Sunscreens designed to protect the skin may actually be a cause for concern for other parts of the body according to a new study from the U.S. Food and Drug Administration. Researchers found the chemicals in sunscreens are being absorbed into the bloodstream at a rate higher than the FDA’s established threshold where they can be presumed safe.
While the FDA did not say there is proof this can cause actual harm, they do believe further testing is warranted to determine if the chemicals being absorbed are a cause for concern.
"The fact that an ingredient is absorbed through the skin and into the body does not mean the ingredient is unsafe," said Dr. Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research. "Rather, this finding calls for further industry testing to determine the safety and effect of systemic exposure of sunscreen ingredients, especially with chronic use."
The FDA has a threshold of 0.5 nanograms per milliliter (ng/mL) for eliminating additional safety testing. If the absorption rate is lower there is no need to test how the ingredients affect the body.
However, their testing last year determined four active ingredients commonly used in sunscreens were absorbed into the bloodstream of volunteers at a concentration far higher than that threshold. The new study just completed included three more active ingredients as well as different sunscreen formulations and all chemicals tested were absorbed at levels exceeding the previously set limit.
"Sunscreen chemicals, like all over-the-counter medications, only undergo safety testing if they are shown to be systemically absorbed above the FDA safety threshold level," said Dr. Kanade Shinkai, a dermatologist at the University of California, San Francisco.
Although they were clearly above the limit in this case, Shinkai added, "Whether this is dangerous is still not known. But this highlights the need for safety testing."
The most common active ingredients in sunscreens are chemicals such as avobenzone, oxybenzone, octocrylene, and ecamsule. The FDA says there is no proof they can cause harm to humans, but animal testing has revealed oxybenzone can disrupt hormone activity.
The latest study had 48 people randomly assigned to use one of four different spray or lotion sunscreens. They applied it to the body once on the first day and four times per day over the next three days. Most volunteers had the active ingredient absorbed into their bloodstream at levels above the FDA limit after just one application.
The chemicals also remained for a long time before leaving the volunteers’ bodies. In more than 50 percent of the people the ingredients avobenzone, octisalate and octinoxate were at elevated levels for up to a week and homosalate and oxybenzone tested above the FDA limit for up to three weeks.
The FDA noted one limitation to their study was the fact it was conducted in a laboratory setting instead of outdoors where sunlight and heat may affect absorption.