Size-dependent pulmonary toxicity of inhaled micro- and nano-polystyrene and initial identification of microplastics in human lung cancer tissue

This study evaluated the carcinogenic potential of inhaled micro-polystyrene (mPS) and nano-polystyrene (nPS) using a murine exposure model. Repeated inhalation of environmentally relevant doses for up to 12 weeks resulted in marked pulmonary toxicity, most prominently in the mPS group. mPS exposure led to greater reductions in lung volume, impaired exercise capacity, and stronger induction of EGFR expression. Transcriptomic profiling further identified AREG and MAP3K13 as key mediators, indicating activation of EGFR-dependent MAPK signalling. Overall, these findings demonstrate that polystyrene (PS) particles exert size-dependent toxic effects, with mPS showing greater pathogenicity than nPS, and provide evidence linking airborne MP exposure to molecular pathways relevant to lung carcinogenesis.