Researchers at the University of Oregon and the University of Leeds have created five different SPF15 chemical sunscreen mixtures containing small molecule UV filter components approved for use in the European Union and the United States.
The authors found that these chemical or non-mineral sunscreens (without zinc oxide) had minimal changes in UVA absorption after exposure to UV for 2 hours, and these formulations were from UVA. It suggests reliable protection.
One of the most representative sunscreen mixtures used in both the EU and the United States is 6% zinc oxide, a hybrid sunscreen made from both chemical and mineral components, combined with a small molecule UV filter. Further tested in the presence of minerals).
After 2 hours of UV exposure, the sunscreen mixture containing zinc oxide showed significant small molecule photolysis, and zinc oxide decomposed other UV absorbers in the mixture.
The authors calculated the amount of UVA blocked by sunscreen to determine the UVA protection factor for each mixture. They found that sunscreens mixed with zinc oxide particles reduced the UVA protection factor from 84.3% to 91.8%, whereas the original zinc oxide-free sunscreen had a UVA protection factor after 2 hours of UV exposure. We found that it showed only a loss of 15.8%.
Professor Richard Blackburn, co-author of the study, said: Or by chance, by mixing sunscreen with other products that contain zinc oxide, such as cosmetics that contain SPF. “
The authors also exposed zebrafish embryos, a model organism in biomedical research, to sunscreen mixtures in experiments to investigate the potential effects of various combinations. They diluted the sunscreen mixture with 99% water (99: 1 ratio) and exposed some to UV light. They placed zebrafish embryos collected 4 hours after fertilization in a diluted mixture.
Embryos remained in solution for 5 days and were monitored at 22 different points.
Zebrafish embryos exposed to sunscreen mixed with zinc oxide showed increased changes to normal development, including underdeveloped fins, and were shorter than normal length. The five non-mineral sunscreen mixtures were found to show minimal changes in zebrafish development.
Control zebrafish embryos placed in a sunscreen that was not exposed to UV light were compared to embryos that were placed in a sunscreen that was exposed to UV light. Differences in the percentage of embryonic physical development in the experimental group compared to controls were considered the “toxicity” of sunscreen.
Only one of the non-mineral sunscreens showed a slight increase in toxicity of less than 10% after UV exposure.
According to the author, zinc oxide was also tested alone and did not significantly increase toxicity. This indicates that it is the combination of zinc and other sunscreen ingredients that is associated with the developmental changes in zebrafish embryos.
The authors emphasized that these effects in mixing products are unknown, as they could not replicate accurate commercial sunscreens because they did not have access to information on accurate measurements of additives, fragrances and ingredients. I am.
They also added that from a variety of conditions to further test the findings, as the formula date and conditions that the bottle may be exposed to in daily use can affect the stability of the formula. Warn you that you will need more samples.