Inorganic "mineral" sunscreens, on the other hand, typically comprise coated titanium dioxide, zinc oxide or a combination of the two. These formulations, found in Badger and California Baby products, typically reflect or scatter UVA and UVB rays.
Organic sunscreens often contain oxybenzone. One of the most well-publicized claims about oxybenzone, also an ingredient in some cosmetics and in plastic food packaging, is that it disrupts hormones to potentially harmful levels. A 2008 study found traces of oxybenzone in the urine of 96.8 percent of a representative sample of the U.S. population, which suggests the molecule is widely used and is absorbed into the body after being applied onto the skin.
But how confident can we be that its hormone-changing effects are actually harming us? Most studies have been conducted on cells or animals and are difficult to draw conclusions from. One study, for instance, found uterine changes in rats that were fed extremely high doses of oxybenzone and other organic sunscreens, but people don't typically eat sunscreen for lunch.
One 2004 intervention study was, however, conducted in humans. Researchers repeatedly measured blood hormone levels in 32 people before and after they applied lotion that contained two commonly used organic U.S. sunscreen ingredients. The subjects' blood levels of several hormones, including testosterone, changed after using the lotion. But the hormone differences were found only at certain times after lotion application, leading researchers to conclude that the changes "did not seem to be related to the exposure to sunscreen compounds."
Organic sunscreens have another potential downside: When they absorb UV light, they become "excited" and unstable. Research has shown that the common sunscreen ingredients oxybenzone, octocrylene, and octylmethoxycinnamate (OMC) dissipate that extra energy in ways that lead to the production of molecules called reactive oxygen species that could damage the lower layers of skin and our DNA. This finding is ironic, because UV light is thought to increase the risk of cancer and accelerate aging in part because it does the exact same thing. You cannot win.