91av

GENDER-BENDING chemicals that mimic the effect of oestrogen are common in
sunscreens, warns a team of Swiss researchers who have found that they trigger
developmental abnormalities in rats. “We need to do more tests to see how they
might be affecting people,” says Margaret Schlumpf from the Institute of
Pharmacology and Toxicology at the University of Zurich, Switzerland.

Researchers know that chemicals which behave like oestrogen can cause health
problems. They can have a dramatic effect on animals, for example turning fish
into hermaphrodites. Some researchers claim that hormonally active chemicals
from the urine of women taking the birth control pill are already swamping the
environment, and may be causing a decline in sperm counts.

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. “Evidence that they’re a real health concern is still lacking,” says
Richard Sharpe from the Medical Research Council’s Reproductive Biology Unit in
Edinburgh. But he adds, “It’s not good news that we are lathering ourselves with
creams with hormonal activity.”

The Cosmetic Toiletry & Perfumery Association, which represents sunscreen
manufacturers in Britain, replies that the levels found by Schlumpf are well
below anything that would cause an effect after a single application. A study by
the association, not yet published, shows no effect from these chemicals in
rats. But, it adds, “If levels are increasing [in the environment] then we’re
aware something would have to be done soon.”

That day may be here since 4-MBC and other sunscreen chemicals have been
shown to accumulate in fish from lakes where people swim. More worryingly, they
have been found in breast milk at levels of nanograms per kilogram of
fat—about the same as other known environmental contaminants. Schlumpf
worries that the large amount of sunscreen used by bathers, especially children,
could dramatically increase this exposure.

Schlumpf says the other 25 or so chemicals used in sunscreens should also be
tested for hormonal activity, and she will be looking more closely at 4-MBC to
see if the offspring of exposed rats develop health problems. For the moment,
she isn’t advising people to ditch sunscreens completely, but suggests that
sunblocks like zinc oxide might make a healthier alternative.