Click here to download pdf: Court Urged To Vacate PFAS Drinking Water Rule Due To Flawed Risk Levels
Toxicology groups led by a former Trump EPA toxics office nominee are urging an appellate court to vacate the
Biden EPA’s drinking water rule setting limits on six PFAS, with the groups charging that officials made mistakes in
their use of scientific studies when determining risk levels for the chemicals that are the basis for the rule.
As a result, the groups say in an April 15 amici brief the U.S. Court of Appeals for the District of Columbia Circuit
should vacate EPA’s Safe Drinking Water Act (SDWA) rule regulating six per- and polyfluoroalkyl substances in
drinking water and remand it to EPA.
They go so far as to suggest revised safety levels for the two most studied PFAS — perfluorooctanoic acid (PFOA)
and perfluorooctane sulfonic acid (PFOS) — at much less stringent levels than EPA’s.
The groups’ argument could provide a roadmap for the Trump administration to reconsider the landmark rule and its
underlying science, helping to justify a review of the closely watched standards.
The International Society for Regulatory Toxicology and Pharmacology (ISRTP) and Toxicology Excellence for Risk
Assessment (TERA), both led by toxicologist Michael Dourson, on April 15 submitted a motion for leave to file a
brief as amici parties as well as their amici brief to the D.C. Circuit court in support of petitioners challenging EPA’s
drinking water rule in American Water Works Association (AWWA), et al. v. EPA.
The briefs were submitted on the groups’ behalf by Susan Bodine, former EPA enforcement chief in the first Trump
administration, and Don Elliott, former EPA general counsel during President George H.W. Bush’s term.
ISRTP is a scientific society and TERA is a nonprofit group that specializes in environmental risk assessment.
Dourson, a toxicologist who was nominated but failed to win confirmation to lead EPA’s toxics office during the first
Trump administration, is president and director of science at TERA and was recently named as president of ISRTP,
which recently launched a new publication aimed at publishing papers for scientists and policymakers to discuss
toxicological and pharmacological science including PFAS.
In their brief laying out arguments in support of the petitioners, ISRTP and TERA effectively contend that EPA
overreached in its use of scientific studies, failed to meet the “substantial likelihood” of risk to the U.S. population
required under SDWA, departed from risk levels developed by other countries because it failed to follow “sound and
objective scientific practices,” and was flawed in its reliance on human studies.
Further, the groups say, “EPA also failed to abide by its own guidelines regarding chemical mixture assessments,
cancer findings, and reference dose determinations.”
In particular, they dismiss EPA’s findings regarding PFOA as carcinogenic — even as an international cancer
research agency in late 2023 reinforced EPA’s determination finding PFOA to be carcinogenic to humans.
EPA’s errors “demonstrate that the PFAS [maximum contaminant level (MCL)] produced by EPA fail to comport with
the mandates in the SDWA and resulted in a rule that is arbitrary and capricious. Accordingly, this Court should
vacate the rule and remand to EPA.”
Reconsider Risk Levels
The groups’ push to influence the litigation is not surprising, as they recently indicated plans to file an amici brief.
ISRTP has also taken its argument directly to EPA, urging Administrator Lee Zeldin in a Feb. 5 letter to
reconsider the risk levels the agency used to set the PFAS drinking water levels.
Dourson has been leading an effort to criticize the PFOA risk value used for the SDWA rule, moving to publish
articles in ISRTP stemming from a 2023 workshop where speakers questioned divergent risk values among the
United States and other countries regarding PFOA, and some scientists criticized the reliability of EPA’s risk value
for PFOA.
Last July, he sent to a lengthy list of email recipients a “Dear Colleagues” message signaling his and others’ interest
in questioning EPA’s drinking water limits.
“Now that the United States Environmental Protection Agency’s PFAS Maximum Contaminant Levels have been
promulgated, a number of parties are thinking to approach US Congress or the courts to ask for a re-evaluation,”
Dourson wrote in the July 23 email. “A couple approaches can be used to support this ask, but nearly all of them
require peer-reviewed and published papers before serious consideration.”
The Natural Resources Defense Council, a national environmental group that is an intervenor in the case in support
of EPA and the rule, objected to the groups’ request to be amici parties, according to ISRTP and TERA’s motion for
leave to file. As a result, the motion asks that they be granted such status instead under the Federal Rule of
Appellate Procedure 29(a)(3), which requires prospective amici parties to provide the reason why their brief is
“desirable” and directly relevant to the case.
The litigation is currently under a temporary stay pending the Trump EPA’s request for a pause “to allow new
Agency leadership to review the underlying rule” and decide on how to proceed in the case.
In AWWA, water utility groups and industry contend that EPA violated legal mandates when it evaluated the rule’s
costs and benefits, bypassed procedural requirements for standard-setting, made novel use of a formula to regulate
mixtures, and failed to use up-to-date occurrence data.
The rule at issue in the case, released in April 2024, sets first-time regulatory limits for PFAS in drinking water,
establishing an MCL of 4 parts per trillion (ppt) individually for PFOA and PFOS, and an MCL of 10 ppt individually
for hexafluoropropylene oxide dimer acid (HFPO-DA), more commonly referred to as a GenX chemical;
perfluorononanoate (PFNA), and perfluorohexanesulfonic acid (PFHxS).
It also establishes a novel dose-additivity approach — a hazard index — for regulating mixtures of up to four PFAS
that incorporates perfluorobutane sulfonic acid (PFBS).
While it is not clear how the Trump administration plans to proceed, EPA Administrator Lee Zeldin said last week
that he expects the agency will grapple with how to implement the rule given utilities’ cost concerns.
“There are water systems that are kicking [and screaming], but they can pay for it. There are water systems that are
kicking, and they can’t. There are communities that are lower income. There are communities where they have a
tax base that can foot the bill. So, we’re going to have to be extremely thoughtful in figuring this out.”
SDWA Determination
In their brief, TERA and ISRTP say their “position is that EPA’s determination under the SDWA that PFOA and
PFOS are found at levels of public health concern and the MCLs promulgated by EPA do not meet the requirements
of the SDWA.”
“In summary, TERA and ISRTP believe that the extremely low exposure levels identified by EPA in its human health
risk assessments do not present levels that reflect a public health concern, EPA’s conclusions that both PFOA and
PFOS are carcinogens are not supported by sound and objective scientific practice, and the PFAS MCLs that EPA
has promulgated do not represent best available science.”
The two groups say they are not criticizing the various studies on PFOA and PFOS, but rather contend that those
studies fail to support EPA’s finding that it has met the statutory standard for setting PFAS MCLs.
They also say they are not arguing against any regulation of PFAS, but rather that the MCLs EPA set are not
backed by the “best available science.”
The groups suggest provisional safe dose levels developed by international teams convened by TERA that arrived
at much less stringent levels for PFOA and PFOS. For PFOA, they recommend a provisional safe dose of between
10 and 70 nanograms/kilograms (ng/kg) body weight-day, in contrast to EPA’s recommended safe dose of 0.03
ng/kg for non-cancer effects, the brief says.
And for PFOS, the international teams derived safe dose levels ranging from 20 to 100 ng/kg body weight-day, as
compared with EPA’s reference dose for non-cancer effects of 0.1 ng/kg, the brief says.
The brief argues, “The most cavalier disregard of EPA guidelines was the agency’s development of its reference
dose (RfD), which is generally used in multiple regulations.” For instance, it says EPA “[e]levated human
observational studies on immune effects to causal significance, similar to its findings for cancer, but in this case
without the actual data nor integration of experimental animal findings at much higher doses that would have
suggested otherwise.”
The brief says that while human observational studies are reliable for developing hypotheses, they are not for
“establishing causation due to the presence of confounding exposures and minimal exposure responses.”
Further, the studies EPA relied on focused on identifying biological effects rather than relevant adverse impacts, it
says. “As a result, few international expert bodies or even U.S. states have used EPA’s choice of studies in their
safety assessments.”
They also argue the broader impacts of the allegedly flawed risk assessments for PFOA and PFOS are driving other
regulatory actions, including EPA’s April 2024 Superfund rule designating the two as “hazardous substances,” its
draft human health water quality criteria for PFAS, and its draft sewage sludge risk assessment for PFOA and
PFOS.
“Accordingly, overregulation and the resultant adverse consequences are expanding as a result of the analyses
EPA performed for this rulemaking.” — Suzanne Yohannan (syohannan@iwpnews.com)