Researchers at the US Food and Drug Administration (FDA) have found that people who regularly use certain sunscreens may be absorbing higher-than-safe levels of active ingredients into their bodies. But the scientists caution that it’s still unclear whether these products could be posing any health risks. And importantly, they recommend that people continue to use sunscreen.
Sunscreens of various formulations have been available for decades, but though these products have helped prevent countless sunburns and cases of skin cancer, there’s been shockingly little research into how the chemicals used in sunscreens affect the human body. Some circumstantial evidence has suggested that at least some ingredients could be capable of disrupting hormones or raising the risk of non-skin cancers, while other studies have suggested they can have a negative effect on the marine environment—though that research is far from conclusive.
Many of these chemicals had already been widely used in sunscreen before the modern era of drug evaluation, and were grandfathered into the FDA’s Generally Recognised as Safe and Effective (GRASE) list, based primarily on animal exposure studies. In recent years, though, the FDA has changed its tack on sunscreen. Earlier this year, it laid out a proposed new rule that would likely mandate additional safety testing in humans for a majority of active ingredients used in sunscreens; only two of the 16 currently marketed active ingredients—zinc oxide and titanium dioxide, the so-called mineral sunscreens—would be still considered GRASE under the new rule.
One gap in evidence cited by the FDA are studies looking at how much of an active ingredient is absorbed through the skin and into the bloodstream. The current randomised trial involving 24 people, published last week in JAMA, is an early attempt to look into that exact aspect of sunscreen safety.
The researchers had 24 healthy volunteers apply one of four sunscreen products chosen at random (two sprays, a lotion, and a cream) to 75 per cent of their body, four times a day, for four days—a maximum level of exposure comparable to what someone would use if they were spending a day outdoors and following reapplication instructions. Then they tested their blood for four active ingredients: avobenzone, oxybenzone, octocrylene, and ecamsule.
The FDA had previously established a threshold for how much of an active ingredient in sunscreen could safely end up in a person’s blood without meriting further toxicology testing—above that level, we’d need to study if and how carcinogenic or hormone-disrupting a particular chemical in that dosage could possibly be. But on average, the team was able to find concentrations of all four ingredients higher than this threshold.
The findings don’t mean that sunscreen products should be seen as a danger, though, nor are the authors claiming they are.
For one, their study has plenty of limitations. Right off the bat, there’s the small sample size. But also, there’s the fact that volunteers never actually went outside during those four days, and it’s possible that heat, humidity, and the Sun’s ultraviolet radiation could have altered how these chemicals were absorbed.
Furthermore, researchers in the EU and other areas of the world have studied the health effects of these same ingredients much more recently than the FDA and have found them to be safe to use.
The authors fully admit to these caveats, only going as far as to declare that the “systemic absorption of sunscreen active ingredients supports the need for further studies to determine the clinical significance of these findings.” These future studies could very well be based on the basic structure of this pilot trial. At the same time, at least right now, there’s no need to avoid your regular sunscreen habit this summer—or to be hesitant in adopting a new one—given their proven benefits in preventing skin cancer.
The authors said it plainly: “These results do not indicate that individuals should refrain from the use of sunscreen.”