ATSDR Releases Draft Toxicological Profile for PFAS

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After a delay which triggered criticism of the Administration by interest groups and some legislators, the Agency for Toxic Substances and Disease Registry (ATSDR) released their draft toxicological profile for Perfluoroalkyl Substances or PFAS.  The announcement was included in the June 21, Federal Register.  ATSDR is accepting comments on the profile until July 23, 2018.

Toxicological profiles are ATSDR’s process for evaluating and determining the health impact of various toxic substances.  The profiles provide Minimal Risk Levels (MRLs) that are commonly used to indicate when actions may be necessary at hazardous waste sites to protect the health of the surrounding community.  The PFAS toxicological profile covers a total of 14 perfluoroalkyl substances, although there are only MRL numbers on four.  These include PFOA and PFOS as well as PFHxS and PFNA.  Data was not adequate for the other 10 compounds.   The MRLs in the draft profile are:

PFOA – 3×10-6 mg/kg/day

PFOS – 2×10-6 mg/kg/day

PFHxS – 2×10-5 mg/kg/day

PFNA – 3×10-6 mg/kg/day

Although ATSDR may use some of the same health studies, their Minimal Risk Levels (MRLs) are not the same as Health Advisories (HAs) or Maximum Contaminant Levels (MCLs) developed by EPA.  The ATSDR may have different health endpoints or include different uncertainty or safety factors in their calculations.  Also, these MRLs consider exposure for an intermediate time period of 15-364 days rather than the lifetime exposure EPA uses for an MCL or HA.  That being said, the new profiles indicate potential health impacts at lower concentrations than the existing Health Advisories from EPA for PFOS and PFOA of 70 parts per trillion (ng/L).  Using the MRLs as a basis for a calculation that approximates how the HA was derived, gives us lower numbers.  These equivalent numbers are:

PFOA – 11 ng/L

PFOS – 7 ng/L

PFHxS – 74 ng/L

PFNA – 11 ng/L

These values come closer to what some states are considering as standards, and in the absence of an MCL from EPA, may drive future calls for action by the public.

For more information on Minimal Risk Levels please visit:  To help answer basic questions about Perfluoroalkyl Substances (PFAS), there are additional supplemental fact sheets, FAQs, and other consumer-oriented resources available at:  To access the existing PFAS HAs from EPA go here.