USA- Environmental Working Group, a highly respected environmental non-profit
More research and more specific FDA guidelines are essential to reduce the risk and maximize the sun protection of mineral sunscreens. Yet, even with the existing uncertainties, we believe that zinc oxide and titanium dioxide lotions are among the best choices on the American market.
- The shape and size of the particles affect sun protection.The smaller they are, the better the SPF protection and the worse the UVA protection. Manufacturers must strike a balance: small particles provide greater transparency but larger particles offer greater UVA protection. The form of zinc oxide most often used in sunscreens is larger and provides greater UVA protection than titanium dioxide products that appear clear on skin.
- Nanoparticles in sunscreen don’t penetrate the skin. Some studies indicate that nanoparticles can harm living cells and organs when administered in large doses. But a large number of studies have produced no evidence that zinc oxide nanoparticles can cross the skin in significant amounts (SCCS 2012). A real-world study tested penetration of zinc oxide particles of 19 and 110 nanometers on human volunteers who applied sunscreens twice daily for five days (Gulson 2010). Researchers found that less than 0.01 percent of either form of zinc entered the bloodstream. The study could not determine if the zinc in the bloodstream was insoluble nanoparticles, therefore the European regulators concluded it was most likely zinc ions, which would not pose any health risk (SCCS 2012). Other FDA- and European Union-sponsored studies concluded that nanoparticles did not penetrate the skin (NanoDerm 2007, Sadrieh 2010).
It is unlikely that nanoparticles in sunscreen cause skin damage when energized by sunlight. Titanium dioxide, and to a lesser extent zinc oxide, are photocatalysts, meaning that when they are exposed to UV radiation they can form free radicals that damage surrounding cells. Nanoparticle sizes of these minerals are more affected by UV rays than larger particles.
However, tests of living skin from human volunteers and animal testing suggest that these hazards are not a concern for human safety because the free radicals that are generated by nanoparticles on skin are quenched by the skin’s own antioxidant protections (Popov 2009, Osmond 2010).
EWG maintains ongoing vigilance in its assessment of sunscreen safety. At present, all available evidence suggests that zinc oxide and titanium dioxide can be safely used in sunscreen lotions applied to healthy skin. The weight of evidence indicates that both zinc oxide and titanium dioxide pose a lower hazard than most other sunscreen ingredients approved for the U.S. market.