Plastic button manufacturing as an under-recognized source of airborne multi-pollutant mixtures: process-resolved...

This study presents a process-resolved airborne characterization of a plastic button manufacturing facility using an unsaturated polyester resin, integrating particle size distributions, volatile organic compounds (VOCs), metals, inorganic anions, phthalates, and per- and polyfluoroalkyl substances (PFAS). Particle number concentrations (10 nm-10 μm) exhibited unit-dependent submicron maxima, reaching 1.10 × 10⁵ particles·cm^-3 in electroplating operations, indicating localized aerosol generation. Emissions displayed clear compositional differentiation across operational domains: styrene was a dominant VOC, with the highest concentration in Plating (Glossy)_1 (1,506 µg·m^-3), while wet-chemical lines showed elevated inorganic burdens, including total Cr (526 µg·m^-3) and SO₄^2- (4,932 µg·m^-3). Among semi-volatile organics, di(2-ethylhexyl) phthalate (DEHP) reached a maximum concentration of 2.67 µg·m^-3, while PFAS detections were confined to wet-chemical operations, with PFOA and PFOS reaching approximately 0.18 µg·m^-3. Principal component analysis resolved solvent-driven, mechanically associated, and wet-chemical emission domains. Risk assessment identified Mn as the principal contributor to the nervous-system HI (Mn, styrene, toluene, xylenes, and n-hexane), whereas F^- determined the skeletal HI. The nervous-system and skeletal HIs reached maxima of 1.17 × 10³ and 2.26 × 10², respectively, while benzene-driven carcinogenic risk peaked at 6.87 × 10^-5, below the 10^-4 benchmark. Plastic button manufacturing is thus characterized as a multi-source emission environment structured by discrete unit operations along the production line, with styrene, transition metals, inorganic anions, and semi-volatile additives serving as principal exposure determinants. These findings establish a quantitative framework for occupational exposure prioritization in plastic button manufacturing systems.