National Drinking Water Advisory Council Working Group on Contaminant Candidate List (CCL) Regulatory Determinations and 6-year Review of Existing Regulations, May 2, 2000

On May 2, 2000, the National Drinking Water Advisory Council (NDWAC) Working Group on Contaminant Candidate List (CCL) Regulatory Determinations and 6-Year Review of Existing Regulations, held a conference call to finalize the recommendations to the full NDWAC later in the month. This conference call was the third and final meeting to discuss CCL Regulatory Determinations. The three remaining Working Group meetings will be devoted to the 6-Year Review of Existing Regulations.

At the April meeting, the Working Group assigned additional subgroups to address outstanding issues related to the protocols for Microbials and Chemicals. The subgroups developed materials and forwarded them to the entire working group for review prior to the May 2 conference call. Working group members independently reviewed the materials and ran trials on sample chemical and microbial contaminants to see if the protocol is an effective tool to analyze and present the data. The May 2 conference call began with a review and discussion of the results of these trials. Information for four chemicals was supplied to the working group prior to the conference call, but the chemical name was withheld to eliminate bias. Each member was asked to respond to three questions and tell of any specific concerns or issues they had regarding the protocol as a result of the trials:

1. What issues or challenges emerged when running sample chemical contaminants through the draft protocol?

2. What revisions or adjustments to the protocol would help to address any of the problems?

3. What are the implications of these issues and challenges for the regulatory determination process overall?

Four major issues arose from the discussion: how to address data gaps, how this information can characterize risk reduction, the effectiveness of data extrapolations and the need to modify some protocol language.

Initially, the Working Group agreed that the scoring and weighting would not compare one contaminant to another, nor would the numbers be "totaled". Rather each number would represent a level of importance, not a score and would primarily serve to document and characterize each factor considered in answering yes or no to each of the three SDWA criteria. However, the Working Group decided to revisit the issue of scoring. The focus of the discussion was to address the issue of qualitative vs semiqualitative scoring. The group agreed that this approach is intended to provide EPA with a semi-quantitative evaluation tool that highlights the relative importance of the various factors in answering the three statutory tests and not a tool to arrive at a "total score". The final recommendation of the Working Group was that this protocol alone can not drive a regulatory decision, but is meant to assist EPA in making the decision and can not substitute the need for expert judgements. The Group also agreed on some language changes and modifications to the chemical and microbial protocols. Changes were primarily for clarification and understanding purposes and did not significantly change content.

The Working Group also discussed the content of the final product for presentation to the full NDWAC. Two teams were established to draft the document components as well as clarify the details of treatment effectiveness, add risk assessment language and explain the criteria for moving between statutory tests 1,2 and 3 for microbials. The final package will include: an executive summary, a background including the assumptions that drove the process, an explanation of why we separated the processes for chemicals and microbials, an explanation of the protocols developed, and the intended use of the protocols. The NDWAC representative on the Working Group will present a status report to the full NDWAC on May 10 and a complete package will be sent later in the month.

Contact

April McLaughlin, Designated Federal Officer, U.S. Environmental Protection Agency, Office of Ground Water and Drinking Water (4607), 401 M St., SW, Washington, DC 20460; E-mail: mclaughlin.april@epa.gov

Attendees

The following is a list of Working Group members. The asterisk (*) indicates members that did not participate in the conference call on May 2, 2000.

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