On February 2, 2022, the EPA released its draft Toxicological Review of PFHxA and Related Salts, the latest risk assessment put forth by the EPA for certain types of PFAS. The PFAS risk assessment related to PFHxA is noteworthy because the Reference Dose (RfD) recommended by the EPA is considerably lower than similar risk assessments released by the EPA at the end of 2021 for other types of PFAS. Nevertheless, the findings and dose response information contained in the toxicity assessment are important for businesses with current or legacy uses of PFHxA to pay attention to, and PFHxA considerations must enter into the equation for any compliance programs in order to avoid significant financial disruption.

PFAS Risk Assessment For PFHxA

At nearly 200 pages in length, the EPA’s PFHxA toxicity assessment provides a great deal of discussion regarding the available scientific literature and information available to support the EPA’s ultimate conclusions as to toxicity and a Reference Dose.

The EPA examined human epidemiological studies and animal studies. The human epidemiological studies provided the EPA with only a “limited” ability to draw conclusions as to PFHxA as a causative agent for several human health issues. The limited number of studies, the low confidence interval stated in the studies, and the inability to measure exposure to PFHxA in the studies were all factors that inhibited the EPA in its assessment. The EPA found the animal studies (which were limited to oral ingestion studies) to be more persuasive, and it concluded that the studies support a conclusion that PFHxA can cause hepatic, developmental, and hematopoietic effects in humans with proper levels of exposure.

The draft toxicity assessment for PFHxA concludes that the evidence supports a reference dose of 5×10^-4 milligrams per kilogram bodyweight per day (mg/kg-day), which represents the most that an adult could consumer of PFHxA over a lifetime without the risk of health effects (the EPA defines a reference dose as follows: “a reference dose is an estimate of the amount of a chemical a person can ingest daily over a lifetime (chronic RfD) or less (subchronic RfD) that is unlikely to lead to adverse health effects in humans.”). This is much less stringent than the EPA’s GenX RfD (3×10^-6 mg/kg-day), stricter than the RfD for PFBA (0.001 mg/kg-day) and similar to the RfD for PFBS (3×10^-4 mg/kg-day).

The draft PFHxA assessment is open for public comment, which closes on April 4. Once finalized, the EPA indicates that the conclusions could factor in to the EPA’s site remediation, waterway remediation, and Toxic Substances Control Act (TSCA) chemicals review.

Impact of PFAS Risk Assessment On Businesses

It should be noted that the PFAS risk assessment for PFHxA was conducted under the EPA’s Integrated Risk Information System (IRIS) Program, which has undertaken to assess and publish five different PFAS toxicological assessments – PFHxA, PFBA, PFHxS, PFNA, and PFDA. The EPA’s Water Office has also pledged to re-assess its current toxicological assessments and associated RfDs for PFOA and PFOS.

The immediate and short-term impact of the PFHxA PFAS toxicity assessment is that it is merely a harbinger of much more significant regulatory action, enforcement action and litigation. The EPA’s toxicity assessment is not a binding regulation; however, the EPA fully intends to utilize the toxicity assessments as support for conclusions that it will soon draw with respect to drinking water regulations, CERCLA designations, RCRA designations, and a number of other regulatory frameworks under which the EPA is addressing PFAS issues. The risk assessments also provide other federal level agencies with scientific support and references for potential future regulatory action for exposure sources other than drinking water.

Conclusion

Companies with current or legacy uses of PFHxA (or any of the PFAS types being evaluated under the IRIS program) must understand that the non-binding nature of the risk assessments cannot simply be ignored. The results in the assessments will inform future regulatory action with respect to those chemicals. As such, compliance programs absolutely must take into consideration all avenues of risk from current or past use of the chemicals. Failing to do so could result in considerable financial disruption that could have been avoided with careful planning.