Last Thursday the U.S. Environmental Protection Agency (EPA) issued a final decision not to regulate perchlorate under the Safe Drinking Water Act (SDWA).
Perchlorate is commonly used in solid rocket propellants, munitions, fireworks, airbag initiators for vehicles, matches, and signal flares. Perchlorate may occur naturally, particularly in arid regions such as the southwestern U.S. and can be found as a byproduct in hypochlorite solutions used for treating drinking water and nitrate salts used to produce fertilizers, explosives, and other products.
At certain levels, perchlorate can prevent the thyroid gland from getting enough iodine, which can affect thyroid hormone production. For pregnant women with low iodine levels, sufficient changes in thyroid hormone levels may cause changes in the child’s brain development. For infants, changes to thyroid hormone function can also impact brain development.
In the Federal Register February 2011
it stated: “EPA has determined that perchlorate meets SDWA's criteria for regulating a contaminant—that is, perchlorate may have an adverse effect on the health of persons; perchlorate is known to occur or there is a substantial likelihood that perchlorate will occur in public water systems with a frequency and at levels of public health concern; and in the sole judgment of the Administrator, regulation of perchlorate in drinking water systems presents a meaningful opportunity for health risk reduction for persons served by public water systems. Therefore, EPA will initiate the process of proposing a national primary drinking water regulation (NPDWR) for perchlorate.”
However, in June 2019 EPA presented an updated occurrence analysis collected using the Unregulated Contaminant Monitoring Rule (UCMR) to collect data that demonstrated that the levels of perchlorate in drinking water and sources of drinking water have decreased since first group of data was collected for the 2011 determination.
The EPA now states
that there has been a decrease in perchlorate levels which include due to:
- The promulgation of a drinking water regulations for perchlorate in California and Massachusetts; and
- The ongoing remediation efforts in the state of Nevada to address perchlorate contamination in groundwater adjacent to the lower Colorado River upstream of Lake Mead.
The above actions have effectively reduced the occurrence of perchlorate in public water supplies; and now perchlorate doesn’t appear in enough public water systems, or at high enough levels, to cause concern for the general population.
EPA had been considering regulating perchlorate at 56 part per billion (ppb). For comparison, Massachusetts' current regulatory standard is 2 ppb, while California is considering lowering its current regulatory standard of 6 ppb to 1 ppb. EPA decided that it should not regulate perchlorate at all under the SDWA, given that it would result in monitoring at 60,000 public water systems and only a handful had been impacted. According to the most recent monitoring data if EPA had regulated perchlorate at a maximum contaminant level of 56 ppb as originally proposed, only two systems would exceed the regulatory threshold. The ongoing analysis costs to all public water supply systems could not be justified.
In other words the steps that EPA, states and public water systems have taken in the past decade had successfully reduced the occurrence of perchlorate to the impacted drinking water companies that the agency determined perchlorate does not meet the criteria for regulation as a drinking water contaminant under the SDWA. Therefore, the agency withdrew the 2011 regulatory determination and is making a final determination to not issue a national regulation for perchlorate at this time.
Stand by for legal challenges from environmental groups especially the Natural Resources Defense Council. There is great concern about perchlorate, it has known significant health impacts, but does not appear to be widespread in drinking water supplies. It does leave you feeling uneasy, though.
The Safe Drinking Water Act, (SDWA), is the Federal law that protects the public from drinking water contaminants that pose a known health concern. Only 91 contaminants are regulated by the SDWA, yet according to the EPA, more than 80,000 chemicals are used within the United States. Not every drinking water contaminant with health consequence gets regulated because they may not be widely present in source waters. And not every regulated contaminant has health consequence. Some contaminants are regulated to control taste and odor. Though the SDWA was adopted in 1974, it has had significant amendments in 1986 and 1996 that added explicit health goals, risk management approaches and methods of gathering data to allow the SDWA to continue to evolve and ensure the public water supply systems in the United States remains among the safest in the world. The 1996 amendments to the SDWA created the Unregulated Contaminant Monitoring Rule, UCMR.
This is the tool the EPA uses to determine if there are contaminants likely to pose a risk to the health of the nation. A contaminant is identified as being of a possible health concern in drinking water, by states, water systems, scientists or other sources. Health information is collected and if deemed appropriate, occurrence and exposure information are collected using the UCMR data collection program for preliminary risk assessment then a determination is then made on whether there exists an opportunity to reduce public health risks by regulation and the contaminant is then added to the Drinking Water Contaminant Candidate List. The costs of the data collection are born by water supply companies that serve more than 10,000 people. The 1996 Safe Drinking Water Act (SDWA) amendments require that once every five years, EPA issue a new list of no more than 30 unregulated contaminants to be monitored by public water systems. The national sampling program provides the EPA with a scientifically valid database on the occurrence of these emerging contaminants in drinking water supplies.
The emerging contaminants lack human health standards so the first step is to identify what substances are present at what levels in the environment using the UCMR list to identify substances with widespread exposure. The next step would be to identify the acceptable human exposure level and need for regulation based on presence in the environment. Much of the environmental work in the past has been done on what are called the persistent priority pollutants, such as trace metals, pesticides, PCBs and PAHs, substances that persist in the environment. Many of the emerging contaminants are environmentally non-persistent, but still may have health impacts. A non-persistent chemical breaks down and these breakdown products may be widely present in the environment.
UCMR 4 is currently underway. Monitoring which began in 2018 will continue to the end of the year and includes monitoring for a total of 30 chemical contaminants: 10 cyanotoxins (nine cyanotoxins and one cyanotoxin group) and 20 additional contaminants (two metals, eight pesticides plus one pesticide manufacturing byproduct, three brominated haloacetic acid [HAA] disinfection byproducts groups, three alcohols, and three semivolatile organic chemicals [SVOCs]).