Request for Public Review and Comment: Draft Human Health Toxicity Assessments for Hexafluoropropylene Oxide Dimer Acid and Its Ammonium Salt (GenX Chemicals) and for Perfluorobutane Sulfonic Acid (PFBS) and Related Compound Potassium Perfluorobutane Sulfonate

The Environmental Protection Agency (EPA) is announcing a 60- day public comment period associated with the release of two draft toxicity assessments for public comment: •  Draft Human Health Toxicity Values for Hexafluoropropylene Oxide (HFPO) Dimer Acid and its Ammonium Salt (GenX Chemicals). •  Draft Human Health Toxicity Values for Perfluorobutane Sulfonic Acid (PFBS) and Related Compound Potassium Perfluorobutane Sulfonate. The EPA developed the draft assessments to provide the health effects information available for GenX chemicals and PFBS and describe how that information was used to derive draft toxicity values. These draft toxicity assessments underwent independent, external expert peer review in June-July 2018. Following closure of this 60-day public comment period, the EPA will consider the comments, revise the draft documents, and consider the need for additional peer review, as appropriate, and then publish final toxicity assessments. The toxicity assessments for GenX chemicals and PFBS are scientific and technical reports that include toxicity values associated with potential noncancer health effects following oral exposure (in this case, oral reference doses [RfDs]). These assessments evaluate human health hazards. The toxicity assessments and the values contained within are not risk assessments as they do not include exposure assessments or provide a risk characterization. Further, the toxicity assessments do not address the legal, political, social, economic, or technical considerations involved in risk management. When issued, the toxicity assessments can be used by the EPA, states, tribes, and local communities, along with specific exposure and other relevant information, to determine, under the appropriate regulations and statutes, if and when it is necessary to take action to address potential risk associated with human exposures to these per- and polyfluoroalkyl substances (PFAS) chemicals.