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   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Understanding how sunscreens damage coral    
      
     Date:   
         May 5, 2022   
     Source:   
         Stanford University   
     Summary:   
         Researchers reveal a mechanism by which oxybenzone, a common   
         sunscreen component, damages corals. The surprising findings   
         could help guide the development and marketing of effective,   
         coral-safe sunscreens.   
      
      
      
   FULL STORY   
   ==========================================================================   
   You can love something to death. That is one way of thinking about a new   
   Stanford University study that reveals how a common component of many   
   sunscreens worn by coral reef-exploring tourists may hasten the demise   
   of these endangered ecosystems. The surprising findings, published May 6   
   in Science, could help guide the development and marketing of effective,   
   coral-safe sunscreens.   
      
      
   ==========================================================================   
   "It would be a sad irony if ecotourism aimed at protecting coral reefs   
   were actually exacerbating their decline," said study lead author Djordje   
   Vuckovic, a PhD student in civil and environmental engineering. "My hope   
   is that our research will help lead the way to developing coral-safe   
   sunscreens."  Up to 6,000 tons of sunscreen -- more than the weight of   
   50 blue whales -- wash through U.S. reef areas every year, according to   
   the National Park Service.   
      
   Scientists have known for some time that oxybenzone, an organic compound   
   found in many sunscreens, can damage corals. As a result, sunscreens with   
   this compound have been banned in the U.S. Virgin Islands and Hawaii,   
   the island nation of Palau, and Bonaire, an island municipality of the   
   Netherlands, among other places.   
      
   However, the mechanisms by which oxybenzone does harm have largely   
   remained a mystery, making it difficult to ensure that sunscreen   
   components proposed as alternatives are truly safer for corals.   
      
   William Mitch, a professor of civil and environmental engineering at   
   Stanford, became interested in the issue several years ago when he   
   heard about Hawaii's then-pending ban. With funding from the Stanford   
   Woods Institute for the Environment, he and John Pringle, a professor of   
   genetics in the Stanford School of Medicine, began work to characterize   
   the chemical and biological mechanisms by which oxybenzone harms corals.   
      
   Protection for humans, damage for corals In their new study, Mitch,   
   Pringle, Vuckovic, and other Stanford researchers used anemones as   
   surrogates for corals, which are harder to experiment with, as well as   
   mushroom corals. Exposed to oxybenzone in artificial seawater under   
   simulated sunshine, the anemones all died within 17 days, whereas   
   anemones exposed to oxybenzone in the absence of simulated sunlight   
   remained viable.   
      
      
      
   ==========================================================================   
   "It was strange to see that oxybenzone made sunlight toxic for corals --   
   the opposite of what it is supposed to do," said Mitch. "The compound is   
   good at absorbing light within the waveband we tested, which is why it's   
   so common in sunscreens."  After absorbing ultraviolet light, oxybenzone   
   is designed to dissipate the light energy as heat, preventing sunburn. The   
   anemones and corals, however, metabolized oxybenzone in such a way that   
   the resulting substance formed damaging radicals when exposed to sunlight.   
      
   In addition to this vulnerability, the researchers found evidence for a   
   coral defense mechanism. Symbiotic algae in corals appeared to protect   
   their hosts by sequestering within themselves the toxins that corals   
   produced from oxybenzone.   
      
   As ocean waters warm, stressed corals expel their algae partners,   
   exposing bone-white coral skeletons. Thus, in addition to being more   
   vulnerable to disease and environmental shocks, such "bleached" corals   
   would be more vulnerable to the depredations of oxybenzone without their   
   algae to protect them.   
      
   Ensuring sunscreens are safe for corals and other marine species   
   Oxybenzone may not be the only sunscreen ingredient of concern, the   
   researchers warn. The same metabolic pathways that appear to convert   
   oxybenzone into a potent toxin for corals may do something similar with   
   other common sunscreen ingredients, many of which share similar chemical   
   structures and so could form similar phototoxic metabolites.   
      
      
      
   ==========================================================================   
   Many sunscreens marketed as coral-safe are based on metals, such as zinc   
   and titanium, rather than organic compounds, such as oxybenzone. Although   
   these sunscreens are fundamentally different in how they function, it   
   is not clear whether they are actually safer for corals, according to   
   the researchers, who are planning to investigate the matter further.   
      
   "In environmental science, as in medicine, a sound understanding of   
   basic mechanisms should provide the best guidance for the development   
   of practical solutions," said Pringle. "Our study also illustrates the   
   enormous power of collaborations between scientists with very different   
   backgrounds and expertise," said Mitch.   
      
   Co-authors of the study also include Amanda Tinoco, a research technician   
   at Stanford School of Medicine at the time of the research; Lorraine   
   Ling, a postdoctoral scholar in genetics at the time of the research;   
   and Christian Renicke, a postdoctoral research scientist in genetics.   
      
   The research was funded by the Stanford Woods Institute for the   
   Environment's Environmental Venture Projects program and the National   
   Science Foundation.   
      
      
   ==========================================================================   
   Story Source: Materials provided by Stanford_University. Original written   
   by Rob Jordan.   
      
   Note: Content may be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Djordje Vuckovic, Amanda I. Tinoco, Lorraine Ling, Christian   
      Renicke,   
         John R. Pringle, William A. Mitch. Conversion of oxybenzone   
         sunscreen to phototoxic glucoside conjugates by sea anemones and   
         corals. Science, 2022; 376 (6593): 644 DOI: 10.1126/science.abn2600   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2022/05/220505143215.htm   
      
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