Associations between physical exercise and serum per- and polyfluoroalkyl substances (PFAS) concentrations: findings from Korean National Environmental Health Survey Cycle 4 (2018–2020)

While physical activity is hypothesized to aid pollutant elimination, its effect on serum per- and polyfluoroalkyl substances (PFAS) remains controversial. We analyzed 2,993 adults from the Korean National Environmental Health Survey (KoNEHS) Cycle 4 (2018-2020). Exercise - defined as activity intense enough to induce sweating - was operationalized as binary status, weekly frequency, and total weekly volume (continuous and quintiles). Outcomes included five individual PFAS and their weight-based sum (ΣPFAS, primary) and molar sum. Survey-weighted linear regressions were fitted with and without adjustment for performance outdoor apparel use, a potential mediator. Exercisers had significantly higher serum PFAS than non-exercisers. A significant negative quadratic term indicated an inverted U-shaped association, with sex-specific patterns: men showed a pronounced inverted U-shape, while women showed a linear positive trend. This suggests a shifting balance between exposure-increasing processes (e.g. internal mobilization, environmental uptake) at lower-to-moderate levels and elimination-related processes at higher levels. Adjustment for outdoor apparel modestly attenuated effect sizes without altering overall trends, suggesting a partial but not predominant mediating role. Notably, even at the highest activity levels, serum PFAS were not significantly lower than in non-exercisers, providing no evidence that exercise reduces PFAS body burden and challenging the detoxification hypothesis.