LOS ANGELES (AP) -- Pregnant women in their first trimester who drink five or more glasses of cold tap water daily may be at higher risk of miscarriage, according to a study of California chlorinated drinking water.
The heightened risk is linked to exposure to a contaminant found in chlorinated water in a majority of municipal water systems nationwide. The chemical -- trihalomethane (TTHM) -- forms when chlorine reacts with acids from plant material.
Chlorine helps purify water and prevents bacterial infections. TTHMs have been associated with increased cancer risk, at least in animals, and federal regulators have limited the amount allowed in drinking water.
The study, led by California health department investigators Kirsten Waller and Shanna Swann, examined the records of 5,144 pregnant women from the Fontana, Santa Clara and Walnut Creek areas.
The study, which will be published in the Feb. 18 issue of the journal Epidemiology, found that women who drank five or more glasses of tap water per day with at least 75 micrograms per liter of TTHMs had an increased risk of miscarriage.
Their risk was calculated at 15.7 percent, compared with 9.5 percent among women who received low exposure. Only about 2 percent of the women were exposed to the highest risk levels, meaning they consumed five or more glasses with at least 75 micrograms per liter.
All the women drank water that met state and federal drinking standards.
``You do run a risk if drinking unboiled water,'' said S. David Freeman, the general manager of the Los Angeles Department of Water and Power, America's largest municipal utility.
``Nobody knows how high,'' he said. ``The most practical thing that we've come up with is to tell women in that category to boil some water and put it in the refrigerator.''
The Environmental Protection Agency allows up to 100 micrograms of TTHMs per liter. The agency plans to reduce that standard to 80 micrograms in November.
State and federal officials said the study is not definitive and more tests are planned. It is part of an effort by the EPA to balance the need for protection against microbes -- such as those that cause dysentery and cholera -- with the need to keep the dangers of disinfection itself to a minimum.
At the Metropolitan Water District, which supplies most of Southern California outside Los Angeles, officials said the average levels of TTHM are well below those that triggered concern in the study.
But within Los Angeles, the average concentration in tap water exceeds that level. State health officials advised women to heed their doctors' recommendations on fluid intake, but offered other steps.
For example, carbon-filtered tap water can be left standing in the refrigerator for several hours or water can be boiled for a minute and then left to cool. But the study was not large enough to allow researchers to calculate precise effects.
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