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Estimation of the Half-Lives of Recently Detected Per- and Polyfluorinated Alkyl Ethers in an Exposed Community
Citation:
Wallis, D., N. Kotlarz, D. Knappe, D. Collier, S. Lea, D. Reif, J. McCord, M. Strynar, J. Dewitt, AND J. Hoppin. Estimation of the Half-Lives of Recently Detected Per- and Polyfluorinated Alkyl Ethers in an Exposed Community. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 57(41):15348�15355, (2023). https://doi.org/10.1021/acs.est.2c08241
Impact/Purpose:
Per- and polyfluoroalkyl substances (PFAS) are a synthetic chemical class that are ubiquitous in environmental and biological systems, including humans. Many chemicals in this class are environmentally persistent and have long biological half-lives. Little is known about the human biological persistence of a new generation of PFAS, which are characterized by one or more ether oxygens in the carbon chain, commonly referred to as fluoroethers. Previous analysis by the EPA and NC State University determined levels of fluoroethers in the serum of residents of Wilmington, NC as part of a biomonitoring study. Using these measurements, and the fact that the state of NC halted all emissions of fluoroethers in 2017, a simple half-life model was used to determine some toxicokinetic parameters for PFAS elimination. These are the first, and possibly only, estimates of human biological half-lives for many of these species due to the unique exposure of the population. The toxicokinetic parameters are of significant value for future exposure/toxicity monitoring both for the novel PFAS modeled here, but also for extrapolation to future PFAS in the same and/or similar classes.
Description:
To estimate half-lives for novel fluoroethers, the GenX Exposure Study obtained two serum measurements for per- and polyfluoroalkyl substances (PFAS) for 44 participants of age 12-86 years from North Carolina, collected 5 and 11 months after fluoroether discharges into the drinking water source were controlled. The estimated half-lives for these compounds were 127 days (95% confidence interval (95% CI) = 86, 243 days) for perfluorotetraoxadecanoic acid (PFO4DA), 296 days for Nafion byproduct 2 (95% CI = 176, 924 days), and 379 days (95% CI = 199, 3870 days) for perfluoro-3,5,7,9,11-pentaoxadodecanoic acid (PFO5DoA). Using these estimates and the literature values, a model was built that predicted PFAS half-lives using structural properties. Three chemical properties predicted 55% of the variance of PFAS half-lives based on 15 PFAS. A model with only molecular weight predicted 69% of the variance. Some properties can predict the half-lives of PFAS, but a deeper understanding is needed. These fluoroethers had biological half-lives longer than published half-lives for PFHxA and PFHpA (30-60 days) but shorter than those for PFOA and PFOS (800-1200 days). These are the first and possibly only estimates of human elimination half-lives of these fluoroethers.
URLs/Downloads:
DOI: Estimation of the Half-Lives of Recently Detected Per- and Polyfluorinated Alkyl Ethers in an Exposed Community
https://pubmed.ncbi.nlm.nih.gov/37801709/