tag:theconversation.com,2011:/us/topics/pigment-12836/articles
Pigment – The Conversation
2024-03-22T12:32:08Z
tag:theconversation.com,2011:article/224815
2024-03-22T12:32:08Z
2024-03-22T12:32:08Z
What’s in tattoo ink? My team’s chemical analysis found ingredients that aren’t on the label and could cause allergies
<figure><img src="https://images.theconversation.com/files/581794/original/file-20240313-30-tf41i8.jpg?ixlib=rb-1.1.0&rect=0%2C17%2C5751%2C3811&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Tattoo ink ingredients don't always match what's labeled on the bottle. </span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/CubaTattoos/b36471bdd2ff4e6e8a19a9b9644768d0/photo?Query=tattoo%20ink&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=406&digitizationType=Digitized&currentItemNo=0&vs=true&vs=true">AP Photo/Desmond Boylan</a></span></figcaption></figure><p>Tattoos are an incredibly common form of permanent self-expression that date back <a href="https://theconversation.com/tattoos-have-a-long-history-going-back-to-the-ancient-world-and-also-to-colonialism-165584">thousands of years</a>. Most tattoo artists follow strict health and sanitation regulations, so you might assume that tattoo inks are carefully regulated, too. </p>
<p>But as work done by <a href="https://scholar.google.com/citations?user=F2mp97YAAAAJ&hl=en">my team of chemistry researchers</a> suggests, <a href="https://doi.org/10.1021/acs.analchem.3c05687">up to 90%</a> of tattoo inks in the U.S. might be mislabeled. This isn’t just a case of a missing pigment or a minor discrepancy. These inks contained potentially concerning additives that weren’t listed on the packaging. </p>
<h2>What’s in an ink?</h2>
<p>All inks are made up of one or more pigments, which are molecules that give tattoos their color, and some kind of carrier for that pigment. Before the 20th century, <a href="https://www.trinitybj.com/blog/articles/tattoo-ink-throughout-time">pigments used in tattooing</a> included ash, charcoal, minerals or other natural materials. Around the middle of the 20th century, though, tattoo artists started making their own inks using synthetic pigments and dyes. </p>
<p>Today, nearly all pigments used in tattoos are made of <a href="https://f1000research.com/articles/6-2034/v2">synthetic molecules</a> that allow for bright colors – with the exception of white and black pigments.</p>
<p>In the past few decades, tattoo ink manufacturing has shifted from individual artists making their own to large companies manufacturing inks and selling them to artists. My team wanted to figure out whether these inks contained the ingredients advertised, so we <a href="https://doi.org/10.1021/acs.analchem.3c05687">analyzed 54 tattoo inks</a> from the U.S. market. </p>
<h2>Unlisted ingredients</h2>
<p>More than half the inks my research team analyzed contained unlisted polyethylene glycol, also known as PEG. A variety of <a href="https://en.wikipedia.org/wiki/Polyethylene_glycol">medical products</a> contain PEG, including laxatives. It can cause <a href="https://doi.org/10.1111/all.14711">allergic reactions</a>, however, and in the case of tattooing, <a href="https://doi.org/10.1007/s00204-016-1739-2">research has suggested</a> that repeated exposure to PEG could lead to kidney failure.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/582031/original/file-20240314-26-uzfyep.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two carbon atoms, with OH groups at each end." src="https://images.theconversation.com/files/582031/original/file-20240314-26-uzfyep.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/582031/original/file-20240314-26-uzfyep.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=256&fit=crop&dpr=1 600w, https://images.theconversation.com/files/582031/original/file-20240314-26-uzfyep.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=256&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/582031/original/file-20240314-26-uzfyep.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=256&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/582031/original/file-20240314-26-uzfyep.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=322&fit=crop&dpr=1 754w, https://images.theconversation.com/files/582031/original/file-20240314-26-uzfyep.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=322&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/582031/original/file-20240314-26-uzfyep.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=322&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Polyethylene glycol’s chemical structure.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:PEG_Structural_Formula_V1.svg">Jü/Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>We also found <a href="https://pubchem.ncbi.nlm.nih.gov/compound/Propylene-Glycol">propylene glycol</a> in 15 inks, though it wasn’t listed as an ingredient in any of them. Propylene glycol is generally nontoxic and structurally similar to glycerin, which is used to thicken the ink. Even though propylene glycol is safe for most people, some people are highly allergic to it. In fact, it was the American Contact Dermatitis Society’s <a href="https://dermnetnz.org/topics/contact-allergy-to-propylene-glycol">2018 Allergen of the Year</a>. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/582037/original/file-20240314-24-hhn63o.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Three carbon atoms, with OH groups connected to the first and 2nd carbons." src="https://images.theconversation.com/files/582037/original/file-20240314-24-hhn63o.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/582037/original/file-20240314-24-hhn63o.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=364&fit=crop&dpr=1 600w, https://images.theconversation.com/files/582037/original/file-20240314-24-hhn63o.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=364&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/582037/original/file-20240314-24-hhn63o.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=364&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/582037/original/file-20240314-24-hhn63o.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=457&fit=crop&dpr=1 754w, https://images.theconversation.com/files/582037/original/file-20240314-24-hhn63o.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=457&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/582037/original/file-20240314-24-hhn63o.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=457&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Propylene glycol’s chemical structure.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Propylene_glycol_chemical_structure.png">Edgar181/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>An <a href="https://www.contactdermatitisinstitute.com/pdfs/allergens/Propylene%20glycol.pdf">allergic reaction</a> to propylene glycol can cause a skin rash, itching and blistering. </p>
<p>In several inks, my research team found unlisted ingredients that are common in cosmetics but have not been tested in tattoo inks. <a href="https://doi.org/10.1080/10915810290096513">These include BHT</a>, <a href="https://www.paulaschoice.com/ingredient-dictionary/ingredient-dodecane.html">dodecane</a> and <a href="https://www.webmd.com/beauty/what-to-know-about-phenoxyethanol">2-phenoxyethanol</a>. In low concentrations, 2-phenoxyethanol can be a preservative. But the <a href="https://doi.org/10.1038/s41598-020-58170-9">Food and Drug Administration has warned</a> that it could get passed to infants through breastfeeding and lead to vomiting and dehydration in babies.</p>
<p>Of the 54 inks we analyzed, 29 reported the correct pigments, while the rest either did not report or reported the wrong pigments. <a href="https://www.kantonslabor.bs.ch/dam/jcr:ba246390-48da-406f-aa4e-9e1b24726a31/JB_Tattoo_PMU_2011_EN.pdf">This is a known</a> <a href="https://doi.org/10.1111/cod.13913">problem in tattoo inks</a> that ink manufacturers have not yet addressed. </p>
<h2>Pigment concerns</h2>
<p><a href="https://doi.org/10.3390/cosmetics10050141">Studies have found</a> that carbon black, the primary black pigment used in tattooing, can be contaminated with some of the same <a href="https://en.wikipedia.org/wiki/Polycyclic_aromatic_hydrocarbon">cancer-causing molecules</a> found in car exhaust and cigarette smoke.</p>
<p>Many red, yellow and orange pigments are azo pigments, which contain two connected nitrogen atoms. These pigments give ink bright, vivid colors, but over time they may <a href="https://doi.org/10.1007/s00204-016-1739-2">break down into carcinogens</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/582029/original/file-20240314-30-w4pn6t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A tattoo artist wearing latex gloves holding a tattooing needle inks a geometric design on an arm." src="https://images.theconversation.com/files/582029/original/file-20240314-30-w4pn6t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/582029/original/file-20240314-30-w4pn6t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/582029/original/file-20240314-30-w4pn6t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/582029/original/file-20240314-30-w4pn6t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/582029/original/file-20240314-30-w4pn6t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/582029/original/file-20240314-30-w4pn6t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/582029/original/file-20240314-30-w4pn6t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The pigments in many tattoo inks are made up of synthetic molecules.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/InkcarcerationMusicandTattooFestival-Day1/7d0d0d2e40d64d4bbe7a0985aa992734/photo?Query=tattooing&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=382&digitizationType=Digitized&currentItemNo=7&vs=true&vs=true">Amy Harris/Invision/AP</a></span>
</figcaption>
</figure>
<p><a href="https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32020R2081#document1">Regulations in Europe</a> prohibit the use of copper-containing pigment blue 15 and pigment green 7, which my work observed to be the only blue and green pigments in the inks we tested. The EU banned these pigments over concern that their use in hair dyes <a href="https://mobil.bfr.bund.de/cm/349/tattoo-inks-risk-assessment-for-pigment-blue-15-3-and-pigment-green-7.pdf">may cause bladder cancer</a>, though researchers haven’t studied that connection in tattoos yet. </p>
<h2>A new focus on regulation</h2>
<p>The FDA is beginning to pay more attention to what is in tattoo inks. In 2022, Congress passed the <a href="https://www.fda.gov/cosmetics/cosmetics-laws-regulations/modernization-cosmetics-regulation-act-2022-mocra">Modernization of Cosmetics Regulation Act, or MoCRA</a>, which gave the FDA expanded authority to regulate tattoo inks. </p>
<p>The FDA is still deciding how to implement MoCRA, but the act will require accurate ingredient labeling and expand the FDA’s authority to recall ink. In the past, tattoo inks have very rarely, and only voluntarily, been recalled because of <a href="https://doi.org/10.3389/fpubh.2023.1279884">bacterial contamination</a>.</p>
<p>So what does this mean for tattoo clients and artists? Right now, there’s no clear research consensus on whether tattoos are safe or not, as they can cause infection and allergic reactions. Plus, tattoos vary widely in size, color and physical location on the body.</p>
<p>Studies like the one from my lab are an important piece in establishing what is actually in a tattoo, so that researchers can better understand any adverse events, such as long-term allergic reactions, that they might cause.</p>
<p>Understanding what is in ink also helps physicians identify what particular health concerns they should look for in tattooed individuals.</p>
<p>The tattoo-related health issues that researchers <a href="https://www.aerzteblatt.de/int/archive/article/182859">do know about</a> come from unskilled artists following poor sanitation protocols. To prevent potential health concerns, those considering a tattoo can work with an experienced and trained artist who follows best practices for hygiene and tattoo aftercare.</p><img src="https://counter.theconversation.com/content/224815/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Swierk receives funding from National Institute of Health, National Science Foundation, and American Chemical Society Petroleum Research Fund. </span></em></p>
Some tattoo inks contain unlabeled materials that can cause allergic reactions.
John Swierk, Assistant Professor, Chemistry, Binghamton University, State University of New York
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/212420
2023-09-04T17:37:53Z
2023-09-04T17:37:53Z
Dogs 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>
</figcaption>
</figure>
<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 Montréal
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/209630
2023-07-27T14:49:42Z
2023-07-27T14:49:42Z
How hidden details in ancient Egyptian tomb paintings are revealed by chemical imaging
<figure><img src="https://images.theconversation.com/files/537110/original/file-20230712-39282-w8qnrv.png?ixlib=rb-1.1.0&rect=8%2C0%2C1888%2C537&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">XRF study of the painting of Ramesses II.</span> <span class="attribution"><span class="source">Martinez et al., 2023, PLOS ONE.</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>The walls of ancient Egyptian tombs can teach us much about the lives of the pharaohs and their entourages. Tomb paintings showed the deceased and their immediate family members involved in religious activities, the burial itself, or feasting at banquets and hunting in the Nile marshes.</p>
<p>But many such tombs were looted in antiquity and later on, or roughly excavated by foreign treasure hunters and early archaeologists. As a result, much of the painted decoration has suffered damage, despite being well-preserved by the arid environment.</p>
<p>Reconstructing those damaged sections of painted decoration has largely been done through educated guesswork, but a <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0287647">new study</a> reveals how a technique called portable X-ray fluorescence (<a href="https://www.fieldmuseum.org/science/special-projects/elemental-analysis-facility/portable-x-ray-fluorescence-pxrf">pXRF</a>) is being used to study ancient materials and identify remnants of decoration which are either faint or entirely invisible to the eye.</p>
<p>Elaborate tomb decoration, designed to reflect the status and esteem of the deceased person within, reached its zenith during Egypt’s <a href="https://www.britannica.com/topic/Eighteenth-Dynasty">18th</a> and <a href="https://www.britannica.com/topic/19th-Dynasty">19th dynasties</a> (1550-1189 BCE) in <a href="https://whc.unesco.org/en/list/87/">ancient Thebes</a> (modern Luxor). Royals were buried in the <a href="https://www.nationalgeographic.com/history/article/valley-of-the-kings">Valley of the Kings</a> and the <a href="https://www.britannica.com/place/Valley-of-the-Queens">Valley of the Queens</a>. </p>
<p>Members of the court and other high-ranking officials were laid to rest in several locations on the western bank of the Nile, close to the mortuary temples of the kings they served in life. Their tombs were cut into the rock, the rough-hewn walls of the chambers covered in plaster to provide a smooth surface for teams of artists and draughtspeople. </p>
<p>The decorative motifs they painted were not static, but changed from the 18th to the 19th dynasties. The former focused on vibrant scenes of the natural landscape and daily life, while more austere religious scenes were preferred during the later period.</p>
<p>The paints and pigments used by the ancient Egyptians were made from minerals and as such, have specific chemical markers. Yellow, as an example, was achieved by grinding up the arsenic sulfide orpiment, whereas blue pigment could be created using hydrated copper chloride, and red with iron oxide. By using portable X-ray fluorescence, scientists can use these chemical markers in the pigments to create a map of damaged areas. </p>
<h2>Physics and Egyptology</h2>
<p>The fields of archaeology and Egyptology have a long history of using tools and techniques developed by other disciplines. Developed in the early 20th century by physicist <a href="https://www.britannica.com/biography/Henry-Moseley">Henry Moseley</a>, XRF and pXRF measure secondary X-rays given off by a material when bombarded with primary X-rays. These signals can then be used to determine the material’s elemental composition. </p>
<p>Rather than the bulky (and immobile) analytical equipment frequently used to study archaeological artefacts in labs, the equipment needed to conduct a pXRF analysis weighs only a couple of kilogrammes and can easily be taken into the field.</p>
<p>While pXRF has been used in the past to determine the chemical composition of ceramics and metals, a new international research project headed by Philippe Martinez from Sorbonne University has recently used it to analyse the complex and beautiful paintings found in the tombs of Egyptian nobles.</p>
<h2>Reconstructing ancient art</h2>
<p>The process is not useful only for reconstructing damaged sections, it also has the potential to illuminate elements of artistic technique. In the 18th dynasty tomb chapel belonging to the Overseer of the Fields of <a href="https://www.ees.ac.uk/the-tomb-of-menna-tt69-luxor#:%7E:text=Menna%20was%20a%20scribe%20and,recommend%20a%20(virtual)%20trip!">Amun, Menna</a> (TT69), the team identified a phantom arm on the portrait of the tomb owner. </p>
<p>This third arm, which would have been invisible when the tomb was first finished, is the result of an alteration to the stance of the subject, made for unknown reasons by the painters. In this way, the technique can show stages of decoration and technical or aesthetic choices made by artists many thousands of years in the past.</p>
<p>In addition to the tomb of Menna, the team also analysed a portrait of <a href="https://www.nationalgeographic.com/culture/article/ramses-ii">Ramesses II</a> found in the <a href="https://www.osirisnet.net/tombes/nobles/nakhtamon341/e_nakhtamon341_01.htm">tomb of Nakhtamun</a>, which has traditionally been dated to the 19th dynasty.</p>
<p>The painting contained several subtle alterations, including to the shape of the royal sceptre held by the ruler (maybe to avoid it colliding with the figure’s face). The necklace worn by the king may also have been changed, and this change, the team behind the project claims, may have significance for the dating of the tomb. </p>
<p>They suggest that the king was first depicted wearing a type of necklace known as a <a href="https://ancientegyptonline.co.uk/jewellerycollar/"><em>shebyu</em></a>, which was popular during the 20th dynasty, some years after Ramesses II’s death.</p>
<p>This original necklace seems to have been altered to another type, known as a <a href="https://ancientegyptonline.co.uk/jewellerycollar/"><em>wesekh</em></a>, which was more popularly used in royal depictions during his lifetime. It seems that the tomb painters originally depicted this 19th-dynasty ruler wearing 20th-dynasty jewellery, realised their error and then made the necessary alterations.</p>
<p>This in turn, may then suggest that the tomb owner, Nakhtamun, actually lived and worked during the 20th rather than the 19th Dynasty, and that the portrait of Ramesses II is not the portrait of the living king, but rather of the deceased and deified ruler.</p>
<p>Scientific analysis is increasingly being incorporated into most facets of Egyptological research from material analysis of pigments, ceramics, metals and wood, to <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6933776/">spectroscopic analysis</a> of ancient <a href="https://www.britannica.com/topic/papyrus-writing-material">Egyptian papyrus</a>.</p>
<p>These techniques not only allow minimally or non-invasive investigations which help to preserve artefacts and prevent further damage, they also illuminate crucial details about the technological and artistic achievements of the ancient Egyptians.</p><img src="https://counter.theconversation.com/content/209630/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicky Nielsen does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
A technique called portable X-ray fluorescence has helped Egyptologists identify changes and adjustments to details of tomb decoration that are invisible to the human eye.
Nicky Nielsen, Senior Lecturer in Egyptology, University of Manchester
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/194251
2022-11-30T02:42:03Z
2022-11-30T02:42:03Z
Chlorophyll water can’t clear your skin or detox your liver. But this TikTok trend got one thing right
<figure><img src="https://images.theconversation.com/files/494378/original/file-20221109-12-y2eyjf.jpg?ixlib=rb-1.1.0&rect=1%2C110%2C772%2C555&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/close-chlorophyll-water-2047018778">Shutterstock</a></span></figcaption></figure><p>If you follow health trends online, you might have heard about “chlorophyll water”. Claims range from <a href="https://www.allure.com/story/tiktok-drinking-liquid-chlorophyll-skin-care-benefits">clearing your skin</a>, stopping <a href="https://www.healthline.com/health/chlorophyll-bad-breath">body odour</a>, increasing <a href="https://chlorophyllwater.com">energy and oxygen</a>, to <a href="https://www.verywellfit.com/health-benefits-liquid-chlorophyll-4686266">detoxing your liver</a> and <a href="https://www.healthline.com/health/liquid-chlorophyll-benefits-risks">preventing cancer</a>. </p>
<p>Chlorophyll water is sold as a liquid concentrate or already mixed with water. Numerous TikTok videos claim its health benefits.</p>
<p><iframe id="tc-infographic-792" class="tc-infographic" height="400px" src="https://cdn.theconversation.com/infographics/792/2a5a434e96e20c6436cb180cbfe25b2f7b8a3dbc/site/index.html" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>Then there are celebrity endorsements for chlorophyll water, including from <a href="https://chlorophyllwater.medium.com/the-benefits-of-drinking-chlorophyll-water-by-kourtney-kardashian-poosh-50a3536cb123">Kourtney Kardashian</a> on her <a href="https://poosh.com/chlorophyll-water-benefits/">lifestyle channel</a>.</p>
<p>So, what is chlorophyll water? And is it really a healthy choice?</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/lemon-water-wont-detox-or-energise-you-but-it-may-affect-your-body-in-other-ways-180035">Lemon water won't detox or energise you. But it may affect your body in other ways</a>
</strong>
</em>
</p>
<hr>
<h2>Remind me again, what’s chlorophyll?</h2>
<p>What you might remember about chlorophyll from high-school science might sound pretty healthy. </p>
<p><a href="http://www.chm.bris.ac.uk/motm/chlorophyll/chlorophyll_h.htm">Chlorophyll</a> is the pigment that gives plants (and some algae and bacteria) their green colour. It is vital for <a href="https://education.nationalgeographic.org/resource/photosynthesis">photosynthesis</a>, the process that uses sunlight to produce oxygen and chemical energy stored in the sugar glucose.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/495581/original/file-20221116-25-16gm08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Light shining through green palm fronds" src="https://images.theconversation.com/files/495581/original/file-20221116-25-16gm08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/495581/original/file-20221116-25-16gm08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495581/original/file-20221116-25-16gm08.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495581/original/file-20221116-25-16gm08.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495581/original/file-20221116-25-16gm08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495581/original/file-20221116-25-16gm08.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495581/original/file-20221116-25-16gm08.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">Yes, you do remember correctly. Plants need chlorophyll to generate oxygen and energy.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/sun-shining-through-radiating-green-leaf-391408468">Shutterstock</a></span>
</figcaption>
</figure>
<p>At the heart of most chlorophyll is <a href="https://ods.od.nih.gov/factsheets/Magnesium-Consumer">magnesium</a> – an essential nutrient for humans – needed for healthy nerves and muscles, regulating blood sugar and blood pressure, and building bones, proteins and DNA. </p>
<p>The chemical structure of chlorophyll looks a bit like <a href="https://pubmed.ncbi.nlm.nih.gov/24670123/">protoheme</a>. That’s the red part of our haemoglobin, the part of red blood cells that carries oxygen in our blood.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-are-leaves-green-86160">Curious Kids: Why are leaves green?</a>
</strong>
</em>
</p>
<hr>
<h2>So, what is chlorophyll water then?</h2>
<p>Water plus pigments that keep plants healthy, and that contain nutrients humans need, sounds great. Unfortunately, it’s not so simple. </p>
<p>First, chlorophyll doesn’t dissolve in water. So, what you get in these products isn’t “natural from plants”. It’s the molecule <a href="https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/chlorophyllin#:%7E:text=Chlorophyllin%20is%20a%20semisynthetic%20chlorophyll,and%20have%20good%20water%20solubility.">chlorophyllin</a>. Chlorophyllin is made from chlorophyll by a process called <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5039533">saponification</a>.</p>
<p>Essentially, this involves reacting it with sodium hydroxide and making a smaller molecule that is water-friendly. Then, to help it stay bright green, another reaction replaces the magnesium with copper, <a href="https://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/chlorophyll-metallo-chlorophyll-derivatives">which is much more stable</a>. </p>
<p>A more accurate name for these products would be “sodium copper chlorophyllin water”. But that’s not quite so marketable.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/495582/original/file-20221116-18-qqvv7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Woman dropping chlorophyll extract into glass of water" src="https://images.theconversation.com/files/495582/original/file-20221116-18-qqvv7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/495582/original/file-20221116-18-qqvv7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=395&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495582/original/file-20221116-18-qqvv7i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=395&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495582/original/file-20221116-18-qqvv7i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=395&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495582/original/file-20221116-18-qqvv7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=497&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495582/original/file-20221116-18-qqvv7i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=497&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495582/original/file-20221116-18-qqvv7i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=497&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Is that ‘chlorophyll water’ or ‘sodium copper chlorophyllin water’? One sounds easier to swallow.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/woman-dripping-chlorophyll-supplement-into-glass-2130227768">Shutterstock</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/does-tiktoks-chia-lemon-internal-shower-really-beat-constipation-heres-what-science-says-188744">Does TikTok's chia-lemon 'internal shower' really beat constipation? Here's what science says</a>
</strong>
</em>
</p>
<hr>
<h2>But is it healthy?</h2>
<p>Just because it’s been converted from its natural form, doesn’t make it automatically unhealthy. So how do the health claims stack up?</p>
<p>There is lots of evidence about diets high in chlorophyll being healthy. But, since evidence is mostly diets <a href="https://www.sciencedirect.com/science/article/pii/B9780128008720000184">high in green plant foods</a>, this can’t be directly translated into water containing a processed derivative of one little part of green plants. </p>
<p>There is <a href="https://pubmed.ncbi.nlm.nih.gov/24670123/">some evidence</a> that comes from the extracted, processed form (chlorophyllin). But that’s mostly from animal or lab studies. These involve very high concentrations that would need you to drink dramatic levels of chlorophyll water to match the doses, or to inject it deep into your cells. To be clear, please don’t do either.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/science-or-snake-oil-can-a-detox-actually-cleanse-your-liver-56344">Science or Snake Oil: can a detox actually cleanse your liver?</a>
</strong>
</em>
</p>
<hr>
<p>There are also some (mostly very small) studies about its impacts on <a href="https://pubmed.ncbi.nlm.nih.gov/25844615/">skin</a> and its use as a <a href="https://jamanetwork.com/journals/jama/article-abstract/287788">deodorant</a>, but most of these are about applying chlorophylls and chlorophyllins directly to the skin. You don’t need to be a scientist to know that’s not the same as drinking it in water.</p>
<p>How about boosting your energy and oxygen? It might make sense on simple logic because this is what it does in plants, and the pigment’s similarities to haemoglobin. </p>
<p>But there is no data to support these claims. We do have a small pilot <a href="https://www.semanticscholar.org/paper/A-pilot-study-on-wheat-grass-juice-for-its-and-on-Chauhan/73f2bb7c0b1129b5da66ca284eb2294d956fa9d2?p2df">study</a> of wheatgrass and the blood disorder thalassemia. But wheatgrass is much more complex than just chlorophyll and what helps someone with a disorder doesn’t necessarily make the rest of us healthier.</p>
<h2>So why do so many people say they feel better?</h2>
<p>First, who’s making the testimonials on social media? Do you trust them? Could it be <a href="https://digitalcommons.uri.edu/tmd_major_papers/2/">advertising</a> rather than someone’s own personal experience?</p>
<p>Second, it could be the “<a href="https://www.jneurosci.org/content/31/45/16117.short">placebo effect</a>”, where just taking something that feels like a treatment makes you feel better. </p>
<p>But most importantly, the main ingredient in chlorophyll water is water.</p>
<p>This is definitely <a href="https://www.eatforhealth.gov.au/nutrient-reference-values/nutrients/water">an essential nutrient</a>, and definitely something we want to encourage people to drink more of. </p>
<p>By turning to chlorophyll water, people may be simply increasing their water intake, and decreasing their intake of sugary drinks or alcohol. <a href="https://www.mdpi.com/2072-6643/11/1/70">Improving hydration</a> alone could explain their reports. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-do-i-wake-up-thirsty-183731">Why do I wake up thirsty?</a>
</strong>
</em>
</p>
<hr>
<h2>Are there any risks?</h2>
<p>Excessive consumption (multiple doses a day) <a href="https://www.tandfonline.com/doi/full/10.3109/19390211.2013.859853">could cause some side effects</a> such as nausea, stomach upsets, discolouring your poo and staining your teeth.</p>
<p>Like all supplements, there is a risk chlorophyll water may interact with <a href="https://www.webmd.com/vitamins-and-supplements/chlorophyll-uses-and-risks">medications</a>. And there haven’t been big safety studies in at-risk groups, such as people who are pregnant or breastfeeding. So caution is advised.</p>
<p><iframe id="tc-infographic-793" class="tc-infographic" height="400px" src="https://cdn.theconversation.com/infographics/793/82c1dfb245279ba2e4f858eac103dad66412fdbc/site/index.html" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>But, stop and think about the potential indirect downsides of drinking chlorophyll water. It’s expensive. Chlorophyll concentrate, which you’d dilute with water, costs about <a href="https://www.chemistwarehouse.com.au/buy/58504/swisse-chlorophyll-spearmint-500ml?gclid=Cj0KCQiA1NebBhDDARIsAANiDD0o1EzK7XgJq3xR0yfswtGg_Uc4U3zJ2Ec1CkEEFe8KXVcFbjmtBZIaAmd_EALw_wcB&gclsrc=aw.ds">A$16</a> for a 500mL bottle. So it could be an expensive way of increasing your water intake if you think you’re not drinking enough, given tap water is safe and cheap. </p>
<p>Even if there are any benefits, you could get these benefits from eating actual plant foods. So the money and time you spend buying chlorophyll water could be taking money and time away from other food and drink choices that could have much bigger health benefits. </p>
<h2>The bottom line</h2>
<p>If you like it, can afford it, and don’t have any medication risks, the choice is yours. </p>
<p>You could also try other ways to increase your chlorophyll intake, such as eating more green veggies. You could add cheaper things to water to make it appealing, such as mint, fruit or teas. </p>
<p>These options could be cheaper and have even better health impacts, but probably won’t get as many views on TikTok. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/wellness-is-not-womens-friend-its-a-distraction-from-what-really-ails-us-177446">Wellness is not women's friend. It’s a distraction from what really ails us</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/194251/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Emma Beckett has received funding for research or consulting from Mars Foods, Nutrition Research Australia, NHMRC, ARC, AMP Foundation, Kellogg, and the University of Newcastle. She is a member of committees/working groups related to nutrition or the Australian Academy of Science, the National Health and Medical Research Council and the Nutrition Society of Australia. </span></em></p>
Health claims for chlorophyll water are all over TikTok. We looked at the evidence to see what stacked up.
Emma Beckett, Senior Lecturer (Food Science and Human Nutrition), School of Environmental and Life Sciences, University of Newcastle
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/169065
2021-11-22T13:28:51Z
2021-11-22T13:28:51Z
Why are barns painted red?
<figure><img src="https://images.theconversation.com/files/431753/original/file-20211112-15043-sjr0rb.jpg?ixlib=rb-1.1.0&rect=0%2C5%2C1688%2C1104&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A dairy barn in Waitsfield, Vermont, built circa 1890.</span> <span class="attribution"><span class="source">Thomas Visser</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>Why are barns painted red? – Elijah B., age 13, Waverly, Tennessee</strong></p>
</blockquote>
<hr>
<p>There are three reasons we see so many red American barns. It’s traditional, it’s practical and the color looks good.</p>
<p>Although a main reason to paint wooden buildings is for appearances, paint also protects the wood so it lasts longer. </p>
<p>During the 1700s and early 1800s, barns on family farms in the Northeast U.S. were typically covered with thick vertical boards. When they were left unpainted, the boards would slowly weather to a brownish-gray color. </p>
<p>But after the mid-1800s, to improve the efficiency of their barns by reducing drafts to help keep their animals more comfortable in winter, many farmers tightened up their barns by having wooden clapboards horizontally nailed on the outside barn walls. These clapboards were sawed quite thin, so painting them provided needed protection and dressed up the appearance of the barns.</p>
<figure class="align-center ">
<img alt="Horses in field with red barn in background." src="https://images.theconversation.com/files/429817/original/file-20211102-17-1xlcy71.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/429817/original/file-20211102-17-1xlcy71.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/429817/original/file-20211102-17-1xlcy71.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/429817/original/file-20211102-17-1xlcy71.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/429817/original/file-20211102-17-1xlcy71.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/429817/original/file-20211102-17-1xlcy71.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/429817/original/file-20211102-17-1xlcy71.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">Horses graze on a farm near Pullman, Washington.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/horses-in-pasture-with-red-barn-in-background-in-the-news-photo/913086614">Wolfgang Kaehler/LightRocket via Getty Images</a></span>
</figcaption>
</figure>
<p>In the 1800s it was common for people to make their own paints by mixing pigments with linseed oil made from flax seeds and other ingredients. Pigments are dry materials that add color. They were available in various hues, but the tint we see so often on older American barns was called <a href="https://press.uchicago.edu/ucp/books/book/distributed/F/bo44306991.html">Venetian red</a>.</p>
<p>According to the 1884 edition of “<a href="https://books.google.com/books?id=_8lPAAAAYAAJ&pg=PP12&lpg=PP12&dq=everybody%27s+paint+book+1884&source=bl&ots=HNAP1o_4_M&sig=ACfU3U2cexaqjXMTz7_llm6fq2scUYB8FQ&hl=en&sa=X&ved=2ahUKEwiFtv_jmevzAhXig-AKHST8C7cQ6AF6BAgbEAM#v=onepage&q=everybody's%20paint%20book%201884&f=false">Everybody’s Paint Book</a>,” by F.B. Gardner, Venetian red was “suitable for any common work, or for brickwork and outbuildings.” This red pigment penetrated well into wooden barn boards and resisted fading when exposed to sunlight, so it could age gracefully for generations.</p>
<p>Venetian red got its name because historically this pigment was produced from natural clays found near Venice, Italy. The clays contained an iron oxide compound that produced this red color. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/429816/original/file-20211102-25-mmrcdb.jpg?ixlib=rb-1.1.0&rect=0%2C7%2C5000%2C3308&q=45&auto=format&w=1000&fit=clip"><img alt="Red side wall of a barn with white framing around windows." src="https://images.theconversation.com/files/429816/original/file-20211102-25-mmrcdb.jpg?ixlib=rb-1.1.0&rect=0%2C7%2C5000%2C3308&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/429816/original/file-20211102-25-mmrcdb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/429816/original/file-20211102-25-mmrcdb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/429816/original/file-20211102-25-mmrcdb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/429816/original/file-20211102-25-mmrcdb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/429816/original/file-20211102-25-mmrcdb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/429816/original/file-20211102-25-mmrcdb.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"></a>
<figcaption>
<span class="caption">Detail from a barn in Grafton, Vermont.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/rustic-red-barn-detail-news-photo/469220409">John Greim/LightRocket via Getty Images</a></span>
</figcaption>
</figure>
<p>But as people found similar iron oxide deposits in many other places, “Venetian red” became a generic term for light red pigments that did not have any purplish tinge. By the 1920s, such “earth pigments” used to make red paints were being dug in Georgia, Pennsylvania, Virginia, Alabama, California, Iowa and Vermont. </p>
<p>By the late 1800s, in addition to red, it became fashionable to paint barns with other color schemes, especially those designed to complement the architectural styles and finishes of owners’ houses. These included various hues of yellows, greens and browns. Also, white paint commonly was applied to barns and houses.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/429807/original/file-20211102-17-1nl4t9u.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Four stamp designs show classic styles of American barns." src="https://images.theconversation.com/files/429807/original/file-20211102-17-1nl4t9u.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/429807/original/file-20211102-17-1nl4t9u.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=536&fit=crop&dpr=1 600w, https://images.theconversation.com/files/429807/original/file-20211102-17-1nl4t9u.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=536&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/429807/original/file-20211102-17-1nl4t9u.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=536&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/429807/original/file-20211102-17-1nl4t9u.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=674&fit=crop&dpr=1 754w, https://images.theconversation.com/files/429807/original/file-20211102-17-1nl4t9u.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=674&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/429807/original/file-20211102-17-1nl4t9u.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=674&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">These stamps, released Jan. 24, 2021, show a round barn surrounded by the hazy light and warm colors of fall; a gambrel-roofed barn in summer; a forebay barn in an early spring countryside; and a Western barn on a winter’s night.</span>
<span class="attribution"><a class="source" href="https://about.usps.com/postal-bulletin/2020/pb22561/html/info_004.htm">USPS, artwork by Kim Johnson</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>But red paint remained popular on many farms because it was the most affordable. In 1922 the <a href="https://archive.org/details/SearsRoebuckAndCoCatalog1922_201812/page/n7/mode/2up">Sears, Roebuck catalogue</a> offered red barn paint for just $1.43 per gallon, while other colors of house paints sold for at least $2.25 per gallon – nearly twice as much. </p>
<p>Today, many modern barns don’t resemble classic versions. Very large barns that hold hundreds of cows or pigs look more like hangars or warehouses, and may be <a href="https://livinghistoryfarm.org/farminginthe40s/crops_07.html">built of metal</a>. But the tradition of painting smaller barns red continues – so strongly that the U.S. Postal Service now celebrates them on <a href="https://store.usps.com/store/product/buy-stamps/barns-postcard-stamp-S_740204">postage stamps</a>. </p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/169065/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Thomas Durant Visser has received grant and contract funding from the National Endowment for the Arts; National Park Service; Department of the Navy, Naval Facilities Engineering Command; Institute for Museum Services, administered by the Foundation of the American Institute for Conservation of Historic and Artistic Works; Vermont Department of State Buildings; Preservation Trust of Vermont. He has provided technical assistance to Photoassist, Inc. for US Postal Service contracts. He is currently a member of the American Institute for Conservation of Historic and Artistic Works (AIC); Association for Preservation Technology International; National Trust for Historic Preservation, Preservation Forum; Heritage Canada; International Council on Monuments and Sites/ US Committee; Association of Critical Heritage Studies; American Alliance of Museums. </span></em></p>
Barns are practical buildings, designed to safeguard farm animals and equipment. Why are so many of them painted to stand out from the landscape?
Thomas Durant Visser, Professor of Historic Preservation, University of Vermont
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/141460
2020-07-28T09:22:56Z
2020-07-28T09:22:56Z
How mutant zebrafish helped unlock the secret to their stripes – new research
<figure><img src="https://images.theconversation.com/files/348379/original/file-20200720-64504-1tn17pj.jpg?ixlib=rb-1.1.0&rect=114%2C572%2C4048%2C2236&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/danio-rerio-236082157">Shutterstock/GrigorevMikhail</a></span></figcaption></figure><p>Zebrafish are one of the most well studied animals on the planet. But how they came by their beautiful black and gold stripes is more of a mystery. Our <a href="https://elifesciences.org/articles/52998">new research</a> used mathematical modelling – and detailed observations of mutant zebrafish patterns – to get to the bottom of one of nature’s oldest secrets. </p>
<p>Estimates suggest that zebrafish are used in over <a href="https://theconversation.com/animals-in-research-zebrafish-13804">600 labs around the world</a> to study diseases that range from <a href="https://academic.oup.com/hmg/article/12/suppl_2/R265/620445">muscular dystrophy</a> to <a href="https://core.ac.uk/download/pdf/2777109.pdf">cancer</a>. It may seem hard to imagine that a tiny tropical fish can tell us anything useful about distinctive human physiology but they are more similar to us than they appear at first glance. They have spines, hearts, livers, bones, eyes and kidneys.</p>
<p>Of equal importance is the opportunity that this hardy fish presents to investigate and understand the fundamental, and beautiful, biological processes that generate the spectacular pattern diversity seen in nature. These patterns are formed by the arrangement of pigments, usually packaged in specialised cells. </p>
<figure class="align-center ">
<img alt="Close up of zebrafish scales" src="https://images.theconversation.com/files/348122/original/file-20200717-21-khndmh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/348122/original/file-20200717-21-khndmh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=334&fit=crop&dpr=1 600w, https://images.theconversation.com/files/348122/original/file-20200717-21-khndmh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=334&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/348122/original/file-20200717-21-khndmh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=334&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/348122/original/file-20200717-21-khndmh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=419&fit=crop&dpr=1 754w, https://images.theconversation.com/files/348122/original/file-20200717-21-khndmh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=419&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/348122/original/file-20200717-21-khndmh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=419&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Zoom into the zebrafish’s alternating pattern and the stripes of colour resolve into individual pigment cells.</span>
<span class="attribution"><span class="source">Wikimedia/JenniferOwen (adapted by Kit Yates)</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>From a distance zebrafish stripes look like long thin blocks of black or gold pigment. But on closer inspection it can be seen that these stripes are made up of thousands of small and distinct dots of colour. Each dot is a single pigment cell. The three cell types that produce the pattern are black melanophores, yellow xanthophores and silver and blue iridophores. Our research focused on understanding how enough of these cells interacting in the right way can result in the alternating striped patterns on a zebrafish.</p>
<figure class="align-center ">
<img alt="A mutant leopardfish" src="https://images.theconversation.com/files/347779/original/file-20200715-27-67r5db.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/347779/original/file-20200715-27-67r5db.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=474&fit=crop&dpr=1 600w, https://images.theconversation.com/files/347779/original/file-20200715-27-67r5db.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=474&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/347779/original/file-20200715-27-67r5db.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=474&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/347779/original/file-20200715-27-67r5db.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=596&fit=crop&dpr=1 754w, https://images.theconversation.com/files/347779/original/file-20200715-27-67r5db.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=596&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/347779/original/file-20200715-27-67r5db.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=596&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The patterns of the leopard mutant are spots rather than stripes.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/carolineccb/4050116019/">Flickr/carolineCCB</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The mathematical theory that has predominated explanations of how zebrafish’s stripes emerged is <a href="https://theconversation.com/how-animals-got-their-spots-and-stripes-according-to-maths-85053">Turing patterning</a>. The mechanism is named after the visionary war hero, computer pioneer and mathematician <a href="https://theconversation.com/alan-turing-visionary-war-hero-and-the-only-choice-for-the-50-note-106470">Alan Turing</a> who first suggested it. In Turing patterns two different types of “agent” (melanophores and xanthophores in most zebrafish models) move around randomly and interact with each other in a special way, giving rise to a range of possible patterns. Although the patterns look convincing, scientists have not been able to prove this theory of <a href="https://www.crg.eu/en/news/new-theory-deepens-understanding-turing-patterns-biology">animal coat patterning</a>.</p>
<p>But <a href="https://elifesciences.org/articles/52998">our study</a> has demonstrated that the pattern formation mechanism is more complicated than a simple Turing model might suggest. As well as melanophores and xanthophores, we know iridophores also play an important role. These reflective cells give zebrafish their characteristic silvery appearance. Experiments have shown that without iridophores (or either of the other two cell types) the zebrafish’s characteristic striped pattern doesn’t form properly.</p>
<h2>Mutant zebrafish</h2>
<p>We wanted to find out which biological phenomena are crucial for pattern formation and which are just incidental. These sorts of questions can be answered with mathematical modelling.</p>
<p>We built an “agent-based” model (a computer code in which each cell is represented as an individual that can move and interact with others) which includes as much of the known biology of zebrafish patterning as possible. Once we had adapted the model to show it could reproduce the patterns seen in normal zebrafish we turned to the patterns formed by mutant zebrafish (fish with a genetic defect which changes their patterning) and tweaked the model rules to make sure it could replicate those too.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Yqcd-GEKm9k?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The model replicates the <em>pfeffer</em> zebrafish mutant’s broken black melanophore stripes on an iridescent iridophore background. <em>Pfeffer</em> mutants are deficient in yellow xanthophores.</span></figcaption>
</figure>
<p>Other mutant zebrafish, whose patterns were not used to build the model in the first place, acted as independent tests of the model’s pattern-replicating ability. Being able to mimic these other patterns gave us confidence in the model rules we had inferred. </p>
<p>As an example, the “choker” mutant has a defect which means silvery iridophores do not migrate to the skin in the normal manner. When we implemented this aberrant delivery of iridohphores in the model (but with essentially all the same rules) it neatly recreated the striking labyrinthine pattern seen in these fish.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/-_D4sO4mMbU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The model replicates the labyrinthine pattern exhibited by <em>choker mutants</em>. These mutant fish lack an initial horizontal stripe of iridophores in the middle of the embryo.</span></figcaption>
</figure>
<p>And then comes the really exciting part. The beauty of mathematical modelling is that once you’re confident your model captures the biology you can start to play around with it and ask biological questions that are difficult to answer through experiments alone.</p>
<p>For example, we were able to show that part of the reason zebrafish stripes are horizontal (as opposed to its mammalian namesake’s vertical stripes) is due to the way in which the body grows as the pattern forms. Faster growth along the head-tail axis (rather than the back-belly axis) of the fish tends to elongate groups of pigment cells into horizontal stripes rather than vertical bars.</p>
<p>Since pattern formation is an important general feature of organ development, there may be medical relevance to our research. A better understanding of pigment pattern formation might give us insights into the diseases caused by defects in cell arrangements.</p>
<p>With a working mathematical model there is no end to the questions we can ask about pigment pattern formation in zebrafish and other species. In particular, our next aim is to investigate the evolutionary origins of stripe formation in the broad family of Danio fish, of which the zebrafish (or Danio rerio) is a member. And that will help us gain an even deeper insight into how the zebrafish really got its stripes.</p><img src="https://counter.theconversation.com/content/141460/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christian Yates 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>
We wanted to find out which biological phenomena are crucial for pattern formation and which are just incidental. These sorts of questions can be answered with mathematical modelling.
Christian Yates, Senior Lecturer in Mathematical Biology, University of Bath
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/135378
2020-04-03T18:01:11Z
2020-04-03T18:01:11Z
Blue dye from red beets – chemists devise a new pigment option
<figure><img src="https://images.theconversation.com/files/324753/original/file-20200401-23143-1032w4i.jpg?ixlib=rb-1.1.0&rect=233%2C170%2C1715%2C1386&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Through the wonders of chemistry, molecules can be rearranged to completely transform color.</span> <span class="attribution"><span class="source">Erick Leite Bastos</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>What’s your favorite color? If you answered blue, you’re in good company. <a href="https://today.yougov.com/topics/lifestyle/articles-reports/2015/05/12/why-blue-worlds-favorite-color">Blue outranks all other color preferences</a> worldwide by a large margin.</p>
<p>No matter how much people enjoy looking at it, blue is a difficult color to harness from nature. As a chemist who <a href="https://www.bastoslab.com/">studies the modification of natural products</a> to solve technological problems, I realized there was a need for a safe, nontoxic, cost-effective blue dye. So my Ph.D. student, Barbara Freitas-Dörr, and I devised a <a href="https://advances.sciencemag.org/content/6/14/eaaz0421">method to convert the pigments of red beets into a blue compound</a> that can be used in a wide range of applications. We call it BeetBlue.</p>
<h2>Natural sources of blue</h2>
<p>Blue is strongly associated with nature, largely because it is reflected in the sky and on bodies of water. But compared to other colors, blue pigments are not commonly found in living organisms.</p>
<p>The feathers of many birds are blue, not because they produce a pigment, but because the microscopic structure of their <a href="https://en.wikipedia.org/wiki/Structural_coloration">feathers is able to filter light</a>. This physical phenomenon is very interesting but difficult to adopt for common applications.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/324747/original/file-20200401-23130-yhy2og.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/324747/original/file-20200401-23130-yhy2og.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/324747/original/file-20200401-23130-yhy2og.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/324747/original/file-20200401-23130-yhy2og.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/324747/original/file-20200401-23130-yhy2og.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/324747/original/file-20200401-23130-yhy2og.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/324747/original/file-20200401-23130-yhy2og.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/324747/original/file-20200401-23130-yhy2og.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"></a>
<figcaption>
<span class="caption">The <em>Lactarius indigo</em> mushroom is one of Mother Nature’s rare examples of blue.</span>
<span class="attribution"><a class="source" href="https://de.wikipedia.org/wiki/Datei:2013-08-06_Lactarius_indigo_(Schwein.)_Fr_359786.jpg">Alan Rockerfeller/Mushroom Observer</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Plants seldom produce blue hues. When they do, their pigments rarely remain stable after extraction. The same is true for blue mushrooms like the indigo milky cap and other species that develop a blue stain when disturbed. </p>
<h2>Turning red into blue</h2>
<p>You might wonder how something red can be turned into something blue. One approach is to change the way its molecules absorb and reflect light.</p>
<p>The white light coming from your lamp contains a rainbow of colors, even though you cannot see them – without the use of a prism, that is. The surface of your red chair looks red because, at the molecular level, it is absorbing all the colors except red, which is reflected and eventually reaches your eyes.</p>
<p>The color of your chair would change from red to blue if you modified the molecular structure of its dye, making it reflect blue light instead of red. The secret is in the number of carbon atoms in the dye and how they are connected to each other. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/325053/original/file-20200402-74889-mrhg0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/325053/original/file-20200402-74889-mrhg0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/325053/original/file-20200402-74889-mrhg0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=148&fit=crop&dpr=1 600w, https://images.theconversation.com/files/325053/original/file-20200402-74889-mrhg0p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=148&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/325053/original/file-20200402-74889-mrhg0p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=148&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/325053/original/file-20200402-74889-mrhg0p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=185&fit=crop&dpr=1 754w, https://images.theconversation.com/files/325053/original/file-20200402-74889-mrhg0p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=185&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/325053/original/file-20200402-74889-mrhg0p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=185&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">By changing the structure of molecular compounds, you can alter color.</span>
<span class="attribution"><span class="source">Erick Leite Bastos</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Beets produce chemical compounds called betalains, which are natural pigments and antioxidants. The chemical structure of betalains can be modified to produce almost any hue. We realized that if we increased the number of alternating single-double bonds in betalain molecules, we could change their color from orange or magenta to blue.</p>
<p>Making blue dye with adequate intensity and light-fastness is difficult because it must absorb yellow and orange light efficiently. Solving this problem required lots of molecular tweaking.</p>
<p>My lab has been working with betalains for over 10 years to understand their function in nature and their unique chemical features, so it took only one experiment to produce BeetBlue. (It took more than two years to optimize the process, though.) </p>
<p>We broke apart the betalain molecules using alkaline water with a pH of 11. Then we mixed the resulting compound, called betalamic acid, with a commercial chemical compound called 2,4-dimethylpyrrole in an open vessel at room temperature. BeetBlue is formed almost instantly. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/FUS95BYqJ24?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">BeetBlue is created in a beaker at room temperature.</span></figcaption>
</figure>
<p>Because we changed the characteristic carbon-nitrogen chemical bond of betalains into a carbon-carbon bond, BeetBlue is a new class of pseudo-natural dyes we call quasibetalains.</p>
<h2>Color your life blue</h2>
<p>The chemical synthesis of BeetBlue is fast and very simple. In fact, it is so simple that anyone can do it if all the chemicals are available.</p>
<p>BeetBlue dissolves easily in water and other solvents, maintains its color in acidic and neutral solutions, and may provide an alternative to expensive blue colorants that often <a href="https://en.wikipedia.org/wiki/List_of_inorganic_pigments#Blue_pigments">contain toxic metals</a>, which limit the scope of their applications. </p>
<p>Live zebrafish embryos as well as cultured human cells were not affected by BeetBlue. Although more experiments are necessary to make sure it is safe for human consumption, maybe you can dye your hair, customize your clothes or color your food in the future using a dye made from beets.</p>
<p>This work shows the importance of basic science for the development of technological applications. We did not patent BeetBlue. We want people to use it freely and understand, by interacting with nature in a different and sustainable way, the future can be bright. </p>
<p>[<em>Insight, in your inbox each day.</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=insight">You can get it with The Conversation’s email newsletter</a>.]</p><img src="https://counter.theconversation.com/content/135378/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Erick Leite Bastos receives funding from the São Paulo Research Foundation (FAPESP), the Brazilian National Council for Scientific and Technological Development (CNPq), and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).</span></em></p>
A simple chemical reaction turns the red pigment of beets into a new, nontoxic blue dye.
Erick Leite Bastos, Associate Professor of Chemistry, Universidade de São Paulo (USP)
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/105526
2018-10-25T15:36:56Z
2018-10-25T15:36:56Z
No safe suntan, but research suggests there may be a way to reduce ‘old leathery’ look
<figure><img src="https://images.theconversation.com/files/242255/original/file-20181025-71032-16n1mmp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/man-reddened-itchy-skin-after-sunburn-714070519?src=R5_pDNKBT77Xrfb0KX-FOQ-1-75">Focus and Blur/Shutterstock</a></span></figcaption></figure><p>Getting a tan may not depend on how much sun people get, but rather when they get it. This is the finding from a new international research project. The study, published in <a href="https://www.cell.com/molecular-cell/fulltext/S1097-2765(18)30793-7">Molecular Cell</a>, found that sun exposure every other day was more effective for tanning and caused less DNA damage than daily exposure.</p>
<p>This kind of exposure also avoided causing the <a href="http://www.who.int/uv/faq/uvhealtfac/en/index2.html">skin “thickening”</a> seen in people exposed to the sun every day. So, according to the research, those wanting a strong tan, while avoiding that “old leather” look often seen in long-term sun worshippers would be best off taking 24-hour breaks between sunbathing sessions.</p>
<p>The study also suggests it might be possible to create cosmetics that can give people a “natural” tan, as well as increasing our understanding of skin cancer, which is <a href="https://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/melanoma-skin-cancer#heading-One">killing</a> an increasing number of people. However, none of this alters the risk of skin cancer from exposure to the sun – or the <a href="https://www.cancer.org/cancer/melanoma-skin-cancer.html">health advice</a> about minimising exposure.</p>
<p>The researchers looked at the impact of the ultra-violet light found in the sun’s rays on human and mouse skin and in cultured cells, and identified the importance of a protein called MITF. This acts like a clock, synchronising and coordinating two systems used to protect the body from the harmful effects of sunlight. One protective process, which starts within a few minutes of exposure, thickens our skin and tries to <a href="https://www.nature.com/scitable/topicpage/dna-damage-repair-mechanisms-for-maintaining-dna-344">repair the sun’s damage</a> to our DNA.</p>
<p>The other process starts within a few hours and produces the <a href="https://www.news-medical.net/health/What-is-Melanin.aspx">dark pigment melanin</a> in specialised skin cells <a href="http://www.jbc.org/content/282/38/27557.full.html">called melanocytes</a>. The pigment then passes to the main type of skin cells, keratinocytes. It is this melanin that absorbs some of the harmful UV energy produced by the sun and gives people a tanned appearance.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/242256/original/file-20181025-71017-1moyzt7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/242256/original/file-20181025-71017-1moyzt7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/242256/original/file-20181025-71017-1moyzt7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/242256/original/file-20181025-71017-1moyzt7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/242256/original/file-20181025-71017-1moyzt7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/242256/original/file-20181025-71017-1moyzt7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/242256/original/file-20181025-71017-1moyzt7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Without protection, the sun will always damage your skin.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/severely-burned-skin-dark-tanned-body-156996335?src=_xqvZWDyOkpDb7X4R9aSTA-1-2">Marko Marcello/Shutterstock</a></span>
</figcaption>
</figure>
<p>The importance of melanin cannot be understated, as it <a href="https://www.scienceabc.com/humans/why-some-people-fair-others-dark-skin-color-determine.html">reduces the amount of damage</a> the sun does to DNA, which can lead to cancer. The researchers were able to show that thre was less damage to DNA in skin exposed to UV light every other day, even though the DNA repair process wasn’t switched on as often. This is probably because exposure every other day produced more melanin.</p>
<p>The researchers showed that the exposing the skin to UV light increased the concentration of MITF protein in the skin. But the level of MITF doesn’t simply increase and then decrease. Instead it displays a decaying oscillation, repeatedly falling and rising again but gradually disappearing over 48 hours. But the researchers also showed that if a second period of exposure started after just 24 hours, before MITF levels have returned to their baseline level, different genes were activated and the result was less tanning and more skin thickening.</p>
<h2>No safe suntan yet</h2>
<p>Interestingly, previous work published <a href="https://www.sciencedirect.com/science/article/pii/S0140673682902148">in The Lancet</a> has also shown that the body’s vitamin D concentrations are also higher when there is a 24-hour gap between sun exposure. Vitamin D is produced in the skin using energy from UV light and is critical for a healthy immune system, heart, protection from cancer, sepsis and a whole host of <a href="https://www.webmd.com/osteoporosis/features/the-truth-about-vitamin-d-why-you-need-vitamin-d">other functions</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/i-nearly-died-from-sepsis-and-ignorance-of-this-condition-is-killing-millions-99051">I nearly died from sepsis – and ignorance of this condition is killing millions</a>
</strong>
</em>
</p>
<hr>
<p>The new findings will be of particular interest to the cosmetics industry. They mean it could be possible to develop products containing proteins that will stimulate the skin into developing a “natural” tan, without being exposed to the harmful effects of the sun. So a risk-free suntan may be possible in the future.</p>
<p>In the meantime, the research suggests it may be best to use a higher factor sunblock – or avoiding the sun altogether – on alternate days. But it’s important to remember that there is <a href="https://www.nhs.uk/news/cancer/new-nice-guidelines-on-sun-exposure-warn-tanning-is-unsafe/">no safe amount of tanning</a>. Any sustained exposure to the sun increases your risk of skin cancer so you should still wear appropriate protection every day.</p><img src="https://counter.theconversation.com/content/105526/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Porter 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>
Exposure to the sun every other day produces more skin pigment than sunbathing every day – but protection is still vital.
Michael Porter, Lecturer in Molecular Genetics, University of Central Lancashire
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/99818
2018-07-17T10:46:56Z
2018-07-17T10:46:56Z
Pigments from microbes provide clue to evolution in ancient oceans – but weren’t pink a billion years ago
<figure><img src="https://images.theconversation.com/files/227876/original/file-20180716-44076-p499t1.jpg?ixlib=rb-1.1.0&rect=308%2C242%2C1628%2C1153&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cyanobacteria filled the ancient oceans and used chlorophyll to harvest the sun's energy.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/28594931@N03/4726914132">Specious Reasons</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>Possibly the most <a href="https://doi.org/10.1126/sciadv.1603076">significant event in the evolution of life</a> on Earth occurred 2.4 billion years ago. That was when the amount of oxygen in the atmosphere and ocean surface waters rapidly increased – setting the stage for a new phase of life on our planet.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/227886/original/file-20180716-44103-139nuoz.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/227886/original/file-20180716-44103-139nuoz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/227886/original/file-20180716-44103-139nuoz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1155&fit=crop&dpr=1 600w, https://images.theconversation.com/files/227886/original/file-20180716-44103-139nuoz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1155&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/227886/original/file-20180716-44103-139nuoz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1155&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/227886/original/file-20180716-44103-139nuoz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1451&fit=crop&dpr=1 754w, https://images.theconversation.com/files/227886/original/file-20180716-44103-139nuoz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1451&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/227886/original/file-20180716-44103-139nuoz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1451&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Most of the forms of life we’re familiar with are relatively recent additions to the planet.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:LifeTimeline-TemplateImage-20170116.png">Drbogdan</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Oxygen is produced by photosynthesis, a process that evolved in a type of bacteria <a href="http://www.ucmp.berkeley.edu/bacteria/cyanointro.html">called cyanobacteria</a>. Also known – incorrectly – as blue-green algae, you can encounter them today as pond scum.</p>
<p>Cyanobacteria are prokaryotes: simple single-celled organisms. <a href="http://www.ucmp.berkeley.edu/greenalgae/greenalgae.html">True algae</a> are eukaryotes: more complex, larger organisms. Both perform the same photosynthetic reactions to turn energy from the sun into oxygen and food molecules. The first true algae, as well as other single-celled eukaryotes, arose at least 1.4 billion years ago, but, mysteriously, appear to have remained in the background of life for another 800 million years, at which point they <a href="https://doi.org/10.1042/ETLS20180039">rapidly expanded in number and diversity</a>.</p>
<p><a href="https://doi.org/10.1073/pnas.1803866115">New research</a> by Australian National University earth scientists <a href="https://nationalmaglab.org/about/around-the-lab/meet-the-users/nur-gueneli">Nur Gueneli</a>, <a href="https://scholar.google.com/citations?user=oqL0DAUAAAAJ&hl=en&oi=ao">Jochen Brocks</a> and colleagues confirms the early importance of cyanobacteria in the primordial oceans and provides insights into why it took so long for the true algae to become the base of the food chain.</p>
<h2>Billion-year-old biomarkers</h2>
<p>Much of our knowledge of evolutionary history comes from the fossil record. Unfortunately, soft-bodied organisms, such as algae, rarely leave fossils. But researchers can recover the biomolecules they contained that are resistant to degradation. Found within ancient sediments, scientists can use these molecular fossils, <a href="http://summons.mit.edu/biomarkers/what-is-a-biomarker/">called biomarkers</a>, to identify what types of organisms were present when the sediments formed.</p>
<p>The new study published in the Proceedings of the National Academy of Science examined extracts of 1.1 billion-year-old sediments from 140 to 200 meters below the surface of a site in Mauritania. This corner in northwest Africa was once covered by an ocean. The researchers didn’t detect any biomarkers indicative of eukaryotes, but did find biomarkers indicating that several types of prokaryotes had been present. So no true algae, but plenty of evidence of photosynthetic bacteria. Of particular interest, they found molecules, <a href="http://physicsopenlab.org/2016/07/04/porphyrins-the-colors-of-life/">called porphyrins</a>, that are the remains of <a href="https://www.worldofmolecules.com/colors/chlorophyll.htm">chlorophyll</a>, the molecular basis of photosynthesis.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/227877/original/file-20180716-44070-1h0p9yy.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/227877/original/file-20180716-44070-1h0p9yy.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/227877/original/file-20180716-44070-1h0p9yy.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=602&fit=crop&dpr=1 600w, https://images.theconversation.com/files/227877/original/file-20180716-44070-1h0p9yy.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=602&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/227877/original/file-20180716-44070-1h0p9yy.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=602&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/227877/original/file-20180716-44070-1h0p9yy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=756&fit=crop&dpr=1 754w, https://images.theconversation.com/files/227877/original/file-20180716-44070-1h0p9yy.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=756&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/227877/original/file-20180716-44070-1h0p9yy.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=756&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Chemical structure of a simple porphyrin ring. The porphyrin in chlorophyll has a magnesium atom in the middle.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Porphyrin.svg">Lukáš Mižoch</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Using a clever analysis, the scientists were able to identify with near certainty what organisms were the source of the porphyrins. <a href="https://www.webelements.com/nitrogen/isotopes.html">Nitrogen has two atomic forms, called isotopes</a>, the most common of which, ¹⁴N, has an atomic weight of 14 while the rare isotope, ¹⁵N, has an atomic weight of 15. Although ¹⁴N is preferred, the various enzymes that make chlorophyll also incorporate ¹⁵N in proportions that differ among different classes of photosynthetic organisms. So the ratio of ¹⁴N to ¹⁵N in porphyrin molecules, which have four nitrogen atoms, can indicate what type of organism produced them. By measuring the N-isotope ratios in the porphyrins from the sediments, the scientists were able to trace the molecules to the cyanobacteria.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/227854/original/file-20180716-44100-1435prr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/227854/original/file-20180716-44100-1435prr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/227854/original/file-20180716-44100-1435prr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/227854/original/file-20180716-44100-1435prr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/227854/original/file-20180716-44100-1435prr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/227854/original/file-20180716-44100-1435prr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/227854/original/file-20180716-44100-1435prr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/227854/original/file-20180716-44100-1435prr.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">A vial of pink-colored porphyrins recovered from sediments that are more than a billion years old.</span>
<span class="attribution"><a class="source" href="http://dx.doi.org/10.1073/pnas.1803866115">The Australian National University</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Not pink, but green</h2>
<p>A dramatic picture in the Gueneli paper showed that some of the extracts of the ancient sediments were brilliant pink. News coverage ran with headlines focused on Earth’s “oldest color” being bright pink. But that’s not quite right.</p>
<p>In order to do its chemical job, the porphyrin in chlorophyll contains a magnesium atom that’s responsible for its green color. This is what makes leaves and algae look green. But in these pink extracts, the porphyrin turned out to have a nickel atom instead. Most likely the nickel replaced the magnesium sometime over the billion-plus years the molecules <a href="https://doi.org/10.1098/rstb.1991.0083">aged in the sediments</a>.</p>
<p>So pink was not the original color of the chlorophyll. It must have been green, as it is in living plants today.</p>
<h2>Algae take over from bacteria</h2>
<p>The researchers’ major conclusion is that 1.1 billion years ago, photosynthetic bacteria, most likely dominated by cyanobacteria, were the base of the food chain in the ocean. Because the bacteria were small, they would sink slowly and be degraded by other bacteria high in the water column. Little of the precious nutrients they contained would reach the ocean bottom.</p>
<p>Nutrient distribution throughout an ocean depends upon <a href="https://oceanservice.noaa.gov/facts/upwelling.html">upwelling from the bottom</a>. So most of the ocean would be nutrient-poor, restricting the development of a community of larger organisms.</p>
<p>In addition, cyanobacteria survive better than eukaryotic algae when nutrients are low, which would further <a href="https://doi.org/10.1042/ETLS20180039">restrict the evolution of these larger-celled photosynthetic organisms</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/227906/original/file-20180716-44070-1fmw20b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/227906/original/file-20180716-44070-1fmw20b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/227906/original/file-20180716-44070-1fmw20b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=404&fit=crop&dpr=1 600w, https://images.theconversation.com/files/227906/original/file-20180716-44070-1fmw20b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=404&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/227906/original/file-20180716-44070-1fmw20b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=404&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/227906/original/file-20180716-44070-1fmw20b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=508&fit=crop&dpr=1 754w, https://images.theconversation.com/files/227906/original/file-20180716-44070-1fmw20b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=508&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/227906/original/file-20180716-44070-1fmw20b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=508&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">True algae have larger and more complex cells than the cyanobacteria they took over from.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/noaaphotolib/9787178153">NOAA MESA Project</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>What caused the shift about 650 million years ago from an ocean dominated by cyanobacteria to one dominated by true algae? One of the authors of the PNAS paper, geobiologist Jochen Brocks, points out in a recent review article that this shift occurred a mere <a href="https://doi.org/10.1042/ETLS20180039">4 million years after the end of a worldwide glaciation</a>, during which the oceans were frozen for more than 50 million years. Then the glaciers melted, probably because rising carbon dioxide levels created a greenhouse effect, heating the Earth. The temperature of the oceans rose rapidly, possibly killing many remaining cyanobacteria. In addition, as the glaciers melted, vast amounts of nutrients would have been swept into the oceans, reversing the competitive disadvantage for the algae, that then were able to evolve and expand.</p>
<p>With the arrival of these larger, rapidly-settling algae as the basis of the food chain, the stage was set for the evolution and expansion of larger eukaryotic consumers.</p><img src="https://counter.theconversation.com/content/99818/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Patricia L. Foster receives funding from the US Army Research Office. She is a member of the American Association for the Advancement of Science, Union of Concerned Scientists and Concerned Scientists at IU.</span></em></p>
Did you recently hear news that Earth’s oldest pigments were hot pink? That’s not quite right. When they were in living bacteria a billion years ago, they were performing photosynthesis – and green.
Patricia L. Foster, Professor Emerita of Biology, Indiana University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/98358
2018-06-27T10:45:33Z
2018-06-27T10:45:33Z
How we discovered three poisonous books in our university library
<figure><img src="https://images.theconversation.com/files/225100/original/file-20180627-112620-14hp9vy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/old-books-green-cover-yellowed-pages-1048053595?src=7divbo7EJk1uZ9Tm-xdhCA-4-16">Raman Saurei/Shutterstock.com</a></span></figcaption></figure><p>Some may remember the deadly book of Aristotle that plays a vital part in the plot of Umberto Eco’s 1980 novel <a href="http://www.nybooks.com/articles/1983/07/21/murder-in-the-monastery/">The Name of the Rose</a>. Poisoned by a mad Benedictine monk, the book wreaks havoc in a 14th-century Italian monastery, killing all readers who happen to lick their fingers when turning the toxic pages. Could something like this happen in reality? Poisoning by books?</p>
<p>Our recent research indicates so. We found that three rare books on various historical topics in the University of Southern Denmark’s library collection contain large concentrations of arsenic on their covers. The books come from the 16th and 17th centuries.</p>
<p>The poisonous qualities of these books were detected by conducting a series of X-ray fluorescence analyses (micro-XRF). This technology displays the chemical spectrum of a material by analysing the characteristic “secondary” radiation that is emitted from the material during a high-energy X-ray bombardment. Micro-XRF technology is widely used within the fields of archaeology and art, when investigating the chemical elements of pottery and paintings, for example.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/223318/original/file-20180615-85830-o9y0od.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/223318/original/file-20180615-85830-o9y0od.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=428&fit=crop&dpr=1 600w, https://images.theconversation.com/files/223318/original/file-20180615-85830-o9y0od.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=428&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/223318/original/file-20180615-85830-o9y0od.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=428&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/223318/original/file-20180615-85830-o9y0od.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=537&fit=crop&dpr=1 754w, https://images.theconversation.com/files/223318/original/file-20180615-85830-o9y0od.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=537&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/223318/original/file-20180615-85830-o9y0od.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=537&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">One of the poisonous books.</span>
<span class="attribution"><span class="source">SDU</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Glaring green</h2>
<p>The reason why we took these three rare books to the X-ray lab was because the library had previously discovered that medieval manuscript fragments, such as copies of Roman law and canonical law, were used to make their covers. It is <a href="https://medievalbooks.nl/2015/12/18/x-rays-expose-a-hidden-medieval-library/">well documented</a> that European bookbinders in the 16th and 17th centuries used to recycle older parchments. </p>
<p>We tried to identify the Latin texts used, or at least read some of their content. But then we found that the Latin texts in the covers of the three volumes were hard to read because of an extensive layer of green paint which obscures the old handwritten letters. So we took them to the lab. The idea was to filter through the layer of paint using micro-XRF and focus on the chemical elements of the ink below, for example on iron and calcium, in the hope of making the letters more readable for the university’s researchers. </p>
<p>But XRF-analysis revealed that the green pigment layer was arsenic. This chemical element is among the most toxic substances in the world and exposure may lead to various symptoms of poisoning, the development of cancer and even death.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/225105/original/file-20180627-112614-twgyc6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/225105/original/file-20180627-112614-twgyc6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/225105/original/file-20180627-112614-twgyc6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=440&fit=crop&dpr=1 600w, https://images.theconversation.com/files/225105/original/file-20180627-112614-twgyc6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=440&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/225105/original/file-20180627-112614-twgyc6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=440&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/225105/original/file-20180627-112614-twgyc6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=553&fit=crop&dpr=1 754w, https://images.theconversation.com/files/225105/original/file-20180627-112614-twgyc6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=553&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/225105/original/file-20180627-112614-twgyc6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=553&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Accidents caused by the use of green arsenic, 1859.</span>
<span class="attribution"><a class="source" href="https://wellcomecollection.org/works/bdgwyugs?query=arsenic&page=1">© Wellcome Collection</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Arsenic (As) is a ubiquitous naturally occurring metalloid. In nature, arsenic is typically combined with other elements such as carbon and hydrogen. This is known as organic arsenic. Inorganic arsenic, which may occur in a pure metallic form as well as in compounds, is the more harmful variant. The toxicity of arsenic does not diminish with time. </p>
<p>Depending on the type and duration of exposure, various symptoms of arsenic poisoning include an irritated stomach, irritated intestines, nausea, diarrhoea, skin changes and irritation of the lungs.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/225102/original/file-20180627-112611-bjz8o6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/225102/original/file-20180627-112611-bjz8o6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/225102/original/file-20180627-112611-bjz8o6.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/225102/original/file-20180627-112611-bjz8o6.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/225102/original/file-20180627-112611-bjz8o6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/225102/original/file-20180627-112611-bjz8o6.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/225102/original/file-20180627-112611-bjz8o6.jpeg?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">
<figcaption>
<span class="caption">Paris Green.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Paris_Green_(Schweinfurter_Gr%C3%BCn).JPG">Chris Goulet/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The green arsenic-containing pigment found on the book covers is thought to be Paris green, copper(II) acetate triarsenite or copper(II) acetoarsenite Cu(C₂H₃O₂)₂·3Cu(AsO₂)₂. This is also known as “emerald green”, because of its eye-catching green shades, similar to those of the popular gemstone. </p>
<p>The arsenic pigment – a crystalline powder – is easy to manufacture and has been commonly used for multiple purposes, especially in the 19th century. The size of the powder grains influence on the colour toning, as seen in oil paints and lacquers. Larger grains produce a distinct darker green – smaller grains a lighter green. The pigment is especially known for its colour intensity and resistance to fading.</p>
<h2>Pigment of the past</h2>
<p>Industrial production of Paris green was initiated in Europe in the early 19th century. Impressionist and post-impressionist painters used different versions of the pigment to create their vivid masterpieces. This means that many museum pieces today contain the poison. In its heyday, all types of materials, even book covers and clothes, could be coated in Paris green for aesthetic reasons. Of course, continuous skin contact with the substance would lead to symptoms of exposure. </p>
<p>But by the second half of the 19th century, the toxic effects of the substance were more commonly known, and the arsenic variant stopped being used as a pigment and was more frequently used as a pesticide on farmlands. Other pigments were found to replace Paris green in paintings and the textile industry etc. In the mid 20th century, the use on farmlands was phased out as well.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/225107/original/file-20180627-112598-1iqk7ja.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/225107/original/file-20180627-112598-1iqk7ja.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/225107/original/file-20180627-112598-1iqk7ja.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=476&fit=crop&dpr=1 600w, https://images.theconversation.com/files/225107/original/file-20180627-112598-1iqk7ja.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=476&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/225107/original/file-20180627-112598-1iqk7ja.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=476&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/225107/original/file-20180627-112598-1iqk7ja.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=598&fit=crop&dpr=1 754w, https://images.theconversation.com/files/225107/original/file-20180627-112598-1iqk7ja.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=598&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/225107/original/file-20180627-112598-1iqk7ja.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=598&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 Arsenic Waltz’.</span>
<span class="attribution"><a class="source" href="https://iiif.wellcomecollection.org/image/V0042226.jpg/full/full/0/default.jpg">© Wellcome Collection</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>In the case of our books, the pigment wasn’t used for aesthetic purposes, making up a lower level of the cover. A plausible explanation for the application – possibly in the 19th century – of Paris green on old books could be to protect them against insects and vermin. </p>
<p>Under certain circumstances, arsenic compounds, such as arsenates and arsenites, may be transformed by microorganisms into arsine (AsH₃) – a highly poisonous gas with a distinct smell of garlic. <a href="https://hyperallergic.com/329747/death-by-wallpaper-alluring-arsenic-colors-poisoned-the-victorian-age/">Grim stories</a> of green Victorian wallpapers taking the lives of children in their bedrooms are known to be factual. </p>
<p>Now, the library stores our three poisonous volumes in separate cardboard boxes with safety labels in a ventilated cabinet. We also plan on digitising them to minimise physical handling. One wouldn’t expect a book to contain a poisonous substance. But it might.</p><img src="https://counter.theconversation.com/content/98358/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors 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>
Interdisciplinary research led to the discovery that three historic books were covered in a layer of arsenic.
Jakob Povl Holck, Research Librarian, University of Southern Denmark
Kaare Lund Rasmussen, Associate Professor in Physics, Chemistry and Pharmacy, University of Southern Denmark
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/93523
2018-03-20T10:42:01Z
2018-03-20T10:42:01Z
Eager to dye your hair with ‘nontoxic’ graphene nanoparticles? Not so fast!
<figure><img src="https://images.theconversation.com/files/211082/original/file-20180319-31624-18d3y07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Subbing new risks for the current dyes’ dangers?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/hairdresser-salon-woman-during-hair-wash-1044886945">Evgeny Savchenko/Shutterstock.com</a></span></figcaption></figure><p>Graphene is something of a celebrity in the world of nanoscale materials. Isolated in 2004 by Nobel Prize winners <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/2010/">Andre Geim and Konstantin Novoselov</a>, these ultrathin sheets of carbon atoms are already finding novel uses in areas like <a href="https://www.nist.gov/programs-projects/graphene-electronics">electronics</a>, <a href="https://spectrum.ieee.org/nanoclast/green-tech/conservation/graphene-heating-system-dramatically-reduces-home-energy-costs">high-efficiency heating systems</a>, <a href="https://www.ft.com/content/d768030e-d8ec-11e7-9504-59efdb70e12f">water purification technologies</a> and <a href="http://cmp.callawaygolf.com/2018/01/23/chrome-soft-golf-balls-need-know/">even golf balls</a>. According to recent research published in the journal Chem, <a href="https://doi.org/10.1016/j.chempr.2018.02.021">hair dyes can now be added to this list</a>. </p>
<p>But how safe and responsible is this new use of the carbon-based wonder-material?</p>
<p>Northwestern University’s <a href="https://www.eurekalert.org/pub_releases/2018-03/nu-gfn031218.php">press release</a> proudly announced, “Graphene finds new application as nontoxic, anti-static hair dye.” The announcement spawned headlines like “<a href="http://www.sciencemag.org/news/2018/03/enough-toxic-hair-dyes-we-could-use-graphene-instead">Enough with the toxic hair dyes. We could use graphene instead</a>,” and “<a href="http://en.brinkwire.com/215369/miracle-material-graphene-used-to-create-the-ultimate-hair-dye/">’Miracle material’ graphene used to create the ultimate hair dye</a>.” </p>
<p>From these headlines, you might be forgiven for getting the idea that the safety of graphene-based hair dyes is a done deal. Yet <a href="https://scholar.google.com/citations?user=b8NhWc4AAAAJ&hl=en&oi=ao">having studied the potential health and environmental impacts</a> of engineered nanomaterials for <a href="http://dx.doi.org/10.1038/nnano.2016.270">more years than I care to remember</a>, I find such overly optimistic pronouncements worrying – especially when they’re not backed up by clear evidence.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/211008/original/file-20180319-31602-zpomir.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/211008/original/file-20180319-31602-zpomir.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/211008/original/file-20180319-31602-zpomir.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/211008/original/file-20180319-31602-zpomir.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/211008/original/file-20180319-31602-zpomir.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/211008/original/file-20180319-31602-zpomir.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/211008/original/file-20180319-31602-zpomir.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/211008/original/file-20180319-31602-zpomir.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">As the dye wears off, where do the nanoparticles go?</span>
<span class="attribution"><span class="source">Jiaxing Huang, Northwestern University</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Tiny materials, potentially bigger problems</h2>
<p>Engineered nanomaterials like graphene and graphene oxide (the particular form used in the dye experiments) aren’t necessarily harmful. But nanomaterials can behave in unusual ways that depend on particle size, shape, chemistry and application. Because of this, researchers have long been cautious about giving them a clean bill of health without first testing them extensively. And while a <a href="http://dx.doi.org/10.1021/acsnano.7b04120">large body of research to date</a> doesn’t indicate graphene is particularly dangerous, neither does it suggest it’s completely safe.</p>
<p>A quick search of scientific papers over the past few years shows that, since 2004, over 2,000 studies have been published that mention graphene toxicity; nearly 500 were published in 2017 alone.</p>
<p>This growing body of research suggests that if graphene gets into your body or the environment in sufficient quantities, it could cause harm. A 2016 review, for instance, indicated that graphene oxide particles could <a href="http://dx.doi.org/10.1016/j.addr.2016.04.028">result in lung damage at high doses</a> (equivalent to around 0.7 grams of inhaled material). Another review published in 2017 suggested that these <a href="http://dx.doi.org/10.1088/2053-1583/aa5476">materials could affect the biology</a> of some plants and algae, as well as invertebrates and vertebrates toward the lower end of the ecological pyramid. The authors of the 2017 study concluded that research “unequivocally confirms that graphene in any of its numerous forms and derivatives must be approached as a potentially hazardous material.” </p>
<p>These studies need to be approached with care, as the precise risks of graphene exposure will depend on how the material is used, how exposure occurs and how much of it is encountered. Yet there’s sufficient evidence to suggest that this substance should be used with caution – especially where there’s a high chance of exposure or that it could be released into the environment.</p>
<p>Unfortunately, graphene-based hair dyes tick both of these boxes. Used in this way, the substance is potentially inhalable (especially with spray-on products) and ingestible through careless use. It’s also almost guaranteed that excess graphene-containing dye will wash down the drain and into the environment. </p>
<p>Here, due diligence is needed to ensure that the material is acceptably safe. This is something that goes beyond the seeming authority of a press release headline. In fact, such misleading headlines could end up being counterproductive, as they undermine efforts to demonstrate trustworthiness with consumers and investors.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/211020/original/file-20180319-31627-1nv890z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/211020/original/file-20180319-31627-1nv890z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/211020/original/file-20180319-31627-1nv890z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=317&fit=crop&dpr=1 600w, https://images.theconversation.com/files/211020/original/file-20180319-31627-1nv890z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=317&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/211020/original/file-20180319-31627-1nv890z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=317&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/211020/original/file-20180319-31627-1nv890z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=398&fit=crop&dpr=1 754w, https://images.theconversation.com/files/211020/original/file-20180319-31627-1nv890z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=398&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/211020/original/file-20180319-31627-1nv890z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=398&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Simulation of a graphene oxide framework, pictured in black, to remove contaminants from water.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/oakridgelab/14006201292">Adrien Nicolaï/RPI</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<h2>Undermining other efforts?</h2>
<p>I was alerted to just how counterproductive such headlines can be by my colleague Tim Harper, founder of <a href="http://g2o.co/">G2O Water Technologies</a> – a company that uses graphene oxide-coated membranes to treat wastewater. Like many companies in this area, G2O has been working to use graphene responsibly by minimizing the amount of graphene that ends up released to the environment.</p>
<p>Yet as Tim pointed out to me, if people are led to believe “that bunging a few grams of graphene down the drain every time you dye your hair is OK, this invalidates all the work we are doing making sure the few nanograms of graphene on our membranes stay put.” Many companies that use nanomaterials are trying to do the right thing, but it’s hard to justify the time and expense of being responsible when someone else’s more cavalier actions undercut your efforts.</p>
<p>Here, naïve claims of safety and gung-ho approaches to promoting graphene-containing products could very easily threaten the responsible development and use of this material. And if companies pull back from acting responsibly, there’s a danger that consumers, investors and even regulators, will lose trust in their ability to ensure the safety of products of all kinds. </p>
<p>If this happens, consumers will be the ultimate losers. Used responsibly, graphene could lead to more sustainable and environmentally benign products. Yet having watched the public backlash against technologies like genetic engineering over the past couple of decades, I’m acutely aware that failing to earn the trust of stakeholders and consumers can stymie technologies, regardless of how safe and beneficial they are.</p>
<h2>Overpromising results and overlooking risk</h2>
<p>This is where researchers and their institutions need to move beyond an “<a href="https://doi.org/10.1038/nnano.2008.14">economy of promises</a>” that spurs on hyperbole and discourages caution, and think more critically about how their statements may ultimately undermine responsible and beneficial development of a technology. They may even want to consider using guidelines, such as the <a href="http://societyinside.com/sites/default/files/Principles%20for%20Responsible%20Innovation%20Short%20February%202018_0.pdf">Principles for Responsible Innovation</a> developed by the organization <a href="http://societyinside.com/">Society Inside</a>, for instance, to guide what they do and say.</p>
<p>To their credit, the authors of the dye study did give a passing mention to research on graphene safety, mostly focusing on an assumed level of safety compared to current dye products. Yet even this perfunctory level of caution failed to make it into the <a href="https://www.eurekalert.org/pub_releases/2018-03/nu-gfn031218.php">press release</a>, which touted a “new hair dye that is nontoxic, nondamaging and lasts through many washes without fading.”</p>
<p>It may turn out that graphene-based hair dyes can be developed safely. To be fair, the reported application isn’t even close to commercial R&D yet, never mind the salon shelf. And certainly, there’s a case to be made for substituting some of the <a href="https://www.nytimes.com/2018/03/16/science/hair-dye-graphene.html">harsh chemicals currently used in some products</a> with more benign ones. But this won’t happen while researchers and their institutions gloss over legitimate concerns and cautions with blind optimism. </p>
<p>Rather, by taking more care in how nanomaterial research is framed and promoted, researchers and their academic institutions could do a lot to ensure future nano-enabled consumer products are safe, beneficial and, above all, responsible.</p><img src="https://counter.theconversation.com/content/93523/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Maynard receives support from the National Science Foundation as part of the Nanotechnology-Enabled Water Treatment (NEWT) Engineering Research Center. </span></em></p>
Less-toxic hair dye would be a great invention. But discounting the risks that come with nanoparticles could undermine other efforts to protect human health and environmental from their effects.
Andrew Maynard, Director, Risk Innovation Lab, Arizona State University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/81031
2017-07-20T20:15:05Z
2017-07-20T20:15:05Z
Friday essay: from the Great Wave to Starry Night, how a blue pigment changed the world
<figure><img src="https://images.theconversation.com/files/178576/original/file-20170718-22039-dlaji.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Detail from Katsushika Hokusai, The great wave off Kanagawa (Kanagawa oki namiura), (1830–34), from the Thirty-six views of Mt Fuji (Fugaku-sanjū-rokkei)</span> <span class="attribution"><span class="source">National Gallery of Victoria, Melbourne Felton Bequest, 1909 (426-2)</span></span></figcaption></figure><p>Hokusai’s The great wave off Kanagawa remains the enduring image of Japanese art. The print depicts a giant wave with unmistakable frothing tentacles poised to smash a boat below. The boat’s occupants toil uncaring or unaware of the hovering deluge - the curve of their vessel matching the lines of the heaving sea around them. With the intense drama unfolding in the foreground, the central image of the work - the white-capped Mount Fuji - is easily missed, or mistaken for another ocean crest. </p>
<p>Although diminutive in scale, the importance of Hokusai’s “Great Wave” cannot be overstated. The work profoundly motivated the French Impressionist movement, which in-turn shaped the course of European Modernism, the artistic and philosophical movement that would define the early 20th century. As such, this small print exhibited at the National Gallery of Victoria from July provides a valuable link to the gallery’s recent <a href="https://theconversation.com/van-gogh-and-the-seasons-is-a-sensitively-curated-crowd-pleaser-despite-a-paucity-of-masterpieces-76803">Van Gogh exhibition</a>. </p>
<p>The most immediate and attractive aspect of Hokusai’s wave is its colour. At 70 years old, Hokusai was a master and created the image using four printing blocks. The astounding power of the work belies its restrictive palette – it’s essentially a study in blue. </p>
<p>The story of this blue pigment highlights the role of cultural exchange at the heart of creative discovery and ranks among the more contradictory tales in the history of art. The vibrant hue, long considered to be quintessentially Japanese, was actually a European innovation.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/178576/original/file-20170718-22039-dlaji.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/178576/original/file-20170718-22039-dlaji.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/178576/original/file-20170718-22039-dlaji.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=414&fit=crop&dpr=1 600w, https://images.theconversation.com/files/178576/original/file-20170718-22039-dlaji.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=414&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/178576/original/file-20170718-22039-dlaji.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=414&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/178576/original/file-20170718-22039-dlaji.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=521&fit=crop&dpr=1 754w, https://images.theconversation.com/files/178576/original/file-20170718-22039-dlaji.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=521&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/178576/original/file-20170718-22039-dlaji.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=521&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Detail from Katsushika Hokusai, The great wave off Kanagawa (Kanagawa oki namiura), (1830–34), from the Thirty-six views of Mt Fuji (Fugaku-sanjū-rokkei). 25.7 × 37.7 cm.</span>
<span class="attribution"><span class="source">National Gallery of Victoria, Melbourne Felton Bequest, 1909 (426-2)</span></span>
</figcaption>
</figure>
<h2>Colourful figures</h2>
<p>In truth, it had been invented half a world away, 130 years before Hokusai’s wave broke, in an accident involving one of Europe’s most colourful figures: Johann Conrad Dippel. Born in the actual “Castle Frankenstein” in Germany in 1673, the enigmatic theologian and passionate dissector believed the souls of the living could be funnelled from one corpse to another, thus becoming the rumoured inspiration for Mary Shelley’s masterpiece, <a href="https://www.goodreads.com/book/show/18490.Frankenstein">Frankenstein</a>. </p>
<p>In his thirties, Dippel had become captivated by the proto-science of alchemy, but like so many in the profession, had failed to convert base metals into gold. He instead settled on the apparently easier task of inventing an elixir of immortality. The consequence was Dippel’s oil, a compound so toxic that two centuries later it would be deployed as a <a href="https://en.wikipedia.org/wiki/Dippel%27s_oil">chemical weapon in World War II</a>.</p>
<p>To cut costs in his Berlin laboratory, Dippel lab-shared with the Swiss pigment maker Johann Jacob Diesbach, a fellow scientist engaged in the lucrative business of producing colours. One fateful evening around 1705, when Diesbach was preparing a batch of crushed insects, iron sulphate and potash in a reliable recipe for a deep red pigment, he accidentally used one of Dippel’s implements infected by the noxious oil. </p>
<p>The following morning the pair found not the expected red, but a deep blue. The immense value of the substance was immediately clear. The recipe for <a href="https://en.wikipedia.org/wiki/Egyptian_blue">Egyptian blue</a> used by the Romans had been lost to history some time in the middle ages. Its substitute, lapis lazuli, consisting of crushed Afghan gemstones, sold at astronomical rates. So the discovery of a stable blue colour was literally more valuable than gold. Adding further worth, the pigment could be blended to produce entirely new colours, a process that the costly lapis lazuli did not allow.</p>
<p><a href="https://www.chemistryworld.com/podcasts/prussian-blue/6101.article">The discovery sparked “blue fever” in Europe</a>. Dippel, suddenly forced to flee legal action in Berlin for his controversial theological positions, failed to commercialise the newly named “Prussian blue”, but his dazzling co-invention was a secret too big to keep.</p>
<p>Within a few short years, the recipe had gone into factory production. It was used extensively in painting, wallpaper, flags, postage stamps, and became the official uniform colour of the Prussian Army. People seemed drunk on the stuff. Indeed, they were actually drinking it. By mid century, the British East India Company was <a href="http://www.tching.com/2011/08/waiter-my-tea-is-blue/">dyeing Chinese tea Prussian Blue</a> to increase its exotic appeal back in Europe .</p>
<h2>Blue arrives in Asia</h2>
<p>In the early 1800s, a Guangzhou entrepreneur deciphered the recipe and began manufacturing the pigment in China at a much lower cost. Despite Japan’s strict ban on all imports and exports, the colour found its way to the printmaking industry in Osaka, Japan where it was trafficked as “bero”, a derivation from the Dutch “Berlyns blaauw” (“Berlin blue”). Its vivid hue, tonal range and foreignness saw it explode in popularity just as it had in Europe. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/178740/original/file-20170719-10341-15oyw01.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/178740/original/file-20170719-10341-15oyw01.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/178740/original/file-20170719-10341-15oyw01.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=876&fit=crop&dpr=1 600w, https://images.theconversation.com/files/178740/original/file-20170719-10341-15oyw01.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=876&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/178740/original/file-20170719-10341-15oyw01.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=876&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/178740/original/file-20170719-10341-15oyw01.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1101&fit=crop&dpr=1 754w, https://images.theconversation.com/files/178740/original/file-20170719-10341-15oyw01.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1101&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/178740/original/file-20170719-10341-15oyw01.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1101&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Katsushika Hokusai, The Amida Falls in the far reaches of the Kisokaidō Road (Kiso no oku Amida-ga-taki) (1834–35) from the A tour to the waterfalls in various provinces (Shokoku taki meguri) series.</span>
<span class="attribution"><span class="source">The Japan Ukiyo-e Museum, Matsumoto</span></span>
</figcaption>
</figure>
<p>Hokusai was one of the first Japanese printmakers to boldly embrace the colour, a decision that would have major implications in the world of art. Using it extensively in his series Thirty Six Views of Mount Fuji (1830), of which the Great Wave was the first, the pigment especially lent itself to expressing both depth in water and distance, crucial atmospheric qualities to render land and seascapes.</p>
<p>Hokusai and his contemporary <a href="https://en.wikipedia.org/wiki/Hiroshige">Hiroshige</a> became renowned for their depictions of pure landscape form. But although extremely popular in mainstream society, these woodblock prints were seen as vulgar by the Japanese literati and beneath consideration for artistic merit.</p>
<p>When Japan’s isolationist policies finally ended under <a href="https://ocw.mit.edu/ans7870/21f/21f.027/black_ships_and_samurai/bss_essay01.html">threat of war from the US Navy in 1853</a>, the prints were used as wrapping paper for more worthy trade trinkets.</p>
<p>Following Paris’s International Exposition of 1867, their value dramatically shifted. A showcase at the inaugural Japanese Pavilion elevated the artistic status of woodblock prints and a craze for their collection quickly followed. Among the most prized were the striking blue landscapes, particularly by Hokusai and Hiroshige, that led European artists to incorrectly deem the colour as idiosyncratically Japanese. </p>
<p>It wasn’t just the colour, style and execution of Hokusai’s prints that made them so radically influential, but the subject matter too. His collection of <a href="http://library.princeton.edu/news/2014-12-16/hokusai%E2%80%99s-manga">“manga” sketches</a> elevated everyday street life in to the realm of art, ideas that were a revelation for Edgar Degas and Henri de Toulouse-Lautrec. Both borrowed heavily from Hokusai’s depictions of marginal society and the <a href="http://slideplayer.com/slide/7334540/24/images/43/(below)+Edgar+Degas,+The+Tub,+1886,+pastel+on+paper,+23+x+32+(left)+Katsushika+Hokusai,+Women+at+the+Public+Bath,+from+the+Manga+vol.+I,+c.+1820,+color+woodblock,+7+x+4+In+the+manga,+Degas+said,+he+found+relief+from+Western+art%E2%80%99s+obsession+with+the+female+form+divine.+European+artists+continually+borrowed+motifs+from+the+manga..jpg">bodies of women in repose</a>. </p>
<p>Claude Monet was so seduced by the “Japonism” aesthetic he acquired 250 Japanese prints, <a href="http://fondation-monet.com/en/giverny-2/the-japanese-prints/">including 23 by Hokusai</a>. The obsession bled from Monet’s art to his life and the painter modelled his garden after a Japanese print while his wife sported a <a href="http://www.mfa.org/collections/object/la-japonaise-camille-monet-in-japanese-costume-33556">kimono around the house</a>. </p>
<p>Perhaps the single most vividly identifiable influence upon the European modernist founders is Van Gogh’s celebrated Starry Night, which owes everything to Hokusai’s blue wave from its <a href="http://carterf.faculty.mjc.edu/humanities/Images__East_Meets_West.html">colour to the shape of its sky</a>. In letters to his brother, Van Gogh professed the Japanese master had left a deep emotional impact on him. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/178741/original/file-20170719-27190-pw9wvq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/178741/original/file-20170719-27190-pw9wvq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/178741/original/file-20170719-27190-pw9wvq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=475&fit=crop&dpr=1 600w, https://images.theconversation.com/files/178741/original/file-20170719-27190-pw9wvq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=475&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/178741/original/file-20170719-27190-pw9wvq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=475&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/178741/original/file-20170719-27190-pw9wvq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=597&fit=crop&dpr=1 754w, https://images.theconversation.com/files/178741/original/file-20170719-27190-pw9wvq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=597&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/178741/original/file-20170719-27190-pw9wvq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=597&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Van Gogh’s Starry Night.</span>
</figcaption>
</figure>
<h2>Hokusai’s European influence</h2>
<p>The importance of Hokusai to the early European modernist movement is both <a href="http://bestarts.org/japanese-culture-european-art-fin-de-siecle/">immense and well mapped</a>. Much less known is the extent to which Hokusai had himself borrowed from European image culture. Although in the artist’s lifetime, Japan was subject to Sakoku, the 250-year policy that forbade exchange with the outside world on penalty of death, a clandestine group of Japanese artists and scientists had dedicated themselves to studying the exotic mysteries of Western representation. </p>
<p>Hokusai drew influence from a particular “<a href="http://laurajohrowland.wikia.com/wiki/Rangakusha">Rangakusha</a>” (scholar of Dutch texts) painter named Shiba Kokan, who experimented with European principles of composition. In The Great Wave, Hokusai abandoned traditional Japanese <a href="http://www.technologystudent.com/designpro/isomet1.htm">isometric view</a>, where motifs were scaled according to importance, and instead adopted the dynamic style of <a href="http://www.olejarz.com/arted/perspective/intro5.html">Western perspective</a> featuring intersecting lines of sight. </p>
<p>This lent the work the dramatic sense of the wave about to break on top of the viewer. The embracing of his final works by Europeans is in part due to Hokusai’s use of a familiar compositional style. </p>
<p>Yet this historical truth lay dormant for decades as it deeply contradicted the European vision of Japan. In the Western imagination, Japan was a land preserved in amber, a pure and innocent people in close communion with nature whose isolation had sealed them from the horrors that industrialisation had wrought upon Europe. </p>
<p>In reality, Hokusai had skillfully blended European colour and structure with Japanese motifs and techniques into a seamless work of international appeal. Certainly, without Hokusai’s striking print, the great wave of European Modernism might never have happened. </p>
<hr>
<p><em>The <a href="https://www.ngv.vic.gov.au/exhibition/hokusai/">art of Hokusai</a> will be showing at the National Gallery of Victoria until October 15 2017.</em></p><img src="https://counter.theconversation.com/content/81031/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hugh Davies has been funded to undertake creative research into game cultures in Japan through Asialink. </span></em></p>
Hokusai’s Great Wave is the enduring image of Japanese art. Less well known is the story of its primary pigment - Prussian blue - which was created in a lab accident in Berlin and sparked ‘blue fever’ in Europe.
Dr Hugh Davies, Post Doctoral Research Fellow, RMIT University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/79414
2017-06-20T01:38:37Z
2017-06-20T01:38:37Z
Research Check: can a new drug really protect redheads from cancer?
<figure><img src="https://images.theconversation.com/files/174375/original/file-20170619-5835-1qbgf3s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The study looked at helping redheads to tan and protect them from the sun. But the redheads were mice, not humans.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/458007013?src=HZaHC68vwVOiFSEJmcHgnA-1-31&size=medium_jpg">from www.shutterstock.com</a></span></figcaption></figure><p>A recently published US <a href="http://www.sciencedirect.com/science/article/pii/S2211124717306848">study</a> on an experimental drug that leads to tanning without sun exposure has generated a host of headlines around the world.</p>
<p>Some went with <a href="http://www.dailymail.co.uk/sciencetech/article-4596644/Tan-treatment-bypasses-need-harmful-sun-beds.html#ixzz4kQ0PMzd9">what the drug means for redheads</a>, with the headline:</p>
<blockquote>
<p>Good news for redheads: Cream can give even the lightest skin a tan WITHOUT exposure to harmful UV radiation</p>
</blockquote>
<p>Others went for the drug’s apparent protection against <a href="https://www.theguardian.com/society/2017/jun/13/scientists-create-fake-tan-which-could-protect-against-skin-cancer">skin cancer</a>:</p>
<blockquote>
<p>Suntans for all: chemical causes any skin to tan – and protects against cancer</p>
</blockquote>
<p>Some coverage was more <a href="http://www.news.com.au/lifestyle/beauty/face-body/scientists-create-chemical-that-changes-skin-colour-without-tanning/news-story/832e1c86060b8a0416c10d9f687ba06c">measured</a>:</p>
<blockquote>
<p>Scientists create chemical that changes skin colour without tanning</p>
</blockquote>
<p>You can read more examples <a href="https://news.google.com/news/story?ncl=dtXq6PxnGa3p9eMBaCVU1nBoHhpyM&q=drug+skin+tanning&lr=English&hl=en&sa=X&ved=0ahUKEwjb1-qI-8jUAhUKS7wKHX4EC-cQqgIILTAA">here</a>.</p>
<p>So, does the media’s reporting of the study, published in the journal Cell Reports, reflect the actual research?</p>
<p>The study’s senior author <a href="http://www.dfhcc.harvard.edu/insider/member-detail/member/david-e-fisher-md-phd/">David Fisher</a>, professor of dermatology at Harvard Medical School, said, of the reports he had read, the coverage was generally accurate and balanced:</p>
<blockquote>
<p>I have not seen any problems (yet) … No particular gaps either.</p>
</blockquote>
<p>However, we found the fact the drug wasn’t tested on live humans, but in mice, was generally buried in media reports. And most coverage failed to mention the research’s real potential, in treating other conditions.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/174604/original/file-20170619-770-fzrub4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/174604/original/file-20170619-770-fzrub4.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=778&fit=crop&dpr=1 600w, https://images.theconversation.com/files/174604/original/file-20170619-770-fzrub4.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=778&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/174604/original/file-20170619-770-fzrub4.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=778&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/174604/original/file-20170619-770-fzrub4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=978&fit=crop&dpr=1 754w, https://images.theconversation.com/files/174604/original/file-20170619-770-fzrub4.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=978&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/174604/original/file-20170619-770-fzrub4.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=978&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"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Skin cancers account for <a href="http://www.cancer.org.au/about-cancer/types-of-cancer/skin-cancer.html">around 80% of all new cancers in Australia</a>, with most caused by overexposure to the sun. </p>
<p>Skin cancers are more common in people with pale skin. And with more than two million Australians getting <a href="http://www.cancer.org.au/news/media-releases/new-research-shows-almost-2.4-million-aussie-adults-sunburnt-on-summer-weekends.html">sunburnt every summer weekend</a>, it’s no wonder interest in damage-free, UV-protective tanning is high.</p>
<h2>How was the study conducted and what did it find?</h2>
<p>The researchers wanted to manipulate the pathway that leads to pigment (melanin) production to see if this could induce tanning. In particular, they hoped to activate the MITF gene, the master-regulator of skin pigment production.</p>
<p>They built on their <a href="https://www.ncbi.nlm.nih.gov/pubmed/?term=forskolin+AND+pigmentation+AND+2006%5BYear%5D">earlier work</a> identifying a group of molecules known as salt-inducible kinase inhibitors (or SIKi for short) that could do this.</p>
<p>First, the researchers grew pigment-producing cells (melanocytes) in a flask in a laboratory and treated them with the SIKi drug or a control substance. They then checked what happened to the MITF gene.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/174366/original/file-20170619-5778-1cjy7a2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/174366/original/file-20170619-5778-1cjy7a2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/174366/original/file-20170619-5778-1cjy7a2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=505&fit=crop&dpr=1 600w, https://images.theconversation.com/files/174366/original/file-20170619-5778-1cjy7a2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=505&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/174366/original/file-20170619-5778-1cjy7a2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=505&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/174366/original/file-20170619-5778-1cjy7a2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=634&fit=crop&dpr=1 754w, https://images.theconversation.com/files/174366/original/file-20170619-5778-1cjy7a2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=634&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/174366/original/file-20170619-5778-1cjy7a2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=634&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 researchers looked at melanin-producing cells (melanocytes) cultured in a flask rather than the melanocytes in someone’s skin (pictured here).</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/177142175?src=dEjd9diNoHTuR2-V4XfuUA-1-39&size=medium_jpg">from www.shutterstock.com</a></span>
</figcaption>
</figure>
<p>The SIKi prompted a 400% increase in gene activity plus pigment production (basically, like tanned cells in a flask). So, the researchers moved on to experiments in mice. </p>
<p>They chose yellow-haired mice, which were specially bred to have defects in the same gene causing red hair and easily-burned skin in humans. In effect, they were “redhead” mice.</p>
<p>The researchers waxed the mice to make a patch of bare skin they treated either with a lotion containing SIKi or plain lotion, applied daily. They also measured skin colour daily. The researchers also took samples of skin and looked at them under the microscope.</p>
<p>There was very noticeable darkening (pigmentation) in the mice treated with the SIKi but not with the control lotion. The darkening gradually increased over the six days of treatment and then gradually faded over two weeks, much like a natural suntan. The mice appeared to have no obvious ill effects.</p>
<p>Microscopic examination of the darkened skin showed the melanin had settled in caps over the nucleus of the cells, just as melanin produced after sun exposure would. So, theoretically it should protect the cell’s DNA in much the same way as naturally produced melanin would.</p>
<p>Then, the researchers used a <a href="http://www.nature.com/nature/journal/v481/n7382/box/481455a_BX1.html">modified form</a> of the SIKi that would be more easily absorbed to see its effects on healthy human skin. Rather than applying it directly to someone’s arm or leg, the researchers used leftover breast skin from reconstructive surgery and cultured it in petri dishes to keep it alive. The darkening also increased gradually.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/174365/original/file-20170619-5774-tytzg0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/174365/original/file-20170619-5774-tytzg0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=147&fit=crop&dpr=1 600w, https://images.theconversation.com/files/174365/original/file-20170619-5774-tytzg0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=147&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/174365/original/file-20170619-5774-tytzg0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=147&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/174365/original/file-20170619-5774-tytzg0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=185&fit=crop&dpr=1 754w, https://images.theconversation.com/files/174365/original/file-20170619-5774-tytzg0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=185&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/174365/original/file-20170619-5774-tytzg0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=185&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Human skin was treated with a control substance (left), a SIKi that couldn’t penetrate the skin (centre) and the new-version SIKi (right).</span>
<span class="attribution"><span class="source">Cell Reports/Nisma Mujahud and David Fisher</span></span>
</figcaption>
</figure>
<h2>How should we interpret the findings?</h2>
<p>While other drugs like Melanotan-II <a href="https://theconversation.com/is-this-injectable-tanning-drug-safe-to-use-60628?sr=1">promote tanning</a>, they are usually delivered by injection. So, finding a way to skip both the UV and a needle makes the SIKi research very biologically interesting. But in terms of medical use, these results are very early in the testing process. </p>
<p>The SIKis have yet to be tested on whole humans (not just loose patches of skin) to check for the effects of the drug leaking into the rest of the body, or discomfort from the drug’s action on the skin.</p>
<p>News outlets followed the research team’s lead in speculating a topical SIKi could help protect against skin cancer. However, these claims may be over-egged, as a tan is only as protective as <a href="https://www.ncbi.nlm.nih.gov/pubmed/24891049">SPF 2-4 sunscreen</a>.</p>
<p>Using a SIKi cream might help reduce a person’s cancer risk if it steers them away from risky behaviour like sunbathing or using solariums, but case reports suggest people might assume they can have more UV exposure once they are tanned, with <a href="http://onlinelibrary.wiley.com/doi/10.1111/jdv.13310/full">cancerous results</a>. </p>
<p>However, Fisher’s idea of including a SIKi in a traditional sunscreen might help combat this.</p>
<h2>What about those headlines?</h2>
<p>Headlines like “Suntans for all” and “Risk-free tanning” are jumping ahead of the research. But fortunately most articles note the “human” research has so far only been done in a petri dish.</p>
<p>The emphasis on tanning for redheads is also overdone in <a href="http://www.sciencealert.com/scientists-have-discovered-a-chemical-that-causes-any-skin-type-to-tan">some</a> <a href="http://www.dailymail.co.uk/sciencetech/article-4596644/Tan-treatment-bypasses-need-harmful-sun-beds.html#ixzz4k7x7HX95">articles</a>. But most mention deeper in the article the redheads were really mice.</p>
<p>Most articles also note Fisher envisions SIKi being used with normal sun-protection measures like sunscreen, rather than instead of them, and safety still needs to be assessed. </p>
<p><a href="https://www.theguardian.com/society/2017/jun/13/scientists-create-fake-tan-which-could-protect-against-skin-cancer">The Guardian</a> quoted Fisher saying:</p>
<blockquote>
<p>It’s obviously critical that safety and toxicity studies need to be done … This is not a toy, it’s not a cosmetic.</p>
</blockquote>
<h2>Could these drugs have other uses?</h2>
<p>One little-reported aspect is SIKis also have potential as a treatment for diseases causing severe sun-sensitivity, like <a href="http://www.dermnetnz.org/topics/erythropoietic-protoporphyria">erythropoietic protoporphyria</a>, or anomalies in skin pigmentation, like <a href="http://www.dermnetnz.org/topics/vitiligo">vitiligo</a>. People with these under-researched conditions might be the real winners from a UV-free tanning cream.</p>
<p>In the meantime, the advice remains to <a href="http://www.cancer.org.au/preventing-cancer/sun-protection/preventing-skin-cancer/">slip, slop, slap, seek and slide</a> whenever the UV index reaches <a href="http://www.cancer.org.au/preventing-cancer/sun-protection/uv-alert/">three or higher</a> – daily from September to April in Australia’s southern states and all year round further north. You can also use the <a href="http://www.cancer.org.au/preventing-cancer/sun-protection/uv-alert/sunsmart-app.html">SunSmart app</a> to find out today’s UV index and sun protection times in your area. – <strong>Katie Lee and Richard Sturm</strong></p>
<hr>
<h2>Peer review</h2>
<p>As this Research Check clarifies, the study into activating a gene to increase skin pigmentation was performed in mice and isolated human skin. This analysis also echoes the researchers’ comment that the drug has never been tested in humans and “would require careful considerations of safety”.</p>
<p>Such considerations might include whether activating the gene could trigger cancer, as the researchers suggest could occur in certain circumstances. </p>
<p>If safe, as the Research Check says, it would be more convenient to be apply a drug to the skin rather than injecting it. And although more pigmented skin reduces the risk of skin cancer with sun exposure, the protection is only the equivalent of SPF 2-4 sunscreen. So I agree with Fisher that, if safe, the drug could only be used in addition to other skin protection measures.</p>
<p>The real issue is all this talk of risk and benefit is simply in pursuit of a fashion, said to have been started by fashion designer <a href="http://www.skincancer.org/prevention/tanning/tale-of-tanning">Coco Chanel</a>. It is not a universal fashion as in South East Asia pale skin <a href="https://theconversation.com/tall-pale-and-handsome-why-more-asian-men-are-using-skin-whitening-products-67580?sr=1">is more highly sought</a>. </p>
<p>Perhaps the more effective protection against cancer is to change Western fashion and promote the message that pale skin and red hair is beautiful too. – <strong>Ian Olver</strong></p><img src="https://counter.theconversation.com/content/79414/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Katie Lee is supported by funding from NHMRC, Epiderm Foundation, Queensland Genomic Health Alliance and the Queensland Cancer Council. </span></em></p><p class="fine-print"><em><span>Richard Sturm currently receives funding from the Australian NHMRC, Queensland Cancer Council, Queensland Genomic Health Alliance and the Epiderm Foundation. In the past he has been the recipient of ARC Discovery grant funding. </span></em></p><p class="fine-print"><em><span>Ian Olver sits on the NHMRC Council.</span></em></p>
A US study into whether a new drug can give us a tan without going into the sun generated headlines around the world. Here’s what the study really says.
Katie Lee, Study coordinator and research assistant, The University of Queensland
Richard Sturm, Principal Research Fellow, Dermatology Research Centre, The University of Queensland
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/64937
2016-09-08T08:28:51Z
2016-09-08T08:28:51Z
Why you can expect a spectacular autumn
<figure><img src="https://images.theconversation.com/files/136867/original/image-20160907-25272-m66f49.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Whether you think autumn officially starts at the beginning or end of September, you only have to look at the trees to see the season is changing. Leaves on deciduous trees always change colour from green to vibrant hues of yellow, orange, and red. But some years the colourful show is more spectacular than others. One of the most outstanding recent years in <a href="http://www.telegraph.co.uk/news/uknews/3256175/Best-autumn-colours-on-trees-for-years.html">the UK was 2008</a>. And the Forestry Commission is expecting 2016 to be <a href="http://www.forestry.gov.uk/newsrele.nsf/AllByUNID/0FE1C5B5C41167528025801400350FEA">another one of the best</a>. </p>
<p>So what produces an autumn to remember? Variation from one year to the next in nature can be seen in a number of phenomena, such as the amount and duration of spring blossom or the quantity of fruit and berries on bushes and trees. Oenophiles (wine lovers) will know that the quality of grapes from which wine is made varies from one year to another. The underlying explanation for all these phenomena is basically the same: the weather.</p>
<p>The distinctive autumnal woodland colours in leaves are formed by the combination of four classes of chemicals: chlorophyll, carotenoids, xanthophylls, and anthocyanins. Chlorophyll, the main chemical involved in photosynthesis, reflects green light, which explains the green colour of most deciduous trees in spring and summer. </p>
<p>As the days shorten in temperate latitudes, trees prepare for their winter dormant period by withdrawing nutrients from their leaves. Chlorophyll is rich in nitrogen. While some chlorophyll breaks down throughout the year, the <a href="http://www.usna.usda.gov/PhotoGallery/FallFoliage/ScienceFallColor.html">process accelerates during autumn</a>. As less green light is reflected, the colours of other chemicals in the leaves become visible.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/136868/original/image-20160907-25279-8q0mop.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/136868/original/image-20160907-25279-8q0mop.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=373&fit=crop&dpr=1 600w, https://images.theconversation.com/files/136868/original/image-20160907-25279-8q0mop.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=373&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/136868/original/image-20160907-25279-8q0mop.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=373&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/136868/original/image-20160907-25279-8q0mop.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=468&fit=crop&dpr=1 754w, https://images.theconversation.com/files/136868/original/image-20160907-25279-8q0mop.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=468&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/136868/original/image-20160907-25279-8q0mop.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=468&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Chlorophyll, xanthophylls, carotenoids and anthocyanins.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Changing pigments</h2>
<p>Carotenoids, another chemical involved in photosynthesis, tend to be orange. The yellow xanthophylls are oxygenated carotenoids. The many anthocyanin compounds produce a palette of reds, ranging from the brightest scarlet to maroons and purple. Put these colours together and you have a vibrant patchwork of colour clothing the countryside, urban parks and gardens.</p>
<p>Data from the Met Office show that August 2016 was warmer (by 0.6°C) and sunnier (110%) <a href="http://www.metoffice.gov.uk/climate/uk/summaries">compared to the long-term average</a>. Combined with a wet spring (rainfall 30% above average in the east and south), this will have led to higher than average levels of sugars in plant tissues – and it is these sugars that are the real key to the richness of the autumnal colours. Anthocyanins are large, complex molecules containing a sugar, usually glucose. So more sunshine means more glucose, more anthocyanins and more vibrant autumnal colours in 2016.</p>
<p>Anthocynanins are produced by some species of tree but not by others and they are also important in the production of the intense colours of many fruits and berries, including the colour of red grapes. In leaves, as the level of chlorophyll decreases, anthocyanins are produced.</p>
<p>It is still not absolutely clear what function is performed by anthocyanins. It costs the plant energy to make them and only some tree species produce anthocyanins. Around <a href="http://bit.ly/2c6uTOk">15% to 30%</a> of tree leaf colour is caused by carotenoids and xanthophylls alone. There is <a href="http://onlinelibrary.wiley.com/doi/10.1046/j.1365-3040.2002.00905.x/abstract;jsessionid=ADFE382A48655FD323BCD47C2AC0872E.f01t01">some suggestion</a> that anthocyanins are antioxidants and perform a protective role by preventing free radicals (reactive atoms or molecules) from destroying plant tissue and DNA. But this explanation is not universally accepted. </p>
<p>Other explanations are that anthocyanins <a href="http://research.haifa.ac.il/%7Ebiology/simcha/Publications/PIB17.pdf">effectively mask the leaves</a> visually from some predators that can see the green leaves but do not possess the photoreceptors required to detect red leaves or insects that find red less attractive than green.</p>
<p>As the chlorophyll breaks down and leaves naturally turn yellow and orange, so that the carotenoids and xanthophylls are no longer masked by the green, they attract sap-sucking aphids. So some species of tree produce a bright red pigment in the leaves to confuse insects.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/136870/original/image-20160907-25253-inyjuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/136870/original/image-20160907-25253-inyjuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/136870/original/image-20160907-25253-inyjuu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/136870/original/image-20160907-25253-inyjuu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/136870/original/image-20160907-25253-inyjuu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/136870/original/image-20160907-25253-inyjuu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/136870/original/image-20160907-25253-inyjuu.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">The hunt for red October.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>How long will it last?</h2>
<p>Although the summer weather means we can expect an impressive autumn, there are still some questions. Will 2016 be a long autumnal season, stretching from mid-September into November – or will it be cut short? In 2008, there were a few early frosts. Frost promotes abscission, the process by which the leaf detaches from the twig.</p>
<p>In 2008, leaves fell from the trees over a <a href="http://www.telegraph.co.uk/news/uknews/3256175/Best-autumn-colours-on-trees-for-years.html">relatively short period</a> of time. That, of course, brings with it the joys of kicking through piles of fallen leaves, but an early frost will shorten the duration of the autumnal show, as might the high winds associated with autumnal storms.</p>
<p>In the absence of early frosts and storms, however, we can look forward to a magnificent display. But for how many more years will this continue? Climate change has seen the onset date of leaf colour change <a href="http://www.bbc.co.uk/earth/story/20140929-why-is-autumn-changing">being pushed back</a>. That narrows the window during which the colours can be seen and enjoyed. If we are lucky this year, we will see a peak of colour in mid to late October with leaves still on the trees in November – but watch the weather forecast for the latest.</p><img src="https://counter.theconversation.com/content/64937/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Philip James 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>
Here’s the science behind the amazing colours we should see on British trees this year.
Philip James, Professor of ecology, University of Salford
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/53888
2016-02-02T04:29:21Z
2016-02-02T04:29:21Z
Tanzania is still failing to protect its children who live with albinism
<figure><img src="https://images.theconversation.com/files/109639/original/image-20160129-27334-10xc8g5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Selina, right, and her friend Mwanaidi play together in a Tanzanian classroom. Children with albinism are very vulnerable to attack, mutilation and murder.</span> <span class="attribution"><span class="source">EPA/Johan Baevman</span></span></figcaption></figure><p>There is no doubt that educational access worldwide has improved in the past two decades. This has been driven by the launch in 1990 of the United Nations’ <a href="http://www.unesco.org/new/en/education/themes/leading-the-international-agenda/education-for-all/the-efa-movement/">Education for All</a> global initiative. By 2011 there were more than 136 million children enrolled in schools <a href="http://unesdoc.unesco.org/images/0022/002266/226662e.pdf">compared</a> with just 82 million in 1999.</p>
<p>The picture is <a href="http://unesdoc.unesco.org/images/0023/002322/232205e.pdf">far less rosy</a> in sub-Saharan Africa. The region is home to half of the world’s children who ought to be in school but are not enrolled. </p>
<p>This is not for lack of hard work and political will. Take Tanzania, for instance. Immediately after its independence from Britain in 1961, the country declared total war against three enemies of development: ignorance, disease and poverty. It introduced a Universal Primary Education program which managed, to some extent, to address several educational challenges. The program made schools far more accessible to and safer for most Tanzanian children.</p>
<p>But not everyone has benefited. People living with albinism are vulnerable to attack, mutilation – and murder. This means they’re not able to freely and comfortably conduct day-to-day activities such as attending school. The United Nations <a href="http://www.ohchr.org/EN/NewsEvents/Pages/DisplayNews.aspx?NewsID=15673&LangID=E">warned</a> in 2015 that many children with albinism are too frightened to leave their homes and go to school. It is clear that children with albinism are not able to benefit from “education for all”.</p>
<h2>A dangerous condition</h2>
<p>Albinism is much more prevalent in sub-Saharan Africa than in other parts of the world. <a href="http://www.ncbi.nlm.nih.gov/pubmed/16916463">Estimates</a> suggest that as many as one in 1400 people in Tanzania are affected. The prevalence is as high as one in 1000 in selected Zimbabwean and other southern African ethnic groups.</p>
<p>Attacks on people with albinism are <a href="http://www.underthesamesun.com/sites/default/files/Attacks%20of%20PWA%20-%201%20page_0.pdf">rife</a> in Africa. Superstitions abound about people with this condition: for example, it is believed that their body parts are potent charms to bring fortune and good luck. Some believe that <a href="http://www.reuters.com/article/us-tanzania-albino-idUSTRE66R3XP20100728?feedType=RSS&feedName=worldNews&utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+reuters%2FworldNews+%28News+%2F+US+%2F+International%29">drinking the blood</a> of people with albinism will imbue them with super strength.</p>
<p>In fact, people with albinism merely suffer from a genetic <a href="http://www.healthline.com/health/albinism">pigmentation deficiency</a> that means their hair, eyes and skin have little or no colour. </p>
<p>Data collected by the advocacy group <a href="http://www.underthesamesun.com/aboututss">Under the Same Sun</a> shows that Tanzania is by far the <a href="http://www.underthesamesun.com/sites/default/files/Attacks%20of%20PWA%20-%201%20page_0.pdf">most dangerous</a> country to be an albino. It also warns that such attacks, mutilations, rapes and murders are likely to be under-reported. </p>
<p>It’s not common for perpetrators to be arrested, tried and convicted. This might be attributed to the fact that even politicians are thought to be <a href="http://news.nationalgeographic.com/news/2013/10/131011-albino-killings-witch-doctors-tanzania-superstition/">complicit</a> in the murders of people with albinism. Some politicians have been <a href="http://mgafrica.com/article/2015-09-14-attackers-in-kenya-try-to-hack-off-body-parts-from-albino-for-sale-in-tanzania-as-polls-near">accused</a> of buying albino body parts as lucky charms to help them during elections. </p>
<p>This badly tarnishes Tanzania’s image and contributes to the perception that the plight of people with albinism is not taken very seriously by the country’s leaders. The country has made some attempts to curb the killings. In 2015 witch doctors, who are central to the trade of body parts, <a href="http://www.theguardian.com/world/2015/jan/14/tanzania-bans-witchdoctors-attempt-end-albino-killings">were banned</a>. Sadly, the attacks continue.</p>
<p>In the past ten years a worrying new trend <a href="http://www.theguardian.com/global-development-professionals-network/2015/may/13/albinism-in-tanzania-slow-progress-in-combatting-violence-and-discrimination">has emerged</a>: children with albinism are often the victims of the brutal attacks described above. This is likely because children are more vulnerable and – since they are expected to be at school every day – easier to find in the same place and at the same time.</p>
<p>Many Tanzanian children walk long distances to and from school. They also play outside unsupervised and, being young and smaller than adults, will not always have the physical strength to resist attackers. </p>
<p>How can this scourge be tackled?</p>
<h2>Seeking solutions</h2>
<p>Poverty is at the core of attacks on people with albinism. Those who are battling to survive are often lured by syndicates which offer a lot of money for the body parts or entire body of a person with albinism. In some cases, people can earn as much as <a href="https://www.washingtonpost.com/news/morning-mix/wp/2015/03/13/how-tanzanias-upcoming-election-could-put-albinos-at-risk-for-attack/">USD $75,000</a> on the black market for this grisly trade. </p>
<p>Tanzania’s authorities will need to take a varied approach towards ending the plight of people and particularly children with albinism. Special attention will have to be paid to children who come from poor families and are more likely to leave school out of fear for their safety during long walks or time spent alone. It is important that they be given the support to stay in school and get the same education as their peers who do not have albinism.</p>
<p>In addition, local community leaders and religious leaders need to be involved in advocacy and education. Through these measures perhaps people will learn to live together peacefully, and Tanzanian children with albinism will no longer have to hide in their own homes.</p><img src="https://counter.theconversation.com/content/53888/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Simon Ngalomba 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>
Children living with albinism are very vulnerable to attack, kidnapping, mutilation and murder. In Tanzania, fear is keeping many children away from school and costing them an education.
Simon Ngalomba, Lecturer in Educational Foundations, Management and Life Long Learning, University of Dar es Salaam
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/48294
2015-10-01T11:45:34Z
2015-10-01T11:45:34Z
Fossils help to reveal the true colours of extinct mammals for the first time
<figure><img src="https://images.theconversation.com/files/96935/original/image-20151001-29638-oi6ss5.jpg?ixlib=rb-1.1.0&rect=0%2C141%2C1024%2C720&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Eocene#/media/File:Eocene.jpg">Jay Matternes/Wikimedia Commons</a></span></figcaption></figure><p>The animal kingdom is full of colour. Animals use it <a href="https://theconversation.com/the-dusky-dottyback-a-master-of-disguise-in-the-animal-world-38730">for camouflage</a>, to advertise themselves and even as various <a href="https://theconversation.com/motion-dazzle-spotting-the-patterns-that-help-animals-outsmart-predators-on-the-run-47219">forms of protection</a>. But we haven’t been paying as much attention to what colours now-extinct mammals might have had – until now. </p>
<p>By matching samples of organic material to their chemical make up we’ve been able to determine the colour of extinct bats and <a href="http://www.pnas.org/content/early/2015/09/24/1509831112">our novel research</a>, published in PNAS, has the potential to work out colours in lots of other organisms.</p>
<p>Fossils usually only leave us information about the harder parts of an animal such as bones and shells. Occasionally, however, <a href="https://theconversation.com/from-bone-to-brawn-ancient-fish-show-off-their-muscles-15098">soft tissues</a>, such as feathers, skin or hair are left behind.</p>
<p>Palaeontologists have previously discovered dark, organic residues in fossils that for decades were thought to be remnants of decaying bacteria from the surface of the dead bodies. However, in 2008 <a href="http://rsbl.royalsocietypublishing.org/content/4/5/522">it was suggested</a> that these little bacteria-like structures were in fact preserved melanosomes, the special sub-units of a cell that carry the pigment melanin. This is the primary source of pigment for feathers, hair and skin across the animal kingdom.</p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/96938/original/image-20151001-29626-12x6e0n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/96938/original/image-20151001-29626-12x6e0n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=374&fit=crop&dpr=1 600w, https://images.theconversation.com/files/96938/original/image-20151001-29626-12x6e0n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=374&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/96938/original/image-20151001-29626-12x6e0n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=374&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/96938/original/image-20151001-29626-12x6e0n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=470&fit=crop&dpr=1 754w, https://images.theconversation.com/files/96938/original/image-20151001-29626-12x6e0n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=470&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/96938/original/image-20151001-29626-12x6e0n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=470&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Palaeontology in black and white.</span>
<span class="attribution"><span class="source">Yale</span></span>
</figcaption>
</figure>
<p>Looking at a fossilised feather from the Cretaceous period (roughly 105m years old) with an alternating black and white pattern revealed that the microscopic structures were only present in the black bands. If these structures were bacteria as originally thought, they would have covered the entire feather. The fact that the structures were missing from the white areas, which would lack pigment, suggested the organic matter was actually melanosomes. What’s more, the structures were aligned along the fine branches of the feather (barbs and barbules), another characteristic feature of melanosomes.</p>
<h2>Colour clues</h2>
<p>Different melanosomes have different shapes. Of the two main types, reddish brown pheomelanosomes are shaped like tiny little meatballs (500 nanometres in diameter). Black eumelanosomes, meanwhile, are shaped like little narrow sausages and are about twice the size at one micrometre in length.</p>
<p><a href="http://www.sciencemag.org/content/327/5971/1369">Subsequent studies</a> have used these facts to reconstruct colour patterns of dinosaurs, with the shape of melanosomes found in different places of a fossil indicating its pigment colour and <a href="http://www.sciencemag.org/content/335/6073/1215.short">even iridescence</a>. But until now, little work has been done to characterise the chemistry of the pigment in these fossil melanosomes and there is little evidence to prove that the melanosome shape actually reflects the original colour in fossils.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/96941/original/image-20151001-29633-zxdfte.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/96941/original/image-20151001-29633-zxdfte.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=816&fit=crop&dpr=1 600w, https://images.theconversation.com/files/96941/original/image-20151001-29633-zxdfte.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=816&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/96941/original/image-20151001-29633-zxdfte.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=816&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/96941/original/image-20151001-29633-zxdfte.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1025&fit=crop&dpr=1 754w, https://images.theconversation.com/files/96941/original/image-20151001-29633-zxdfte.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1025&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/96941/original/image-20151001-29633-zxdfte.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1025&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Bacteria or colour carriers?</span>
<span class="attribution"><span class="source">Jakob Vinther</span></span>
</figcaption>
</figure>
<p>Using a combination of techniques, we <a href="http://www.pnas.org/content/early/2015/09/24/1509831112">have been able</a> to describe melanin and melanosomes in animals ranging from fish to birds to squids, and for the first time, frogs, tadpoles and mammals. We looked at the shape of the melanosomes under a scanning electron microscope. We also analysed the molecules directly associated with these structures and found that their chemical signature resembled modern melanin samples. However, there were also some clear differences. </p>
<p>We speculated that perhaps the melanin had changed its chemical composition over millions of years buried in the ground under high pressure and temperature. In order to test this, we subjected melanin to even higher pressures and temperatures to replicate within 24 hours the conditions it would have experienced over millions of years. The chemical signature from our cooked melanin then looked more similar to the fossils. </p>
<p>Furthermore, we found that we could quantify the difference between red and black melanin in both fresh and fossil samples. This meant we could test the idea that melanosome shape correlated to chemical colour in the skin of the now fossilised animal – and we found that it did.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/96939/original/image-20151001-29638-4617pl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/96939/original/image-20151001-29638-4617pl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/96939/original/image-20151001-29638-4617pl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/96939/original/image-20151001-29638-4617pl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/96939/original/image-20151001-29638-4617pl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/96939/original/image-20151001-29638-4617pl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/96939/original/image-20151001-29638-4617pl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Secret in the bones.</span>
<span class="attribution"><span class="source">A. Vogel, Senckenberg Institution, Messel Research</span></span>
</figcaption>
</figure>
<p>Most excitingly, this also meant that we could for the first time determine the colour of long-extinct mammals just by studying their fossils. We looked at two fossilised bat species from Messel in Germany that lived in the Eocene period (around 49m years ago). Based on the small spherical melanosomes – which are indicative of pheomelanosomes – and the chemical signature associated with the related pigment, we were able to infer that these bats originally sported a reddish brown coat. This means they did not look much different from modern bats.</p>
<p>The study of fossil melanin and other pigments is a <a href="http://www.nature.com/scitable/blog/accumulating-glitches/how_we_know_the_colors">blooming research area</a>. Knowing something about fossilised creatures’ original colours will not only make Jurassic Park sequels more realistic, but will also inform us about the whole ecology of dinosaurs and other extinct animals.</p><img src="https://counter.theconversation.com/content/48294/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jakob Vinther received funding from National Geographic and from UT Austin. </span></em></p><p class="fine-print"><em><span>Caitlin Colleary 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>
Scientists have shown how tiny organic tissue remnants in fossils correspond to the pigments in the animals’ original skin and hair.
Jakob Vinther, Lecturer in macroevolution, University of Bristol
Caitlin Colleary, PhD candidate in paleontology, Virginia Tech
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/32012
2014-10-21T09:52:14Z
2014-10-21T09:52:14Z
Fall foliage in the crosshairs of climate change
<figure><img src="https://images.theconversation.com/files/60803/original/mnj3gxc3-1412364346.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Enjoy the color while you can before climate change makes a mess of this too.</span> <span class="attribution"><a class="source" href="http://commons.wikimedia.org/wiki/File:Vermont_fall_foliage_hogback_mountain.JPG">chensiyuan</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>One of nature’s most spectacular events occurs every autumn, when the leaves of hardwood trees burst into brilliant color before falling to the ground. These autumnal displays in the eastern United States, Europe, eastern Asia and a few locales in South America and New Zealand entice people to experience nature in all its raw beauty.</p>
<p>Leaf peeping can pump hundreds of millions of <a href="http://www.uvm.edu/%7Esnrvtdc/publications/2001_Fall_Foliage_Report.pdf">tourist dollars</a> into the economies of particularly colorful areas. But now climate change hovers in the background, threatening to alter future versions of this annual color show.</p>
<h2>Business as usual</h2>
<p>Tree leaves turn color in the fall in response to shorter days and cooler temperatures. In August and September, trees begin an <a href="http://www.plantphysiol.org/content/139/4/1635.short">orderly process</a> of leaf senescence – or dying – characterized by the loss of chlorophyll. That’s the green pigment that plants use to capture light for photosynthesis.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/60804/original/bmm3mgyy-1412364885.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/60804/original/bmm3mgyy-1412364885.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/60804/original/bmm3mgyy-1412364885.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/60804/original/bmm3mgyy-1412364885.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/60804/original/bmm3mgyy-1412364885.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/60804/original/bmm3mgyy-1412364885.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/60804/original/bmm3mgyy-1412364885.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/60804/original/bmm3mgyy-1412364885.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"></a>
<figcaption>
<span class="caption">Red and yellow now … brown in the future?</span>
</figcaption>
</figure>
<p>Some species, such as <a href="http://www.plantphysiol.org/content/127/2/566.short">dogwoods</a>, red maples and red oaks, begin to make <a href="http://treephys.oxfordjournals.org/content/21/1/1.short">anthocyanins</a>, the pigments that give leaves their bright red color. Other trees, such as birches, tulip poplars and beech, don’t make anthocyanins. Instead, when their chlorophyll breaks down, pigments hidden during the summer months become visible. Called carotenoids and xanthophylls, they’re the pigments responsible for producing orange and yellow leaves. </p>
<h2>Too warm, too cool</h2>
<p>If the <a href="http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0057373#pone-0057373-g005">fall is cool</a>, trees develop leaf color earlier. Warmer years, the display of color is <a href="http://onlinelibrary.wiley.com/doi/10.1111/geb.12206/full">delayed</a>. In a world warmed by climate change, the onset of colors would always come later in the season. Some trees are more sensitive to temperature than others. As the climate warms, the finely-tuned timing of the fall’s color display may lose its <a href="http://rstb.royalsocietypublishing.org/content/365/1555/3247.short">synchronization</a>. Rather than the well-timed symphony of color that we’re used to now, we might see unsynchronized patches as each species changes over the course of the season.</p>
<p>Warmer temperatures may also allow pests such as insects, fungi or bacteria – not to mention exotic tree species such as the Princess Tree – to move farther north than usual. These pests could alter the composition of the forest, much as when chestnuts were eliminated by blight 100 years ago. If the species composition of future forests changes in response to climate change, the quality of the fall foliage display will be quite different from what we see now.</p>
<h2>Sugars from sun</h2>
<p>Sunshine plays a role here too. Later in the season, the days are shorter and the sun is lower in the sky due to the earth’s tilt. This reduced sunlight slows down the process of photosynthesis and lowers sugar reserves. Without those sugars to stimulate the synthesis of anthocyanins, we get duller red leaves.</p>
<h2>Too wet, too dry</h2>
<p>Global climate change might also alter precipitation amounts and timing. Too much rain lowers the intensity of fall color – not because it washes out the colors (an old wives’ tale), but rather because cloudy skies and low light cut down on photosynthesis and production of those vital anthocyanins. Conversely, drought causes trees to drop their leaves prematurely before they get a chance to turn color.</p>
<p>Nitrogen is another <a href="http://treephys.oxfordjournals.org/content/23/5/325.short">factor</a> that could mute the color display. Excess levels, which can result from pollution and increased precipitation, also reduce anthocyanin production. Again the result is less red leaf color. We may already be seeing less vibrant red fall displays than those prior to industrialization, since most eastern <a href="http://nadp.sws.uiuc.edu/committees/tdep/tdepmaps/preview.aspx#n_td">forests today</a> get from two to seven times the natural input of nitrogen.</p>
<h2>Migrating trees</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/60801/original/nxqhhnr7-1412363868.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/60801/original/nxqhhnr7-1412363868.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/60801/original/nxqhhnr7-1412363868.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/60801/original/nxqhhnr7-1412363868.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/60801/original/nxqhhnr7-1412363868.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/60801/original/nxqhhnr7-1412363868.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/60801/original/nxqhhnr7-1412363868.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/60801/original/nxqhhnr7-1412363868.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">Fall foliage display as seen from space.</span>
<span class="attribution"><a class="source" href="http://earthobservatory.nasa.gov/IOTD/view.php?id=1893&eocn=image&eoci=related_image">NASA’s Earth Observatory</a></span>
</figcaption>
</figure>
<p>If it becomes too warm or too dry for some tree species, they may have to migrate to more suitable habitats. Individual trees, of course, can’t pick up and move in response to climatic conditions. But the trees in inhospitable areas would die out and seedlings would take hold in new cooler areas. </p>
<p>In Vermont, where temperatures have increased by 2.5F (1.5C) in the past 50 years, hardwood trees have <a href="http://www.pnas.org/content/105/11/4197.short">migrated</a> around 328ft (100m) upslope, where it’s cooler. For trees on flatter terrain, warmer temperatures will force them to migrate north. Sugar maple, one of the major fall color trees in New England, may <a href="http://www.sciencedirect.com/science/article/pii/S0378112707005439">move</a> right out of the United States into Canada. What will autumn in New England feel like without the brilliant red colors we’re used to? Such migrations will alter the <a href="http://www.nrs.fs.fed.us/atlas/tree/">composition of our forests</a> forever. A new fall color balance will eventually emerge. </p>
<h2>Don’t forget carbon dioxide</h2>
<p>Of course, an increase in the amount of carbon dioxide in Earth’s atmosphere is one of the reasons the climate is warming in the first place. Trees will need to adapt as carbon dioxide levels continue to rise over the coming decades. <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2010.03184.x/full">Research</a> suggests that more CO<sub>2</sub> might actually enhance fall colors. So score one point for global warming – even if this one factor won’t tip the balance.</p>
<h2>Catch this show while you can</h2>
<p>Global climate change will not eliminate fall leaf color, but the best displays will move northward and upward in elevation in response to warming. For forests in their present location, fall foliage displays will occur later in the season and may last longer, but will be of diminished quality due to less intense red colors. The fall foliage displays that our grandchildren will see at the end of this century will not be the ones we see today.</p><img src="https://counter.theconversation.com/content/32012/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Howard Neufeld 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>
One of nature’s most spectacular events occurs every autumn, when the leaves of hardwood trees burst into brilliant color before falling to the ground. These autumnal displays in the eastern United States…
Howard Neufeld, Professor of Physiological Plant Ecology, Appalachian State University
Licensed as Creative Commons – attribution, no derivatives.