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Posted: May 8th, 2012 Another study points to sunscreen material's skin cancer risk ( Nanowerk News ) As vacationers prepare to spend time outdoors this summer, manyof them will pack plenty of sunscreen in hopes it will protecttheir bodies from overexposure, and possibly from skin cancer. Butresearchers at Missouri University of Science and Technology arediscovering that sunscreen may not be so safe after all. Celltoxicity studies by Dr. Yinfa Ma, Curators' Teaching Professor ofchemistry at Missouri S&T, and his graduate student QingboYang, suggest that when exposed to sunlight, zinc oxide, a commoningredient in sunscreens, undergoes a chemical reaction that mayrelease unstable molecules known as free radicals. Free radicalsseek to bond with other molecules, but in the process, they candamage cells or the DNA contained within those cells. This in turncould increase the risk of skin cancer. Ma also found that the longer zinc oxide is exposed to sunlight,the greater the potential damage to human cells. "Zinc oxide may generate free radicals when exposed to UV(ultraviolet) sunlight," May says, "and those free radicals cankill cells." Ma studied how human lung cells immersed in a solution containingnano-particles of zinc oxide react when exposed to different typesof light over numerous time frames. Using a control group of cellsthat were not immersed in the zinc oxide solution, Ma compared theresults of light exposure on the various groups of cells. He foundthat zinc oxide-exposed cells deteriorated more rapidly than thosenot immersed in the chemical compound. Even when exposed to visible light only, the lung cells suspendedin zinc oxide deteriorated. But for cells exposed to ultravioletrays, Ma found that "cell viability decreases dramatically." When exposed to ultraviolet long-wave light (ultraviolet A or UVA)for 3 hours, half of the lung cells in the zinc oxide solutiondied. After 12 hours, 90 percent of the cells in that solutiondied, Ma found. Why does zinc oxide, an ingredient used in sunscreen to help blockharmful UV rays, cause cells to deteriorate when exposed tosunlight? According to Ma, when the zinc oxide nano-particles inthe solution absorb the UV rays, the reaction releases electrons,which in turn may produce unstable free radical molecules in thezinc oxide solution. Those free radical molecules then bond withother molecules and act as parasites, damaging the other moleculesin the process. Ma and his colleagues at Missouri S&T published their initialresearch results in the January 2009 edition of the Journal of Nanoparticle Research . The paper, titled "Toxicity of nano- and micro-sized ZnO particles in human lungepithelial cells" , was the first comprehensive study ever published on this subject.Lead author Weisheng Lin was Ma's Ph.D. student at the time. Otherauthors of the paper were Chuan-Chin Huang, a graduate student inbiological sciences at the time, and two members of S&T'sbiological sciences faculty, Dr. Katie Shannon (assistantprofessor) and Dr. Yue-Wern Huang (associate professor). Now, Ma is preparing to publish his latest research results in thejournal Toxicology and Applied Pharmacology . A publication date has not been determined. Ma's research on zinc oxide's effect on cells is still in the earlystages, so he cautions people from drawing conclusions about thesafety or dangers of sunscreen based on this preliminary research. "More extensive study is still needed," May says. "This is just thefirst step." For instance, Ma plans to conduct electron spin resonance tests tosee whether zinc oxide truly does generate free radicals, as hesuspects. In addition, clinical trials will be needed before anyconclusive evidence may be drawn from his studies. In the meantime, Ma advises sunbathers to use sunscreen and tolimit their exposure to the sun. "I still would advise people to wear sunscreen," he says."Sunscreen is better than no protection at all." Besides sunscreen, zinc oxide is used in many commercial products,including plastics, paints, ointments and sealants. I am an expert from grocerystoreshelves.com, while we provides the quality product, such as China Metal Display Racks , Supermarket Shelf Manufacturer, Grocery Store Shelves,and more.
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