Health risk assessment of heavy metals in Tympanotonum fuscatus along Mbo River, Cross River Estuary, South Eastern Nigeria

Abstract

Heavy metals are considered contaminants, and when present in aquatic environment, may lead to pollution of aquatic organisms through their toxic effects and bioaccumulation. Health risk associated with the consumption of contaminated sea food had become a global concern. The study was conducted to assess concentrations of heavy metals: lead (Pb), cadmium (Cd), chromium (Cr), copper (Cu) and Iron (Fe) in Tympanotonum fuscatus samples, as well as estimating the potential human health risk associated with the consumption of this fish obtained from Mbo Channel of the Cross River Estuary. The USEPA Guidelines for health risk based concentrations were employed for estimation of target hazard quotient (THQ), hazard index (HI) and target cancer risk (TCR). Water quality variables were also measured following standard protocols. Results showed significant differences (p < 0.05) in metal contamination indices in both water and fish samples. The principal component analysis (PCA) results showed that the total variance was 92.48%, and PC 1 was represented by Cd and Cr while PC 2 was dominated by Pb. The results for HI were: Cr (2.541 mg/kg), Cd (7.131 mg/kg), Pb (1.657 mg/kg), Cu (0.344 mg/kg) and Fe (0.193 mg/kg). The levels of Pb, Cd and Cr in fish fresh all exceeded the WHO permissible limit of 1.0 mg/kg. Although these metals have not been associated to toxicity, a potential adverse health risk may be associated with the consumption of T. fuscatus from the estuary. TCR values of the metals analyzed showed that Cr and Cd had high potential cancer risk while Pb had moderate risk factor in humans over 70 years of consumption. The health risk associated with accumulated metals in T. fuscatus underscores the need for periodic biomonitoring of the Cross River Estuary system.