On June 26, 2019, the United States Environmental Protection Agency (EPA) issued a draft perchlorate rule proposing a Maximum Contaminant Level (MCL) of 56 micrograms per liter (µg/L) for drinking water. Thousands of U.S. public water supply systems will experience increased administrative and monitoring costs once an MCL for perchlorate is finalized.

While EPA estimated that only two water supply systems in the U.S. would exceed the proposed MCL, the total cost to comply nationally would range from $9.67 million to $10.28 million annually. Based on a cost-benefit     analysis, and in apparent conflict with the proposed MCL, EPA determined that the benefits of establishing an MCL “…for perchlorate do not justify the costs” (FR Vol. 84, No. 123, page 30555, June 26, 2019). Therefore they asked for public comment on whether the MCL should be higher or lower or if regulation of perchlorate should be re-evaluated based on updated data.

The public comment period expired in July 2019 and the deadline for the final perchlorate rule is scheduled for June 19, 2020.

What Is Perchlorate?

Perchlorate, which is primarily a man-made contaminant, also forms naturally and exists as mineral deposits – particularly in arid regions such as the Southwestern United States. Perchlorate contamination is most commonly associated with the use and manufacture of rocket fuel, munitions, blasting materials and fireworks. Over 90% of the perchlorate manufactured in the U.S. is used in the defense and aerospace industries. Naturally-occurring perchlorate is also an impurity present in nitrate salts imported from Chile which are used to manufacture nitrate fertilizers, explosives, and other products – such as signal flares, airbag initiators, matches, some disinfectants, and various herbicides.

Chemically, perchlorate is one chlorine atom bound to four oxygen atoms. Ammonium perchlorate is the most common form of the man-made perchlorate compounds; potassium perchlorate and sodium perchlorate are also manufactured. Perchlorate can interfere with iodine uptake into the thyroid gland. In fact, perchlorate has been used in some medicines to treat hyperthyroidism (excess thyroid hormone production). In the environment,    perchlorate is relatively stable, is soluble and mobile in water, and has been found in drinking water and food.

History of Perchlorate Regulation

Perchlorate regulations have been contemplated since it was discovered in Imperial Valley, California lettuce (uptake from irrigation water) and traced to Lake Mead via the Colorado River in 1997. Ultimately, two industrial facilities in Henderson, Nevada were identified as the source of the perchlorate in Lake Mead. In 1999, sampling for perchlorate began at selected public water supplies under the EPA’s Unregulated Contaminant Monitoring Rule (UMCR). The UMCR required sampling of water supply systems in all 50 states, the District of Columbia, four U.S. territories, and tribal lands.

As of 2009, perchlorate had been reported in drinking water, groundwater, surface water, soil or sediment in 45 states. In January 2009, EPA set an Interim Drinking Water Health Advisory Level for perchlorate at 15 µg/L and on February 11, 2011 they issued a formal Regulatory Determination that perchlorate was a contaminant under criteria established in the Safe Drinking Water Act (SDWA). These criteria determined that perchlorate (a) may have adverse health effects; (b) is known to occur in public water supply systems with a frequency and at levels that are a public health concern; and (c) regulation may achieve a meaningful opportunity for health risk reduction. As a result, EPA continued the rule-making process.

Perchlorate is known to disrupt thyroid function – resulting in adverse effects on neurodevelopment in humans, particularly fetuses and infants. Therefore, in 2013, the Scientific Advisory Board recommended that EPA evaluate the risks of perchlorate exposure during sensitive life stages using a Biologically Based Dose Response approach. This resulted in a 2013 EPA decision to evaluate the levels of perchlorate in drinking water that would correspond to one, two and three percent decreases in intelligence quotient (IQ) as an indicator of neurodevelopmental effects.

In 2016, the Natural Resources Defense Council filed a complaint with the courts that EPA had not issued an MCL or Maximum Contaminant Level Goal (MCLG) as required by the SDWA. Subsequently, a Consent Decree (dated October 18, 2016) required EPA to issue an MCL – leading to the current proposed perchlorate rule that evaluated three potential MCLs:

• 18 µg/L – exposure to perchlorate at this concentration is expected correspond to a one percent decrease in IQ of the mean population
• 56 µg/L – expected to correspond to a two percent decrease in IQ
• 90 µg/L – expected to correspond to a three present decrease in IQ

The EPA selected 56 µg/L as the proposed MCL but also asked for public input regarding higher and lower MCL levels or if an MCL is even needed.

Regulatory Support…from HETI

As stated earlier, EPA’s public comment period for the proposed perchlorate rule has expired and the deadline for the final rule is June 19 of this year. Given the years of study, various proposals, and litigation surrounding        perchlorate, whatever EPA’s final rule concludes will likely not be the end of the perchlorate discussion.

HETI’s staff continually reviews new and proposed changes to regulations and standards to make sure we have current knowledge of compliance and environmental issues. We have extensive experience in supporting our    clients through a comprehensive range of regulatory support and other services.