Serum Half-Lives for Short- and Long-Chain Perfluoroalkyl Acids after Ceasing Exposure from Drinking Water Contaminated by Firefighting Foam

Abstract

Background: Firefighting foam-contaminated ground water, which contains high levels of perfluoroalkyl substances (PFAS), is frequently found around airports. In 2018 it was detected that employees at a municipal airport in northern Sweden had been exposed to high levels of short-chain PFAS along with legacy PFAS (i.e., PFOA, PFHxS, and PFOS) through drinking water.

Objectives: In this study, we aimed to describe the PFAS profile in drinking water and biological samples (paired serum and urine) and to estimate serum half-lives of the short-chain PFAS together with legacy PFAS.

Methods: Within 2 weeks after provision of clean water, blood sampling was performed in all 26 airport employees. Seventeen of them were then followed up monthly for 5 months. PFHxA, PFHpA, PFBS, PFPeS, and PFHpS together with legacy PFAS in water and biological samples were quantified using LC/MS/MS. Half-lives were estimated by assuming one compartment, first-order elimination kinetics.

Results: The proportions of PFHxA, PFHpA, and PFBS were higher in drinking water than in serum. The opposite was found for PFHxS and PFOS. The legacy PFAS accounted for about 50% of total PFAS in drinking water and 90% in serum. Urinary PFAS levels were very low compared with serum. PFBS showed the shortest half-life {average 44 d [95% confidence interval (CI): 37, 55 d]}, followed by PFHpA [62 d (95% CI: 51, 80 d)]. PFPeS and PFHpS showed average half-lives as 0.63 and 1.46 y, respectively. Branched PFOS isomers had average half-lives ranging from 1.05 to 1.26 y for different isomers. PFOA, PFHxS, and linear PFOS isomers showed average half-lives of 1.77, 2.87, and 2.93 y, respectively.

Discussion: A general pattern of increasing half-lives with increasing chain length was observed. Branched PFOS isomers had shorter half-lives than linear PFOS isomers. https://doi.org/10.1289/EHP6785.

Figure 1.

Map of Arvidsjaur municipality, Sweden, and the regional airport, with information of fire drill area, two waterworks, the private well, and area of four raw-water wells for municipal waterworks. Background map data: © OpenStreetMap contributors, CC BY-SA.

Figure 2.

Composition (molar-concentration basis) of perfluorinated carboxylic acids (PFCAs, dotted bars) and perfluorinated sulfonic acids (PFSAs, open bars; branched PFOS in hatched bar) in the airport drinking water and in the first serum samples obtained from the 26 airport employees (detailed data are presented in Table S6). PFCAs and PFSAs with same number of carbons in the carbon chain (i.e., PFHxA vs. PFHxS, PFHpA vs. PFHpS, and PFOA vs. PFOS) are illustrated with the same color. The relative composition (percentage) for each PFAS is embedded in the box. Although PFBA and PFPeA were elevated in the drinking water, they were below the LOD in all the serum samples, so they were not presented. Note: PFAS, perfluoroalkyl substances; PFBS, perfluorobutane sulfonic acid; PFHpA, perfluoroheptanoic acid; PFHpS, perfluoroheptane sulfonic acid; PFHxA, perfluorohexanoic acid; PFHxS, perfluorohexane sulfonic acid; PFOA, perfluorooctanoic acid; PFOS, perfluorooctane sulfonic acid; PFPeS, perfluoropentane sulfonic acid.