I’ve long had a certain morbid curiosity about sunscreen — are the chemicals in sunscreen worse for you than the UV radiation they block? According to Sun block, they just might be:
Schlumpf and her colleagues tested six common UV screening chemicals used in sunscreens, lipsticks and other cosmetics. All five UVB screens — benzophenone-3, homosalate, 4-methyl-benzylidene camphor (4-MBC), octyl-methoxycinnamate and octyl-dimethyl-PABA — behaved like oestrogen in lab tests, making cancer cells grow more rapidly.
Three caused developmental effects in animals. Only one chemical — a UVA protector called butyl-methoxydibenzoylmethane (B-MDM) — showed no activity.
One of the most common sunscreen chemicals, 4-MBC, had a particularly strong effect. When the team mixed it with olive oil and applied it to rat skin, it doubled the rate of uterine growth well before puberty. ‘That was scary, because we used concentrations that are in the range allowed in sunscreens,’ Schlumpf says.
Nobody knows if doses are high enough to create problems for people, says Schlumpf.