Occurrence and human health risks of microplastics in the Bay of Bengal using Perna viridis as sentinel species

• Microplastics (MPs) were detected in water, sediment, and tissues of the green mussel ( Perna viridis ) across five coastal sites in the Bay of Bengal. • The digestive gland of P. viridis exhibited the highest MP burden (up to 4.9 ± 2.69 MPs g⁻¹). • Filament-shaped MPs predominated, with LDPE and PP as the dominant polymers. • Histological analysis revealed necrosis, inflammation, and tissue damage in P. viridis. Microplastics (MPs) pollution is an increasing threat to marine environments, particularly in vulnerable areas such as the Bay of Bengal (BoB). This study assessed MP distribution and biological impacts in surface water, sediment, and Perna viridis tissues across five coastal stations in the BoB. MPs were isolated through density separation, digestion, and morphological analysis under stereomicroscopy, followed by polymer analysis using FTIR. MPs were detected in all environmental matrices and mussel tissues at every site. Surface water MPs ranged from 3.13 ± 0.46 to 8.94 ± 0.55 items/L, while sediment concentrations varied between 152 ± 54.32 and 540 ± 82.73 items/kg dry weight. Mussel tissues contained 2.4 ± 1.43 to 4.9 ± 2.69 items/g wet weight, with the digestive gland showing significantly higher accumulation than gills, visceral mass, and muscle (p < 0.001). Fibre-type MPs dominated all matrices. Particles <0.5 mm were most abundant in surface water, while particles 1–5 mm were most abundant in mussel tissues; both size classes were common in sediments. Polypropylene and low-density polyethene were the dominant polymers. Histological analysis revealed tissue damage and immune responses in mussels due to physiological stress. Multivariate analyses indicated site-specific MP profiles associated with local anthropogenic activities. Health risk assessment showed higher chronic daily intake and carcinogenic risk in children than adults, with polypropylene and polyvinyl chloride exceeding acceptable carcinogenic risk thresholds. These results emphasise the importance of ongoing monitoring and enhanced waste management strategies to safeguard coastal ecosystems and ensure the safety of seafood in the BoB.