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TORONTO – Researchers suggest there may be a link between estrogen from oral contraceptives that has found its way into the environment and rising rates of prostate cancer among men around the world.

In a study in the online publication BMJ Open, researchers at Princess Margaret Hospital in Toronto looked at the percentage of women using the pill, intrauterine devices, condoms and vaginal barrier contraceptives in 87 countries, then examined the incidence and deaths from prostate cancer.

“Looking at these percentages, we find a strong correlation between female use of oral contraceptives at a population level and both new cases of prostate cancer and mortality from prostate cancer,” said lead author Dr. David Margel, a urologist and fellow in uro-oncology.

“This was not found among other contraceptive modes,” he said. “We also checked the percentage use of intrauterine devices or condoms or vaginal barriers and the same relation was not found.”

The research team used data from the International Agency for Research on Cancer and the UN World Contraceptive Use report to determine rates of prostate cancer and associated deaths as well as the proportion of women using common methods of contraception in 2007.

Margel said estrogen in birth-control pills is excreted in the urine and gets into the environment, particularly into water, and scientific evidence suggests that low levels may cause cancer, including prostate cancer.

“What we found was that in countries where the oral contraceptive was used more often, prostate cancer had a greater incidence,” said Margel. But he stressed there may be many factors involved, and teasing out the effect of pill-based estrogen alone would take much more research.