# High serum PFAS levels in a population after exposure through drinking water in western Tokyo, Japan and their half-lives estimation

## TL;DR

This study found high PFAS levels in residents of western Tokyo after drinking water contamination and estimated the long half-lives of these chemicals in the human body.

## Contribution

The study provides novel half-life estimates for PFAS in a Japanese population following drinking water exposure.

## Key findings

- 95% of participants had total PFAS concentrations exceeding 20 ng/mL in 2023.
- Estimated half-lives for PFOS, PFHxS, and PFOA ranged from 2.7 to 8.0 years.
- PFAS levels in serum decreased from 2000 to 2023 after reduced exposure.

## Abstract

Per- and polyfluoroalkyl substances (PFAS) have raised significant health concerns. In 2019, drinking water source was changed due to PFAS contamination in the Tama region, Tokyo, Japan. This study aims to determine the PFAS exposure levels after reduction in drinking water contamination, and to estimate the half-lives of linear isomers of perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), and perfluorooctanoic acid (PFOA) in serum samples from residents.

17 participants in 2020 and 2023 from Tama region, Tokyo, Japan (all females, age 53–83 years) were examined. PFAS concentrations in serum in 2023 were measured using gas chromatography-mass spectrometry. Biological half-lives were estimated using first-order kinetics model.

The investigated population was exposed to six PFAS at levels associated with potential health risks, with 95% of them having total PFAS concentrations exceeding 20 ng/mL in 2023. Serum PFOS, PFHxS and PFOA levels decreased from 2000 to 2023 (p < 0.05 by paired t-test). The estimated half-lives for PFOS, PFHxS, and PFOA were 3.9 years (95% CI: 3.4–4.6), 5.7 years (95% CI: 4.6–7.5), and 8.0 years (95% CI: 6.0–10.0), respectively. After subtraction of background values in Japan, the estimated half-lives were 2.7 years (95% CI: 2.3–3.4) for PFOS, 5.6 years (95% CI: 4.5–7.4) for PFHxS, and 5.1 years (95% CI: 4.1–6.8) for PFOA.

This study demonstrates participants had still higher serum PFAS levels and these PFAS elimination half-lives in the investigated Japanese population are at years order.

The online version contains supplementary material available at https://doi.org/10.1265/ehpm.25-00330.