Assessment of metal-associated health risk in different trophic levels in tropical estuary on the southeast coast of India

Abstract

Metal contamination in coastal and marine ecosystems has become a significant global concern due to its hazardous characteristics, environmental persistence, and ability to bioaccumulate in aquatic ecosystems. This poses a serious threat to the environment and the health of humans worldwide. To address these concerns, this study estimated the concentrations of metals in various trophic levels, including phytoplankton, zooplankton, bivalve, and fish. Monthly sampling was carried out in Pondicherry Fishing Harbor (PFH) and Pondicherry Open Sea (POS) between January 2017 and December 2018. The value of Cd, Pb, Cr, Co, Ni, Cu, Zn, and Mn in sediment at the PFH was considerably higher compared to the POS, indicating the impact of human activity there. The contamination factor (CF) for other metals was < 0.5, suggesting minor contamination in the Pondicherry coastal sediment, the CF value for Cd was higher at PFH. Comparably, the risk index (RI) at the PFH was likewise greater because of Cd, leading to an overall risk grade of "considerable" at the PFH whereas it was "low" at the POS. The marine pollution index (MPI) showed minimal values in fish regardless of the collection sites, which was calculated based on the values of all metals. The estimated daily intake, target hazard quotient, and hazard index assessed for potential human health risk suggest that the values were within acceptable thresholds for adults and children for fish consumption from POS. However, the direct consumption of bivalve for the long term poses significant non-carcinogenic health risks in both age groups, particularly in children, who are 1.31 times more susceptible than adults. These findings highlight the need to evaluate the presence of metals in the food chain to determine their transfer to the different trophic levels, which can help mitigate the associated risks for sustainable coastal ecosystem management.