Effects of Atmospheric Photochemical Aging on Chemical Characteristics and Toxicity of PM _2.5 Emissions from Forest Vegetation Combustion

Frequent forest fires emit substantial amounts of PM_2.5, exacerbating air pollution and endangering public health. However, the chemical composition and toxicity evolution of forest fire PM_2.5 during atmospheric aging remains uncertain. This study investigated the chemical composition and toxicity on BEAS-2B cells of PM_2.5 emitted from forest vegetation combustion under different atmospheric aging times (fresh, 2, 5, and 15 days) and explored the intervention of astaxanthin on the toxicity of PM_2.5. Photochemical aging promoted the formation of secondary organic matter, NO₃^-, SO₄^2- and NH₄⁺, and the increase of acidic ions accelerated the dissolution of heavy metal elements in the particle phase. The concentration and toxic potency of PAHs and their derivatives declined with aging due to photo-oxidation. Oxidative stress induced by oxidative potential is a key factor in PM_2.5-induced cytotoxicity and genotoxicity. Variations in toxicity among vegetation types and aging times highlight the complexity of PM_2.5 composition and its health impacts. Importantly, this study demonstrates that astaxanthin, a natural antioxidant, effectively mitigates PM_2.5-induced toxicity, providing a promising therapeutic strategy. These findings underscore the urgent need for enhanced forest fire management, air quality interventions, and the development of targeted mitigation strategies to minimize the adverse health and environmental effects of forest fire PM_2.5.