This report originally appeared Nov. 5 in Environmental Health News. Exposure to two banned pesticides may be associated with an increased risk of endometriosis, according to researchers from Washington state. Endometriosis, a disease in which uterine tissue grows in the ovaries or other parts of the body, often causes pelvic pain and infertility. The researchers focused on organochlorine pesticides, which were widely used for decades but have mostly been banned due to health concerns. They break down slowly in the environment and persist for many years in human tissue. Links to endometriosis were found for the insecticides lindane and mirex. Mirex was banned in the United States in 1978. Most uses of lindane have also been banned, although it is still used in some doctor-prescribed lice shampoos. Previous studies in rodents suggest that organochlorine pesticides and other chlorinated compounds may act as hormone disruptors, altering uterine and ovarian function and raising the risks of reproductive diseases. The new study is one of the first to examine the association between organochlorine pesticides and endometriosis in women in the general population. Six to 10 percent of reproductive-age women in the U.S. suffer from endometriosis. “Our study suggests that exposure from extensive past use of environmentally persistent OCPs in the United States, or present use in other countries may impact the health of the current generation of reproductive-age women with regard to a hormonally-mediated disease,” the study authors wrote. Researchers tested blood from 248 women with clinically diagnosed endometriosis and 538 healthy women for traces of 11 organochlorine pesticides and byproducts. The women ranged in age from 17 to 49. The majority were white. The women were divided into four groups, or quartiles, based on the level of pesticide in each woman’s blood. Women in the second-highest exposure group for beta-hexacyclochlorohexane (beta-HCH), a byproduct of lindane, had a 70-percent greater risk of endometriosis than women with the lowest levels. Women with the highest levels of mirex had a 50-percent greater risk of endometriosis than women with the lowest levels. When the researchers looked only at women with ovarian endometriosis (uterine tissue growing in the ovaries), the association was much stronger – a 2.5-times greater risk – for those with the highest blood levels of the lindane byproduct than those with the lowest levels. There were no statistically significant associations for other pesticides, including chlordane, DDT and hexachlorobenzene. The researchers collected the blood samples an average of 1.2 years after diagnosis of endometriosis, so it’s possible that the concentrations may not reflect the levels that existed in the women’s blood while the disease was developing. However, their results are consistent with those of a smaller study published last year, which linked HCH exposure and endometriosis.