Does chlorination lead to miscarriage?

Fears that chemical by-products resulting from purifying drinking water with chlorine boost the chances that pregnant women will miscarry are not supported by the results of a major study conducted by the University of North Carolina at Chapel Hill.

"We think our new work should be an important contribution to policy studies," contends David A. Savitz of the School of Public Health. "While it is not the final answer, what we found is largely reassuring relative to what had come before. The vast majority of the U.S. population is living with these exposures to drinking water by-products. If they clearly increased women's miscarriage rates, that would be a very big, very expensive problem to solve."

Scientists selected and repeatedly tested disinfection by-products in three properly functioning water purification facilities, including one with moderate levels of chlorination, one with moderate levels of bromination, and one with low levels of both. None of the utilities was selected because of water quality or health problems. Thousands of women then were recruited in the three areas who were planning a pregnancy or who had been pregnant for fewer than 12 weeks. The researchers collected extensive information on the volunteers, including their patterns of water use, such as drinking and bathing, and what later happened with their pregnancies and births.

The study uncovered no clear-cut evidence that trihalomethanes harmed women or their developing infants. The work did suggest, however, that brominated compounds and total organic halides at normal-range levels in purified drinking water might modestly increase the risk of miscarriages.

"These latter findings suggest that we or others should take a closer look at individual and groups of chemicals that might have a negative effect on pregnancy," Savits indicates. "I don't want to downplay those findings and say they were perfectly reassuring because they were not. But overall--on balance--I'd say this work moves the evidence in a reassuring direction and should serve to lessen concerns."

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