A new study from researchers at the U.S. Food and Drug Administration (FDA) has found that four active ingredients in sunscreen can leech into a person's bloodstream at levels high enough to warrant further toxicology testing. Cancer experts say while these results do demand more clinical research, it's unclear whether these chemical concentrations are dangerous to humans and at this stage no one should discontinue their use of sunscreen.
The study involved 24 adults, split into four groups, with each group testing one of four different commercially available sunscreen formations: one lotion, one cream, and two different sprays. Each group applied the sunscreen formulation to 75 percent of the body, four times per day, for four days.
Regular blood tests closely examined the participants for plasma concentrations of four key sunscreen chemicals: avobenzone, oxybenzone, octocrylene, and ecamsule. After just one day of administration almost all the participants, regardless of the sunscreen formulation, displayed systemic levels in their blood higher than 0.5 ng/mL (nanograms per milliliter) of all four active ingredients.
The threshold of 0.5 ng/mL used in the study does not imply the chemical concentrations are inherently unsafe. A recent FDA proposal suggested this threshold be used to update regulatory requirements for sunscreen products in the United States. Chemicals in sunscreen that are absorbed into the bloodstream at levels above this threshold will be flagged for extensive further testing.
At this point it is vital to note that this study does not in any way suggest sunscreen is unsafe, and only presents data pointing to the need for further study. Terry Slevin, from the Cancer Council Australia, notes this is a small preliminary study that also tracked a volume of sunscreen use that is much more excessive than what people generally apply.
"The amount of sunscreen used in the study of 24 people was far in excess of what most people use," says Slevin. "While they followed the recommended application levels, consistent evidence suggests most people use half or less of the recommended amount of sunscreen and many do not reapply once, let alone four times. There remains no evidence of 'clinical significance'. That means we still have no evidence that any such absorption has any adverse effects on any individual."
Other limitations to the research include the fact the study was conducted in indoor environments, which is noted to eliminate heat, sunlight, and humidity – all factors that could fundamentally alter the absorption of these chemicals.
The researchers behind the study add in the published paper that the, "results do not indicate that individuals should refrain from the use of sunscreen." However, concerns have been raised by cancer experts worried this FDA study may cause confusion in the general public, and lead to some people not using sunscreen.
"I think it's confusing," says dermatologist Michele Green to HealthDay. "While it's more than the FDA recommends for their toxicology, we really don't know what that means in terms of human health. I would not want people to stop using sunscreen based on this one study."
Sanchia Aranda, CEO of the the Cancer Council in Australia, agrees, suggesting all evidence collected to date points to sunscreen ingredients being safe, whereas what we do know for sure is that skin cancer is caused by UV and prevented by sunscreen.
"Even if the sunscreen chemicals were absorbed, there is limited evidence to suggest that this would cause harm, but we do know that excess UV causes skin cancer and that sunscreen helps prevent skin cancer," says Aranda.
More research is of course necessary to ascertain whether these blood concentrations of sunscreen chemicals are dangerous, and cancer experts suggest alongside consistent sunscreen use people should cover up with protective clothing and seek shade in order to reduce melanoma and skin cancer risk.
The new research was published in the journal JAMA.
Source: FDA
