Endometriosis affects about 10 percent of women during their reproductive years. A new study shows a link between endometriosis and two pesticides once used widely in the U.S. for pest control and agriculture.

Endometriosis is a condition in which tissue that normally grows inside the uterus begins to grow outside the womb. This abnormal tissue growth can attach to nearby tissue or organs, potentially affecting the ovaries, fallopian tubes, and lining of the pelvic cavity. Symptoms of endometriosis include painful menstrual periods, pelvic pain, and infertility.

Endometriosis is not a form of cancer but the symptoms of the disease can be chronic and debilitating. This condition negatively affects health-related quality of life for millions of women as it can interfere with personal relationships and work productivity.

The hormone estrogen seems to promote endometriosis so the researchers were interested in learning whether exposure to environmental chemicals that contain estrogen-like properties increased the risk for endometriosis. The researchers found that one group of chemicals, organochlorine pesticides, increased that risk. Two chemicals within that group raised the risk significantly: beta-hexachlorocyclohexane and mirex.

These manmade chemicals were important agricultural pesticides at one time and used widely in the United States. Beta-hexachlorocyclohexane was widely used on cotton crops and mirex was used to kill fire ants. While the federal government banned the use of both these chemicals in the 1970s due to health concerns, large quantities of these chemicals are still present in the environment.

Published in Environmental Health Perspectives, a journal of the National Institute of Environmental Health Sciences, the study used blood sample results and other data gathered in previous research on endometriosis in women aged 18 to 49 years. There were 248 women with endometriosis in that study and 538 women without the condition to serve as controls. The researchers found that the women exposed to beta-hexachlorocyclohexane and mirex had a 30 to 70 percent increased risk of endometriosis. The researchers noted that these chemicals showed up in the blood samples of study participants, even though the pesticides had not been in use for years.

"The take-home message from our study," says the author of the study Kristen Upson, Ph.D., "is that the persistent environmental chemicals, even those used in the past, may affect the health of the current generation of reproductive-age women with regard to a hormonally driven disease."

Source: Upson, Kristen, et al. Organochlorine Pesticides and Risk of Endometriosis: Findings from a Population-Based Case-Control Study. Environmental Health Perspectives. DOI:10.1289/ehp.1306648. Web. Retrieved 14 Nov 2013.