Safe Drinking Water: EPA’s Misguided Policy on Chloroform

Published June 1, 1999

Late last year, the Environmental Protection Agency (EPA) rendered one of the most troubling decisions in its stormy 29-year history.

Faced with having to choose between science and politics, the agency opted for the latter. In doing so, EPA took a perilous step toward undermining one of the pillars of public health in the United States: the purification of the nation’s drinking water supply.

Under mounting pressure from environmental groups to ignore the recommendation of the agency’s own scientists, EPA Administrator Carol Browner last December scrapped a science-based standard for the permissible amount of chloroform in drinking water.

Browner’s decision reveals a great deal about what role, if any, science will play in forming the basis for EPA’s regulatory actions in the final two years of the Clinton administration. It also sheds light on how close Browner’s agency will follow its draft cancer risk guidelines of 1996, which acknowledge that exposure to carcinogens below a certain level, or threshold, often poses little or no threat to human health.

In March 1998, EPA proposed raising the Maximum Containment Level Goal (MCLG) for chloroform in drinking water from zero to 300 parts per billion (ppb). The recommendation came after EPA scientists at the agency’s Office of Water had undertaken a painstaking review of toxicological data on human exposure to chloroform going back 20 years, and after they had taken into account the threshold principle contained in the agency’s draft cancer guidelines. EPA’s proposal was hailed by scientists outside the agency, even drawing praise from the Society of Toxicology, the largest professional association of toxicologists in the world.

That praise, however, was not enough to save the agency’s science-based chloroform proposal from political sabotage. In rejecting the recommendations of its own scientists, EPA turned its back on a key requirement of the 1996 Safe Drinking Water Act, which directs the agency to use “the best peer-reviewed science.”

Acknowledging the Trade-off

Chloroform is created when drinking water is chlorinated to remove microbial pathogens. Trace elements of chloroform and other disinfectant byproducts (DBPs) are an inevitable result of the water purification process. Water suppliers in the U.S. have come to view them as posing a far lower risk to public health than the pathogens that would otherwise remain in drinking water.

Since chlorination was adopted by water systems across the U.S. beginning in 1908, it has resulted in the virtual elimination of such deadly waterborne diseases as cholera, typhoid, dysentery, and hepatitis A.

A 1994 report published by the International Society of Regulatory Toxicology and Pharmacology concluded that “the reduction in mortality due to water-borne infectious diseases, attributed largely to chlorination of potable water supplies, appear to outweigh any theoretical cancer risks (which could be as low as 0) posed by the minute quantities of chlorinated organic chemicals reported in drinking waters disinfected with chlorine.”

That view is supported by the American Academy of Microbiology: “It is important to point out that there is no direct or conclusive evidence that disinfection byproducts affect human health in the concentrations found in drinking water. . . . Concerns over the toxicology of DBPs should not be allowed to compromise successful disinfection of drinking water, at least without data to support such conclusions.”

In proposing a 300 ppb MCLG for chloroform, EPA scientists were in effect acknowledging that current levels of chloroform in drinking water are safe. For water system operators, however, EPA’s final word on chloroform means they must spend their limited resources not only on combating the real dangers posed by microbial pathogens, but also battling the fictitious threats associated with disinfectant byproducts at levels below which EPA scientists say is safe.

While the agency’s original chloroform proposal was welcomed by scientists outside EPA, it did not go down well with environmental groups, many of which have been carrying on a longstanding crusade against chlorine and chlorinated compounds. Led by the Natural Resources Defense Council (NRDC), environmental advocacy groups bombarded EPA with negative comments on the proposed MCLG for chloroform. Brushing aside expert scientific opinion, NRDC urged the agency to “reject the unproven and probably incorrect hypothesis that there is a threshold for its carcinogenic effect, a theory that ignores human evidence of chlorination byproducts’ carcinogenicity.”

This latest triumph of environmental correctness over science will cast a long, foreboding shadow over the nation’s public health policies for years to come. “If we cannot use the abundant scientific information available to make rational decisions on chloroform,” asks Michigan State University toxicologist Jay Goodman, “then what chemical can we make a respectable decision on?”

Bonner R. Cohen is a senior fellow with the Lexington Institute.