Safe Drinking Water: Politics Trumps Science
By Bonner R. Cohen, Ph.D.
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 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 for the duration 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
In March 1998, EPA proposed raising the Maximum Contaminant 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 (itself a newsworthy event), 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. Moreover, in rejecting the recommendations of its own scientists, EPA also 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." That's just what EPA scientists had done, only to be overruled by
the agency's politicized top brass.
Acknowledging the Trade-off
Chloroform is created when drinking water is chlorinated to remove microbial pathogens. Together with
dibromochloromethane and bromodichloromethane, it belongs to a class of disinfectant byproducts
(DBPs) known as trihalomethanes. Since trace elements of disinfectant byproducts are an inevitable
result of the water purification process, water suppliers in the US have come to see them as posing a
far lower risk to public health than the pathogens that would otherwise remain in drinking water.
Indeed, since chlorination was adopted by water systems across the US 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
stated that "the reduction in mortality due to water-borne infectious diseases, attributed largely to
chlorination of potable water supplies, appears to outweigh any theoretical cancer risks (which may be
as low as 0) posed by the minute quantities of chlorinated organic chemicals reported in drinking
waters disinfected with chlorine."
This 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
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
In proposing a 300 ppb MCLG for chloroform, agency scientists were in effect acknowledging that
current levels of chloroform in drinking water are safe. For water system operators, however, EPA's
insistence on a zero standard for chloroform (unobtainable in any event) means that water system
operators will have to devote their limited resources to combating the fictitious risks posed by
disinfectant byproducts and the real threats to public health arising from the presence of microbial
pathogens in drinking water.
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),
green 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."
Historically, the big, Washington-based environmental groups have been allied with EPA (particularly
Browner's EPA) and have been the recipients of generous grants from the agency. Yet for them to
acquiesce in the agency's adoption of a science-based standard which acknowledges that there is
little or no risk below a certain threshold is to undermine one of the key tenets of modern
environmentalism, which, as the NRDC statement makes clear, denies the existence of such
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?"
Dr. Bonner R. Cohen is a Senior Fellow at the Lexington Institute.
But hey, what do I know? I'm just an unlettered blue-collar who sits at your feet.