The best available science supports EPA’s regulatory decision on perchlorate. More than 60 years of scientific research have repeatedly demonstrated that perchlorate does not meet the requirements for additional nationwide regulation, nor would a national drinking water standard offer a meaningful opportunity to improve public health. The Perchlorate Study Group therefore concurs with EPA’s decision to withdraw its 2011 perchlorate regulatory determination and its final determination not to regulate perchlorate.

In June 2019, EPA proposed setting the perchlorate maximum contaminant level (MCL) at 56 parts per billion, and asked for public comment on its proposal. EPA also asked for public comment on three regulatory alternatives: a higher MCL at 96 ppb, a lower MCL at 18 ppb, and a determination not to regulate perchlorate at the federal level.

The Perchlorate Study Group (PSG) has consistently taken the position that perchlorate does not satisfy the criteria for regulation set forth in the Safe Drinking Water Act and therefore federal regulation is not required or appropriate. The PSG is one of 13 stakeholders that have filed comments demonstrating the best available science, public health information, statutory direction from Congress, Federal law and long-standing agency practice oblige EPA to withdraw its 2011 perchlorate regulatory determination.

The Safe Drinking Water Act is designed to address drinking water contaminants of national concern. The most recent data demonstrates that the number of people exposed to perchlorate in drinking water is very low and most of that exposure occurs in states that already regulate perchlorate. Considering that EPA’s own analysis finds that the costs of a nationwide perchlorate drinking water regulation would significantly outweigh the benefits, EPA should focus its limited resources on more immediate and significant public health concerns.

Additional background: Six Facts Every Journalist Covering Perchlorate Should Know

1. EPA’s modeling demonstrates that environmental levels of perchlorate have essentially no effects on either the typical U.S. consumer or the most sensitive subpopulations. EPA has conducted more extensive modeling on perchlorate than almost any other constituent. The National Research Council of the National Academy of Sciences (NAS) determined in 2005 that levels of perchlorate below 24.5 parts per billion (ppb) have no measurable effect on human health. More…

2. EPA’s traditional method of evaluating Safe Drinking Water Act (SDWA) contaminants—calculation of a Health Reference Level (HRL)—demonstrates there is very little exposure to perchlorate above the HRL and thus very little potential risk. EPA calculated a HRL of 15 ppb for perchlorate in 2008, based on a toxicity value developed by the NAS. Recent studies show that concentrations of perchlorate are below 15 ppb in nearly all drinking water systems in the U.S.

3. The scientific database on perchlorate dates back to its use as a medicine, involving doses thousands of times higher than amounts in the environment today. After reviewing this wealth of research, the findings of the NAS made clear that the levels of perchlorate that could pose a risk to public health are higher than currently found in any known public drinking water system.

4. A comparison of perchlorate and other SDWA contaminants shows that a decision to withdraw the perchlorate determination is consistent with past EPA decisions not to regulate. As one example, EPA decided not to regulate the contaminant aldrin in drinking water in 2002 because aldrin occurred above its HRL in only 0.2% of drinking water systems in the U.S. Perchlorate occurs above its HRL even less frequently than aldrin.

5. The U.S. Food and Drug Administration already concluded that perchlorate does not warrant regulation in food packaging. The decision was based on doses that are greater than those found in US public drinking water systems.

6. The Safe Drinking Water Act requires three key criteria be met before a compound can be regulated: (1) it may have an adverse effect on human health, (2) it occurs in public drinking water systems at a frequency and at levels of public health concern, and (3) federal regulation of the substance presents a meaningful opportunity for health risk reduction. Perchlorate meets none of these criteria.

Please visit for factual information on perchlorate, or contact Bill Romanelli at 916-276-0467.