Occupational predictors of serum per- and polyfluoroalkyl substance concentrations in a national biomonitoring survey of adults in Canada

Background Per- and polyfluoroalkyl substances (PFAS) are a class of chemicals widely used in industrial applications and consumer products, which have been associated with negative health outcomes, including cancer. Comprehensive identification of highly exposed occupations is needed. Objective We aim to examine serum PFAS concentrations across occupation and industry of employment and other exposure determinants in a national sample of adults in the cross-sectional Canadian Health Measures Survey (CHMS). Methods Serum concentrations of six PFAS compounds (perfluorooctanoic acid [PFOA], perfluorooctane sulfonate [PFOS], perfluorohexane sulfonate [PFHxS], perfluorononanoic acid [PFNA], perfluorodecanoic acid [PFDA], and perfluoroundecanoic acid [PFUnA]) were measured in a total of 5956 participants (ages 20–79 years) from four cycles of the CHMS (2007–2019). Multivariable linear regression models were used to predict geometric means (GM), adjusted for demographic, dietary, and environmental determinants. Adjusted geometric mean ratios (GMR) and 95% confidence intervals (CIs) for each exposure determinant vs. its reference group, and each of the 152 occupation or industry groups vs. all other participants, were estimated overall and by sex. Results PFAS concentrations declined substantially over time and were elevated among participants who were older, male, or East/Southeast Asian. GMRs for various PFAS were elevated in healthcare, assembly manufacturing, and agriculture occupations. Overall, laborers in manufacturing had 21-25% higher GM serum concentrations of PFOA, PFOS, and PFHxS, while those employed in the clothing manufacturing industry had two-fold higher PFOS (GMR = 2.39, 95%CI: 1.53–3.73) and PFHxS (2.12, 1.18–3.82). Females in front-line public protection had elevated PFOA (1.56, 0.99–2.46), and females in industrial, electrical and construction trades had 87% higher PFHxS. Significance PFAS exposure was elevated in several occupations and industries with known or plausible sources of occupational exposure, with some important differences by sex. Further targeted assessment is needed to identify and mitigate exposure in highly exposed groups. Impact statement This Canadian cohort analysis advances the understanding of occupational exposure to PFAS by identifying several novel occupational groups with validated elevated serum PFAS concentrations, including healthcare; construction trades; laborers and assemblers in manufacturing; clothing manufacturing; and electrical manufacturing, alongside more established groups such as chemical manufacturing and front-line protection. Among females, a historically understudied group, elevated levels were observed among front-line protection; construction trades; manufacturing supervisors and operators; and specialty trade contractors. To our knowledge, this is the first population-based study to investigate sex-stratified PFAS biomarker concentrations among adults employed in a wide range of occupations and industries.