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Final Minimum Risk Levels For PFAS: What Do They Mean?

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In May 2021, the federal Agency for Toxic Substances and Disease
Registry (ATSDR) finalized a report containing toxicological
profiles and associated Minimal Risk Levels (MRLs) for several
perfluoroalkyls (PFAS), a family of chemicals marked by their
persistence in the environment, bioaccumulation in human and animal
tissue, and toxicity at extremely low levels (in the parts per
trillion).1 You may have seen PFAS flagged as
contaminants of concern at sites across the country or seen the
film “Dark Waters” about PFAS toxic tort litigation.
Whatever the context, you probably know that PFAS regulation and
liability issues are evolving at a rapid pace. So what does
ATSDR’s new report mean going forward?


Bottom line: this report sets the stage for what is likely to be
a contentious battle regarding PFAS clean-up levels in the years
ahead. Although the general potential for harmful effects from PFAS
was identified several decades ago, definitive guidance on valid
screening and cleanup levels for specific PFAS chemicals has lagged
further behind as the science around PFAS toxicity and testing
methodologies has developed. Prior to the ATSDR report, the U.S.
Environmental Protection Agency (U.S. E.P.A.) had set a non-binding
health advisory level of 70 parts per trillion (ppt) combined for
perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid
(PFOS) for lifetime chronic exposure and also issued a December
2019 interim recommendation for a 40 ppt combined PFOA/PFOS
screening level for federal cleanup programs (leaving 70 ppt as a
preliminary remediation goal). U.S. E.P.A. has yet to designate any
PFAS chemical as a hazardous substance for purposes of the
Comprehensive Environmental Response, Compensation, and Liability
Act (CERCLA) or a hazardous waste for purposes of Resource
Conservation and Recovery Act (RCRA).2

In the absence of binding federal standards, state environmental
regulators have followed various approaches to monitoring and
responding to PFAS. Many states have conducted testing of major
drinking water sources for PFAS, either on their own initiative or
under U.S. E.P.A.’s Unregulated Contaminant Monitoring
Regulation 3 requiring sampling under the Safe Drinking Water Act,
but sampling of private wells and smaller non-community systems has
been sporadic. Some states have developed screening and action
levels lower than U.S. E.P.A.’s, while others have relied on
the federal 70 ppt health advisory level as a credible number to
guide agency action. Overall, this has created a patchwork of
information and regulation across U.S. jurisdictions.


ATSDR’s new report, developed as part of its statutory role
in researching health effects of toxic substances under CERCLA
section 104(i), 42 U.S.C. § 9604(i), now offers new
estimated MRLs for oral ingestion of PFOA, PFOS, perfluorohexane
sulfonic acid (PFHxS), and perfluorononanoic acid (PFNA). These
recommendations are intended to serve as screening tools rather
than cleanup standards.3 ATSDR set reference doses of:
3×10-6 mg/kg/day for PFOA; 2×10-6 mg/kg/day
for PFOS; 2×10-5 mg/kg/day for PFHxS; and
3×10-6 mg/kg/day for PFNA. The reference doses for PFOA
and PFOS are, respectively, 7 and 10 times more stringent than the
reference doses used to calculate the 2016 health advisory level of
70 ppt, while U.S. E.P.A. had not set any reference dose for PFHxS
and PFNA.

Given the unsettled status of PFAS regulation to date, these
MRLs have the potential to spur debate on all ends of the spectrum.
In a state like Michigan, which has developed its own drinking
water standards for PFAS chemicals that are in some cases based on
reference doses even lower than those in the ATSDR
report,4 the question becomes whether the state will
adopt differing federal values that it may see as less stringent.
Conversely, a state like Ohio that has utilized the 70 ppt health
advisory level will need to consider how to respond to this new
research. A range of stakeholders will have to determine how to
evaluate existing drinking water testing results in light of the
ATSDR report. And U.S. E.P.A. itself will inevitably incorporate
the ATSDR analysis in its ongoing consideration of whether to
designate any PFAS chemicals as hazardous under CERCLA and/or RCRA
and whether to set maximum contaminant levels for PFAS in drinking
water. In all cases, regulators will continue to face choices
around how to apply the growing universe of PFAS research as
experts continue to refine methodologies for sampling, analyzing
fate and transport, source identification through available
“fingerprinting” approaches, and treatment.

Dickinson Wright has been on the vanguard of these issues in
Michigan, a hotspot for PFAS regulatory action, and stands ready to
assist clients in this arena going forward.


1. ATSDR, Toxicological Profile for Perfluoroalkyls (May
2021) (“ATSDR PFAS Report”), available at

2. U.S. EPA has taken other actions, including adding
over 150 PFAS compounds to the Toxic Release Inventory reporting
requirements for reporting years 2020 and 2021. U.S. EPA, Chemicals
Added to the Toxics Release Inventory Pursuant to Section 7321 of
the National Defense Authorization Act,

3. ATSDR PFAS Report at 15.

4. Michigan Science Advisory Workgroup, Health-Based
Drinking Water Value Recommendations for PFAS in Michigan (June 27,
(PFHxS reference dose of 9.7 x 10-6

The content of this article is intended to provide a general
guide to the subject matter. Specialist advice should be sought
about your specific circumstances.

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