Why is chlorine added to tap water? Do water filters effectively filter it out?
—J.P. Miller, Hudson, WI
Chlorine is a highly efficient disinfectant, and it is added to public water supplies to kill disease-causing bacteria that the water or its transport pipes might contain. “Chlorine has been hailed as the savior against cholera and various other water-borne diseases, and rightfully so,” says Steve Harrison, president of water filter maker Environmental Systems Distributing. “Its disinfectant qualities
have allowed communities and whole cities to grow and prosper by providing disease-free tap water to homes and industry.”
But Harrison says that all this disinfecting has not come without a price: Chlorine introduced into the water supply reacts with other naturally occurring elements to form toxins called trihalomethanes (THMs), which eventually make their way into our bodies. THMs have been linked to a wide range of human health maladies ranging from asthma and eczema to bladder cancer and heart disease. In addition, Dr. Peter Montague of the Environmental Research Foundation cites several studies linking moderate to heavy consumption of chlorinated tap water by pregnant women with higher miscarriage and birth defect rates.
A recent report by the non-profit Environmental Working Group concluded that from 1996 though 2001, more than 16 million Americans consumed dangerous amounts of contaminated tap water. The report found that water supplies in and around Washington, D.C., Philadelphia and Pittsburgh in Pennsylvania, and the Bay Area in California were putting the greatest number of people at risk, although 1,100 other smaller water systems across the country also tested positive for high levels of contaminants.
“Dirty 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 to clean up our lakes, rivers and streams, not just bombard our water supplies with chlorine.”
Eliminating water pollution and cleaning up our watersheds are not going to happen overnight, but alternatives to chlorination for water treatment do exist. Dr. Montague reports that several European and Canadian cities now disinfect their water supplies with ozone instead of chlorine. Currently a handful of U.S. cities do the same, most notably Las Vegas, Nevada and Santa Clara, California.
Those of us who live far from Las Vegas or Santa Clara, though, do have other options. First and foremost is filtration at the faucet. Carbon-based filters are considered the most effective at removing THMs and other toxins. The consumer information website WaterFilterRankings.com compares various water filters on the bases of price and effectiveness. The site reports that filters from Paragon, Aquasana, Kenmore, GE and Seagul remove most if not all of the chlorine, THMs and other potential contaminates in tap water.
Concerned consumers without the money to spend on home filtration, though, can just rely on good old-fashioned patience. Chlorine and related compounds will make their way out of tap water if the container is simply left uncovered in the refrigerator for 24 hours.