Setting Priorities for Drinking Water Contaminants (1999) / Chapter Skim
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5 Selecting Contaminants on the CCL for Future Action: Recommended Decision Process
5 Selecting Contaminants on the CCL for Future Action: Recommended Decision Process
Pages 70-102
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From page 70... ...
As explained in Chapter 2, existing algorithms for ranking environmental contaminants are of limited use for this purpose, because many of them were designed for priority setting, not necessarily for regulatory action, and because of data gaps and the need for policy judgments. This chapter presents a decision-making framework for selecting contaminants from a CCL for future action.
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From page 71... ...
While data on the ability of drinking water treatment technologies to remove the contaminant and analytical methods to measure the contaminant should be gathered at this stage to avoid delays in future regulatory action, these data should not be part of the decision about whether to regulate a contaminant. Any contaminant that poses a health risk in drinking water, as defined in the SDWA Amendments of 1996, should be considered for regulation.
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From page 73... ...
Although a critical step in the process, the preliminary risk assessment should not be overly detailed, time consuming, or resource intensive. It should resemble risk assessments conducted by EPA under the Toxic Substances Control Act to evaluate data on new chemicals, rather than the massive multi-year risk assessments (e.g., for dioxins)
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From page 74... ...
This step should begin in tandem with issuance of the health advisory and should not wait until the advisory is completed. For contaminants not slated for regulation, research results should be fed back into another preliminary risk assessment, and a new decision document should be issued based on the results of this second risk assessment.
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From page 75... ...
Appendix A explains in mathematical terms why this is so. As shown in the appendix, a highly accurate decision process, when applied to such an enriched list, can still result in nearly a third of substances that need to be regulated going unregulated, while at the same time slating for regulation just three percent of substances that do not need to be regulated.
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From page 77... ...
SELECTING CONTAMINANTS ON THE CCL FOR FUTURE ACTION 77 exposure data on the contaminant followed by policy judgments about the significance of the risk as indicated by the available data and additional research to close essential data gaps. Treatment and analytical data are not described in these examples because they are not part of the initial decision about whether a contaminant should be moved forward to the list of contaminants to consider for regulation, although assessment of these data needs to begin in tandem with exposure and health effects assessments in order to avoid delaying regulatory action and to help set research priorities.
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From page 79... ...
However, EPA cautioned that the future regulatory action categories of the final CCL were based on current information, and some movement between categories could be expected as additional data are obtained and evaluated. GENERAL GUIDELINES FOR EVALUATING CONTAMINANT-RELATED DATA Because of the variability in the types and quality of data available on different contaminants, defining precise criteria for placing contaminants in the three
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From page 80... ...
Assessing Exposure Data Exposure data should be gathered from sources that will predict the dose of drinking water contaminants for individuals, whether it be through ingestion, inhalation or dermal absorption. Table 5-1 represents a hierarchy of data types for the assessment of exposure.
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From page 81... ...
that distribution transport might not affect, finished water sampling may be sufficient. Similarly, determining exposure of consumers to contaminants by using data collected in a watershed for a surface water resource or samples collected from a groundwater aquifer has the potential for producing a misleading picture; many changes in contaminant concentration can occur during transport from the source to the treatment plant intake and during subsequent treatment.
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From page 82... ...
Considerations for Research and Monitoring For contaminants that do not have sufficient exposure information to conduct a preliminary risk assessment, additional research and/or monitoring will be needed. To achieve this, sensitive analytical methodologies with sufficient spatial and temporal measurements are needed for each contaminant.
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From page 83... ...
A combination of models could be used to predict tap water concentrations of a contaminant from finished water data, environmental measurements, measurement of surrogates that are readily analyzed, or production/release data. For example, environmental measurement data for microbial contaminants could be used to model exposure from tap water using a fate-and-transport model coupled with a distribution system model.
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From page 84... ...
Toxicological Data Information gained from studies in laboratory animals is commonly employed in estimating whether there might be potentially adverse human health risks associated with exposure to contaminants in drinking water. In preparing preliminary risk assessments of contaminants on the CCL, EPA should summarize in narrative form the available toxicological studies and highlight aspects relevant to the health effects the contaminant may cause.
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From page 85... ...
Thus, greater weight should be given to toxicity data obtained from laboratory animals given lower-dose, continual exposures than to acute toxicity tests using high doses. The toxicity measurements made in laboratory animals should be as extensive as is practical and include lethality, organ damage, tissue and cell abnormalities at the microscopic level, and relevant biochemical parameters associated with physiological dysfunction in the animal.
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From page 86... ...
for an association between human exposure to a drinking water contaminant and a particular adverse health effect enhances a conclusion of causality in an epidemiological study. However, a lack of supportive animal data for an association between contaminant exposure and a health outcome may indicate (among other possible explanations)
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From page 87... ...
include differences in study design, in the distributions of susceptible subgroups in the study populations, and in the ability to adjust for potential confounders and the impact of other biases. In assessing available epidemiological studies, the findings are usually stratified by type of study design (case report, ecological study, individual-level "case-control" or cohort study)
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From page 88... ...
. "Chance" is reasonably judged as unlikely to account for the positive association (or failure to find a positive association)
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From page 89... ...
and quantitative structure-activity relationship (QSAR) models are used to predict biological activity or effects through the identification of correlations between chemical structure or properties of molecules and biological activities, including those that can be identified through in vitro or in vivo screens and tests.
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From page 90... ...
Assessing Treatment Data Before a final regulatory plan can be established for CCL contaminants, the Safe Drinking Water Act requires that available treatment methods be screened for each contaminant to determine which methods are technologically and economically feasible, which are affordable for small systems, and the degree of risk reduction that can be expected by each of the treatment technologies. The SDWA Amendments of 1986 require EPA to designate a best available technology (BAT)
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From page 91... ...
As for health effects data, EPA should prepare a narrative summary of treatment data for each contaminant on the CCL, but treatment data should not be considered in the preliminary risk assessment recommended in this chapter. The key principle to keep in mind when assessing treatment options for contaminants on the CCL is that the effectiveness of a treatment technology depends on the physical and chemical characteristics of the contaminants in question, and the aquatic matrix in which the contaminants are found.
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From page 92... ...
The greatest analytical challenges lie in the identification of new contaminants and the quantification of emerging contaminants that are intrinsically difficult to measure. Along with written summaries of health effects, exposure, and treatment techniques data, EPA will need to summarize available analytical methods for contaminants on the CCL, focusing especially on newly recognized contaminants.
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From page 93... ...
in Water by Microextraction and Gas Chromatography Analysis of Organohalide Pesticides and Commercial Polychlorinated Biphenyl Products in Water by Micro-Extraction and Gas Chromatography Determination of Nitrogen- and Phosphorus-Containing Pesticides in Water by Gas Chromatography with a Nitrogen-Phosphorus Detector Determination of Chlorinated Pesticides in Water by Gas Chromatography with an Electron Capture Detector 508A Screening for Polychlorinated Biphenyls by Perchlorination and Gas Chromatography Determination of Chlorinated Acids in Water by Gas Chromatography with an Electron Capture Detector Measurement of Purgeable Organic Compounds in Water by Packed Column Gas Chromatography/Mass Spectrometry Measurement of Purgeable Organic Compounds in Water by Capillary Column Gas Chromatography/Mass Spectrometry Determination of Organic Compounds in Drinking Water by Liquid-Solid Extraction and Capillary Column Gas Chromatography/Mass Spectrometry 531.1 Measurement of N-Methylcarbamoyloximes and N-Methylcarbamates in Water by Direct Aqueous Injection HPLC with Post Column Derivatization Source: EPA, 1988 Microbiological Contaminants Methods are available for detecting the presence of almost any microorgan ism of concern, although difficulties can arise in collecting samples, determining frequency and sample sites, and interpreting the relationship between positive samples and public health (Hurst et al., 1997~. Bacteria While cultivation techniques are well developed for enteric bacterial indica tors, such as coliform and fecal coliform bacteria, little attention has been paid to the development of methods for analyzing enteric bacterial pathogens in water.
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From page 94... ...
For the most part, culturable analytical methods have been used for bacteria, however, in some cases, only a small percentage of the total viable organisms present may be detected using these methods of bacterial detection (Colwell et al., 1996~. Microscopic techniques, such as the use of antibodies, genetic probes, image analysis, and flow cytometry, have become highly sophisticated, specific, and rapid for the detection of bacteria (Lawrence et al., 1998~.
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From page 95... ...
A final problem is that sometimes substances are concentrated from the water that are toxic to the cell culture. Additional research is needed to overcome these problems and to develop better techniques for assessing all types of waterborne viruses, not just enteric viruses.
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From page 96... ...
It is not clear whether this is an artifact of sample processing. New analytical methods are currently under development for improving both the recovery and detection of protozoa as well as interpretation of the results (Jakubowski et al., 1996~.
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From page 97... ...
SUMMARY: CONCLUSIONS AND RECOMMENDATIONS In summary, the committee recommends that EPA use a phased process (see Figure 5-1) for determining which contaminants on the CCL are appropriate candidates for regulatory action and which will require research.
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From page 98... ...
. After completing the preliminary risk assessment for each contaminant, EPA should prepare a separate decision document, that indicates whether the contaminant will be dropped from the CCL because it does not pose a risk, will be slated for additional research (on health effects, exposure, or risk reduction)
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From page 99... ...
However, EPA should fill data gaps in treatment technologies and analytical methods to avoid delaying regulatory action for contaminants for which current information on treatment and detection is inadequate. In implementing this phased process, EPA should keep in mind that it should act immediately on all contaminants that meet the statutory tests of (1)
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From page 100... ...
in surface water supplies. Applied and Environmental Microbiology 57(9)
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From page 101... ...
Applied and Environmental Microbiology 61: 1714-1719. Reynolds, K
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From page 102... ...
Pp. 184-194 in Manual of Environmental Microbiology, C
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