United States: EPA Proposes Perchlorate Rule After Years Of Study

Last Updated: June 13 2019
Article by Dianne Phillips

Dianne Phillips is a Partner in Holland & Knight's Boston office


  • The U.S. Environmental Protection Agency (EPA) recently issued a 171-page pre-publication version of its proposed perchlorate rule in accordance with the Safe Drinking Water Act (SDWA), just days before a court-ordered deadline. The proposed rule released on May 23, 2019, follows years of study, various proposals, actions by stakeholders and litigation.
  • Pursuant to SDWA Section 1412(b)(4)(C), the EPA Administrator has determined in the pre-publication version of the proposed rule that the benefits of establishing a National Primary Drinking Water Regulation (NPDWR) for perchlorate do not justify the associated costs.
  • EPA specifically seeks comments on the proposed rule regarding the adequacy of the underlying estimates, assumptions and analysis used to estimate costs and benefits. The agency also seeks comments on whether it should withdraw its 2011 Regulatory Determination – which concluded that perchlorate meets the SDWA criteria for regulating a contaminant – and issue no NPDWR for perchlorate.

The U.S. Environmental Protection Agency (EPA) recently issued a 171-page pre-publication version of its proposed perchlorate rule in accordance with the Safe Drinking Water Act (SDWA), just days before a court-ordered deadline (which had been extended) arising from the case Natural Resources Defense Council, Inc. v. U. S. Environmental Protection Agency et al., filed Feb. 18, 2016 in the U.S. District Court for the Southern District of New York as civil action 2:16-cv-01251-ER. The proposed rule released on May 23, 2019, follows years of study, various proposals, actions by stakeholders and litigation. Indeed, a 2006 article by Holland & Knight described efforts by Massachusetts to enact the nation's first drinking water standard for perchlorate at 2 parts per billion (ppb). Since then, perchlorate has been virtually eliminated from the Massachusetts public drinking water supply based upon the results of 16,123 samples reported in the Massachusetts Energy & Environmental Affairs data portal.


The pre-publication notice summarily describes EPA's history of addressing perchlorate in drinking water, which is also summarized on EPA's website. Beginning with EPA's Unregulated Contaminant Monitoring Rule (UCMR) promulgated Sept. 17, 1999, EPA began collecting data from public drinking water suppliers on perchlorate, which is a highly soluble compound commonly used in solid rocket propellants, munitions, fireworks, signal flares and blasting materials. EPA and other federal agencies asked the National Research Council (NRC) to evaluate the health implications of perchlorate ingestion, with the results published in 2005. The NRC concluded that perchlorate exposure inhibits the transport of iodide into the thyroid, which may lead to decreases in thyroid hormone function and was especially concerning to pregnant women and their fetuses.

On May 1, 2007, EPA published the results of its analysis of the perchlorate data, concluding it was not making a statutorily authorized determination as to whether a national primary drinking water regulation is needed but stating that "the Agency has placed a high priority on making a regulatory determination for perchlorate and will publish a preliminary determination as soon as possible." (72 Fed. Reg. 24038) Thereafter, EPA established a reference dose (RfD) of 0.7 ug/kg/day for perchlorate consistent with the NRC recommendation. From that, EPA derived a Health Reference Level (HRL) of 15 micrograms per liter (ug/L). Despite this HRL, EPA published its Preliminary Regulatory Determination on Perchlorate on Oct. 10, 2008, indicating that "a national primary drinking water regulation would not provide a meaningful opportunity to reduce health risk." (73 Fed. Reg. 60265)

In response to comments on EPA's preliminary determination, including from the Massachusetts Department of Environmental Protection (DEP), EPA issued an Interim Drinking Water Health Advisory of 15 ug/L in December 2008, which remains in effect today. This Health Advisory is a non-regulatory (not legally enforceable) informal technical guidance identifying the concentration of perchlorate as a drinking water contaminant at which adverse health effects are not anticipated to occur over a specific exposure duration. The purpose is to assist state and local officials in advance of a final regulatory determination.

Thereafter, EPA once again sought comment on whether there is a meaningful opportunity for human health risk reduction of perchlorate through a national primary drinking water rule. In addition, EPA sought comment on its derived potential alternative HRLs for 14 different age groups that ranged from 1 ug/L to 47 ug/L. EPA received approximately 39,000 comments from individuals and organizations. Massachusetts DEP once again filed comments, urging EPA to set the HRL on the basis of the life stage(s) with the highest exposure and risk, which Massachusetts concluded would support an HRL of 2 ppb.

On Feb. 11, 2011, EPA issued a formal Regulatory Determination concluding that perchlorate meets the SDWA criteria for regulating a contaminant. Specifically, EPA concluded that perchlorate 1) may have an adverse health effect, 2) is known to occur or is at risk for occurring in public water systems with frequency and at levels of public health concern, and 3) regulation presents a meaningful opportunity for health risk reduction. EPA concluded that as many as 16 million people could be exposed to perchlorate at levels of concern. Having concluded that perchlorate meets the criteria for regulating a contaminant under SDWA Section 1412(b)(1)(A), EPA announced it would "initiate the process for proposing a NPDWA [National Primary Drinking Water Regulation] for perchlorate." (76 Fed. Reg. 7765)

Thereafter, EPA went about the regulatory process, including further evaluation of the scientific approach and modeling of adverse health effects. It sought the advice of the Science Advisory Board (SAB), which provided recommendations in a 2013 report, and it conducted peer review studies of its modeling efforts. The SAB recommended a robust and transparent process by which to consider sensitive life stages explicitly because perchlorate was known to disrupt thyroid function, and interference with the thyroid and available thyroid hormones is known to produce adverse effects on neurodevelopment in humans, with fetuses and infants being most vulnerable. Specifically, the SAB recommended that EPA address sensitive life stages through "physiologically-based pharmacokinetic/pharmacodynamic modeling based upon its mode of action" – also known as Biologically Based Dose Response (BBDR) – rather than the default approach using the RfD.

Overview of Pre-Publication Draft

As described in detail in the EPA pre-publication draft, EPA developed a two-step approach combining the BBDR model results with epidemiology literature that relates incremental changes in maternal thyroid hormones to neurodevelopmental outcomes in children. As a result of its analysis, EPA made a policy decision to evaluate the level of perchlorate in water associated with a 1 percent, 2 percent and 3 percent decreases in the mean population IQ as a surrogate for neurodevelopmental effects. EPA concluded that the corresponding concentrations for the 1 percent, 2 percent or 3 percent IQ decreases were 18 ug/L, 56 ug/L and 90 ug/L, respectively. EPA selected a 2 percent decrease in IQ for the proposed perchlorate Maximum Contaminant Level Goal (MCLG) and corresponding MCL because this value represents a small change in IQ well below one standard deviation for the subpopulation of interest. However, EPA seeks comment on all three values. In addition, EPA is specifically soliciting comments on the adequacy and uncertainties of the BBDR model it developed to predict thyroid hormone level changes caused by perchlorate exposure and its application of the epidemiologic literature to quantify the relationship between thyroid hormone changes and neurodevelopmental effects.

The remainder of the pre-publication draft includes a discussion of the feasibility of achieving the MCLG as well as a cost-benefit analysis of the three potential MCL values. This discussion focuses on a number of factors. First, EPA evaluates (or reevaluates) the occurrence data collected from the UCMR and other monitoring, including the data generated by Massachusetts and California, which each had previously adopted their own, much lower MCLs of 2 ppb and 6 ppb, respectively. This data reevaluation is in response to a request for correction filed by a trade association under the Information Quality Act challenging the data used in the Regulatory Determination EPA issued in 2011. Based on this data reevaluation, EPA concludes that only 15 regulated water systems in the U.S. would exceed even the lowest proposed value under consideration (18 ug/L).

Next, EPA evaluated analytical methods, monitoring and compliance requirements, treatment technologies, cost estimates and affordability to arrive at a determination of the health risk reduction cost analysis. Similarly, EPA attempted to quantify the benefits of the proposed rule by first identifying the nationwide population of children that will experience a quantifiable benefit of avoided IQ decrements and then estimating the present value of lifetime income reductions attributable to a 1 percent reduction in IQ at birth. In all cases, the total costs are substantially higher than the potential range of quantifiable benefits. As a result, pursuant to SDWA Section 1412(b)(4)(C), "the EPA Administrator has determined based upon the available information that the benefits of establishing an NPDWR [National Primary Drinking Water Regulation] for perchlorate do not justify the associated costs." (p. 110 of 171.) EPA specifically seeks comments on the adequacy of the underlying estimates, assumptions and analysis used to estimate costs and benefits.

Although not related to the cost-benefit analysis (and explicitly based upon the reevaluation of occurrence data), EPA seeks comments on whether it should withdraw its 2011 Regulatory Determination and issue no NPDWR for perchlorate. While this may seem like a dramatic reversal given the history, EPA does identify prior cases where contaminants did not occur with frequency at levels of public health concern or there was not a meaningful opportunity for health risk reduction. However, it does not appear that any of the prior cases involved a formal Regulatory Determination as was made here.

Conclusion and Considerations

Most of the press to date has focused on two simple bottom lines: 1) the fact that EPA is proposing a value for the MCL (56 ug/L) that is substantially higher than the existing Health Advisory (guidance) value of 15 ug/L and 2) the fact that EPA is considering making no regulation at all. While both of those points are true, the regulatory history and EPA's analysis is far more complex. Only time will tell what the 60-day comment period (which won't begin until the formal Federal Register publication) will yield.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.

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