Corvallis, Oregon-According to a collaboration that includes scientists from Oregon State University, sunscreens containing zinc oxide are a common ingredient that lose most of their effects and become toxic after two hours of exposure to ultraviolet radiation .
Toxicity analysis involves zebrafish. Zebrafish have significant similarities with humans at the molecular, genetic and cellular levels, which means that many zebrafish studies are directly related to humans.
The results of the research were published today in "Photochemistry and Photobiology Science".
A research team that includes faculty members Robyn Tanguay and Lisa Truong of the Faculty of Agricultural Sciences and graduate student Claudia Santillan is trying to answer important but largely ignored questions about the huge global sunscreen market. Market data company Statista predicts that the market is worth more than 24 billion U.S. dollars by the end of this century.
Question: What is the stability, safety and effectiveness of the combination of sunscreen ingredients rather than individual compounds—this is how the Food and Drug Administration approves them—and how safe is any chemical product resulting from a reaction caused by exposure To the sun?
"Sunscreen is an important consumer product that helps reduce UV exposure, thereby reducing skin cancer, but we don't know whether the use of certain sunscreen formulations will cause unexpected toxicity due to the interaction between certain ingredients and UV rays," The famous Tanguay of Oregon State University said. Professor and international toxicology expert.
She said the public’s perception of sunscreen safety has led manufacturers to use large amounts of certain ingredients based on limited data while restricting others. For example, oxybenzone has actually been discontinued due to fear of harm to coral reefs.
"Sunscreens containing inorganic compounds such as zinc oxide or titanium dioxide can block ultraviolet rays, and are increasingly being introduced to the market as safe alternatives to organic small molecular compounds that absorb ultraviolet rays," Tanguay said.
Scientists including James Hutchinson and Aurora Ginzburg of the University of Oregon and Richard Blackburn of the University of Leeds prepared five blends of UV filters (active ingredients in sunscreens) from different products in the United States and Europe. They also made additional blends with the same ingredients, plus zinc oxide at the lower limit of the commercially recommended amount.
Then, the researchers exposed the mixture to ultraviolet radiation for two hours and used spectroscopy to check their photostability—that is, what effect does sunlight have on the compounds in the mixture and its UV protection?
Scientists have also studied whether any mixture of ultraviolet radiation is toxic to zebrafish, which is a widely used model organism, from egg to swimming in five days, and found that the ultraviolet exposure mixture without zinc oxide does not cause any signs of fish. Changing.
"Several studies have shown that sunscreens can react quickly to UV exposure-this is the special setting they use-so surprisingly, there are very few toxicity tests for photodegradable products," Truong said. "Our research results show that the commercially available small molecule formulas, which are the basis for our research formulas, can be combined with different ingredient ratios to minimize photodegradation."
However, when zinc oxide particles (nanoparticles or larger particles) were added, the scientists found a huge difference in photostability and phototoxicity.
"Regardless of the size of the particles, zinc oxide will degrade the organic mixture and cause the organic filter to lose more than 80% of the protection against ultraviolet A rays, which account for 95% of the ultraviolet radiation reaching the earth," Santilan said . "In addition, zinc oxide-induced photodegradation products have led to a significant increase in zebrafish defects that we use to test toxicity. This suggests that zinc oxide particles can cause degradation products, which are harmful to the environment when introduced into aquatic ecosystems."
Tanguay said she was surprised that all five small-molecule mixtures are generally photostable, but not surprised that the addition of zinc oxide particles can cause toxicity from ultraviolet radiation.
"As a team at Oregon State University that specializes in the toxicity of nanoparticles, these results are not shocking," she said. "This discovery will surprise many consumers who are misled by the'nano-free' labels on mineral sunscreens, which imply that sunscreens are safe because they do not contain those smaller particles. Metals of any size Oxide particles can have reactive surface sites, whether smaller than 100 nanometers or not. More important than size are the metal properties, its crystal structure and any surface coatings."
The National Science Foundation and the National Institutes of Health supported this research.
About Oregon State University College of Agricultural Sciences: Through its world-class research in agriculture and food systems, natural resource management, rural economic development, and human health, the college provides solutions to Oregon’s most pressing challenges and contributes to a sustainable environment And contribute to a prosperous future for Oregonians.
Steve Lundeberg, 541-737-4039 [email protection]
Robyn Tanguay, 541-737-6514 [email protection]
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