Dose Response, Dosimetric, and Metabolic Evaluations of Replacement PFAS Perfluoro-(2,5,8-trimethyl-3,6,9-trioxadodecanoic) Acid (HFPO-TeA)

Abstract

Few studies are available on the environmental and toxicological effects of perfluoroalkyl ether carboxylic acids (PFECAs), such as GenX, which are replacing legacy PFAS in manufacturing processes. To collect initial data on the toxicity and toxicokinetics of a longer-chain PFECA, male and female Sprague Dawley rats were exposed to perfluoro-(2,5,8-trimethyl-3,6,9-trioxadodecanoic) acid (HFPO-TeA) by oral gavage for five days over multiple dose levels (0.3-335.2 mg/kg/day). Clinically, we observed mortality at doses >17 mg/kg/day and body weight changes at doses ≤17 mg/kg/day. For the 17 mg/kg/day dose level, T3 and T4 thyroid hormone concentrations were significantly decreased (p < 0.05) from controls and HFPO-TeA plasma concentrations were significantly different between sexes. Non-targeted analysis of plasma and in vitro hepatocyte assay extractions revealed the presence of another GenX oligomer, perfluoro-(2,5-dimethyl-3,6-dioxanonanoic) acid (HFPO-TA). In vitro to in vivo extrapolation (IVIVE) parameterized with in vitro toxicokinetic data predicted steady-state blood concentrations that were within seven-fold of those observed in the in vivo study, demonstrating reasonable predictivity. The evidence of thyroid hormone dysregulation, sex-based differences in clinical results and dosimetry, and IVIVE predictions presented here suggest that the replacement PFECA HFPO-TeA induces a complex and toxic exposure response in rodents.

Keywords: IVIVE; PFAS; PFECA; dosimetry; hepatic clearance; non-targeted analysis (NTA); plasma protein binding; thyroid disruption.

Figure 1

Chemical structures of hexafluoropropylene oxide (HFPO) homologues: (Left) HFPO-DA, (Center) HFPO-TA, and (Right) HFPO-TeA.

Figure 2

Percent dose of HFPO-TeA per gram of plasma following five days of exposure. Data points represent mean ± standard deviation (n = 4).

Figure 3

Percent dose of HFPO-TeA per gram of liver following five days of exposure. Data points represent mean ± standard deviation (n = 4).

Figure 4

High-resolution MS/MS spectrum of the in-source ion (m/z 350.9680) of HFPO-TeA.

Figure 5

High-resolution MS/MS spectrum of the ion of m/z 516.9552, where X in the proposed structure is an unknown headgroup.

Figure 6

Structure of perfluoro(2,5,8,10-tetramethyl-3,6,9-trioxaundecanoic) acid (CAS 1212077-14-9|DTXSID40892441). The compound can be represented by a C₃HF₄O₂ headgroup attached to a backbone structure similar to HFPO-TeA but with a branched tail (labeled with a red asterisk). The headgroup, labeled here with an X and the exact mass of the substructure, could be the unknown headgroup for the proposed structure of the ion of m/z 516.9552 shown in Figure 5.

Figure 7

High-resolution TOF MS/MS spectrum and proposed structure of the ion of m/z 328.9661.

Figure 8

A mirror plot of: (Top) high-resolution TOF MS/MS spectrum of the ion of m/z 990.9106 observed only in plasma, and (Bottom) high-resolution TOF MS/MS spectrum of the (2M-H)⁻ dimer of HFPO-TA obtained from an authentic commercial standard.