Classifying Drinking Water Contaminants for Regulatory Consideration (2001) / Chapter Skim
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Pages 93-106
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4PCCL to CCL: Attributes of Contaminants INTRODUCTION As described earlier in this report, the committee continues to recommend a two-step process for the creation of future Drinking Water Contaminant Candidate Lists (CCLs) (see Figure 1–3)
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was to develop and use five attributes that contribute to the likelihood that a particular PCCL contaminant or group of related contaminants could occur in drinking water at levels and frequencies that pose a public health risk. In this regard, the committee devised a scoring system for each of these five attributes whereby the highest-priority PCCL contaminants are selected in conjunction with expert judgment for inclusion on a CCL.
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should be based, when feasible, on plausible exposures via drinking water. This information can be ascertained from clinical reports, from animal bioassay results, or by inference from effects of similar compounds.
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TABLE 4–1 Scoring of Severity Attribute Severity Score Characteristic 0 No effect 1 Changes in organ weights with minimal clinical significance 2 Biochemical changes with minimal clinical significance 3 Pathology of minimum clinical importance (e.g., fluorosis, warts, common cold) 4 Cellular changes that could lead to disease; minimum functional change 5 Significant functional changes that are reversible (e.g., diarrhea)
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If contaminants act via diverse health effect end points (e.g., a carcinogen that also has noncarcinogenic effects) , then an appropriate potency score would be the worst (i.e., the highest)
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TABLE 4–2 Overall Prevalence Score Related to Temporal and Spatial Prevalence Temporal Prevalence (%) Spatial Prevalence (%)
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Magnitude Magnitude can be defined as the concentration or expected concentration (e.g., based on chemical production) of a contaminant relative to a level that causes a perceived health effect.
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the magnitude score is )
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It should be possible to assess these characteristics for a large number of contaminants (both chemical and microbial) by applying a simple, semiquantitative scoring scheme such as that illustrated in Tables 4–3 to 4–5.
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LESSONS LEARNED IN APPLYING THESE CRITERIA The contaminant attributes and associated scoring criteria outlined in this chapter were applied to a panel of chemical and microbial validation test contaminants. The details of this demonstration are given in Chapter 5 to illustrate the utility of using such a classification approach for the creation of future CCLs.
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population exposed and number of analyses with detects for prevalence. Expanding on the recommendation in Chapter 3 that EPA review the EDPSD database to determine whether it can be used to help develop a PCCL and perhaps help select PCCL contaminants for inclusion on a CCL, the committee also recommends that EPA consider the possibility of including information on temporal and regional occurrence.
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NOAELs, and RfDs5 from readily available health effects-related databases such as EPA's Integrated Risk Information System (IRIS)
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potency and then severity also affected the magnitude score since the potency score is used in calculating the magnitude score. Vulnerable subpopulations were considered, when readily feasible, in the scoring.
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for public and other stakeholder input and undergo scientific review. The committee also makes the following related recommendations: • The assessment of severity should be based, when feasible, on plausible exposures via drinking water.
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