Dirty Tap Water May Cause Birth Defects

Jan. 8, 2002 -- Two groups report that hundreds of thousands of pregnant women are at risk of birth defects and miscarriages from contaminated tap water.

The Environmental Working Group and U.S. Public Interest Research Group say that the problem is due to byproducts that form when adding chlorine to the tap water.

They admit that adding chlorine to tap water saves thousands of lives each year by reducing the number of harmful bacteria in the water. However, they say that this process itself actually creates hundreds of toxic chemicals called "chlorination byproducts," or CBPs.

According to the report, chlorine added to water interacts with organic matter, particularly the soil and plant material that comes from run-off by agriculture and urban sprawl.

And the problem seems to affect large and small cities alike. They note that a handful of large cities with a history of high CBP levels account for a large portion of the women at risk -- suburban Washington, D.C., and Pittsburgh, as well as urban centers like Philadelphia and San Francisco.

But more than 1,100 small towns (with fewer than 10,000 people) have also reported potentially dangerous levels of CBPs in their tap water over the past six years, according to the report.

They write that pregnant women living in small towns supplied by rivers and reservoirs are more than twice as likely to drink tap water with elevated levels of CBPs than women in large communities.

In total, the investigators list 42 cities across the U.S. -- both large and small -- that expose more than 500 pregnant women each year to trihalomethanes (THM), the most common chlorination byproduct.

A new standard put forth by the Environmental Protection Agency went into effect just this month that will lower the allowed levels of chlorination byproducts, including THMs.

However, the investigators list multiple cities with lower levels of THM in tap water that they say still expose thousands of women to potentially dangerous toxins for an entire trimester.

"It's not a big surprise," Joel Schwartz, PhD, tells WebMD. He is an associate professor of environmental epidemiology at the Harvard School of Public Health in Boston.

Schwartz says a number of recent studies have linked chlorine byproducts to reproduction risks. His group, for example, has found the substances could affect a baby's birth weight. Other research has pointed to risk of birth defects and miscarriage.

"There is potential to cause harm. But there are things we can do to reduce the risk," he says, adding that the following measures won't drop your risk to zero, but they can make things safer:

• First, don't kid yourself with the bottled water. There may be no way to tell how long it has been since the company last tested it.
• You may want to install filters on the sinks you use for your drinking water. Products that use charcoal can filter out the chlorine byproducts. The more charcoal a particular filter uses, the more contaminants can be sifted from the water before you drink it.
• You also may want something for your shower, since these contaminants could evaporate in the steam and be inhaled.