Quantification, characterization and risk assessment of microplastics and mesoplastics in aquafarms of a leading fish-producing nation

Plastic contamination in aquaculture farms remains underexplored, with most studies focusing on microplastics while overlooking mesoplastics. This gap may lead to an underestimation of total plastic contamiantion and its associated ecological risks. This study evaluated contamination status, characteristics, and potential risks of plastic particles (micro and meso) in water, sediment, and fish samples from different aquaculture farms of Northern Bangladesh. Plastic (micro and meso) contamination levels in farm waters ranged from 5.6 ± 4 to 20 ± 0.6 items/L, in sediments from 67 ± 2 to 307 ± 1 items/kg dry weight, and in fish gastrointestinal tracts (GIT) from 8 ± 0.8 to 16 ± 2 items/g. Among fish species, Clarias batrachus exhibited the highest accumulation, followed by Ompok pabda and Mystus cavasius . The contamination levels in the fish GIT were 4–5 times higher than in muscle tissues across all species. Over 80% of ingested plastic particles were fibers, with >30% violet-colored and > 75% measuring <0.5 mm in size. Polyamide (30%) and polyethylene (25%) were the predominant polymers, likely originating from fishing activities and packaging materials. Risk assessments using the Polymer Hazard Index indicated hazard levels ranging from Grade I (<1) to Grade IV (100–1000). Contamination Factor values between 1 and 5, along with Pollution Load Index values > 1, signified low to moderate pollution levels. These findings emphasized the necessity of incorporating mesoplastics into regulatory frameworks to ensure comprehensive risk assessments and effective mitigation strategies. • Plastic (micro and meso) contamination levels varied from 5.6 ± 4–20 ± 0.6 items/L in water, 67 ± 2–307 ± 1 items/kg in sediment, and (8 ± 0.8–16 ± 2 items/g in fish gut. • Fibers (>80%) dominated, mainly violet (>30%) and <0.5 mm (>75%) in size. • Polyamide and polyethylene were dominant polymers. • Polymeric hazard score demonstrated low to medium risk of plastic particles. • Contamination factor and pollution load index indicated significant pollution.