Researchers discovered that countries with the highest numbers of women using oral contraceptives also have the highest rates of death from prostate cancer. What does this mean? They think estrogen from the urine of women who take birth control pills could be to blame.

While more research is needed to solidify the link, Dr. David Margel, a uro-oncology fellow at the University of Toronto, said, “Several studies now have found an association between estrogen exposure and prostate cancer… We think this is environmental — [estrogen] goes into the water, into our food chain.”

According to the study, which looked at prostate cancer mortality and contraceptive use in 88 countries, birth control pills often contain a type of estrogen called ethinyloestradiol. Women taking the pills excrete the hormone in their urine, thus sending the hormone into the water supply, where it can be taken up by plants or animals that use the water and then passed up the food chain.

Eric Jacobs, strategic director of pharmacoepidemiology at the American Cancer Society, is interpreting the results of the study cautiously. “Many lifestyle and medical care factors vary between countries, therefore differences in cancer rates between countries can be difficult to ascribe to particular factors,” he said.

Dr. Margel concurs, saying follow-up studies are planned to test the hypothesis. “We can’t establish a cause-and-effect relationship,” he said. “We definitely don’t think the take-home message is women should stop taking the pill.”

More From WOMI-AM