Setting Priorities for Drinking Water Contaminants (1999) / Chapter Skim
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3 Review of Methods for Assessing Microbial Pathogens
3 Review of Methods for Assessing Microbial Pathogens
Pages 47-56
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From page 47... ...
In the past, the only database on microbiological contaminants has been a national database on waterborne disease outbreaks (discussed in Chapter 1~. Until recently, this database was used to support the zero tolerance and fecal indicator regulatory strategy for microbial pathogens.
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From page 48... ...
However, exposure in these studies is rarely specific or quantitative for microbial contaminants, and in many cases the health hazard is defined by symptomology, rather than by the specific hazard, because a more extensive investigation is required to undertake clinical or antibody tests. Regardless, epidemiological studies can help control the occurrence of future waterborne disease outbreaks, as in the Broad Street pump study.
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From page 49... ...
New detection techniques using the polymerase chain reaction have demonstrated that viral contamination of ground water is much more common than previously recognized (see Table 3-1~. Diarrhea has been one of the risks associated with many of the enteric viruses, such as the Norwalk virus; more serious chronic diseases have now been associated with viral infections, and these risks need to be better defined.
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From page 50... ...
of the reported waterborne disease outbreaks in the United States have been associated with the consumption of ground water (Craun and Calderon, 1997~. PRIORITIZATION SCHEMES FOR RULE MAKING Selection of microbial contaminants for development of regulations has been based on reported waterborne disease outbreaks.
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From page 51... ...
In a direct comparison of microbial risk from Giardia infection to cancer risk for several DBP control scenarios, the predicted increases in Giardia infection were orders of magnitude higher than decreases in cancer rates. To ensure that implementation of the D/DBP rule did not increase microbial risk, the regulatory negotiating committee convened by EPA considered it necessary to review the adequacy of the existing SWTR.
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From page 52... ...
Since July 1997, all utilities serving more than 100,000 people have been required to collect samples from their treatment plant influents and analyze for Cryptosporidium, Giardia, and enteric viruses (as well as chemical disinfection byproducts)
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From page 53... ...
Estimate raw water type and level of contamination in different raw water types and determine spatial variations. Determine reduction by waste treatment, drinking water treatment, and distribution; consider resistance to disinfection, removal by filtration, etc., and adequacy of surrogates (coliform bacteria, turbidity)
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From page 54... ...
only in medical care and days lost from work but in costs accrued in assessment of the outbreak, recall of food products, boil orders, communication efforts, remediation, and future safety efforts. The waterborne disease outbreak in Milwaukee in 1993 cost the community an estimated $25 billion, not including subsequent costs of aversion behavior because of loss of confidence in the water supply (e.g., purchase of bottled water and point-of-use devices to further treat the water)
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From page 55... ...
Rather, microbial contaminants have been controlled by specifying treatment methods for various types of source water and by monitoring for fecal coliform bacteria, which indicate possible presence of contamination but are not in themselves pathogenic. This system for regulating microbial contaminants has been relatively effective, but emerging new pathogens have raised concerns about whether the system is sufficient (Craun et al., 1997~.
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From page 56... ...
1997. National Primary Drinking Water Regulations: Interim Enhanced Surface Water Treatment Rule Notice of Data Availability; Proposed Rule.
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