Occurrence, polymer composition, and polymer-specific ecological and human health risks of microplastics in the Sundarbans mangrove ecosystem, Bangladesh: An integrated multi-compartment assessment.
Abstract
Microplastic (MP) pollution poses an increasing threat to mangrove dominated estuarine systems, yet comprehensive multi-compartment assessments remain limited in South Asia. However, comprehensive MP assessments linking sources, transport, and risks remain scarce in South Asian mangrove ecosystems. This study investigated the occurrence, characteristics, sources, and risks of MPs in surface water, sediment, fish, and shrimp from three brackish rivers (Pasur, Kholpetua, and Rai) and adjacent shellfish farms within the Sundarbans mangrove ecosystem, Bangladesh. MP concentrations ranged from 50 to 480 items/m3 in water and 58.55-269.25 items/kg in sediment, with the highest contamination consistently observed in the Pasur River, reflecting intense anthropogenic pressure near the Mongla port region. MPs were detected in all fish (100%) and 93% of shrimp samples, predominantly as fibers (>90%), with gills and gastrointestinal tracts (GIT) showing higher burdens than muscle tissues. Fourier-transform infrared spectroscopy (FT-IR) identified nylon, polypropylene (PP), polyethylene (PE), and polyvinyl chloride (PVC) as the dominant polymers, indicating inputs from fishing gear, textile waste, industrial effluents, and domestic discharge. Bioaccumulation analysis revealed species-specific differences, with Polynemus paradiseus exhibiting the highest accumulation potential. Ecological risk indices (PLI, PHI, and PRI) indicated moderate to high pollution risk at several sites, while estimated annual intake values suggested potential human exposure concerns, particularly for children. Overall, these findings provide a monsoon-season snapshot of MP contamination, offering baseline insights into its distribution, transport, and associated ecological and human health risks in the Sundarbans. As sampling was conducted over a short period, the results should not be considered annual baselines. Long-term seasonal monitoring, along with improved waste management and industrial regulation, is needed to assess temporal variability and establish reliable ecosystem baselines.