Posted on April 14, 2010 by Jarred O. Taylor, II
EPA recently completed a six year review of the National Primary Drinking Water Regulations (NPDWRs) “to identify those NPDWRs for which current health effects assessments, changes in technology, and/or other factors provide a health or technical basis to support a regulatory revision that will support or strengthen public health protection.” This six-year review is mandated by the Safe Drinking Water Act. The first six year review was completed in 2003. The sixty-plus page March 29, 2010 Federal Register issuance of the notice and request for comments can be found here.
EPA reviewed the 85 NPDWRs, included in the Federal Register Statement a detailed explanation for 71, and is proposing that four of them be considered for revision. Not surprisingly, the proposed revisions are to decrease the maximum contaminant level (MCL) closer to the maximum contaminant level goal (MCLG). As a reminder, the MCLG is “set at the level at which no known or anticipated adverse effects on the health of persons occur and which allows an adequate margin of safety.” The MCL, a term with which many are more familiar, is the highest allowed level of a contaminant in water delivered to one using a public water system, and is supposed to be as close to the MCLG as possible. MCLs, however, are not used by regulators just to judge official public drinking water systems, but also groundwater. If you are involved at a site where cleanup standards have been set, or are in the process of being set, for these four NPDWRs, be prepared for some re-negotiation. And, it will not be long after any such changes are made that many states will follow.
The primary reason an MCL is higher than an MCLG is technology—our testing methods and analytical abilities cannot detect as low as the MCLG, many of which are zero—aka the practical quantitation limit (PQL). Thus, one of the pieces of EPA’s six year review was whether technology had advanced, with sufficient confidence, to allow a reduction in the MCL closer to the MCLG.
The four contaminants EPA is proposing receive revised NPDWRs are acrylamide, epichlorohydrin, and two more common contaminants with which most of us have run into before—tetrachloroethylene (PCE), and tricholorethylene (TCE). PCE and TCE received almost identical recommendations, and both have a current MCLG of 0.0, and an MCL of 0.005 mg/L because of PQL. EPA made no final recommendation on PCE and TCE because the risk assessment for these two contaminants was still in progress and, thus, EPA could not determine whether revised MCLs would gain potential health benefits. However, EPA concluded that advancements in analytical and treatment technologies were such that “analytical feasibility could be as much as ten times lower [than the current MCL] (~ 0.0005 mg/L)”, noting that its review also concluded that levels of PCE and TCE in the environment at this reduced level are “relatively widespread”. EPA is giving stakeholders the opportunity to submit information to it about what laboratories “can reliably and consistently achieve.”
Stay tuned—technology’s exponential increase in our ability to detect smaller and smaller concentrations of contaminants in the environment may very well exponentially increase treatment costs and higher costs at cleanup sites. Whether health risks decrease sufficiently from driving down MCLs is yet to be determined, but the writing appears on the wall for now.