Micro(nano)plastics as an Emerging Skeletal Toxicant in Aquatic Organisms: Evidence and Mechanisms

Micro(nano)plastics (MNPs) are emerging contaminants, but their skeletal toxicity in aquatic organisms remains poorly understood. This review synthesizes evidence on MNP sources, distribution, and exposure pathways relevant to skeletal tissues. Because direct detection of MNPs in aquatic skeletal tissues is scarce, mechanistic insights from mammalian models are also examined to identify conserved pathways. Current evidence indicates that MNPs impair skeletal homeostasis through oxidative stress, inflammatory and immune dysregulation, autophagy disturbance, and disrupted osteogenic differentiation, causing skeletal deformities, impaired mineralization, and exoskeletal damage in fish, bivalves, and crustaceans. MNPs may also carry coexisting pollutants, amplifying combined toxicity. This review identifies skeletal toxicity as an underexplored but biologically significant hazard. Key gaps include limited direct evidence of MNP accumulation in aquatic skeletal tissues, poor dose–response understanding, and insufficient mechanistic insight into combined pollutant toxicity. Future research should prioritize environmentally relevant exposure models, mechanistic validation, and field studies linking MNP pollution to skeletal disease risk in aquatic organisms.