May 11, 2012 -- Certain chemicals that are widely used in sunscreens and other products because they protect against UV light are associated with an increased risk of developing the gynecological condition endometriosis, a new study shows.
But the Personal Care Products Council, a group that represents cosmetics manufacturers, called the study "weak" and "unconvincing" and said it shouldn't scare people away from safe sun practices, including sunscreen use.
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Sunscreen Ingredient May Mimic Estrogen
The study, which is published in Environmental Science & Technology, measured concentrations of five kinds of chemicals called benzophenones in the urine of more than 600 women who were evaluated for endometriosis.
Benzophenones are used in a variety of products because they protect against UV light. In small amounts, that helps to stabilize the formulations of products that are stored in clear containers, like nail polish. At higher concentrations, and when they are applied to the skin, they are powerful sunscreens.
Endometriosis is a painful condition that occurs when tissue from the inside of the uterus grows outside of the uterus. When this tissue grows in other parts of the body, typically spilling into the abdomen around the ovaries or fallopian tubes, it behaves as if it were still in the uterus, thickening and shedding each month in sync with a woman's menstrual cycle. Endometriosis can lead to scarring and infertility.
Studies estimate that about 1 in 10 women have the condition, and some research suggests that it is becoming more common.
Benzophenones are easily absorbed through the skin. Studies by the CDC have found benzophenones in the urine of 97% of people tested.
Scientists are concerned about benzophenones because the body may mistake them for hormones.
"These compounds are estrogenic. They mimic estrogen in the body," says researcher Kurunthachalam Kannan, PhD, a professor of public health and environmental health sciences with the New York State Department of Health's Wadsworth Center in Albany.
Kannan says benzophenone-3, which appears on sunscreen labels as oxybenzone, is even more strongly estrogenic than bisphenol-A (BPA), a chemical found in certain plastics that's recently been the subject of regulatory scrutiny.
The cause of endometriosis is not known, but the condition is fed by the female hormone estrogen. Treatment sometimes involves taking medications that lower estrogen levels.