Endometriosis is a painful and puzzling condition in which the tissue that lines the inside of the uterus — the endometrium — grows outside the uterus, often on the ovaries and fallopian tubes. In addition to causing pain, endometriosis can result in heavy bleeding and infertility. One in 10 women of reproductive age is thought to be affected.
One of the most frustrating aspects of endometriosis is that the cause is unknown. A couple of new studies have focused on environmental triggers, with mixed results. Both studies appear in an upcoming issue of the journal Environmental Health Perspectives.
The first study used data from the large Nurses’ Health Study II, involving more than 84,000 female nurses. The researchers identified those who lived near roadways, exposing them to more particulate matter in the air as adults. (Particulate matter is a type of pollution that can come from vehicle exhaust and other sources, such as coal-burning power plants.) The authors report that they did not find any significant association between exposure and the incidence rate of endometriosis, but also note this is the first human study to assess the relationship between particulate matter exposure and endometriosis.
Future research is likely needed to confirm the result, and other factors may need to be considered, such as the amount of exposure to particulate matter where women grew up or where they work.
The second study did find a link between another type of pollution and endometriosis. Researchers used data from the Women’s Risk of Endometriosis study conducted in Washington state, analyzing blood samples of women with and without endometriosis to gauge their levels of organochlorine pesticides (OCPs). The researchers found associations between levels of two pesticides — β-hexachlorocyclohexane (HCH) and mirex — and a greater chance of having endometriosis.
Organochlorine pesticides, such as DDT, were commonly used in agriculture and for mosquito control during the 20th century. While their use has been greatly restricted in the United States, these pesticides accumulate in bodies and are still often detected in blood studies. The researchers note that most U.S. exposures are now from consumption of fatty foods, fish, and dairy products where the toxins have built up. Global use of OCPs is also a concern, as the contamination may spread.
These pesticides are known to be potential endocrine disruptors, but the exact nature of any link with endometriosis is unclear. The researchers involved in the study also found that the link was stronger when they looked just at ovarian endometriosis, although they don’t speculate on why that may be, except that ovarian cases may differ in some way from other cases of endometriosis.
All of this points to the need for more research.
For more information, visit the Endometriosis Association, which offers free informational packets and other resources. You can also read excerpts from “Our Bodies, Ourselves,” and learn more about both endometriosis and pesticides via the National Library of Medicine.