Toxicity and Human Health Risk Assessment of Heavy Metals in the sediments of the Korle Lagoon Using Fish Bioassay

Abstract

This study evaluated the toxicity of sediments from the Korle Lagoon, a heavily polluted water body, by assessing the bioaccumulation of heavy metals in Sarotherodon galilaeus through a 10-day fish bioassay. Sediment heavy metal concentrations were analyzed using USEPA Method 3050B, while heavy metals in fish tissues were assessed before and after exposure using USEPA Method 200.11. The results revealed an alarming mortality rate of 90–100% in fish exposed to the sediments, compared to only 10% in the control group. This high mortality correlated with elevated heavy metal concentrations in the sediments. The geoaccumulation index of heavy metals in sediments showed that the Korle Lagoon is moderately polluted with Cd (0-1.85), Pb (0.37-1.56) and Zn (1.14); moderately to strongly polluted with As (0.03-2.88); and extremely polluted with Fe (9.90-13.10). Post-exposure analysis showed significant accumulation of heavy metals in fish tissues, with recorded concentrations of Cu (103.75 mg/kg), Cd (0.31 mg/kg), As (13.95 mg/kg), Cr (16.02 mg/kg), Ni (7.97 mg/kg), Pb (5.83 mg/kg), and Hg (0.72 mg/kg). Most values exceeded WHO guideline limits, except for Ni and Cd. The estimated hazard index values for adults (328.52) and children (191.63) suggest a severe risk of non-carcinogenic health effects from consuming exposed fish. Additionally, lifetime cancer risk values (LCR > 0.0006) indicated potential carcinogenic threats. These findings confirm the toxicity of Korle Lagoon sediments and highlight significant ecological and public health risks, particularly for local communities dependent on fish from the lagoon as a dietary staple. Urgent mitigation measures are necessary to address heavy metal contamination and protect aquatic and human health.