Development of an oral reference dose for the perfluorinated compound GenX. Issue 9 (18th June 2019)

• Record Type: Journal Article
• Authors: Thompson, Chad M.; Fitch, Seneca E.; Ring, Caroline; Rish, William; Cullen, John M.; Haws, Laurie C.
• Is Part Of: Journal of applied toxicology. Volume 39:Issue 9(2019)
• Page Start: 1267
• Page End: 1282
• Publication Date: 2019-06-18
• Subjects: benchmark dose (BMD) modeling -- GenX -- per‐ and polyfluoroalkyl substances (PFAS) -- reference dose (RfD) -- risk assessment; Toxicology -- Periodicals; Industrial toxicology -- Periodicals; Environmentally induced diseases -- Periodicals; Toxicology -- Periodicals; 615.9005
• DOI: 10.1002/jat.3812
• Languages: English
• ISSNs: 0260-437X

Abstract

Abstract: Ammonium 2, 3, 3, 3‐tetrafluoro‐2‐(heptafluoropropoxy)‐propanoate, also known as GenX, is a processing aid used in the manufacture of fluoropolymers. GenX is one of several chemistries developed as an alternative to long‐chain poly‐fluoroalkyl substances, which tend to have long clearance half‐lives and are environmentally persistent. Unlike poly‐fluoroalkyl substances, GenX has more rapid clearance, but has been detected in US and international water sources. There are currently no federal drinking water standards for GenX in the USA; therefore, we developed a non‐cancer oral reference dose (RfD) for GenX based on available repeated dose studies. The review of the available data indicate that GenX is unlikely to be genotoxic. A combination of traditional frequentist benchmark dose models and Bayesian benchmark dose models were used derive relevant points of departure from mammalian toxicity studies. In addition, deterministic and probabilistic RfD values were developed using available tools and regulatory guidance. The two approaches resulted in a narrow range of RfD values for liver lesions observed in a 2‐year bioassay in rats (0.01–0.02 mg/kg/day). The probabilistic approach resulted in the lower, i.e., more conservative RfD. The probabilistic RfD of 0.01 mg/kg/day results in a maximum contaminant level goal of 70 ppb. It is anticipated that these values, along with the hazard identification and dose‐response modeling described herein, should be informative for risk assessors and regulators interested in setting health‐protective drinking water guideline values for GenX. Abstract : Ammonium 2, 3, 3, 3‐tetrafluoro‐2‐(heptafluoropropoxy)‐propanoate, also known as GenX, is a processing aid used in the manufacture of fluoropolymers. There are currently no federal drinking water standards for GenX in the USA. Frequentist benchmark dose models and Bayesian benchmark dose models were used to derive points of departure from mammalian toxicity studies. Deterministic and probabilistic reference dose values were developed and resulted in a narrow range of values (0.01‐0.02 mg/kg/day). The lower reference dose results in a maximum contaminant level goal of 70 ppb.