Diet, lifestyle, and sociodemographic influences on serum concentration of PFASs: Insights from human biomonitoring in Switzerland.

Per- and polyfluoroalkyl substances (PFASs) are synthetic pollutants with documented health risks, yet identifying the most relevant paths for human exposure remains a challenge. We measured serum concentrations of 30 PFASs in a representative sample of 630 Swiss adults and linked them to 36 sociodemographic, dietary, lifestyle, environmental, and occupational variables. We applied clustering methods to define PFAS profiles, and used Bayesian regression to quantify associations with PFAS profiles and individual compounds. Variable importance was assessed with Bayesian Additive Regression Trees, and selected pathways were examined by mediation analysis. Fourteen PFASs were detected in at least five participants, including PFOS, PFOA and PFHxS in 100%, and PFNA, PFDA, PFHpS and PFUnDA in more than 50%. PFAS profiles clustered into three ordered groups: "low" (30%), "intermediate" (37%), and "high" (33%). Age and male sex were the strongest determinants of PFAS levels (adjusted odds ratio for "high" vs "low" cluster: 2.9 per 10 years of age [95% credible interval: 2.4 to 3.7]; 14.3 for males compared to females [8.3 to 25.3]). Diet was a key driver: plant-based and dairy-focused were linked to lower PFAS serum concentrations, whereas western diet (meat-focused) was linked to higher. Fish consumption, especially of salmon and local freshwater fish, was positively associated with overall PFAS levels and with several individual substances including PFUnDA. Alcohol consumption and use of ski wax or impregnation sprays were also associated with higher PFAS levels. Mediation analyses suggested that regional differences were largely explained by diet, particularly fish consumption. These findings provide a comprehensive understanding of the multifactorial determinants of PFAS exposure in a European adult population. Effective mitigation will require coordinated strategies considering both individual behaviors and broader environmental and regulatory interventions.