A new study funded by the Food and Drug Administration (FDA) and published Monday in the journal JAMA reveals that chemicals in many sunscreens are absorbed in the bloodstream at far higher levels than the threshold set by the FDA to trigger further study.
However, according to a FDA press release following the publication of the study, the findings don't necessarily mean that the ingredients in sunscreen are unsafe. Rather, the findings mean that "further testing to determine the safety of that ingredient for repeated use" needs to be conducted.
"Such testing is part of the standard pre-market safety evaluation of most chronically administered drugs with appreciable systemic absorption," the FDA explains.
During the study, 24 participants (12 men and 12 women) applied one of four different types of sunscreen four times a day over the course of a week to all areas of their bodies that would not be covered by bathing suits. Thirty blood samples were collected from each volunteer during the course of the study to measure blood concentrations of active ingredients commonly found in sunscreens, namely avobenzone, oxybenzone, octocrylene and ecamsule.
"The FDA has provided guidance that sunscreen active ingredients with systemic absorption greater than 0.5 nanograms per milliliter or with safety concerns should undergo nonclinical toxicology assessment including systemic carcinogenicity and additional developmental and reproductive studies," the study states.
The results revealed that all four chemicals in blood samples were at higher levels than the threshold, particularly oxybenzone, which reached the maximum threshold within two hours of the sunscreen being applied. On the last day of the study, the concentration of oxybenzone in the blood samples was above 20 nanograms per milliliter. Some studies have identified oxybenzone as a potential hormone disruptor, the study notes.
In addition, the researchers found that the levels of chemicals remained elevated in the bloodstream for up to three days after the participants stopped using the UV-blocking products.
"Everyone had always thought that because these are intended to work on the surface of the skin that they wouldn't be absorbed, but they are," said Theresa Michele, a co-author of the FDA-funded study, Wired reports.
In a Monday press release, the American Academy of Dermatology (AAD) noted that the study raises important questions about chemicals in sunscreens being absorbed into the bloodstream. However, the statement also warns that "more research is needed before it can be determined if the absorption of sunscreen ingredients has any effects on a person's health."
"These sunscreen ingredients have been used for several decades without any reported internal side effects in humans. Importantly, the study authors conclude that individuals should not refrain from the use of sunscreen, which the AAD encourages as one component of a comprehensive sun protection plan, as sunscreen use has been shown to reduce the risk of skin cancer in a number of scientific studies," the statement adds.