Sunscreen Chemicals Soak All the Way Into Your Bloodstream


BY NOW, YOU’VE probably been taught to gird your sun-starved skin for battle with cancer-causing cosmic rays every time you go outside. If they sink into tissues and get absorbed into the bloodstream, that could be a problem. Then, like other over-the-counter drugs the Food and Drug Administration oversees, sunscreens should be studied to make sure they don’t mess up people’s hormones, affect their reproductive systems, or cause cancer. Such safety testing has never been done on the active ingredients in sunscreen, because those chemicals were approved decades ago, before anyone suspected they could be absorbed into the body.

Today, researchers at the FDA revealed the results of a small clinical trial designed to test how four of the most common sun-filtering molecules on the market behave after they’ve been sprayed on and rubbed in. The results, published in the journal JAMA, show that contrary to what sunscreen manufacturers have been saying, UV-blocking chemicals do seep into circulation. Her team found that it took only a few hours after the application of sunscreen for the photoprotective chemicals to infiltrate the bloodstream and shoot up to concentrations above the FDA’s toxicology threshold that triggers further safety testing. The fact that these sun-filtering molecules do penetrate into the circulatory system does not on its own mean that such ingredients are unsafe.

Particularly urgent is learning more about long-term exposure and how absorption rates differ in infants and children, with their larger ratio of body surface to volume. Yet the trial’s results underscore the need for more data on sunscreen absorption, as the FDA has long demanded from manufacturers, without success. The history of sunscreen regulation is long and contentious, but the core of the conflict boils down to the fact that the US treats sunscreen as an over-the-counter drug, and the rest of the world considers it a cosmetic. When new research emerged in the late ’90s and early 2000s suggesting that UV-blocking ingredients in chemical-based sunscreens could be absorbed into the human body, the agency began to ask any companies bringing new molecules to market to include such data in their safety studies.

Meanwhile, Europe added at least eight new, more advanced photoprotective filters to its sun-shielding arsenal. In an effort to end the stalemate, Congress passed the Sunscreen Innovation Act in 2015. As part of that effort, in February the FDA announced it was overhauling the way the agency regulates sunscreens, to «keep pace with evolving science.» Chief among the proposed changes was subjecting the 16 UV-filtering chemicals currently on the US market to the same scrutiny as new molecules. To prove they’re safe and effective, the FDA is now asking US sunscreen makers to submit additional data measuring how these ingredients absorb into the bloodstream.

If they don’t absorb above the toxicological threshold, no problem. The idea was to make it easier for new ingredients to compete against the legacy ones that hadn’t been assessed by the FDA in decades. If US manufacturers fail to conduct absorption studies and provide that data to the FDA by the time the agency’s new rules are finalized in November, it would mean the removal of those products from shelves. The FDA has said they will grant deferrals to companies willing to commit to undertaking the necessary studies for the remaining 12 molecules in question.

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