Impact of Seasonal PM(2.5) Exposure on Metabolic and Hormonal Profiles in Healthy Individuals and Individuals with Metabolic Syndrome in Chiang Mai, Thailand.

Exposure to fine particulate matter (PM(2.5)) is linked to metabolic dysfunction, yet evidence on its impact on hormonal regulation remains limited. This study examined seasonal changes in insulin, adiponectin, leptin, and HOMA-IR levels among healthy individuals and those with metabolic syndrome (MS) in Chiang Mai, Thailand. Fifty participants (25 healthy, 25 with MS) were assessed during high (February-April)- and low (May-July)-PM(2.5) seasons. Insulin levels increased in healthy individuals (mean: 9.3 to 14.9 µIU/mL; p = 0.051) and decreased in participants with MS (22.0 to 13.7 µIU/mL; p = 0.214), with a significant interaction effect (p = 0.020). Leptin increased significantly in both groups, but more markedly in the MS group (p < 0.001), also with a significant interaction (p < 0.001). HOMA-IR rose significantly in healthy individuals (p = 0.036) but not in participants with MS. Adiponectin remained stable across groups and seasons. At baseline, the MS group had significantly higher rates of diabetes (p = 0.050), hypertension (p = 0.001), and hyperlipidemia (p = 0.049). These findings suggest that PM(2.5) may influence metabolic and hormonal profiles, particularly in individuals with existing metabolic disorders.