Assessment of ecological and human health concerns associated with heavy metal poisoning in the sediments of Western St. Martin’s Island, Bangladesh

St. Martin’s Island (SMI) was designated an Ecologically Critical Area by the Bangladesh government in 1999 to preserve its biodiversity. Heavy metals (HMs) pollution is a critical environmental problem, driven primarily by anthropogenic activities, that causes various environmental impacts, including the contamination of marine resources. This study aimed to investigate the presence of HMs in marine sediments and evaluate the potential risks they pose to the marine environment and human health (adults and children). Atomic Absorption Spectrometry was used to assess the HMs in composite sediment samples collected from 12 sampling sites along the west coast of SMI. The average (±SD) HM concentrations (mg/kg) found, in descending order, were Mn (317.58±48.1) > Fe (168.42±35.46) > Zn (31.17±6.34) > Ni (24.17±6.41) > Cr (12.17±3.18) > Pb (6.52±1.03) > Cu (5.16±0.94). All detected HMs concentrations were below the allowable levels and considerably lower than those reported in other studies. The Risk Index (RI) results suggest that the marine ecosystem along the west coast of SMI did not surpass the low-moderate risk line (ranging from 0.23 to 6.18 with a mean of 4.68). Furthermore, the sediment quality indices used, including the contamination factor, geo-accumulation index, and pollution load index, indicated that metal contamination levels were within acceptable limits and did not adversely affect sediment quality. Human health risk assessment demonstrated that for each age group of the SMI population, the non-carcinogenic Hazard Index (HI) was significantly below the threshold limit (HI < 1), indicating low risk. In addition, the total carcinogenic risk was below the risk threshold range (10 -4 to 10 -6 ). Safeguarding the health of the SMI population and the integrity of the marine ecosystem will require HM monitoring and the execution of strict regulations to reduce HM pollution.