Characterization and in silico toxicity assessment of polypropylene photodegradation leachates in a simulated marine environment.

Polypropylene (PP) is a major contributor to marine plastic pollution, where photodegradation under ultraviolet (UV) light leads to the formation of complex mixtures of low-molecular-weight compounds and leached additives. However, the chemical identity and toxicity of these leachates are still not well understood. In this study, PP was exposed to simulated solar UV irradiation in artificial seawater, and the resulting leachates were analyzed using liquid chromatography-high-resolution mass spectrometry (LC-HRMS) coupled with cyclic ion mobility-mass spectrometry (cIM-MS). To better reflect environmental conditions, PP rope, a material commonly used in the shipping industry, was also analyzed alongside the PP samples. The degradation patterns of both PP and PP rope were compared to identify whether similar degradation products are formed in both laboratory conditions and real-world marine environments. A total of 29 compounds were identified with Schymanski Level 2a confidence, using spectral matching and experimental collision cross-section (CCS) validation. Multipass cIM-MS allowed the resolution of isomeric species, which were further confirmed using theoretical CCS values. The high correlation between experimental and calculated CCS values provided strong evidence for confident structure assignment. In silico toxicity profiling via ProTox-II revealed multiple hazard classes, including acute toxicity, endocrine disruption, and aquatic toxicity. These findings underscore the importance of comprehensive chemical characterization coupled with in silico hazard screening to identify and prioritize compounds with potential hazardous properties among plastic leachates in marine systems.