Male babies exposed in the womb to chemicals that mimic estrogen -- compounds found in birth control pills and some plastics -- are at risk of being born with deformities in their prostate and urethra that may lead to diseases in adulthood, a new study of lab animals has shown.
Some researchers say the wider use of the chemicals may have contributed to a surge in prostate cancer in the last two decades, particularly in men under 65.
Prostate cancer is the most common cancer in the United States other than skin cancer. The reported rate in men under 65 quadrupled from the mid-1980s to mid-1990s. Much of that increase is attributed to a new cancer-screening test, according to the National Cancer Institute. But some experts believe that the shift began before the new test, and may be due partly to environmental factors.
In the new study, biologists from the University of South Dakota School of Medicine and the University of Missouri at Columbia said they fed pregnant mice doses of two chemicals. One was ethinylestradiol, the drug found in birth control pills; the other was bisphenol A, found in polycarbonate -- a hard, clear plastic used in beverage containers and tin can linings. Both chemicals are estrogenic -- they imitate the natural female hormone estrogen -- and were given in doses considerably smaller than those some pregnant women were exposed to.
When given either compound, the male offspring of the mice were found, on average, to have microscopic defects in the prostate, that could lead to disease. With both chemicals, researchers also found the mice had a narrowing of the urethra, the channel that carries urine, which could lead to bladder disorders. Previous animal studies linked estrogenic chemicals to enlarged prostates.
Medical experts estimate that nearly 2 million women each year in the United States and Europe who take birth control pills become pregnant, primarily because of missed doses. They often do not know they are pregnant for several weeks and pass the chemicals to their fetuses by continuing to take the pills. The dose in oral contraceptives is typically four to five times higher than the dose that harmed the mice in the experiment, according to the study, published in this week's online edition of the Proceedings of the National Academy of Sciences.
