Scientists are reporting a possible link between the use of sunscreen containing a certain ingredient that mimics the effects of the female sex hormone estrogen and an increased risk of being diagnosed with endometriosis, a painful condition in which uterine tissue grows outside the uterus.

They describe the report, published in ACS' journal Environmental Science & Technology, as the first to examine whether such a connection may exist.

Kurunthachalam Kannan and colleagues explain that some sunscreens and other personal care products contain benzophenone (BP)-type ingredients that are very effective in blocking potentially harmful ultraviolet rays from the sun. Small amounts of BPs can pass through the skin and be absorbed into the blood, where they mimic the effects of estrogen. Endometriosis, which affects up to 1-in-10 women of reproductive age, needs estrogen to develop. Despite those facts, scientists until now had not checked for a connection between the use of BP sunscreens and the likelihood of being diagnosed with endometriosis.

To fill that knowledge gap, the scientists analyzed BP levels in the urine of 625 women who underwent surgery for endometriosis. They found that high levels of one BP called 2,4OH-BP were associated with an increased risk of an endometriosis diagnosis. Women tended to have higher levels of BPs during the summer months and if they lived in sunny California, further suggesting a link with sunscreens. "Our results invite the speculation that exposure to elevated 2,4OH-BP levels may be associated with endometriosis," say the researchers.

The researchers acknowledge funding from the Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health.

Story Source:
The above story is reprinted from materials provided by American Chemical Society, via EurekAlert!, a service of AAAS. Note: Materials may be edited for content and length. For further information, please contact the source cited above. Journal Reference:
Tatsuya Kunisue, Zhen Chen, Germaine M. Buck Louis, Rajeshwari Sundaram, Mary L. Hediger, Liping Sun, Kurunthachalam Kannan. Urinary Concentrations of Benzophenone-type UV Filters in U.S. Women and Their Association with Endometriosis. Environmental Science & Technology, 2012; 46 (8): 4624 DOI: 10.1021/es204415a