Women with higher levels of pesticides in their blood are also more likely to have endometriosis, according to a new study published Tuesday in the journal Environmental Health Perspectives.
Endometriosis is a chronic condition in which tissue normally lining the uterus’ interior walls also grows outside the uterus, commonly to the ovaries, fallopian tubes, or pelvis –- causing pelvic pain and infertility.
"It affects women during their reproductive years and it could be that as many as 10 percent of women during reproductive ages have endometriosis," says Victoria Holt, a researcher at the Fred Hutchinson Cancer Research Center, a professor of epidemiology at the University of Washington and lead study author.
More than 5 million women have endometriosis, according to the U.S. Department of Health and Human Services' Office of Women's Health.
“What we know about endometriosis is that it's an estrogen-driven disease. Women who have more estrogen are more likely to have it," Holt says.
Once in the body, some organochlorine pesticides are believed to mimic estrogen, possibly contributing to endometriosis.
For the study, researchers measured OCPs in blood serum samples from 248 surgically-confirmed endometriosis cases and 538 women without diagnosed endometriosis.
Overall, 90 percent of all women had detectable levels of one such pesticide, called beta-HCH, in their blood.
Compared to women in the lowest quartile, women in the upper 50 percent for beta-HCH levels were 2.5 times more likely to have ovarian endometriosis.
Another organochlorine pesticide – Mirex – increased the risk of endometriosis overall by 50 percent when comparing women in the highest category of exposure to those with the lowest exposures, the study suggested.
Eight other organochlorine pesticides measured in the study showed no clear correlation with endometriosis.
"Women in this study were likely exposed simply on the basis of their chronically ingesting contaminated food,” says Dr. Leo Trasande, associate professor of Environmental Medicine, NYU School of Medicine.
Organochlorine pesticides were widely used in the United States from the 1940s through the 1960s, but the Environmental Protection Agency now restricts their use, along with the United Nations’ Stockholm Convention.
However, after all these decades, these pesticides are still present in the environment and can accumulate in the food chain.
According to the Centers for Disease Control and Prevention, beta-HCH has a half-life of seven years in the body – where it is stored in fat. It can be found in some dairy products, fatty foods and fish. It's also still produced as a by-product of some lice shampoos and lotions. The FDA recommends using a safer alternative first; California banned one product in 2002.
"What piqued our interest is that these chemicals are so highly persistent and take years to degrade in the environment. We detected these chemicals in the blood of women despite their being banned or severely restricted in the United States for the past several decades," says Kristen Upson, a postdoctoral fellow at the National Institute of Environmental Health Sciences, and study author.
"More broadly, this speaks to the reality that often chemicals are introduced into the market without much in the way of safety testing," says Trasande.
"And then many decades later, we find out the unfortunate consequences of this hazardous exposure."