Distribution, Bioaccumulation and Human Health Risk of Mercury and Cadmium in Coastal Sediments and Oysters along the...

Coastal ecosystems are vital for biodiversity and livelihoods. However, increasing anthropogenic pollution has deteriorated quality and health of these important ecosystems. This study investigates the concentrations, spatial distributions, ecological, and consumer health risks of Cadmium (Cd) and Mercury (Hg) in surface sediments and oyster Saccostrea cucullata, collected from coastal locations along the Goa coast, India. Average concentration of Cd and Hg in sediment samples was measured as 0.16 ± 0.04 mg kg^- 1 and 0.005 ± 0.004 mg kg^- 1 (dry wt.), respectively. In oyster, the mean concentration of Cd and Hg was 3.37 ± 0.66 mg kg^- 1 and 0.071 ± 0.005 mg kg^- 1 (dry wt.), respectively. Sediment analysis revealed that Cd concentrations were generally low and below established sediment quality guideline thresholds; however, high bioaccumulation was observed in Saccostrea cucullata, with concentrations exceeding the permissible limit at most sampling sites. In contrast, Hg concentrations remained below sediment quality guideline values and seafood safety thresholds across all locations. Geochemical indices (CF, Igeo, and EF) identified localized Cd enrichment, particularly at Baga, while Hg showed negligible contamination. Consumer health risk assessment indicated that Cd was the major contributor to elevated THQ and HI values, highlighting Cd-driven consumer health concerns associated with oyster consumption. Overall, the findings suggest that cadmium represents the primary environmental and public health concern along the Goa coast, whereas mercury currently poses comparatively low ecological and human health risks.