib=rb-1.1.0&rect=0%2C113%2C4749%2C3675&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">To pollinators, which can see in the ultraviolet, sunflowers have an additional range of colours</span> <span class="attribution"><span class="source">(Unsplash/Marco de Hevia)</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><iframe style="width: 100%; height: 175px; border: none; position: relative; z-index: 1;" allowtransparency="" src="https://narrations.ad-auris.com/widget/the-conversation-canada/the-secret-ultraviolet-colours-of-sunflowers-attract-pollinators-and-preserve-water" width="100%" height="400"></iframe>
<p>Flowers are one of the most striking examples of diversity in nature, displaying myriad combinations of colours, patterns, shapes and scents. They range from colourful tulips and daisies, to fragrant frangipani and giant, <a href="https://www.kew.org/plants/titan-arum">putrid-smelling corpse flowers</a>. The variety and diversity is astounding — consider the <a href="https://www.inaturalist.org/taxa/321088-Caleana-major">duck-shaped orchid</a>. </p>
<p>But as much as we can appreciate the beauty and diversity of flowers, it is quite literally not meant for our eyes.</p>
<p>The purpose of flowers is to attract pollinators, and it is to their senses that flowers cater. A clear example of this are ultraviolet (UV) patterns. Many flowers accumulate UV pigments in their petals, forming patterns that are invisible to us, <a href="https://doi.org/10.1016/S0169-5347(00)89179-X">but that most pollinators can see</a>. </p>
<p>The disconnect between what we see and what pollinators see is particularly striking in sunflowers. Despite their iconic status in popular culture (as testified by the arguably dubious honour of being <a href="https://unicode.org/emoji/charts/full-emoji-list.html">one of the only five flower species with a dedicated emoji</a>), they hardly seem the best example of flower diversity. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/2gduA3EM26M?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">How do insects see the world?</span></figcaption>
</figure>
<h2>Different light</h2>
<p>What we commonly consider a single sunflower is actually a cluster of flowers, referred to as an inflorescence. All wild sunflowers, of which there are about <a href="https://www.jstor.org/stable/pdf/43390641.pdf">50 species in North America</a>, have very similar inflorescences. To our eyes, their ligules (<a href="https://cronodon.com/BioTech/asteraceae.html">the enlarged, fused petals of the outermost whorl of florets in the sunflower inflorescence</a>) are the same uniform, familiar bright yellow.</p>
<p>However, when looked at in the UV spectrum (that is, beyond the type of light that our eyes can see), things are quite different. Sunflowers accumulate UV-absorbing pigments at the base of the ligules. Across the whole inflorescence, this results in a <a href="https://www.researchgate.net/publication/268075987_A_Microscopic_Review_of_the_Sunflower_and_Honeybee_Mutualistic_Relationship">UV bullseye pattern</a>. </p>
<p>In a recent study, we compared almost <a href="https://doi.org/10.7554/eLife.72072.sa0">2,000 wild sunflowers</a>. We found that the size of these UV bullseyes varies extensively, both between and within species.</p>
<p>The sunflower species with the most extreme diversity in the size of UV bullseyes is <em>Helianthus annuus</em>, the common sunflower. <em>H. annuus</em> is the <a href="https://dx.doi.org/10.3390/genes11030266">closest wild relative to cultivated sunflower</a>, and is the most broadly distributed of wild sunflowers, growing almost everywhere between southern Canada and northern Mexico. While some populations of <em>H. annuus</em> have very small UV bullseyes, in others, the ultraviolet-absorbing region covers the whole inflorescence.</p>
<h2>Attracting pollinators</h2>
<p>Why is there so much variation? Scientists have been <a href="https://doi.org/10.1007/BF00340242">aware of floral UV patterns</a> for a long time. Some of the numerous approaches that have been used to study the role of these patterns in attracting pollinators have been quite inventive, including <a href="https://doi.org/10.1242/bio.20146445">cutting and pasting petals</a> or <a href="https://doi.org/10.1111/1365-2435.12242">coating them with sunscreen</a>.</p>
<p>When we compared sunflowers with different UV bullseyes, we found that pollinators were able to discriminate between them and preferred plants with intermediate-sized UV bullseyes. </p>
<p>Still, this doesn’t explain all the diversity in UV patterns that we observed in different populations of wild sunflowers: if intermediate UV bullseyes attract more pollinators (which is <a href="https://doi.org/10.2135/cropsci2017.03.0148">clearly an</a> <a href="https://doi.org/10.1073/pnas.0600929103">advantage</a>), why do plants with small or large UV bullseyes exist?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/446033/original/file-20220211-25-1brx0ew.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="images of sunflowers under ultraviolet light showing bullseye colour distributions" src="https://images.theconversation.com/files/446033/original/file-20220211-25-1brx0ew.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/446033/original/file-20220211-25-1brx0ew.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=321&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446033/original/file-20220211-25-1brx0ew.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=321&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446033/original/file-20220211-25-1brx0ew.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=321&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446033/original/file-20220211-25-1brx0ew.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=404&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446033/original/file-20220211-25-1brx0ew.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=404&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446033/original/file-20220211-25-1brx0ew.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=404&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sunflowers with different UV bullseye patterns as we see them (top) and as a bee might see them (bottom).</span>
<span class="attribution"><span class="source">(Marco Todesco)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Other factors</h2>
<p>While pollinator attraction is clearly the main function of floral traits, there is increasing evidence that <a href="https://www.researchgate.net/publication/254469747_Non-pollinator_agents_of_selection_on_floral_traits">non-pollinator factors</a> like temperature or herbivores can affect the evolution of characteristics like flower colour and shape. </p>
<p>We found a first clue that this could also be the case for UV patterns in sunflowers when we looked at how their variation is regulated at the genetic level. A single gene, <em>HaMYB111</em>, is responsible for most of the diversity in UV patterns that we see in <em>H. annuus</em>. This gene controls the production of a family of chemicals called <a href="https://dx.doi.org/10.1111/j.1365-313X.2007.03078.x">flavonol glycosides</a>, which we found in high concentrations in the UV-absorbing part of ligules. Flavonol glycosides are not only UV-absorbing pigments, but play also an important role in helping plants <a href="https://dx.doi.org/10.1093/aob/mcr234">cope with different environmental stresses</a>.</p>
<p>A second clue came from the discovery that the same gene is responsible for UV pigmentation in the petals of the <a href="https://doi.org/10.7554/eLife.06100">thale cress, <em>Arabidopsis thaliana</em></a>. Thale cress is the most commonly used model system in plant genetics and molecular biology. These plants are able to pollinate themselves, <a href="https://doi.org/10.1055/s-2003-44784">and therefore generally do without pollinators</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/447391/original/file-20220219-2552-1d64kx2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a small white flower in a meadow" src="https://images.theconversation.com/files/447391/original/file-20220219-2552-1d64kx2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/447391/original/file-20220219-2552-1d64kx2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/447391/original/file-20220219-2552-1d64kx2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/447391/original/file-20220219-2552-1d64kx2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/447391/original/file-20220219-2552-1d64kx2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/447391/original/file-20220219-2552-1d64kx2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/447391/original/file-20220219-2552-1d64kx2.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">Thale cress can pollinate itself without the help of pollinators.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>Since they don’t need to attract pollinators, they have small, unassuming white flowers. Still, their petals are full of UV-absorbing flavonols. This suggests that there are reasons not related to pollination for these pigments to be present in the flowers of the thale cress.</p>
<p>Finally, we noticed that sunflower populations from drier climates had consistently larger UV bullseyes. One of the known functions of flavonol glycosides is to <a href="https://dx.doi.org/10.1111/tpj.12388">regulate transpiration</a>. Indeed, we found that ligules with large UV patterns (which contain large amounts of flavonol glycosides) lost water at a much slower rate than ligules with small UV patterns. </p>
<p>This suggests that, at least in sunflowers, patterns of floral UV pigmentation have two functions: improving the attractiveness of flowers to pollinators, and helping sunflowers survive in drier environments by preserving water.</p>
<h2>Thrifty evolution</h2>
<p>So what does this teach us? For one, that evolution is thrifty, and if possible will use the same trait to achieve more than one adaptive goal. It also offers a potential approach for improving cultivated sunflower, by simultaneously boosting pollination rates and making plants more resilient to drought.</p>
<p>Finally, our work, and other studies looking at plant diversity, can help in predicting how and to which extent plants will be able to cope with climate change, which is already altering the environments they are adapted to.</p><img src="https://counter.theconversation.com/content/175723/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Marco Todesco received funding from Genome Canada and Genome British Columbia, and from HFSPO.</span></em></p>Sunflowers have hidden patterns of ultraviolet colours — visible to pollinators, these colours are due to the presence of pigments that also help plants retain moisture.Marco Todesco, Research associate, Biodiversity, University of British ColumbiaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1415122020-09-09T12:28:47Z2020-09-09T12:28:47ZUltraviolet light can make indoor spaces safer during the pandemic – if it’s used the right way<figure><img src="https://images.theconversation.com/files/356596/original/file-20200904-22-1k2iek3.jpg?ixlib=rb-1.1.0&rect=6%2C0%2C4384%2C2923&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Institutions like hospitals and transit systems have been using UV disinfection for years.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/lamps-that-produce-ultraviolet-light-disinfect-a-moscow-news-photo/869395818">Sergei Bobylev\TASS via Getty Images</a></span></figcaption></figure><p>Ultraviolet light has a <a href="https://spectrum.ieee.org/tech-history/dawn-of-electronics/weve-been-killing-deadly-germs-with-uv-light-for-more-than-a-century">long history as a disinfectant</a> and the SARS-CoV-2 virus, which causes COVID-19, is <a href="https://doi.org/10.1101/2020.06.05.20123463">readily rendered harmless by UV light</a>. The question is how best to harness UV light to fight the spread of the virus and protect human health as people work, study, and shop indoors.</p>
<p>The virus <a href="https://www.who.int/news-room/commentaries/detail/transmission-of-sars-cov-2-implications-for-infection-prevention-precautions">spreads in several ways</a>. The main route of transmission is through person-to-person contact <a href="https://doi.org/10.1073/pnas.2009637117">via aerosols and droplets</a> emitted when an infected person breathes, talks, sings or coughs. The virus can also be transmitted when people touch their faces shortly after touching surfaces that have been contaminated by infected individuals. This is of particular concern in health-care settings, retail spaces where people frequently touch counters and merchandise, and in buses, trains and planes.</p>
<p>As an <a href="https://scholar.google.com/citations?user=uAS7KNUAAAAJ&hl=en">environmental engineer</a> who studies UV light, I’ve observed that UV can be used to reduce the risk of transmission through both routes. UV lights can be components of mobile machines, whether robotic or human-controlled, that disinfect surfaces. They can also be incorporated in heating, ventilating, and air-conditioning systems or otherwise positioned within airflows to disinfect indoor air. However, UV portals that are meant to disinfect people as they enter indoor spaces are likely ineffective and potentially hazardous.</p>
<h2>What is ultraviolet light?</h2>
<p>Electromagnetic radiation, which includes radio waves, visible light and X-rays, is measured in nanometers, or millionths of a millimeter. UV irradiation consists of wavelengths between 100 and 400 nanometers, which lies just beyond the violet portion of the visible light spectrum and are invisible to the human eye. UV is divided into the UV-A, UV-B and UV-C regions, which are 315-400 nanometers, 280-315 nanometers and 200-280 nanometers, respectively.</p>
<p>The ozone layer in the atmosphere filters out UV wavelengths below 300 nanometers, which blocks UV-C from the sun before it reaches Earth’s surface. I think of UV-A as the suntanning range and UV-B as the sun-burning range. High enough doses of UV-B can cause skin lesions and skin cancer.</p>
<p>UV-C contains the <a href="https://www.infectioncontroltoday.com/view/study-says-ultraviolet-disinfection-977-effective-eliminating-pathogens">most effective wavelengths for killing pathogens</a>. UV-C is also <a href="https://orm.uottawa.ca/my-safety/em-radiation/uv/exposure-limits">hazardous to the eyes and skin</a>. Artificial UV light sources designed for disinfection emit light within the UV-C range or a broad spectrum that includes UV-C.</p>
<h2>How UV kills pathogens</h2>
<p>UV photons between 200 and 300 nanometers are absorbed fairly efficiently by the nucleic acids that make up DNA and RNA, and photons below 240 nanometers are also well absorbed by proteins. These essential biomolecules are damaged by the absorbed energy, rendering the genetic material inside a virus particle or microorganism unable to replicate or cause an infection, inactivating the pathogen. </p>
<p>It typically takes a very low dose of UV light in this germicidal range to inactivate a pathogen. The UV dose is determined by the intensity of the light source and duration of exposure. For a given required dose, higher intensity sources require shorter exposure times, while lower intensity sources require longer exposure times.</p>
<h2>Putting UV to work</h2>
<figure class="align-center ">
<img alt="a robot emitting ultraviolet light in an empty hospital room" src="https://images.theconversation.com/files/356593/original/file-20200904-16-14v8pul.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/356593/original/file-20200904-16-14v8pul.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=419&fit=crop&dpr=1 600w, https://images.theconversation.com/files/356593/original/file-20200904-16-14v8pul.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=419&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/356593/original/file-20200904-16-14v8pul.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=419&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/356593/original/file-20200904-16-14v8pul.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=527&fit=crop&dpr=1 754w, https://images.theconversation.com/files/356593/original/file-20200904-16-14v8pul.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=527&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/356593/original/file-20200904-16-14v8pul.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=527&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">UV disinfection, which can be performed by robots like this, reduces hospital-acquired infections.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:WBAMC_fights_back_151230-A-EK666-003.jpg">Marcy Sanchez/William Beaumont Army Medical Center Public Affairs Office</a></span>
</figcaption>
</figure>
<p>There is an established market for UV disinfection devices. Hospitals have been using robots that emit UV-C light for years to disinfect patient rooms, operating rooms and other areas where bacterial infection can spread. These robots, which include <a href="https://tru-d.com/">Tru-D</a> and <a href="https://www.xenex.com/">Xenex</a>, enter empty rooms between patients and roam around remotely emitting high-power UV irradiation to disinfect surfaces. UV light is also used to disinfect medical instruments in special UV exposure boxes.</p>
<p>UV is being used or tested for disinfecting <a href="https://www.theverge.com/2020/5/20/21265221/nyc-mta-ultraviolet-light-uvc-coronavirus-disinfect-puro-pictures">buses, trains</a> and <a href="https://www.reuters.com/article/us-health-coronavirus-germfalcon/coronavirus-pandemic-inspires-demand-for-uv-airplane-cleaner-idUSKCN2263AC">planes</a>. After use, UV robots or human-controlled machines designed to fit in vehicles or planes move through and disinfect surfaces that the light can reach. Businesses are also considering the technology for <a href="https://www.cnn.com/2020/07/04/tech/mit-csail-coronavirus-robot-scn-trnd/index.html">disinfecting warehouses and retail spaces</a>. </p>
<figure class="align-center ">
<img alt="ultraviolet light filling the interior of an empty New York City subway car" src="https://images.theconversation.com/files/356592/original/file-20200904-14-1pf8a8p.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/356592/original/file-20200904-14-1pf8a8p.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/356592/original/file-20200904-14-1pf8a8p.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/356592/original/file-20200904-14-1pf8a8p.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/356592/original/file-20200904-14-1pf8a8p.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/356592/original/file-20200904-14-1pf8a8p.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/356592/original/file-20200904-14-1pf8a8p.png?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">
<figcaption>
<span class="caption">The New York City Metropolitan Transit Authority (MTA) is testing the use of ultraviolet light to disinfect out-of-service subway cars.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:MTA_Moves_Forward_with_Ultraviolet_Pilot_for_Disinfecting_Full_Trains_(49998855202).png">MTA</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>It’s also possible to use UV to <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2789813/">disinfect air</a>. Indoor spaces like schools, restaurants and shops that have some air flow can <a href="https://khn.org/news/scientists-want-to-know-more-about-using-uv-light-to-fight-covid-19-spread/">install UV-C lamps overhead</a> and aimed at the ceiling to disinfect the air as it circulates. Similarly, HVAC systems can contain UV light sources to disinfect air as it travels through duct work. Airlines could also use UV technology for disinfecting air in planes, or use UV lights in bathrooms between uses.</p>
<h2>Far UV-C – safe for humans?</h2>
<p>Imagine if everyone could walk around continuously surrounded by UV-C light. It would kill any aerosolized virus that entered the UV zone around you or that exited your nose or mouth if you were infected and shedding the virus. The light would also disinfect your skin before your hand touched your face. This scenario might be possible technologically some day soon, but the health risks are a significant concern. </p>
<p>As UV wavelength decreases, the ability of the photons to penetrate into the skin decreases. These shorter-wavelength photons get absorbed in the top skin layer, which minimizes DNA damage to the actively dividing skin cells below. At wavelengths below 225 nanometers – the Far UV-C region – UV appears to be safe for skin exposure at doses below the <a href="https://www.icnirp.org/cms/upload/publications/ICNIRPUVWorkers.pdf">exposure levels</a> defined by the International Committee on non-Ionizing Radiation Protection. </p>
<p>Research is <a href="https://doi.org/10.1371/journal.pone.0138418">confirming these numbers</a> using <a href="https://doi.org/10.1111/php.13269">mouse models</a>. However, less is known about <a href="https://iuva.org/resources/covid-19/Far%20UV-C%20in%20the%20200%20_%20225%20nm%20range,%20and%20its%20potential%20for%20disinfection%20applications.pdf">exposure to eyes and injured skin</a> at these Far UV-C wavelengths and people should avoid direct exposure above safe limits. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/YATYsgi3e5A?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Research suggests that far UV-C light might be able to kill pathogens without harming human health.</span></figcaption>
</figure>
<p>The <a href="https://www.nature.com/articles/s41598-020-67211-2">promise of Far UV-C</a> for safely disinfecting pathogens opens up many possibilities for UV applications. It’s also led to some premature and potentially risky uses. </p>
<p>Some businesses are <a href="https://www.businessinsider.com/uv-light-cleanse-portals-used-to-kill-germs-coronavirus-2020-6">installing UV portals</a> that irradiate people as they walk through. While this device may not cause much harm or skin damage in the few seconds walking through the portal, the low dose delivered and potential to disinfect clothing would also likely not be effective for stemming any virus transmission. </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>Most importantly, eye safety and long-term exposure have not been well studied, and these types of devices <a href="https://collateral-library-production.s3.amazonaws.com/uploads/asset_file/attachment/26057/CT_26219573_UVC-Germicidal-Devices-flyer_digital_FINAL_073020.pdf">need to be regulated</a> and validated for effectiveness before being used in public settings. The impact of continuous germicidal irradiation exposure on the overall environmental microbiome also needs to be understood. </p>
<p>As more studies on Far UV-C bear out that exposure to human skin <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/php.13269">is not dangerous</a> and if studies on eye exposure show no harm, it is possible that validated Far UV-C light systems installed in public places could support attempts at controlling virus transmission for SARS-CoV-2 and other potential airborne viral pathogens, today and into the future.</p><img src="https://counter.theconversation.com/content/141512/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Karl Linden receives funding from The National Science Foundation for his UV research. He is affiliated with the International UV Association (IUVA). </span></em></p>UV disinfection is a proven means of killing pathogens like the SARS-CoV-2 virus, but it’s not risk-free.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/1169792019-05-14T10:46:10Z2019-05-14T10:46:10ZSunscreen wouldn’t have saved Bob Marley from melanoma, and it won’t help other dark-skinned people<figure><img src="https://images.theconversation.com/files/274101/original/file-20190513-183096-t3jmon.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An image of Bob Marley at a Bob Marley Exhibit in Miami Oct. 16, 2013. </span> <span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Florida-Daily-Life/ac24b40be10e4d9caf1f60aed22a4dfa/56/0">Lynne Slakdy/AP Photo</a></span></figcaption></figure><p>Melanoma is a potentially deadly form of skin cancer linked to overexposure to ultraviolet, or UV, rays from the sun. Sunscreen can block UV rays and therefore reduce the risk of sun burns, which ultimately reduces the risk of developing melanoma. Thus, the promotion of sunscreen as an effective melanoma prevention strategy is a reasonable <a href="https://www.ncbi.nlm.nih.gov/pubmed/25208462">public health message</a>. </p>
<p>While this may be true for light-skinned people, such as individuals of <a href="https://www.ncbi.nlm.nih.gov/pubmed/21135266">European descent</a>, this is not the case for darker skinned people, or individuals of African descent. </p>
<p>The public health messages promoted by many <a href="https://www.ncbi.nlm.nih.gov/pubmed/24485530">clinicians</a> and <a href="https://www.skincancer.org/prevention/skin-cancer-and-skin-of-color">public health groups</a> regarding sunscreen recommendations for dark-skinned people is incongruent with the available evidence. Media <a href="https://www.npr.org/sections/codeswitch/2018/07/05/559883985/will-your-melanin-protect-you-from-the-sun">messaging</a> exacerbate the problem with <a href="http://www.npr.org/templates/story/story.php?storyId=5623503">headline</a> after <a href="http://www.nbcnews.com/news/nbcblk/just-one-thing-protecting-your-skin-summer-n410841">headline</a> warning that <a href="http://www.theroot.com/black-don-t-crack-but-you-can-still-get-skin-cancer-1790855455">Black people can also develop melanoma</a> and that Black people are not immune. To be sure, they can get melanoma, but the risk is very low. In the same way, men can develop breast cancer, however, we do not promote mammography as a strategy to fight breast cancer in men.</p>
<p>This message is important to me as a Black, board certified dermatologist and health services researcher at Dell Medical School at the University of Texas at Austin, where I am director of the pigmented lesion clinic. In this capacity I take care of patients at high risk for melanoma.</p>
<h2>Melanoma in Black people is not associated with UV exposure</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/274103/original/file-20190513-183089-143tn1g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/274103/original/file-20190513-183089-143tn1g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/274103/original/file-20190513-183089-143tn1g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/274103/original/file-20190513-183089-143tn1g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/274103/original/file-20190513-183089-143tn1g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/274103/original/file-20190513-183089-143tn1g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/274103/original/file-20190513-183089-143tn1g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Darker skin provides more protection from damage by the ultraviolet rays of the sun.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/happy-african-american-family-father-son-116979724?src=8lZJLe5GKU-Gie1opBfdOA-1-17">Spotmatik/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>In the U.S., melanoma is <a href="https://seer.cancer.gov/explorer/application.php?site=53&data_type=1&graph_type=2&compareBy=race&chk_sex_1=1&chk_race_3=3&chk_race_2=2&chk_age_range_1=1&chk_data_type_1=1&advopt_precision=1&advopt_display=1&showDataFor=sex_1_and_age_range_1_and_data_type_1">20 to 30 times</a> more common among white people compared to Black people. </p>
<p>In Black people, melanoma usually develops in parts of the body that get less sun exposure, such as the palms of the hands and soles of the feet. These cancers are called “acral melanomas,” and sunscreen will do nothing to reduce the risk of these cancers. </p>
<p>When was the last time you had a sunburn on the palms or soles? Even among white people, there is no relationship between <a href="https://www.ncbi.nlm.nih.gov/pubmed/16911282">sun exposure and the risk of acral melanomas</a>. Famously, Bob Marley died from an acral melanoma on his great toe, but sunscreen would not have helped.</p>
<p>The research on the association of UV radiation and melanoma among Black people is lacking. Most studies assessing the relationship exclude patients of darker skin types. In the <a href="https://www.ncbi.nlm.nih.gov/pubmed/?term=15837865">largest study</a> of this question to date, no connection was found between UV index or latitude and melanoma among black people. </p>
<h2>Racial disparities in melanoma outcomes are not related to UV exposure</h2>
<p>Many dermatologists often point out that Black patients tend to show up to the doctor with <a href="https://www.ncbi.nlm.nih.gov/pubmed/27476974">later stage melanoma</a>, which is true. However, this is an issue of access and awareness and has nothing to do with sunscreen application. Black people should be aware of growths on their skin and seek medical attention if they have any changing, bleeding, painful, or otherwise concerning spots, particularly on the hands and feet. </p>
<p>However, the notion that regular application of daily sunscreen will reduce an already extremely rare occurrence is nonsensical. </p>
<p>UV radiation does affect dark skin and can cause DNA damage; however, the damage is <a href="https://www.ncbi.nlm.nih.gov/pubmed/12692083">seven to eight times lower</a> than the damage done to white skin, given the natural sun-protective effect of increased melanin in darker skin. To be clear, using regular sunscreen may help with reducing other effects of the sun’s rays such as sun burns, wrinkling, photoaging and freckling, which are all positive, but for the average black person sunscreen is unlikely to reduce their low risk of melanoma any further.</p>
<p>If sunscreen was important in the prevention of melanoma in dark-skinned patients, then why have we never heard of an epidemic of melanoma in sub-Saharan Africa, a region with intense sun, a lot of Black people and little sunscreen? </p>
<p>In certain sub populations of Black people, such as those with disorders causing sun sensitivity, albino patients, or patients with suppressed immune systems, sunscreen use may reduce risk of melanoma. But if you don’t fall into one of these categories, any meaningful risk reduction from the application of sunscreen is unlikely.</p>
<h2>One-size-fits-all public health messaging</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/274116/original/file-20190513-183080-l4tvmw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/274116/original/file-20190513-183080-l4tvmw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/274116/original/file-20190513-183080-l4tvmw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/274116/original/file-20190513-183080-l4tvmw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/274116/original/file-20190513-183080-l4tvmw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/274116/original/file-20190513-183080-l4tvmw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/274116/original/file-20190513-183080-l4tvmw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Sunscreens have not been shown to protect black skin from melanoma.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/smiling-african-american-woman-applying-sunscreen-1117468151?src=64x7xqSo6p1rSR92dBOq2Q-1-1">LightField Studios/Shutterstock</a></span>
</figcaption>
</figure>
<p>When it comes to the public health message related to sunscreen, skin cancer and Black people, a one-size-fits-all approach misses the mark. The facts simply do not add up for the recommendation of sunscreen as prevention of melanoma in Black people. Many dermatology and skin cancer-focused organizations (a few of which I’m a member), promote the public health message of sunscreen use to reduce melanoma risk among Black patients. However, this message is not supported by evidence. There exists no study that demonstrates sunscreen reduces skin cancer risk in Black people. Period.</p>
<p>This issue of regular sunscreen use in Black people was made even more pressing after the release of a study last week on sunscreen absorption in <a href="https://jamanetwork.com/journals/jama/fullarticle/2733085">the Journal of the American Medical Association</a>. This study showed that significant amounts of certain chemical sunscreen ingredients can get in the blood when used at <a href="https://twitter.com/AdeAdamson/status/1125522416837517312">maximal conditions</a>, with unknown impacts on human health. To me, the most shocking part of the study was that most of the participants were Black, the group least likely to derive any meaningful associated health benefits from sunscreen, while being exposed to potentially harmful levels of chemicals.</p>
<p>As dermatologists and public health advocates, we can do a better job educating patients and the public about melanoma prevention, without promoting public health messages that are <a href="https://www.instagram.com/tv/BxPUuGUFR6X/?utm_source=ig_share_sheet&igshid=1jqzljkns187e">grounded in fear</a> and/or that lack evidence. Black people should be informed that they are at risk of developing melanoma, but that risk is low. </p>
<p>Any dark-skinned person who develops a new, changing or symptomatic mole should see their doctor, particularly if the mole is on the palms or soles. We don’t know what the risk factors are for melanoma in Black or dark-skinned people, but they certainly are not UV rays.</p><img src="https://counter.theconversation.com/content/116979/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Adewole S. Adamson 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>While sunscreen has the potential to reduce skin cancer for light-skinned people, it has never been shown to do the same for Black people.Adewole S. Adamson, Assistant Professor of Internal Medicine (Division of Dermatology), The University of Texas at AustinLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/924382018-04-10T19:56:23Z2018-04-10T19:56:23ZCurious Kids: How does glow in the dark paint work?<figure><img src="https://images.theconversation.com/files/209656/original/file-20180309-30954-f1bl33.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">While some things glow all the time, glow-in-the-dark paint must be 'told to glow' - just like a phone needs to be charged or it won't work.</span> <span class="attribution"><span class="source">Mai Lam/The Conversation NY-BD-CC</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!</em></p>
<hr>
<blockquote>
<p><strong>How does glow in the dark paint work? – Roman, age 5, Katoomba.</strong></p>
</blockquote>
<hr>
<p>To answer your question, we need to talk about light. This is not an easy thing to do. About 100 years ago, the world’s smartest scientists even argued about what light really is. And they argued for many years. </p>
<p>Light is actually a bunch of tiny things that scientists call “photons”. These little things can travel unbelievably quickly.</p>
<p>How quickly? Well, imagine this: photons can go around the entire world more than seven times in just one second.</p>
<p>When these photons reach our eyes, we see them as light. The more photons there are, the brighter the light. </p>
<p>Photons can come in all the colours of the rainbow. They also hold energy which can turn into heat. This is why it feels warm when the sun shines. </p>
<p>But, not all light is the same. Blue and violet photons both have more energy than red ones, for example.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-does-rain-only-come-from-grey-clouds-90325">Curious Kids: why does rain only come from grey clouds?</a>
</strong>
</em>
</p>
<hr>
<h2>Invisible light</h2>
<p>Now here is a weird thing: there are some types of light that are invisible! </p>
<p>For example, ultraviolet (UV) light, which has even more energy than blue and violet light, is invisible.</p>
<p>Sunlight contains some of this powerful UV light. Because it has so much energy, it can cause a lot of damage, like sunburn, if you get too much of it on your skin.</p>
<p>Another invisible type of light is infrared light. Infrared means “less than red”, so this light has even less energy than red light.</p>
<h2>Making paint glow</h2>
<p>Many light sources, like the Sun or an old light bulb in your bathroom, glow because they are really hot. Normal glowing, like that of the Sun and a light bulb, requires objects to be really hot for us to see it. </p>
<p>As you already know, you can see glow-in-the-dark paint, but if you touch it, it is just as cold as the bedroom wall. So, the glowing of the paint must be different to the glowing of a light bulb. </p>
<p>The paint has a special kind of glowing called “luminescence” and it can only be created from a few types of material. One such material is what scientists call “luminescent phosphors”, and this is what makes your paint glow. Scientists make luminescent phosphors in the lab by mixing special chemicals together, and then add them to the paint. The paint is then sold to factories and manufacturers who put it on toys, stickers, and even inside colouring pens.</p>
<p>While some things glow all the time, like the sun, glow-in-the-dark paint must be “told to glow”. Just like your parents need to charge their phones every night to make them work, these materials need to be “charged” before they start glowing. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-is-x-ray-vision-possible-90393">Curious Kids: Is x-ray vision possible?</a>
</strong>
</em>
</p>
<hr>
<p>In fact, the charging of your glow-in-the-dark paint is done by other types of light. The invisible UV light with lots of energy can charge the special phosphors in your paint and make it glow in your bedroom at night. </p>
<p>There are different types of glow-in-the-dark paint. One type can be charged during the day and can glow for hours in the dark at night. The charging that happens during the day, for example by sunlight, is stored in the paint for some time, just like in the battery of a phone. </p>
<p>This type of paint is called phosphorescent. The other type, called fluorescent paint, only glows while an invisible UV light is turned on to charge it.</p>
<p>You might have heard that some animals can glow. Here’s a video all about that:</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/jp-jYVktx7s?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<hr>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. You can:</em></p>
<p><em>* Email your question to curiouskids@theconversation.edu.au
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* Tell us on <a href="https://twitter.com/ConversationEDU">Twitter</a> by tagging <a href="https://twitter.com/ConversationEDU">@ConversationEDU</a> with the hashtag #curiouskids, or
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* Tell us on <a href="http://www.facebook.com/conversationEDU">Facebook</a></em></p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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</figure>
<p><em>Please tell us your name, age and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/92438/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Thorsten Trupke 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>You can see glow-in-the dark paint, but if you touch it, it is just as cold as the bedroom wall. So the glowing of the paint is different to the glowing of a light bulb.Thorsten Trupke, Professor of Photovoltaic and Renewable Energy Engineering, UNSW SydneyLicensed 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>
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<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>
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<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/731842017-03-01T02:21:56Z2017-03-01T02:21:56ZReprintable paper becomes a reality<figure><img src="https://images.theconversation.com/files/158375/original/image-20170224-22986-jzy0pm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Achievement unlocked: Rewritable paper.</span> <span class="attribution"><span class="source">Yadong Yin</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Since its invention around 100 B.C. in China, paper as a material for spreading information has greatly contributed to the development and spread of civilization. Even in today’s information age, with electronic media omnipresent in homes, offices and even our pockets, paper still plays a critical role.</p>
<p>Our brains process information differently on paper and on screen. <a href="http://www.millwardbrown.com/docs/default-source/insight-documents/case-studies/MillwardBrown_CaseStudy_Neuroscience.pdf">Information presented on paper</a> involves more emotional processing and produces more brain responses connected with internal feelings. That can make printed material more effective and more memorable than digital media. Of course, paper is still in common use, and <a href="http://dx.doi.org/10.1016/j.envsci.2009.01.011">global consumption</a> is expected to grow. </p>
<p>But paper use comes with significant environmental and sustainability problems. For many years, scientists have worked to develop reading media that have the format of conventional paper but can be <a href="https://phys.org/news/2014-01-chemists-unveil-water-jet-printer.html">reprinted</a> without first having to be <a href="https://web.archive.org/web/20111130061422/http://www.tappi.org/paperu/all_about_paper/earth_answers/EarthAnswers_Recycle.pdf">industrially recycled</a>. One promising option has been to coat paper with a thin film of <a href="https://dx.doi.org/10.1021/cr980068l">chemicals that change color</a> when exposed to light. But previous efforts have encountered problems such as high cost and high toxicity – not to mention difficulty both remaining readable and being erased for reuse. </p>
<p>My research group at the University of California, Riverside, in collaboration with <a href="http://www.nccm.sdu.edu.cn/cn/newsshow.php?pcid=8&cid=46&id=444">Wenshou Wang</a> at Shandong University in China, has recently developed a <a href="http://dx.doi.org/10.1021/acs.nanolett.6b03909">new coating</a> for regular paper that needs no ink, and can be printed on with light, erased and reused more than 80 times. The coating combines the functions of two types of nanoparticles, particles <a href="https://www.nano.gov/nanotech-101/what/nano-size">100,000 times thinner than a piece of paper</a>; one particle is able to get energy from light and initiates color change of the other. This represents an important step toward the development of reprintable paper.</p>
<h2>Environmental effects of paper</h2>
<p>About <a href="http://www.ecology.com/2011/09/10/paper-chase/">35 percent</a> of all harvested trees in the world are used to make paper and cardboard. Worldwide, the pulp and paper industry is the <a href="http://www.thepaperlessproject.com/facts-about-paper-the-impact-of-consumption/">fifth largest</a> consumer of energy and uses more water to produce a ton of product than any other industry.</p>
<p>Pulp extraction consumes large amounts of energy and can involve dangerous chemicals like dioxin. Paper production results in the <a href="http://www.ifc.org/wps/wcm/connect/7b62180048855aef878cd76a6515bb18/pulp_PPAH.pdf?MOD=AJPERES">emission of the nutrient phosphorus</a>. That, in turn, boosts plant growth, which can use up all the oxygen in the water and kill any animal life.</p>
<p>Even after paper is made, its use damages the environment. Trucking paper from where it’s made to where it’s used generates air pollution. And making and using ink and toner also <a href="http://globalwarmingisreal.com/2012/07/12/what-effect-does-ink-cartridge-waste-have-on-the-environment/">harm the environment</a>, by contaminating water, poisoning soil and destroying the natural habitats of wildlife.</p>
<p>Our method uses nontoxic ingredients and permits repeated reuse of paper, thereby reducing the environmental effects.</p>
<h2>Switching colors</h2>
<p>In developing a coating for paper, it’s important to find one that is transparent but can change color to something visible – and back. That way, any text or images can be made readable like on normal paper, but also easily erased.</p>
<p>Our method combines <a href="https://www.nano.gov/nanotech-101/what/nano-size">nanoparticles</a> – particles between 1 and 100 nanometers in size – of two different materials that can change from clear to visible and back again. The first material is Prussian blue, a widely used blue pigment most familiar as the blue color in architectural blueprints or inks. Prussian blue nanoparticles normally appear blue, of course, but can become <a href="http://dx.doi.org/10.1016/j.materresbull.2011.08.021">colorless</a> when they are supplied with additional electrons.</p>
<p>The second material is nanoparticles of titanium dioxide. When exposed to ultraviolet light, they release the electrons the Prussian blue needs to turn colorless.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/wnCyTb6bgJA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Printing with UV light and erasing with heat.</span></figcaption>
</figure>
<p>Our technique combines these two nanoparticles into a solid coating on conventional paper. (It can also be applied to other solids, including plastic sheets and glass slides.) When we shine ultraviolet light on the coated paper, the titanium dioxide produces electrons. The Prussian blue particles pick up those electrons and change color from blue to clear.</p>
<p><a href="https://youtu.be/wnCyTb6bgJA">The printing</a> can be done through a mask, which is a clear plastic sheet printed with letters and patterns in black. The paper starts out entirely blue. When UV light passes through the blank areas on the mask, it changes the corresponding areas on the paper underneath into white, replicating the information from the mask to the paper. The printing is fast, taking only a few seconds to complete. </p>
<p>The resolution is very high: It can produce patterns as tiny as 10 micrometers, 10 times smaller than what our eyes can see. The paper will remain readable for more than five days. Its readability will slowly degrade, as the oxygen in the air takes electrons from the Prussian blue nanoparticles and turn them back to blue. The printing can also be done using a laser beam, which scans across the paper surface and exposes the areas that should be white, in a way similar to how today’s laser printers work.</p>
<p>Erasing a page is easy: Heating the paper and film to about 120 degrees Celsius (250 degrees Fahrenheit) speeds up the oxidation reaction, erasing the printed content completely within about 10 minutes. This temperature is far lower than the temperature at which paper ignites, so there is no danger of fire. It is also lower than the temperature involved in current laser printers, which need to reach about <a href="http://dx.doi.org/10.1016/j.jaerosci.2010.02.015">200 degrees Celsius</a> (392 degrees Fahrenheit) to instantly fuse the toner onto the paper. </p>
<h2>Improved chemical stability</h2>
<p>Using Prussian blue as a part of this process offers a significant number of advantages. First, it is <a href="http://dx.doi.org/10.1021/ja066273x">highly chemically stable</a>. Previous rewritable papers usually used organic molecules as the main color-change materials, but they <a href="https://link.springer.com/chapter/10.1007/978-3-540-38522-6_7#page-1">break down</a> easily after being exposed to UV light during printing. As a result, they don’t allow very many cycles of printing and erasing. </p>
<p>By contrast, Prussian blue molecules remain essentially intact even after long-term exposure to ultraviolet light. In our lab, we have been able to write and erase a single sheet more than 80 times without observing any apparent changes to the intensity of the color or the speed of the switch. </p>
<p>In addition, Prussian blue can be easily modified to produce different colors, so blue isn’t the only option. We can change the pigment’s chemical structure, replacing some of its iron with copper to make a green pigment, or entirely replacing the iron with cobalt to make brown. At present, we’re able to print in only one color at a time. </p>
<p>As we develop this technology further, we hope to make rewritable paper available for many uses of displaying information, especially temporary uses like newspapers, magazines and posters. Other uses extend to manufacturing, health care and even simple organizing, such as making rewritable labels. </p>
<p>It’s probably not feasible to hope for a completely paperless society, but we are working on helping people use far less paper than they do – and more easily reusing it when they’re ready.</p><img src="https://counter.theconversation.com/content/73184/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Yadong Yin receives funding from U.S. Department of Energy. </span></em></p>Coating paper with an inexpensive thin film can allow users to print and erase a physical page as many as 80 times. That reduces both the cost and the environmental effects of paper use.Yadong Yin, Professor of Chemistry, University of California, RiversideLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/715312017-02-03T02:08:44Z2017-02-03T02:08:44ZMelanoma: Taming a migratory menace<figure><img src="https://images.theconversation.com/files/155417/original/image-20170203-1650-w41ap0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Former President Jimmy Carter in Aug., 2015 at Maranatha Baptist Church in Plains, Ga. Carter was undergoing treatment for advanced melanoma at the time. Via AP.</span> <span class="attribution"><span class="source">David Goldman/AP</span></span></figcaption></figure><p>The deadliest cancer of the skin is cutaneous melanoma. In 2017 <a href="https://www.melanoma.org/understand-melanoma/what-melanoma/melanoma-facts-and-stats">over 160,000 Americans are expected to be diagnosed with melanoma</a>, and over half will have invasive disease, or one that has gone beyond the skin and which carries greater risk of recurrence. About <a href="https://www.cancer.org/cancer/melanoma-skin-cancer/about/key-statistics.html">9,700 people </a>are expected to die from melanoma this year. </p>
<p>Unlike most common cancers, such as breast and lung cancer, the incidence of melanoma continues to increase, <a href="https://www.cancer.org/cancer/melanoma-skin-cancer/about/key-statistics.html">mainly in young people </a>below the age of 30. There has been a <a href="http://www.washingtonpost.com/wp-dyn/content/article/2008/07/10/AR2008071001231.html">more than 50 percent</a> increase in melanoma in young women since 1980. </p>
<p>The <a href="https://www.cancer.org/cancer/melanoma-skin-cancer/about/key-statistics.html">vast majority</a> of melanomas are caused by exposure to UV light from sun or indoor tanning. Reducing these exposures by changing habits or using sun protection – sun screens and clothing coverage – is the best way to avoid melanoma and other skin cancers.</p>
<p>As a researcher who studies what makes melanoma spread, or metastasize, I’m acutely aware of how hard this deadly cancer is to tame. To be sure, advances have been made. Former President Jimmy Carter – probably the most high-profile melanoma survivor in history – benefited from new treatments resulting from immunotherapy, a technique my lab and many others are using to combat cancer. </p>
<h2>A challenging cancer</h2>
<p>For reasons that aren’t fully understood, even quite small melanomas can spread in the body, or metastasize. Detection very early, when the tumor is less than 1 millimeter thick, allows surgery that provides a near cure. </p>
<p>Survival with the earliest Stage 0 or 1A melanomas, or local disease, is <a href="https://www.cancer.org/cancer/melanoma-skin-cancer/detection-diagnosis-staging/survival-rates-for-melanoma-skin-cancer-by-stage.html">greater than 95 percent at ten years</a> after diagnosis. This fact has prompted the Melanoma Research Foundation to promote its <a href="http://join.melanoma.org/site/PageNavigator/GetNaked/UnderstandingMelanoma.html">#GETNAKED campaign</a> for monthly skin checks to identify new moles or skin changes that might be an early indication of melanoma. Catching it early is critical because once it spreads, melanoma can become a monster.</p>
<p>Let’s consider the process of cancer metastasis, which involves at least four distinct steps. </p>
<p>First the cancer cells have to leave the vicinity of the primary tumor. They do this by invading through tissue barriers that sustain the normal tissue architecture. </p>
<p>Second, they need to invade through the blood vessel wall to get into the bloodstream. </p>
<p>These two steps are called intravasation, which means “into the blood stream.” Once there, the cancer cells need to survive. </p>
<p>Most cells in normal tissues require cell attachment, or contact with surfaces or other cells, to survive. When normal cells are detached from those contacts, they usually undergo a type of cell suicide called anoikis. This process of cell suicide is lost in many cancers. </p>
<p>The cancer cells then need to leave the bloodstream by invading through the wall of the blood vessel in a process called extravasation. This third step allows the cancer cells to spread to other parts of the body.</p>
<p>Finally, the cancer cells need to adapt and grow in the new environment, such as in the lung or brain. </p>
<p>One unique characteristic of melanoma is that it is not uncommon to have melanoma metastases show up after 10 or more years with no evidence of disease. </p>
<p>These late recurrences may be due to several underlying mechanisms, but one explanation is a process called cellular dormancy. While in this dormant state, cells can not be detected, and it is thought that the patient may have been cured. </p>
<p>Finding a way to prevent dormancy could reduce the chances of a late recurrence of metastatic disease. </p>
<h2>Recent advances bring hope</h2>
<p>Beyond prevention of the cancer in the first place, which is the best approach, there have been tremendous advances in the treatment of cutaneous melanoma. A critical development was the discovery in 2002 that over half of cutaneous melanomas have a <a href="http://www.nature.com/nature/journal/v417/n6892/full/nature00766.html">mutation in the BRAF gene</a>. </p>
<p>The mutation of this gene plays a key role in melanoma cell growth and proliferation. The BRAF protein is a member of the protein kinase family which has become a <a href="http://www.annualreviews.org/doi/abs/10.1146/annurev-pharmtox-011613-135943">major target class</a> for drug development in the pharmaceutical sector. </p>
<p>In 2010, <a href="http://www.nejm.org/doi/full/10.1056/NEJMoa1002011">remarkable results</a> were presented on clinical benefits of a BRAF inhibitor, vemurafenib. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/155415/original/image-20170203-1652-1e53f4x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/155415/original/image-20170203-1652-1e53f4x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=520&fit=crop&dpr=1 600w, https://images.theconversation.com/files/155415/original/image-20170203-1652-1e53f4x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=520&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/155415/original/image-20170203-1652-1e53f4x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=520&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/155415/original/image-20170203-1652-1e53f4x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=653&fit=crop&dpr=1 754w, https://images.theconversation.com/files/155415/original/image-20170203-1652-1e53f4x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=653&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/155415/original/image-20170203-1652-1e53f4x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=653&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A new drug, vemurafenib, has been shown to block the path of a mutated gene called BRAF, seen in more than half of cutaneous melanomas.</span>
<span class="attribution"><span class="source">Author provided.</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>In the same year, a major advance in immune therapy for melanoma was reported where ipilimumab, an antibody that enhances the body’s immune responses, showed a <a href="http://www.nejm.org/doi/full/10.1056/NEJMoa1003466">significant survival benefit</a> in patients with diffuse metastatic melanoma. These were the first breakthroughs in melanoma treatment in more than a decade.</p>
<p>In addition to these two early developments, other drugs acting like vemurafenib as well as improved immunotherapies have been developed. These have further improved therapy of cutaneous melanoma. Immune modulation has even resulted in <a href="http://www.nejm.org/doi/pdf/10.1056/NEJMoa1611299">long-term survival in a fraction</a> (10-20 percent) of patients.</p>
<h2>Limits to new treatments</h2>
<p>Despite these advances, however, there are still key problems with current therapies. Many rapidly lose effectiveness; drugs like vemurafenib that were controlling the tumor stop working through the development of <a href="http://www.nature.com/news/2010/101124/full/468490a.html">resistant cancer cells</a>, often within less than one year. </p>
<p>Also, the immune therapies only benefit a fraction of patients. When combinations of two immune therapy drugs are used to give a better effect on the cancer, the patients’ <a href="http://www.nejm.org/doi/full/10.1056/NEJMoa1504030">immune systems begin attacking normal tissues</a>, which leads to autoimmune side effects. </p>
<p>Consequently, we need new approaches to prevent or treat the progression of melanoma and especially the development of metastases.</p>
<p>Work in <a href="http://mct.aacrjournals.org/content/16/1/193.long">our lab</a> and that of <a href="http://www.nature.com/ncb/journal/v11/n3/full/ncb1833.html">others</a> has identified a cellular mechanism similar to the BRAF pathway that appears to play a role in the migration and metastasis of melanoma. A pathway is a series of biological steps that lead to changes in cell function, such as growth or migration. </p>
<p>If we could confirm this new pathway as a possible drug target, we may be able to develop a therapy to prevent metastasis. </p>
<h2>A protein to examine</h2>
<p>In the BRAF pathway, a small protein called Ras works upstream of BRAF to activate it. Ras is one of the most commonly mutated genes in all of cancer biology. The particular version in melanoma is called NRAS. It is mutated and activated in about 20 percent of melanomas. Combined, mutations in BRAF and NRAS are found in 80-90 percent of melanomas. This is why the BRAF pathway is a prime target for therapy. </p>
<p>The new pathway we have identified starts with something called the Rho protein, which is very closely related to Ras.</p>
<p>When this Rho mechanism is activated, cancer cells move more actively and will invade the tissue that surrounds a tumor.</p>
<p>Along with Rho, a second critical player is a protein called MRTF that turns on gene expression (i.e. the production of RNA and proteins) when it is activated. Rho activates MRTF by driving it into the nucleus of the cell, where it can turn on gene expression.</p>
<p>We found that this <a href="http://mct.aacrjournals.org/content/16/1/193.long">Rho/MRTF pathway is activated in some melanoma tumors but not others</a>. When it is turned on, the MRTF protein is in the nucleus and the cells migrate very quickly and form large lung metastases when injected into mice. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/155412/original/image-20170203-1673-117ild.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/155412/original/image-20170203-1673-117ild.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=350&fit=crop&dpr=1 600w, https://images.theconversation.com/files/155412/original/image-20170203-1673-117ild.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=350&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/155412/original/image-20170203-1673-117ild.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=350&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/155412/original/image-20170203-1673-117ild.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=440&fit=crop&dpr=1 754w, https://images.theconversation.com/files/155412/original/image-20170203-1673-117ild.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=440&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/155412/original/image-20170203-1673-117ild.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=440&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The rapid invasion into a collagen matrix by the aggressive human melanoma cells with a high level of activity of the Rho/MRTF pathway.
Tumor cells were formed into spheres which were embedded in a collagen then watched over 2 days as they invade into the collagen..</span>
<span class="attribution"><span class="source">Author provided.</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Our lab, in collaboration with Dr. Scott Larsen at the University of Michigan, has developed some chemical inhibitors of the Rho/MRTF pathway. In our recent <a href="http://mct.aacrjournals.org/content/16/1/193.long">publication</a>, we showed that one of these compounds was able to reduce melanoma cell migration and invasion in lab studies and to reduce metastasis of a human melanoma to the lung in a mouse model. We observed a remarkable decrease in the number and size of lung metastases in this study. </p>
<p>Our current studies are trying to determine whether measurements of Rho/MRTF pathway activity can be used to predict which melanoma tumors will metastasize and which early-stage melanomas are more likely to recur. If so, identification of high activity would trigger the need for very close clinical monitoring after surgery or possible drug treatment with existing drugs, or our compounds if they become available for clinical use.</p>
<p>We are also trying to determine whether we can prevent metastases only before the cancer cells have arrived in the lung, for example. Alternatively, if we prevent dormancy so that the cells die before setting up shop in the distant tissue or prevent the reactivation of the dormant cells in their new environment, the compounds might work even after the earliest stage of tumor spread.</p>
<p>The road from studies in mice to the clinic is long and full of pitfalls. We are continuing efforts to demonstrate that these compounds are safe enough for human studies in a few years. There are still many questions, but this approach could add a new arrow in the quiver of cancer treatment specialists.</p><img src="https://counter.theconversation.com/content/71531/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Richard Neubig receives funding from the National Institutes of Health related to the compounds being discussed here. </span></em></p>Melanoma, the deadliest form of skin cancer, can usually be cured when caught early. When it has spread, however, it becomes a challenge. Recent findings are bringing hope. Here are a few examples.Richard Neubig, Professor of Pharmacology and Toxicology, Michigan State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/598342016-05-23T15:11:35Z2016-05-23T15:11:35ZMystery in northern Scotland that is baffling multiple sclerosis experts<figure><img src="https://images.theconversation.com/files/123580/original/image-20160523-11012-1aj0t7g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Kirkwall harbour, Orkney.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/teflon/8465715232/in/photolist-dU61cs-4yuk6K-g7KGor-4yukgB-nQu6RJ-egi5nb-eh9Dqm-83nkjZ-fdNw8d-6tRs8a-eFyNu4-6tRrZV-oHwrNM-or2SkF-8kVJW6-83qrLu-or3hNM-opqCge-cA2UtJ-anYQfZ-atSQoK-atSQiR-2m1kum-4yndSY-pMbeqp-atSQq6-cckkeh-eeyFYY-opbpU7-FxXuch-puVnk6-oQBwWZ-puVkzH-anAzEG-att5Pf-2S5XL4-E8cfFq-6CJVBX-k9HoX-k9Hpa-73xH3b-e6TfjV-e6YSGf-e6TfDt-e6YT8S-e6Tg12-e6YSRj-e6YTvW-4yndNW-6jKFAp">Martin Deutsch</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>The north of Scotland has long been an important part of our quest to understand what causes multiple sclerosis (MS). Though we have known about the region’s high rate of the disease for some time, it moved centre stage after a 2012 study <a href="http://www.ncbi.nlm.nih.gov/pubmed/22577232">comprehensively revealed</a> staggering levels in the Orkney isles which lie off the northernmost mainland. </p>
<p>The study appeared to heavily support <a href="http://overcomingms.users41.interdns.co.uk/ms-a-to-z/ms-encyclopedia/sunlightvitamin-d-and-ms/">the theory</a> that low UV-B sunlight is a key initiating factor in the damage to pathways transmitting signals to and from the brain that we see in MS sufferers. People who are exposed to less of this light <a href="http://press.endocrine.org/doi/abs/10.1210/jcem-67-2-373">tend to</a> have lower levels of vitamin D in their blood, and studies have repeatedly <a href="http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1001866">shown links between</a> low vitamin D and higher MS incidence – <a href="http://www.thelancet.com/journals/laneur/article/PIIS1474-4422(03)00663-X/abstract">most likely</a> interacting with other factors like genetics and plain bad luck. </p>
<p>But now a <a href="http://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0155633">more recent study</a> has shown that Orcadians have higher vitamin D levels than the Scottish average. So what is going on? Is it back to the drawing board for understanding MS?</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/123634/original/image-20160523-10984-pt2dvv.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/123634/original/image-20160523-10984-pt2dvv.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/123634/original/image-20160523-10984-pt2dvv.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=598&fit=crop&dpr=1 600w, https://images.theconversation.com/files/123634/original/image-20160523-10984-pt2dvv.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=598&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/123634/original/image-20160523-10984-pt2dvv.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=598&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/123634/original/image-20160523-10984-pt2dvv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=752&fit=crop&dpr=1 754w, https://images.theconversation.com/files/123634/original/image-20160523-10984-pt2dvv.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=752&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/123634/original/image-20160523-10984-pt2dvv.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=752&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">Google Maps</span></span>
</figcaption>
</figure>
<p>In fact, the authors are careful to point out that the study is not as straightforward as the headline numbers make it appear. They monitored the vitamin D levels in the blood of individuals who have lived on Orkney for at least a generation and compared them to individuals in the same age group from the rest of Scotland. They did find higher than average vitamin D levels among Orcadians, but this was entirely due to two age groups, 60 to 69-year-olds and the 70s and over. </p>
<p>In all other age groups, the study found that vitamin D levels were lower than the rest of Scotland. Indeed the average levels of vitamin D in Orcadians under the age of 40 was substantially lower than their Scottish equivalent, who are <a href="http://www.gov.scot/Topics/Health/Healthy-Living/Food-Health/vitaminD">themselves considered</a> to be at risk of deficiency. This age range is probably the most relevant to understanding MS, since they are more likely to be child bearing and there is a <a href="http://www.ncbi.nlm.nih.gov/pubmed/21786297">strong correlation</a> between vitamin D levels in the womb and MS susceptibility for the offspring. The group also includes those most likely to develop MS, <a href="http://apps.who.int/iris/bitstream/10665/43968/1/9789241563758_eng.pdf">which are</a> women in their late 20s and early 30s. </p>
<h2>Vikings and screen addicts</h2>
<p>There are at least two possible explanations for this difference in the age groups: it could be that Orcadians enjoy greater exposure to sun as they get older; or it could be that the younger generation is spending less time outdoors. To assess that first possibility, the study’s authors used lifestyle questionnaires. This helped them establish that the vitamin D data was being skewed by two groups – farmers and financially secure over-60s who take regular foreign holidays. </p>
<p>The prospect of a generational change in Orcadians is more worrying because it might mean that MS levels will rise on the islands. Indeed, there is already evidence of a rise in the past 35 years. Yet the new study hints that lifestyle changes in the older generations is actually the reason for the discrepancy. We will need to see further studies to clarify this. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/123583/original/image-20160523-10986-1kj0cpo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/123583/original/image-20160523-10986-1kj0cpo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/123583/original/image-20160523-10986-1kj0cpo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/123583/original/image-20160523-10986-1kj0cpo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/123583/original/image-20160523-10986-1kj0cpo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/123583/original/image-20160523-10986-1kj0cpo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/123583/original/image-20160523-10986-1kj0cpo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/123583/original/image-20160523-10986-1kj0cpo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">‘Hay-men to that.’</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/robert_scarth/62846207/in/photolist-6y6Zi-4wYC45-ehktwc-e3gLSG-6DS4j-4Sed7W-aZLu7T-6Jujjn-4Se8VA-6ymtu-4S9XxX-jfuRE-ika2f-6xHLy-f7MR7Z-6ynnE-6y68T-7Wrc2-6y9Md-6y5WC-avumps-djGuRV-6ykX4-2yN7Uh-6yoVe-6ymaa-nh9FZ-79wnHD-6ymCf-6y6La-6y6jF-82RAae-6ymki-6Lw2JR-6ymZh-6ymP4-6N4PcR-6y9Zv-6ykH2-jfuRA-79jUJm-2yN9jJ-iQGZL-6y9dH-6ykv7-4Sa2Le-4Sn8CQ-6y91k-2tiZQ-2yHLoM">Robert Scarth</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>So can we reinstate the lack of UV-B light and vitamin D as the prime suspect in Orcadians’ increased risk of MS? Maybe not entirely. <a href="http://jnnp.bmj.com/content/early/2012/05/09/jnnp-2011-301546.full.pdf?hwshib2=authn%3A1464093632%3A20160523%253A114f893b-57ad-4fa6-9ff3-096471e42295%3A0%3A0%3A0%3AQzPtM4gB11BA93TvzPhr7A%3D%3D">While the</a> incidence of MS in Orkney is 402 cases per 100,000, <a href="https://www.mstrust.org.uk/a-z/prevalence-and-incidence-multiple-sclerosis">compared to</a> around 200 in the rest of Scotland and 165 in England, in the even more northerly Shetlands <a href="http://jnnp.bmj.com/content/early/2012/05/09/jnnp-2011-301546.full.pdf?hwshib2=authn%3A1464093632%3A20160523%253A114f893b-57ad-4fa6-9ff3-096471e42295%3A0%3A0%3A0%3AQzPtM4gB11BA93TvzPhr7A%3D%3D">it is</a> 295. Yet Shetlanders should be even more sunlight-deficient than Orcadians. </p>
<p>Maybe the populations of the two island groups are exposed to different levels of sunlight because of differences in their culture or lifestyle, but the work has not been done in the Shetlands to take us beyond speculation here. We also know that genes play a substantial role in MS susceptibility and it cannot be ruled out that genetic difference between populations may play some role. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/123582/original/image-20160523-10994-nk2cgz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/123582/original/image-20160523-10994-nk2cgz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/123582/original/image-20160523-10994-nk2cgz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/123582/original/image-20160523-10994-nk2cgz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/123582/original/image-20160523-10994-nk2cgz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/123582/original/image-20160523-10994-nk2cgz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/123582/original/image-20160523-10994-nk2cgz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/123582/original/image-20160523-10994-nk2cgz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">‘Not guilty.’</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/nuwandalice/5676900731/in/photolist-9DDANP-5sL5rP-dnvwSe-NAQxv-qYQ7v-edw3A3-4VW71p-gRqXwf-pzDM2E-4ALoQ5-bvLyVm-9h1Qfk-9pJWPX-4isFLs-acQhio-493JpW-bkyXzi-jG36St-jdKVzh-r6Zfvk-cz5s3Q-6W53ot-7ETjUX-r2Ci7s-e71Xgu-riHE35-6W53on-oZBfYQ-6VRzbJ-5rZ7zS-9n33En-qUqhdL-bw7sCn-gRqXCC-7caDtg-2912Rf-fMiSe5-dCSLDZ-bw7t4x-bw7rpx-DBAHy7-bwEGFT-4aqyDC-qmU38A-54VZfR-9n33kP-r6ZfbH-uanhv-8wSqdk-235Kx">Alice</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>In this regard, the press has in the past <a href="http://www.dailymail.co.uk/health/article-2245978/Vikings-blame-Scots-highest-levels-multiple-sclerosis.html">wondered whether</a> the Vikings brought MS to the Orkneys. This seems fanciful because Vikings probably had an even greater influence on the Shetlands. MS incidence in Scandinavian countries <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1468-1331.2006.01342.x/full">is meanwhile</a> lower than the Scottish average. So if genetics is partly to blame, it’s more subtle than longboats and horned helmets. </p>
<p>In short, the study does raise a mystery, though not the one it first appeared to. It seems to support the sunlight theory of MS after all, but it leaves us asking what cultural shift is occurring in Orkney that is resulting in over 60s having higher vitamin D levels than the rest of the population. Getting to the bottom of that could be a major step towards refining our understanding of what causes the disease.</p><img src="https://counter.theconversation.com/content/59834/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Graham Wright receives Wellcome Trust funding to explore cell-therapy-based treatment for MS.</span></em></p>Orkney’s ultra-high incidence has been linked to the weak northern sun. So how come the more northern Shetlands are less afflicted?Graham Wright, Lecturer in Immunology, Edinburgh Napier UniversityLicensed as Creative Commons – attribution, no derivatives.