presence of microbial contamination of drinking water from human waste. The use of coliforms was later expanded and adopted for ambient, recreational, and shellfish waters and continues to focus on identification of fecal contamination.

Over the long history of their development and use, the current bacterial indicator approaches have become standardized, are relatively easy and inexpensive to use, and constitute a cornerstone of local, state, and federal monitoring and regulatory programs. An increased understanding of the diversity of waterborne pathogens, their sources, physiology, and ecology, however, has resulted in a growing understanding that the use of bacterial indicators may not be as universally protective as was once thought. For example, the superior environmental survival of pathogenic viruses and protozoa raised serious questions about the suitability of relying on relatively short-lived coliforms as an indicator of the microbiological quality of water. That is, while the presence of coliforms could still be taken as a sign of fecal contamination, the absence of coliforms could no longer be taken as assurance that the water was uncontaminated. Thus, existing bacterial indicators and indicator approaches do not in all circumstances identify all potential waterborne pathogens. Furthermore, recent and forecasted advances in microbiology, molecular biology, and analytical chemistry make it timely to reassess the current paradigm of relying predominantly or exclusively on traditional bacterial indicators for waterborne pathogens. Nonetheless, indicator approaches will still be required for the foreseeable future because it is not practical or feasible to monitor for the complete spectrum of microorganisms that may occur in source waters for drinking water and recreational waters, and many known pathogens are difficult to detect directly and reliably in water samples.

This report was written by the National Research Council (NRC) Committee on Indicators for Waterborne Pathogens—jointly overseen by the NRC’s Board on Life Sciences and Water Science and Technology Board—and comprised of 12 volunteer experts in microbiology, waterborne pathogens (bacteriology, virology, parasitology), aquatic microbial ecology, microbial risk assessment, water quality standards and regulations, environmental engineering, biochemistry and molecular biology, detection methods, and epidemiology and public health. This report’s contents, conclusions, and recommendations are based on a review of relevant technical literature, information gathered at four committee meetings, a public workshop on indicators for waterborne pathogens (held on September 4, 2002), and the collective expertise of committee members. Furthermore, because of space limitations, this Executive Summary includes only the major conclusions and related recommendations of the committee in the general order of their appearance in the report. More detailed conclusions and recommendations can be found within individual chapters and are summarized at the end of each chapter.

The committee was formed in early 2002 at the request of the U.S. Environmental Protection Agency (EPA) Office of Water and originally charged to report on candidate indicators and/or indicator approaches (including detection technologies) for microbial pathogen contamination in U.S. recreational waters



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