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Staying Green in the SunIs my sunscreen bad for the environment?

By Nina Shen RastogiPosted Tuesday, May 26, 2009, at 9:54 AM ET

How green is sunscreen?I just spent the weekend frolicking on the beach, slathered in sunscreen. By protecting myself from the elements, am I doing any harm to the elements? What effect does my Coppertone have on the planet?

Most of us are aware by now that our medicines, soaps, and cosmetics wind up in the environment, where they have the potential to wreak havoc on plants and wildlife. While sunscreen hasn't generated as much concern as, say, birth control, scientists have begun to look more closely at the issue in the past few years. However, there's still a lot we don't know.

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To figure out how a particular sunscreen might affect the environment, you have to look at its active ingredients. This is more complicated than you might think: Most UV-protection creams sold in the United States will contain some combination of 17 FDA-approved active ingredients. Two of these are minerals—zinc oxide and titanium dioxide—and the rest are carbon-based chemicals, like octinoxate, oxybenzone, and octisalate, each of which might go by a number of different names.

Both classes of ingredients bring their own health worries. Concerns over the minerals focus on the increasing presence of new, nano-formulations of zinc oxide and titanium dioxide. Though studies suggest that these tiny particles are actually better at blocking UV rays than their larger counterparts, and a number of studies have shown that they don't penetrate healthy skin, many skeptics worry that there just hasn't been enough research done to substantiate safety claims. Certain chemical ingredients, on the other hand, may penetrate the skin and act as endocrine disrupters, affecting users' hormones and reproductive functions.

Though human health and planetary health aren't exactly the same thing, they are related issues: Any mineral or chemical that might be harmful to humans could also damage wildlife and destabilize ecosystems. Though the studies aren't exhaustive, researchers have found detectable levels of chemical UV filters in lakes, oceans, and rivers around the world, with the highest concentrations found near wastewater treatment plants. (Tracing mineral compounds back to sunscreens is more difficult, since it's hard to tell which are naturally occurring and which were synthetically produced; even nano-sized particles may have become so through natural erosion.)

The accumulation of both kinds of UV filters in the water is troubling to some toxicologists because of their potential to build up inside the cells of fish and other marine life. A series of studies conducted in Switzerland found two commonly used chemicals inside fish living in rivers and lakes, though the reports didn't indicate that animals' overall health was suffering.

One of the chemicals analyzed in the Swiss studies was 4-Methylbenzylidene camphor, or 4-MBC, which has been the focus of much international attention due to its potential as an endocrine disrupter—it's been shown to affect birth weight and survival rate in rat studies—but 4-MBC isn't approved as an active ingredient in the United States. However, the Environmental Working Group has found the potential hazard listed in three sunscreens as an "inactive" ingredient (and also in a handful of men's deodorants).

Fewer data are available on the major UV filters used in the United States. Researchers from the University of Riverside did test the effects of one common ingredient, oxybenzone, on a pair of fish species. They found it diminished reproductive abilities but only at concentrations much higher than those observed in suspected areas of contamination in California and New York.