Heavy metal contamination in coastal waters of the southeastern Bay of Bengal: Spatial distribution, potential source patterns, and human health risk assessment.

Abstract

This study assessed heavy metal contamination and ecological and human health implications in waters of mudskipper habitats along the southeastern Bay of Bengal coast, Bangladesh. Concentrations of Cu, Pb, Cd, Cr, Ni, Co, Mn, Zn, and Fe were quantified by atomic absorption spectrophotometry. Nickel had the highest concentration (0.33 mg/L), followed by Co (0.15 mg/L), Pb (0.09 mg/L), Mn (0.06 mg/L), Cd (0.04 mg/L), and Cu and Zn (0.03 mg/L), while Cr and Fe were below detection limits. Significant spatial variation (p < 0.05) indicated contamination linked to maritime activities, agricultural runoff, hatchery effluents, domestic waste, and coastal transport. Correlation, principal component, and cluster analyses revealed co-occurrence patterns consistent with mixed anthropogenic and natural influences. Cu, Pb, Cd, Ni, Co, and Zn were associated with localized human activities, whereas Mn, Fe, and Cr patterns may reflect geochemical inputs, low concentrations, or analytical non-detection. These findings indicate potential source patterns rather than definitive source apportionment. Human health risk assessment identified dermal absorption as the dominant exposure pathway, with children more susceptible than adults. Several hazard quotient and hazard index values exceeded the screening threshold (HI > 1.00), particularly for Cd, Ni, Co, and Mn, indicating possible non-carcinogenic concern. Carcinogenic risk was mainly associated with Cd, Ni, and Pb, although estimates were sensitive to exposure assumptions and cancer slope factors. Overall, the study provides baseline evidence for contamination in mudskipper-associated intertidal waters and supports integrated coastal monitoring programs for water, sediment, and biota along Bangladesh's southeastern coast.