Evaluation of Heavy Metal Pollution in Commonly Consumed Mollusc (Crassostrea gasar) from Elechi Creek, River State, Nigeria and the Health Risk Implications

Marine biotas are used to assess potential adverse human health risks associated with consuming protein-rich aquatic organisms. Heavy metal content of Mangrove oysters (Crassostrea gasar) was evaluated between January and June 2022 in 3 stations. Six heavy metals (copper, cadmium, zinc, lead, arsenic and iron) were determined using standard methods. Target Hazard Quotient (THQ) and Hazard Index (HI) were used for the non-carcinogenic assessment while Target Cancer Risk (TR) was used for the carcinogenic assessment of the potential human health risk of consuming the oysters. The heavy metal values recorded were Cu (473.2 – 596.7 mg/kg), Cd (2.33 – 3.84 mg/kg), 209.02 – 246.41 mg/kg), Pb (6.16 – 12.07 mg/kg), As (0.012 – 0.016 mg/kg) and Fe (1609.0 – 1846.0 mg/kg). All the heavy metals were above the acceptable limits except arsenic. Stations 2 and 3 had relatively higher values; attributed to anthropogenic activities. The THQ and HI values were less than 1 in all the metals and stations while TR for Pb and arsenic were within the negligible range in all the stations. However, Cd was unacceptable among the children in station 2. Station 3 had relatively higher values while the children were more vulnerable to both non-carcinogenic and carcinogenic risks. In conclusion, the consumption of oysters from Elechi Creek is considered safe based on acceptable levels of the THQ, HI and TR; though Cd-TR for children (Station 2) was unacceptable.