Pregnant women might want to think twice before drinking a lot of tap water.
New research, to be published later this month in the journal Epidemiology, found women in their first trimester who drink more than five glasses daily of cold tap water containing high levels of common contaminants have higher rates of miscarriage than women who don’t drink as much.
The four contaminants, known together as trihalomethanes, are a byproduct of chlorination and decaying plant material. They are found in just about every water district that uses surface water, such as reservoirs, lakes and rivers.
More disturbing, women exposed to high levels of a particular trihalomethane - bromodichloromethane - had three times the average miscarriage rate.
“Are we really sitting on a major public health problem? At this point we don’t know,” said an official with the U.S. Environmental Protection Agency who asked not to be identified. “This is just one study. There are a lot of reasons why this could be true, and a lot of reasons why it couldn’t.”
The researchers themselves agree.
“First, pregnant women shouldn’t panic. And second, she should still drink a lot of water,” said Shanna Swann, chief of the reproductive epidemiology section of the California Department of Health and one of the report’s authors. “If people are worried, they should call their local water utilities and find out if the level of trihalomethane is high.”
Although the studies are inconclusive, the EPA is concerned enough to be considering lowering the accepted standard for trihalomethanes from 100 to 80 micrograms per liter and is proposing several similar studies in other parts of the country to check the findings of Swann and Waller.
But the authors and EPA officials are quick to point out that chlorinated water has done far more good, wiping out microbes that cause cholera, dysentery and typhus. And, they caution, other methods of disinfecting water, such as using ozone, are not only expensive but might have unknown side effects.
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