WASHINGTON, November 7, 2013—Two pesticides, banned for decades in the U.S., may be linked to a higher risk for endometriosis, according to a study published this week in Environmental Health Perspectives, a peer-reviewed journal published with support from the National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health (NIH).
Affecting around five million women in the U.S., endometriosis occurs when uterine tissue grows outside the organ, causing pain and infertility. Even though up to 10 percent of reproductive-age women are diagnosed with endometriosis, doctors are unsure what causes this noncancerous condition.
“Since endometriosis is an estrogen-driven condition, we were interested in investigating the role of environmental chemicals that have estrogenic properties, such as organochlorine pesticides, on the risk of the disease,” said Kristen Upson, study author and fellow of epidemiology at NIEHS, reports Science Daily.
The study analyzed the levels of beta HCH and mirex, two organochlorines, in blood samples from 248 women diagnosed with endometriosis and 538 women who did not have the condition. The women were all members of Group Health Cooperative, a Seattle-based nonprofit health care system.
The results were adjusted for age, race or ethnicity, smoking, reference date year, serum lipids, education, and alcohol intake.
Researchers found that women with high levels of two pesticides had a higher risk for endometriosis. The risk was 50 percent greater for women with the highest levels of beta HCH and 30 to 70 percent higher for those with the highest levels of mirex in their blood.
“We found it interesting that despite organochlorine pesticides being restricted in use or banned in the U.S. for the past several decades, these chemicals were detectable in the blood samples of women in our study and were associated with increased endometriosis risk,” Upson said in a press release.
Beta HCH is a byproduct of technical grade HCH, an agricultural insecticide used in the 1970s. According to the Centers for Disease Control and Prevention (CDC), production and use of technical grade HCH was banned in the U.S. in 1976, but is still used in some countries. Gamma HCH is restricted, but still used as a pesticide.
Mirex was sprayed aerially over the southeast U.S. in the 1960s and 70s as a part of a fire-ant control program. It was also used as an additive for fire retardants in plastics, paint, rubber, paper and electrical goods. Mirex was banned as a pesticide in 1978 and has also been heavily restricted in the U.S.
However, both can still be found in the environment because they persist in soil and water. Because OCPs also accumulate in animal tissues, they are found in some fish and dairy products decades after being banned and restricted.
“If you have chemicals sitting in the sediment of water and you have the (contaminated) little fish being eaten by big fish, you’re having this chemical become more and more concentrated,” Upson stated.
Residue may also remain on products imported from places where they are not banned, according to the Toxicological Profile for HCH by the U.S. Department of Health and Human Services (HHS).
“The key message from our study is that persistent environmental chemicals may affect the current generation of reproductive age women,” said Upton. “We hope our findings will help inform current global policymaking to reduce or eliminate their use.”