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  Controlling Disinfection By-Products and Microbial Contaminants in Drinking Water (330 pp, 12.6 MB) (EPA/600/R-01/110) December 2001

Historically, drinking water utilities in the United States have played a major role in protecting public health through the reduction of waterborne disease outbreaks. These reductions were brought about by the use of sand filtration, disinfection, and the application of drinking water standards. Coincident with the passage of the Safe Drinking Water Act of 1974, it was discovered that chloroform was a disinfection by-product (DBP) resulting from the interaction of chlorine and natural organic matter in water. (Chloroform is one of a class of compounds called trihalomethanes.)

The finding posed a serious dilemma because it raised the possibility that chemical disinfection, which clearly reduced the risk of infectious disease, might also result in the formation of potentially harmful chemical by-products. Although disinfection of public drinking water had dramatically reduced outbreaks of diseases attributable to waterborne pathogens, the identification of chloroform in drinking water raised questions about possible health risks associated with these exposures.

Since 1974, additional DBPs have been identified and concerns have intensified about health risks resulting from exposures to DBPs. Although a causal relationship between DBP exposures and these health risks has not been conclusively established, risk managers have responded in the interest of protecting public health by developing alternative treatment systems and issuing rules and regulations designed to maintain protective levels of disinfection while reducing potentially harmful levels of DBPs.

In 1981, EPA issued a report summarizing the state of the science regarding the control of DBPs in drinking water. Today, EPA's drinking water research program is more sophisticated. For example, the current technology research program includes more than just treatment-oriented research. It includes source water protection, treatment technology, and distribution system studies. The research also reflects a concern for balancing the risks of potential carcinogenic exposure against the risks from microbial infection.

This document summarizes the research conducted by EPA since the publication of the 1981 treatment technology document.


Robert M. Clark

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