Temporal decline in serum PFAS concentrations among metropolitan firefighters: Longitudinal study on post-exposure changes following PFAS foam cessation.

Firefighters are at a high risk of exposure to per- and polyfluoroalkyl substances (PFAS) due to their frequent use of PFAS-containing foams in training and emergency situations. This longitudinal study aimed to investigate the changes in serum PFAS levels among firefighters following cessation of their exposure to PFAS-containing foams. The study involved 130 firefighters from the South Australian Metropolitan Fire Services (SAMFS), and serum samples were collected at two time points: baseline in 2018-19 and follow-up in 2021-22. Along with the collection of samples, a survey questionnaire was administered to gather information on firefighters' employment and demographic characteristics. Regression models were employed to assess the association between these factors and the outcome variable (annual percentage change in serum PFAS concentration). The results indicated a decline in serum PFAS concentrations over time, with the main contaminants being perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonate (PFHxS), and perfluorooctanoic acid (PFOA). The median and Interquartile Range (IQR) of total PFAS (∑PFAS) concentration reduced from 21.5 ng/ml (IQR: 11 to 53 ng/ml) at baseline to 15 ng/ml (IQR: 8 to 33 ng/ml) at follow-up. On average, there was an annual reduction of 13%, 7%, and 4.4% in serum concentrations of PFOS, PFHxS, and PFOA, respectively. Firefighters under the age of 55, those who used PFAS in the past ten years, or those who had little to no frequency of PFAS exposure in their previous employment, encountered a significantly higher annual percentage reduction (P < 0.05) in both ∑PFAS and PFOS concentrations. None of the independent variables analysed could significantly predict the annual percentage change in PFOA and PFHxS. This study provides evidence for a declining temporal trend in serum PFAS concentrations among metropolitan firefighters following workplace interventions that involved the removal of PFAS-containing foams.