Photoaging accelerates volatile organic compound emissions from microplastics in air and water: Mechanism insights and environmental-health implication.

Volatile organic compounds (VOCs) emitted from aging plastics represent an emerging source of atmospheric reactivity and human exposure, yet their emission dynamic across different environmental media remain poorly understood. This study investigates the impact of photoaging on VOC emissions from polystyrene microplastic (PS MPs) to elucidate their degradation mechanisms and environmental implications. PS MPs were exposed to 365-nm UV irradiation for 60 days in air, pure water, and synthetic seawater. VOC emissions were quantified using headspace solid-phase microextraction coupled with GC-MS (HS-SPME/GC-MS), while surface physicochemical changes were characterized by ATR-FTIR, XPS, and SEM. UV exposure markedly enhanced emissions and shifted the chemical profile from styrene-dominated aromatics toward oxygenated products like alcohols, ketones, and acids. In air, the total VOC signal increased 2.66-fold over 60 days. Notably, aqueous media (pure water and seawater) accelerated PS degradation, with benzene accumulation reaching 27910 ng g-1 in pure water - nearly triple the amount observed in air. Consequently, the ozone and secondary organic aerosols (SOA) formation potentials increased linearly with irradiation time, driven by the evolving VOC composition. Our findings reveal that photoaging transforms PS MPs into a persistent source of hazardous VOCs, including known carcinogens and endocrine disruptors. These results underscore that aging plastic debris contributes substantially to regional air pollution and poses long-term risks to human health, highlighting the need to integrate plastic-derived emissions into environmental risk assessments.