Assessment of Heavy Metal Concentration in Gills, Muscles, Liver and Gonads of Chrysichthys Nigrodigitatus Reaped from Great Kwa River, and the Potential Human Health Risk.

ABSTRACT This study was carried out to examine the concentration of some selected heavy metals in four organs (gills, gonads, liver, muscles) of Chrysichthys nigrodigitatus collected from the Great Kwa River, Calabar, Nigeria. And to also evaluate the potential human health hazard due to the consumption of C. nigrodigitatus reaped from the river. Six (6) heavy metals viz; Lead (Pb), mercury (Hg), cadmium (Cd), arsenic (As), chromium (Cr), zinc (Zn) was analysed using atomic absorption spectrophotometer (AAS). The accumulation levels of the heavy metals differed between the different organs. The results showed that Mean concentrations of lead in the muscles, liver, gills, gonads (sperm) and gonads (ovary) of C. nigrodigitatus across the different sampling stations ranged between 0.050±0.022 mg/kg to 0.242±0.027 mg/kg. The difference in lead content of the C. nigrodigitatus organs was significant (ANOVA, p ≤ 0.05) and displayed the trend: gills > liver = muscles > gonads (sperm) = gonads (ovary). Cadmium and mercury concentrations were not detected in the organs while Arsenic was only detected in the liver and gills of C.nigrodigitatus with mean concentrations of 0.333±0.578 and 0.167±0.289 respectively. The difference in arsenic concentrations between the gills and liver was statistically significant at 95% confidence levels. Mean concentrations of zinc in the muscles, liver, gills, gonads (sperm) and gonads (ovary) of C. nigrodigitatus across the different sampling stations were 1.673±0.019 mg/kg, 3.176±0.804 mg/kg, 2.378±0.543 mg/kg, 0.721±0.052 mg/kg and 3.915±0.0116 mg/kg respectively. The lowest concentration of lead (0.661 mg/kg) was recorded in the gonads (sperm) and the highest concentration (3.998 mg/kg) in the gonads (ovary). The difference in lead content of the C. nigrodigitatus tissues was significant (ANOVA, p ≤ 0.05) and displayed the trend: gonads (ovary) > liver > gills > muscles > gonads (sperm). The Recommended Daily Intake (RDI) and the Tolerable Upper Intake Level (UL) were compared to determine the safe levels of lead, cadmium, mercury, Zinc and arsenic that can be obtained from the consumption of C. nigrodigitatus sampled from the river. With the exception of zinc, all of the metals' average EDIs were found to be below the suggested daily consumption threshold. There is no harm to humans from Pb and Cr intake by ingestion of C. nigrodigitatus from Great Kwa River, as indicated by the average estimated daily intake values being below the tolerated upper intake range. However, the average EDI for zinc was higher than the lower limit, indicating a potential danger of zinc poisoning. For every metal in the research, the average Target Hazard Quotient (THQ) was less than 1.00. Hazard index in this study was found to be less than unity. Findings suggests that there is little risk of cancer from lead, arsenic, and cadmium in C. nigrodigitatus, therefore continuous monitoring of these metals in the study area is necessary and advocated to ensure the good quality of the aquatic environment. Keywords: Heavy metal, pollution, C. nigrodigitatus, bioaccumulation, organs.