The United States Environmental Protection Agency (EPA) recently announced that EPA will publish a notice of rulemaking in the Federal Register to seek public opinion on how to regulate perchlorate in drinking water. The agency is proposing a 56 micrograms per liter as a Maximum Contaminant Level (MCL) and a health-based Maximum Contaminant Level Goal (MCLG) but also seeking comment on three alternative regulatory options, including: (1) an MCL and MCLG for perchlorate at 18 micrograms per liter; (2) an MCL and MCLG for perchlorate at 90 micrograms per liter; and (3) withdrawing the EPA’s prior 2011 determination to regulate perchlorate in drinking water.
Perchlorate is a chemical anion that includes one chlorine atom bonded with four oxygen atoms (ClO4-). Perchlorate occurs both naturally and through chemical manufacturing. The most common use of perchlorate is an oxidizer in propellants used in fireworks, munitions, airbags, matches, and rocket fuel. It is also used to control static electricity in food packaging. The anion is extremely water soluble and can be persist for decades in ground or surface water. Currently, many public water systems and wells contain some level of perchlorate.
Research is ongoing about potential adverse effects to human health from low levels of perchlorate in drinking water or food. However, at high levels of concentration, perchlorate has been found to interfere with iodine uptake in the thyroid gland for adults and children. As the thyroid gland plays an important role in the development of children, high concentrations of perchlorate can impair proper brain development. While perchlorate effects on the thyroid gland are reversible, its effects on brain development are not. Thus perchlorate can pose a specific risk to children.
On February 11, 2011, EPA determined that perchlorate meets the Safe Drinking Water Act criteria for regulation as a contaminant. The Agency found that perchlorate may have an adverse effect on the health of persons and is known to occur in public drinking water systems with a frequency and at levels that present a public health concern. Since that time, EPA has been reviewing the best available scientific data on a range of issues related to perchlorate in drinking water including its health effects, occurrence, treatment technologies, analytical methods, and the costs and benefits of potential standards. …As part of EPA’s commitment to ensuring the safety of America’s drinking water, the Agency conducted two independent, expert peer reviews to determine the appropriate scientific approach for understanding the adverse health impacts of perchlorate in drinking water.EPA collaborated with Food and Drug Administration scientists to implement the 2013 Science Advisory Board (SAB) recommendations to develop a Physiologically Based Pharmacokinetic/Pharmacodynamic (PBPK/PD) or Biologically Based Dose Response (BBDR) model that integrated available health related information in a robust and transparent analysis of the effects of perchlorate on thyroid hormone production. A peer review was conducted on the draft model and model report in January 2017. After considering the findings of this review, EPA revised the Perchlorate BBDR Model to focus on increasing the scientific rigor of the model and modeling results. In addition, EPA developed a two-stage approach linking the revised BBDR model results with quantitative information on neurodevelopmental outcomes from epidemiological studies. EPA also developed an alternative population-based approach that uses the revised Perchlorate BBDR Model to evaluate a shift in the population of pregnant women who could be hypothyroxinemic.