Insights into the physical fragmentation of plastics into airborne microplastics

Understanding how plastics break down in the airborne environment is essential for improving the assessment of exposure levels and health risks to humans. Fragmentation is one of the processes that plastics undergo when exposed to environmental conditions. Earlier studies focused on identifying the occurrence, sources, fate, sampling methods, analysis, and health impacts of microplastics. However, this review examines the dynamics and mechanisms of plastic fragmentation into microplastics. In particular, the release of inhalable particles <10 μm and gaseous additives is discussed, as this affects exposure via the airborne route. We consider mechanical abrasion, impact friction, thermal degradation, UV-induced weathering, chemical reactions, and macrofaunal interaction, which play essential roles in the fragmentation process. We identified 28 relevant studies. Of these, 23 were conducted in the laboratory and five in real-world environments, indicating the limited literature on the mechanism of plastic fragmentation into airborne microplastics. Given the increasing global use of plastics, airborne environments remain a potentially critical area for research. This review highlights the need to thoroughly understand the processes governing plastic fragmentation in the airborne phase, the resulting particle size distributions, and the implications for human exposure to microplastics and associated additives through inhalation.