Water chlorination and air pollution could cause birth defects

Exposure to two common air pollutants could be causing pregnant women to give birth to babies with heart defects, says new research by the University of Los Angeles (UCLA). A second study by two environmental groups also claims that more than 100,000 women in the US are at risk of miscarriage or of having children with birth defects because of chlorination byproducts (CBPs) in municipal tap water.


According to the first study, carried out by the UCLA School of Public Health and the California Birth Defects Monitoring Programme, pregnant women living in regions of higher ozone and carbon monoxide pollution within the Los Angeles area are three times more likely to give birth to babies with serious heart defects. The critical period appears to be the second month of pregnancy – the time when the child’s organs begin to develop, say the researchers.

“The greater a woman’s exposure to one of these two pollutants in the critical second month of pregnancy, the greater the chance that her child would have one of these serious cardiac birth defects,” said Beate Ritz, the UCLA epidemiologist who led the study. “More research needs to be done, but these results present the first compelling evidence that air pollution may play a role in causing some birth defects.”

“We’re not sure carbon monoxide is the culprit because it could be just a marker for something else in tailpipe exhaust,” said Gary Shaw of the California Birth Defects Monitoring Program and a co-author of the study.

“There may be some other chemical culprit in tailpipe emissions, which we can’t identify at this time, that is causing the problem,” Ritz agreed. “Since carbon monoxide is released in motor vehicle exhaust along with these other pollutants that we don’t measure, these other pollutants also may be important.”

The scientists did not evaluate other potential risk factors for birth defects, such as maternal smoking, occupational exposures, vitamin supplement use, diet and obesity. However, researchers did not find a link between birth defects and exposure to nitrogen dioxide and larger-sized particulate matter.

“The dose-response aspect of this study certainly strengthens the findings and underscores the need for additional research,” said Shaw. “Unlike other health factors like diet or lifestyle, a pregnant woman has almost no control over the quality of air she breathes – we need answers.”

The second study, by the Environmental Working Group (EWG) and U.S. Public Interest Research Group (U.S. PIRG), the results of which are published in the report, Consider the Source, has examined the effects of CBPs, formed when chlorine used to treat municipal water reacts with organic material. According to the research, Texas has the greatest number of women at risk of miscarriage or producing babies with birth defects due to the effects of CBPs.

The report estimates that from 1996 to 2001, more than 16 million people in over 1,200 communities in the US were served water contaminated with CBPs for at least 12 months at levels higher than the country’s new legal limit. A handful of large cities put the greatest number of people at risk, namely the suburbs of Washington, DC, Philadelphia, Pittsburgh and San Francisco, but more than 1,100 smaller water systems also reported potentially dangerous contaminant levels. The highest levels of CBPs, from five to 10 times the level allowed by the new standard, were reported by small rural drinking water utilities, says the report.

“Dirty source water going into the treatment plant means water contaminated with chlorination byproducts coming out of your tap,” said Jane Houlihan, EWG’s Research Director. “The solution is cleaning up our lakes, rivers, and streams, not just bombarding our water supply with chlorine.”

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