A second major study has found that active ingredients in sunscreen are absorbed into blood at potentially dangerous levels. The US government is now investigating the potential risks – but how much damage has already been done?

As the warmer weather continues, people caged up for months by the coronavirus lockdowns are beginning to book holidays in the sun. Countries popular with travelers are eager to lure as many foreign punters as they can to keep their tourism industries afloat, even if many restrictions remain in place.

One thing holidaymakers will be making sure to pack is sun cream. The intense ultraviolet rays from our nearest star can act as a mutagen to DNA, causing damage to the genetic material in skin cells. Tanning, sunburn and freckles are all different responses to this. And sunscreen cream does protect against sunburn, but does that mean that it is beneficial overall?

Two recent studies have come from the US Food and Drug Administration (FDA) on that very issue. The agency’s own guidelines state that the levels of chemicals absorbed from sun cream into the blood must not exceed 0.5 nanograms per milliliter. Above this threshold, they have to make sure that the chemicals in question are not carcinogenic or otherwise harmful.

But the research found that all six active ingredients (avobenzone, oxybenzone, octocrylene, homosalate, octisalate, and octinoxate) in sunscreen exceeded this limit. Furthermore, they persist in the bloodstream for weeks after application. Their effects in the blood are unknown, but the FDA has opened an investigation to determine whether they could heighten the risk of cancer, birth defects, or other ailments.

Some of the active ingredients in sun cream, such as oxybenzone, can mimic estrogen. Dermatologist Dr Whitney Bowe told ABC News: “we don’t know what those mean for humans,” but she nonetheless strongly recommends that people regularly use sun cream.

Humans evolved on the baking African savannah. Pale skin is an adaptation to the weaker sun striking the Earth farther from the equator; it admits more essential vitamin D than darker skin. None of our ancestors used sun cream, because it did not exist. But there is no suggestion that previous generations were ravaged by inordinately high rates of skin cancer.

In the midst of the coronavirus outbreak, trust in scientists and scientific institutions is probably at its lowest since the Enlightenment. Questions about funding, powerful vested interests and even corruption are plaguing Western university systems more and more. Many people doubtless believed that an issue like sun cream was settled – it protects against skin cancer, and that’s that. But as with so much other ‘conventional wisdom’ rooted in the US academic-industrial complex, it may not be as clear-cut as it seems. 

However, if you still put your trust in institutions like the US FDA, or legacy publications like JAMA, you stand on steadier ground. Both of the research articles end with exactly the same sentence: “These findings do not indicate that individuals should refrain from the use of sunscreen.”

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