Untargeted Analysis of Plastic Additives in Organic and Aqueous Extracts of Road Marking Paint Microplastics for Screening of Leachable Toxicants

Abstract

Road marking paint represents a significant source of microplastic (MP) pollution in roadside environments, generated primarily through traffic abrasion. Additives such as plasticizers, pigments, and antioxidants can leach from these paint MPs into surrounding environments, potentially causing toxic effects on environmental organisms. This study conducted an untargeted analysis of organic and aqueous extracts from road marking paint MPs to assess their potential environmental risks. Two types of road marking paints were investigated: waterborne and room-temperature curing plastics, each prepared in yellow and white colors. Paint samples were applied to glass substrates, cured, and cryo-milled to produce microplastic samples. Organic-soluble additives were extracted in ethanol (1 h, vortex), while aqueous-soluble fractions were extracted in water (30 d, shaking). Both extracts were filtered and analyzed using GC-MS and LC-MS, with solid microplastics characterized by ATR-FTIR and ICP-MS. ATR-FTIR analysis confirmed all samples contained acrylic-based polymers, though room-temperature-curing paints exhibited stronger C=O stretching (~1720 cm⁻¹), indicating distinct polymer compositions. ICP-MS analysis revealed different metallic profiles between paint types: chromium concentrations were higher in room-temperature-curing paints, while manganese was more abundant in waterborne paints. Arsenic, lead, and zinc were detected at lower concentrations in waterborne paints, with metallic content showing minimal color dependence, suggesting metal sources extend beyond specific pigments. Features detected by GC-MS and LC-MS were tentatively identified using the NIST23 library and annotated for function and toxicity using the PlasticMAP database. Known plastic additives including plasticizers, antioxidants, and intermediate products were detected in paint extracts. Notable chemicals identified include the carcinogen o-anisidine and the endocrine disruptor dicyclohexyl phthalate. These findings demonstrate that additive leaching from road marking paint microplastics poses potential environmental risks, highlighting the need for improved paint formulations and environmental monitoring strategies.