Polymer- and size-dependent toxicological behavior of environmentally relevant secondary microplastics: a...

Microplastics (MPs) generated from commonly used consumer polymers are increasingly recognized as emerging contaminants of toxicological concern. Despite growing evidence, a consolidated understanding of how polymer identity and particle size influence the biological behavior and systemic effects of environmentally relevant secondary MPs remains limited. This review summarizes recent in-vivo evidence using fragmented MPs derived from five major polymers-polyethylene (PE), polytetrafluoroethylene (PTFE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET). Across studies, smaller particles exhibit greater tendencies for systemic distribution, epithelial barrier disruption, and immune activation compared with larger fragments. Comparative evaluation of biodistribution, histopathology, and physicochemical characteristics highlights consistent polymer- and size-dependent patterns, with PE, PS, and PET showing higher translocation potential, while PTFE and PP often display limited retention. By integrating findings from these in-vivo evaluations, this review provides a clearer understanding of the mechanistic factors governing MP toxicity and identifies key gaps related to exposure duration, environmentally aged particles, and analytical limitations. These insights contribute to establishing polymer-specific and size-resolved perspectives necessary for future microplastic risk assessment.

The online version contains supplementary material available at 10.1007/s43188-025-00331-x.