Polystyrene-associated pulmonary fibrosis: a summary based on the available evidence and prospects.

Microplastics have become a pervasive component of the atmosphere and of indoor and occupational air, and the human respiratory tract is now recognized as a major and largely unavoidable route of exposure. Polystyrene, one of the most abundant commodity plastics, is a dominant model and real-world airborne microplastic, and mounting evidence links inhaled polystyrene microplastics (PS-MPs) to a spectrum of pulmonary injuries that increasingly implicate fibrogenesis. This review synthesizes the current mechanistic understanding of how PS-MPs may contribute to pulmonary fibrosis, drawing primarily on preclinical experimental evidence. We first outline the sources, physicochemical determinants and respiratory deposition behavior of airborne PS-MPs, and summarize the human, epidemiological and experimental evidence for pulmonary accumulation and harm. On the basis of converging but heterogeneous evidence we propose, as a working model rather than a validated cascade, that these upstream disruptions converge on a shared profibrotic signaling hub - coupled Wnt/