Health Symptoms Related to Polycyclic Aromatic Hydrocarbon (PAH) Exposure in Chiang Mai, Thailand: Associations with Biomarkers of Exposure and Oxidative Stress.

Northern Thailand experiences seasonal surges in PM₂.₅ pollution, posing significant respiratory health risks. This cross-sectional study aimed to evaluate associations between PAHs exposure and early health biomarkers. In April 2024, 127 rural residents in Chiang Mai were recruited during a high-exposure period (mean monthly PM_2.5 = 41.7 μg/m³). Participants reporting eye irritation and pneumonia showed significantly higher 8-iso-PGF₂α levels (p = 0.010 and 0.012, respectively). Smokers exhibited elevated CC16 levels (130.0 ± 65.3 ng/mL) compared to non-smokers (96.3 ± 39.9 ng/mL, p < 0.05). CC16 was also significantly associated with self-reported symptoms, including fatigue, poor sleep quality, and activity limitation. For example, participants who reported difficulty performing daily activities (i.e., disagreed with the statement "I can do things at home without any restrictions") had significantly higher CC16 levels (108 ± 47 ng/mL) than those without such limitations (74 ± 35 ng/mL; p < 0.001). A weak but significant positive correlation was observed between respiratory rate and CC16 (R² = 0.334, p = 0.001). Interestingly, serum 8-iso-PGF₂α was inversely associated with diabetes (OR = 0.965; 95% CI: 0.935-0.997; p = 0.033), potentially indicating a compensatory or phenotype-specific oxidative stress response. In addition, CC16 levels were positively associated with diabetes (p = 0.022), suggesting altered epithelial responses in individuals with metabolic disease. CC16 and 8-iso-PGF₂α demonstrated significant associations with respiratory symptoms and metabolic status, suggesting their potential as early indicators for environmental health surveillance in haze-affected populations.