Cardno Chem Risk Blog US EPA Final Action: Perchlorate No Longer to be Regulated as a Drinking Water Contaminant Under the Safe Drinking Water Act

Posted on Behalf of Ricardo Ramirez and Ruth Hwang.   The Environmental Protection Agency’s (EPA) final action on June 18, 2020, determined that perchlorate levels in drinking water are not a public health concern and will not require a national regulation at this time, withdrawing the Agency’s February 2011 regulatory determination on perchlorate (EPA, 2020). The decision came after the EPA determined perchlorate did not satisfy two of the three criteria required for regulation under the Safe Drinking Water Act (SDWA): (1)    “the contaminant may have an adverse effect on the health of persons”; (2)    “the contaminant is known to occur or there is a substantial likelihood that the contaminant will occur in public water systems with a frequency and at levels of public health concern”; and (3)    “in the sole judgment of the Administrator, regulation of such contaminant presents a meaningful opportunity for health risk reduction for persons served by public water systems” (SDWA 1412(b)(1)(A)) (EPA, 2020). Naturally occurring perchlorate is commonly found in dry regions where its ability to infiltrate groundwater is limited (Kumarathilaka, 2016). Despite limited occurrence in groundwater, perchlorate remains a potential cause of concern. Upon ingestion, perchlorate is readily absorbed into the bloodstream and disrupts normal thyroid function which can negatively impact growth and metabolism and lead to hypothyroidism (Steinmaus, 2016). The EPA acknowledged the effects perchlorate can have on health, such as hypothyroidism, however, concluded, “perchlorate does not occur in public water systems with a frequency and at levels of public health concern and that regulation of perchlorate does not present a meaningful opportunity to reduce health risks for persons served by public water systems” (EPA, 2020). This decision was based on an occurrence and monitoring analysis which reported that perchlorate levels exceeded 18 μg/L in 15 water systems (0.03% of all US water systems) serving a total of 620,560 people (EPA, 2020). The concentration of 18 μg/L was the most restrictive of three potential maximum contaminant level goals proposed by the EPA in 2019 and the prevalence of contaminated systems at this level was significantly lower than the threshold (4% to 0.39% of water systems) set by the 2011 regulatory determination (EPA, 2019, 2020). Cardno ChemRisk has extensive experience in evaluating the potential human exposure and health risks to perchlorate. Our scientists conduct in-depth exposure assessments and identify the health risks associated with various chemicals. We provide recommendations for screening level testing and assistance, exposure and toxicological assessments, and comparative risk calculations. For more information regarding Cardno ChemRisk’s testing and assessment capabilities, please contact Dr. Paul Scott or Dr. Amy Madl.