What about nanoparticles?

Many sunscreens make non-nano claims, indicating they don’t contain the tiny particles used to achieve sheer coverage. But the FDA doesn’t require nano testing or enforce labeling standards. “Nano is really tricky because there’s no formal definition of what size is a nano particle,” Lunder says. Sunscreen makers often define nano as anything less than 100 nanometers. 

But should you always avoid nanoparticles? The EWG maintains that they’re safe in lotion form but not in sprays, which may cause lung damage when inhaled. Research implies that particles larger than 30 nanometers aren’t absorbed by the skin. However, 2012 research published in the Chemical Engineering Journal indicates an unforeseen risk of titanium dioxide sunscreen nanoparticles: Chlorine may strip the nanoparticles’ coating and react with water, forming compounds that could contribute to skin damage and even cancer.

If you have concerns, look for products that provide specific nano information on labels; you might even want to contact companies directly.

Is oxybenzone that bad?

If you need more reason to switch to mineral sunscreens, this should do the trick: Approximately 52 percent of beach and sport sunscreens use oxybenzone, a benzophenone chemical that the EWG gives a high-hazard “8” ranking for its link to cellular damage, endocrine disruption, and skin absorption.

Recent research published in Environmental Science & Technology showed that benzophenone chemicals may have stronger estrogenic activities than even bisphenol-A (BPA). According to the study, a form of benzophenone called benzophenone-1, which forms when the body breaks down oxybenzone, was significantly associated with endometriosis. What’s more, the Centers for Disease Control reports that benzophenones are found in the urine of 97 percent of Americans.