Public health risk assessment and possible contamination with heavy metals in Saint Martin's Island, Bay of Bengal

• Heavy metals coming from different sources get mix with water and sediments of Saint Martin's Island, Bay of Bengal and eventually contaminate the fish as well as their parasites and other aquatic biota which become a public health concern. • Low to moderate contamination were detected in the Island water and sediment but the concentrations of Pb and Cr in the fish muscle were higher than the regulatory limits. • Nematode parasite had a better bio-accumulative tendency might be a good indicator of heavy metal pollution. The study examined heavy metal contamination in sediment, water, fish, and their parasites from Saint Martin's Island, Bay of Bengal, with an emphasis on bioaccumulation and associated human health hazards. We utilized various critical pollution indicators to assess ecological quality. Heavy metals (Pb, Fe, Cu, Co, Mn, Ni, Zn, Cr, and Cd) were analyzed in samples collected from five sites around the Island using atomic absorption spectrometry (AAS). Results revealed that the heavy metal concentrations in the water with the lowest mean values were Pb, Fe, Mn, Ni, Cu, and Co, with the mean Pb content exceeding the permissible levels. Copper and iron had a substantial positive correlation ( r = 0.910, p < 0.05). The concentrations in sediment were Fe > Zn > Cr > Pb > Cd, exhibiting elevated levels of Pb and Cr. Correlations were identified for Zn-Cr ( r = 0.935), Fe-Pb ( r = 0.938), and Cr-Cd ( r = 0.935) at p < 0.05, and for Zn-Cd ( r = 1.000, p < 0.01). The concentrations of heavy metals in fish and parasite muscle were observed Fe>Pb>Zn>Cr>Cd, and Fe>Zn>Pb>Cr>Cd, respectively, with Pb and Cr in fish muscle beyond regulatory limits. Health risk assessments revealed possible non-carcinogenic hazards from Pb, Fe, and Cr, as well as carcinogenic risks associated with Cr and Cd. The maximum bioaccumulation among the observed fishes was noted in Terapon jerboa . The nematode parasite Philometra cephalopholidis demonstrates a higher bioaccumulation tendency for Fe and Cd than fish. The research found that nematode infection is a reliable biomarker for heavy metal pollution.