http___www.jutarnji.hr_uznemirujuce-vijesti-za-ljubitelje-suncanja--kreme-za-suncanje-mozda-su-kancerogene-kada-se-izloze-suncu-_1026862__1.xml
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As vacationers prepare to spend time outdoors this summer, many of them will pack plenty of sunscreen in hopes it will protect their bodies from overexposure, and possibly from skin cancer. But researchers at Missouri University of Science and Technology are discovering that sunscreen may not be so safe after all. Cell toxicity studies by Dr. Yinfa Ma, Curators' Teaching Professor of chemistry at Missouri S&T, and his graduate student Qingbo Yang, suggest that when exposed to sunlight, zinc oxide, a common ingredient in sunscreens, undergoes a chemical reaction that may release unstable molecules known as free radicals. Free radicals seek to bond with other molecules, but in the process, they can damage cells or the DNA contained within those cells. This in turn could 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," Ma says, "and those free radicals can kill cells." Ma studied how human lung cells immersed in a solution containing nanoparticles of zinc oxide react when exposed to different types of light over numerous time frames. Using a control group of cells that were not immersed in the zinc oxide solution, Ma compared the results of light exposure on the various groups of cells. He found that zinc oxide-exposed cells deteriorated more rapidly than those not immersed in the chemical compound. Even when exposed to visible light only, the lung cells suspended in zinc oxide deteriorated. But for cells exposed to ultraviolet rays, Ma found that "cell viability decreases dramatically." When exposed to ultraviolet long-wave light (ultraviolet A or UVA) for 3 hrs, half of the lung cells in the zinc oxide solution died. After 12 hrs, 90% of the cells in that solution died, Ma found. Why does zinc oxide, an ingredient used in sunscreen to help block harmful UV rays, cause cells to deteriorate when exposed to sunlight? According to Ma, when the zinc oxide nanoparticles in the solution absorb the UV rays, the reaction releases electrons, which in turn may produce unstable free radical molecules in the zinc oxide solution. Those free radical molecules then bond with other molecules and act as parasites, damaging the other molecules in the process. Ma's research on zinc oxide's effect on cells is still in the early stages, so he cautions people from drawing conclusions about the safety or dangers of sunscreen based on this preliminary research. "More extensive study is still needed," Ma says. "This is just the first step." For instance, Ma plans to conduct electron spin resonance tests to see whether zinc oxide truly does generate free radicals, as he suspects. In addition, clinical trials will be needed before any conclusive evidence may be drawn from his studies. In the meantime, Ma advises sunbathers to use sunscreen and to limit their exposure to the sun. 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. Missouri University of Science and Technology
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ROLLA - Prema najnovijem istraživanju provedenom na Sveučilištu znanosti i tehnologije u Missouriju, jedan od glavnih spojeva u kremama za sunčanje, cinkov oksid, možda postaje kancerogen kada se izloži suncu - što se sigurno dešava svaki put kada koristimo kremu za sunčanje, piše PhysOrg. Izložen suncu, cinkov oksid započinje kemijsku reakciju koja može otpustiti nestabilne molekule znane kao slobodni radikali, koje mogu oštetiti ljudske stanice ili DNK u stanicama. Također, što je duže izložen suncu, to je veća potencijalna štetnost. - Cinkov oksid može generirati slobodne radikale kada ga se izloži ultraljubičastom zračenju, i radikali mogu ubijati stanice, rekao je dr. Yinfa Ma, profesor kemije na Sveučilištu u Missouriju i vođa najnovijeg istraživanja. Istraživanje je provedeno na stanicama plućnog tkiva pod ultraljubičastom svjetlosti, pri čemu je zapaženo da su stanice koje su bile izložene cinkovom oksidu propadale neusporedivo brže od stanica koje su bile samo izložene svjetlosti. Ma napominje kako je istraživanje tek u svojoj ranoj fazi, i smatra da je još prerano izvlačiti zaključke. - Potrebna su dodatna istraživanja, ovo je samo prvi korak, rekao je Ma. U međuvremenu, Ma savjetuje ljudima da i dalje koriste kreme za sunčanje, no da paze koliko se izlažu suncu. - I dalje bih savjetovao korištenje krema za sunčanje, kreme su bolje od nikakve zaštite, rekao je Ma. Cinkov oksid također se nalazi u mnoštvu drugih proizvoda, poput plastike, boja, krema za ruke i tijelo, te brtvila.