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Enhanced Leaching of Plasticizers from Polyvinyl Chloride Plastics Weathered by Simulated Solar Light
Summary
A weathering study of plasticized PVC microplastics found that solar photo-aging dramatically accelerated the leaching of phthalate and non-phthalate plasticizers compared to thermal aging alone, with plasticizer half-lives dropping from decades to less than a year after 18 years of simulated aging. This demonstrates that environmental weathering of PVC dramatically increases the release of potentially endocrine-disrupting chemicals into water, compounding the hazards of microplastic pollution beyond the particles themselves.
Plasticized polyvinyl chloride (PVC), widely used in various applications, contains plasticizers that can pose environmental risks when leached into ecosystems. This study examines the effects of weathering (viz. thermal and photo-aging) on the leaching kinetics of phthalates and non-phthalate plasticizers, along with physical and chemical changes of PVC microplastics (MPs) by weathering. The PVC mass and plasticizer concentrations are significantly decreased, and light induced photo-aging process shows greater decrease compared to thermal-aging under heat. The desorption rate constants (kd) of di(2-ethylhexyl) terephthalate (DEHT) and diisononyl phthalate (DINP) increased with PVC aging time, which ranged from 3.2 × 10–3 to 1.8 year⁻1 (DEHT) and 1.1 × 10–2 to 3.7 year⁻1 (DINP) across both PVC types and aging process (kd: heat < light). The initial half-lives decreased within 18-year aging period under both exposures as; DEHT: from 26 to 0.4 year (cPVC-1), 217 to 54–72 year (cPVC-2); and DINP: 66 to 0.6–1.1 year (cPVC-1), 3.1 to 0.2–0.3 year (cPVC-2). Moreover, the logarithm of PVC-water partition constant (log KPVCw) was decreased as; DEHT: 7.2 to 5.7–5.9 (cPVC-1), 8.4 to 7.8 (cPVC-2); and DINP: 7.9 to 5.9–6.2 (cPVC-1), 6.8 to 5.4–5.6 (cPVC-2), suggesting enhanced hydrophilicity under both weathering process. Besides, the surface characterization shows that aging leads to significant changes in thermal properties and PVC structure, including a reduction in thermal stability and notable alterations in surface morphology. The findings of this kinetic study highlight that aging accelerates the plasticizer release, which increases the ecotoxicological risks of PVC MPs and emphasizes the importance of considering aging in assessments of microplastic pollution and environmental impacts.