With EPA’s February 2013 statutory deadline for proposing a perchlorate drinking water regulation fast approaching, several key issues that set the foundation for developing a draft regulation remain unresolved. In particular, significant questions remain related to setting a maximum contaminant level goal (MCLG) and baseline perchlorate occurrence, issues that have a large influence on the level at which a regulatory limit may be set.
EPA’s Science Advisory Board Perchlorate Advisory Panel released a draft report (available at http://amwa.net/SABPerchPanel) outlining its preliminary recommendation for setting a MCLG for perchlorate. The key take-away from the draft report is that significant data gaps still exist for setting an MCLG and EPA would be best served by developing a robust and transparent physiologically-based pharmacokinetic (PBPK) model to derive an MCLG. The panel cites this as “a more facile, transparent, and rigorous way to address differences in biology and exposure between adults and sensitive life stages than is possible with the traditional approach for deriving an MCLG.”
Development of a PBPK model as described by the Perchlorate Advisory Panel would require additional research and data collection to address current gaps in key model parameters, an effort that does not appear to be compatible with EPA’s current statutory proposal deadline. During a September 25 conference call held to discuss the draft report, the issue of timing became a topic of debate among panel members, with some questioning whether timing should even be considered within the context of their recommendations. Rather, it was suggested that the panel’s role was to solely provide feedback on the best, scientifically defensible approach for deriving an MCLG, and the question of timing, which is actually a policy or legal issue, should be left to EPA. Even further complicating timing issues, the SAB panel requested additional meetings (scheduled for December 5 and 7, 2012) before issuing its final recommendations, further delaying EPA from getting important feedback necessary to develop its perchlorate proposal. Additional information on the upcoming perchlorate panel meetings and links to previous reports and other panel reference materials are available at http://amwa.net/SABPerchPanel.
Adding to the perchlorate issues EPA is considering, the U.S. Chamber of Commerce submitted a Request For Correction (RFC) to EPA (available at:http://amwa.net/ChamberRFC) requesting that EPA withdraw its determination to regulate perchlorate in drinking water based on flaws in the monitoring data used to make the regulatory determination. According to its petition, “the Chamber seeks correction of this information, as it complies with neither the Information Quality Act (IQA) as implemented under Office of Management and Budget (OMB) guidelines nor EPA guidelines.”
The Chamber contends that EPA improperly used raw water data instead of data from post-treatment samples, as required under the first Unregulated Contaminant Monitoring Rule (UCMR1), to inform its baseline occurrence estimates. In addition, EPA did not use the most current information available at the time of its regulatory determination. More current perchlorate occurrence data, available since the UCMR1 was conducted, show that perchlorate levels in many areas have been greatly reduced due to greater awareness of potential issues, including new advisory levels in many states and successful industrial cleanup efforts, particularly in the Colorado River basin. Additional flaws in specific pieces of UCMR1 data are also documented. The Chamber concludes that had EPA used the correct data “it is likely that EPA would not have been able to make the required finding [that the contaminant occurs with a frequency and at levels of public health concern in public water systems], and thus would not have made a corresponding decision to regulate perchlorate.” The Chamber has asked for corrections (or an alternate timeline for corrections) outlined in its request, including the potential withdrawal of the regulatory determination, within 90 days.
Despite the uncertainties presented by the issues discussed above and other schedule pressures (the required, typically 90-day, OMB review has yet to begin), as of the end of October EPA continues to publically stick by its goal to issue a perchlorate proposal by the February 2013 statutory deadline.