Researcher study publish in the Journal of the American Medical Association (JAMA) has attract widespread media attention after it find chemicals contain in sunscreen could get into people’s bloodstreams: A variety of different chemicals in sunscreen are use to absorb or scatter UV light both long wavelength (UVA) and short wavelength (UVB)  to protect us from the harmful effects of the Sun.

But while small amounts of these chemicals may enter the bloodsteam; so there is no evidence they are harmful. Ultimately, using sunscreen reduces your risk of skin cancer; so this study gives us no reason to stop using it. The US Federal Drug Administration (FDA) recently update its guidelines on sunscreen safety.

The plasma concentration

The guidelines indicate that if long term users were likely to have a plasma concentration; so of greater than 0.5 nanograms per millilitre of blood, further safety studies need to be undertaken. This level is just a trigger for investigation; it does not indicate whether the chemical has any actual toxic effect.

The JAMA study was done to determine whether commonly use sunscreen compounds; which exceed these limits, which would indicate that further safety studies were require under the new guidelines. The study look at the absorption of some common organic sunscreen ingredients (avobenzone, oxybenzone, octocrylene, and ecamsule); hence in 24 healthy participants after they applied four commercially available sunscreen formulations.

Each formulation contain three of the four organic sunscreen ingredients list above. The concentrations of each individual compound; which were typical of commercial sunscreens and well within the permit levels. For example, they all contained 3% avobenzone, and the maximum permit concentration is 5%.

The researchers then examine the absorption of these compounds; so  by measuring participants blood over seven days using highly sensitive tests. In all subjects, the blood levels of the sunscreen chemicals rapidly rose above the FDA guidance levels regardless of the sunscreen formulation (spray, lotion or cream).

Worst case scenario

The levels remain above the FDA guidance levels for at least two days. But the conditions of the test were extreme. Some 75% of body surface was covered, and the sunscreen was reapply every two hours and under conditions where the compounds were unlikely to be broken down or removed. This was deliberately a test of a worst case scenario, as mandate by FDA guidelines to determine whether safety testing was needed.

Looking specifically at the chemical avobenzone; so the safety studies show no toxic effect or potential harm to human health, aside from a small risk of skin sensitivity. The level of avobenzone report in the blood after regularly applying sunscreen, is around 1,000 times lower than the threshold levels for harm to skin cells. And the safety studies report no increased risk for cancer.

European researchers have also investigate whether the chemicals in sunscreens can mimic the effects of the female sex hormone estrogen. They found the levels have to be 100 times higher than are absorb during normal sunscreen use to have any effect. This study find that under a worst case scenario, blood levels of organic sunscreen chemicals exceed the FDA guidance threshold. Under more realistic use the levels will be even lower.

The research check is a fair and reasonable summary and interpretation of the JAMA paper on the absorption of active sunscreen ingredients. It is worth noting that the reference to “extreme” conditions in which the research was conduct is correct; however, in terms of dose, it does align with the recommend level of use of sunscreen.