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Other chemicals in the study that had the multi-generational effects were dioxins, a pesticide mixture including permethrin and DEET and a plastic mixture including BPA and two widely used phthalates.
"What we are seeing in animal models is sobering," said John McLachlan, a biomedical scientist at Tulane University in New Orleans. The gene mechanisms responsible for transmitting such harmful effects across generations are essentially the same in humans, he said.
In the case of uterine fibroids, the body's natural estrogens turn genes on and off in the smooth muscle of the uterus that allow the tumors to grow, according to research by McLachlan and colleagues. They are now investigating whether estrogen-mimicking chemicals in the environment affect these same genes.
The danger of estrogen-like chemicals already has been well-documented with DES, or diethylstilbestrol, a drug that was prescribed to millions of women at risk of miscarriages from 1940 through 1971. Daughters and granddaughters of the pregnant women who took the potent estrogenic drug had an increased risk of endometriosis, uterine fibroids and rare reproductive cancers.
But pesticides, sunscreen ingredients and PCBs are less potent hormone mimics than DES. The effects on women's health are not as clear.
Some studies have found no connection between women's exposure to environmental chemicals and gynecological diseases. For instance, among several hundred women in Italy highly exposed to dioxins from a 1976 factory explosion, UC Berkeley scientists found no significant increase in endometriosis linked to their contaminant levels. And in Japan, there was no increased rate of the disease among 139 infertile women with higher exposures to hormone-disrupting compounds including PCBs and dioxins, according to a 2005 study.
Newbold said because decades can pass between exposure during fetal development or early childhood and the manifestation of the disease in adult life, it can be difficult to nail down a link.
"Only recently are studies starting to focus on developmental risk factors in relation to adult disease," she said.
Endometriosis and fibroids are referred to as "benign uterine diseases," characterized mostly by painful periods, according to McLachlan. "Because these growths are not life-threatening or malignant, traditionally, these diseases haven't garnered the attention they should," he said.
But the disorders sometimes are linked to fertility problems, and researchers also are beginning to realize that such symptoms can be a sign of serious diseases to come.
"Gynecological problems during the reproductive years may be a predictor of diseases, such as cancer, later in life," said Barbara Cohn, a reproductive health scientist and director of Child Health and Development Studies at the Public Health Institute in Berkeley, Calif.
Endometriosis has been associated with an increased risk of some ovarian cancers. However, the risk remains small, according to a study published in Lancet Oncology in May. Women with endometriosis have a 1.5 percent lifetime chance of developing ovarian cancer compared with 1 percent in the general female population.
The research is less clear on a link between cancer and other gynecological diseases, such as uterine fibroids.
Lee was terrified that her fibroids and extreme menstrual periods were signs of cervical or ovarian cancer. Several doctors recommended that she have her uterus removed--standard treatment for severe fibroids. But she refused.
"You wouldn't cut your nose off because you got frequent nose bleeds," said Lee. "No one seemed concerned with trying to figure out why I was having such heavy periods."
Pesticides and other environmental chemicals may not have contributed to Lee's gynecological problems, since other factors, such as age and genetic predisposition, also increase a woman's risk.
Nevertheless, since leaving the Okanagan in 2010 and moving to Nova Scotia, Lee has seen a marked decrease in her symptoms. She now avoids processed foods and buys only organic produce. The fibroid is no longer growing. In fact, according to Lee, it has shrunk in size.
"I can no longer feel it, but I know it is still there," she said. "I worry constantly what the health effects will be down the road."
To read more about health risks, read "Bitter Taste."