In the January 25 “Earth Talk” column, Tapped Out?, Scientific American offers an alarming, but highly inaccurate discussion on the safety of chlorinated drinking water.  By highlighting unsupported claims from water filter manufacturers and linking to their product websites, the column reads more like an advertisement than an objective article.  This does a disservice to Scientific American readers and to public health.

Scientific American should “stand up for science” and set the record straight:

• Chlorinated drinking water is widely recognized as one of the most important public heath advances in history.  The title of column asks, “Are Chlorine's Beneficial Effects in Drinking Water Offset by Its Links to Cancer?”  The resounding answer to this question is “NO.” 
• EPA requires treated tap water to have a detectable level of chlorine to help prevent recontamination.  Only chlorine disinfectants can provide this “residual” protection all the way to consumers’ taps.
• According to U.S. EPA, allowable chlorine levels in drinking water (up to 4 parts per million) pose “no known or expected health risk [including] an adequate margin of safety.”
• Chlorine is not considered a known or suspected carcinogen by EPA or the International Agency for Cancer Research.
• EPA has enacted strict regulations to limit levels of trihalomethanes (THMs) and other disinfection byproducts in drinking water.  Tap water meeting EPA standards should be considered safe to drink.
• Cities like Las Vegas are not “switching over to…ozone instead of chlorine.”  Ozone can be used as a supplemental treatment method, but does not replace the need for chlorine.
• The “recent study” on breast cancer conducted in Hartford, Connecticut was actually published in 1992. This study (Falck et al.) looked at chemicals like DDT and PCBs—not chlorine or any byproducts of water chlorination. Furthermore, two major review articles by leading scientists cast doubt about the link reported in the Connecticut study (Adami et al., and Ahlborg, et al.,)

Sponsored by the Chlorine Chemistry Division of the American Chemistry Council.

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