Abstract:
Aquatic foods (e.g., fish food) is among the priority concern as the pathway through which
humans exposed to considerable amount of trace heavy metals and become vulnerable to the
metals caused human health risks. Nine heavy metals including Fe, Pb, Zn, Cd, Cu, Cr, Mn Ni,
and Co were quantified in different organs of fish (gill, muscle and liver) of fish species (C.
carpio) collected from Gafarsa Reservoir, Oromia, Ethiopia. The levels of these heavy metals
were quantified by flame atomic absorption spectrometry after preparing the samples using wet
digestion method. The fish organs were digested, each of the powder samples was then
transferred into a digestion flask where a mixture with HNO3 (65%) and hydrogen peroxide
(30%), prepared in a 3:1 (v/v) ratio was added and also HClO4 in polypropylene vial. Hazard
quotient (HQ) was calculated to assess risk of the metals to the consumer's health. The mean
concentrations measured were 5.95±0.581-40.43±1.778, 2.25±0.687-5.05±0.229, 54.45±3.33-
131.33±5.121, 5.51±0.115-7.00±0.953, 7.93±0.840-18.46±2.814, 4.78±1.674-19.23±12.07,
10.40±1.19-46.90±0.687, 17.75±0.912-55.53±6.915 and 7.46±0.490-18.33±0.981 mg/kg for Fe,
Pb, Zn, Cd, Cu, Cr, Mn, Ni, and Co, respectively. The concentration levels of the studied heavy
metals generally the highest in the liver followed by gill, but in muscle the lowest mean values of
the metals were observed. In all samples the concentration of heavy metals compared to
available quality guideline value is higher than permissible limit. THQ of all metals were below
1, except cobalt these results indicated that Co can pose non-carcinogenic human health risk. The
carcinogenic risk associated with fish consumption by human was also assessed. The elevated
value of target cancer risk (TCR) for Pb (5.9×10−4), Cd (6.2×10−2) Cr (7.03× 10−2) and Ni
(8.8×10−2) were higher than the acceptable risk limit (1×10−6) indicated that the inhabitants
consuming the fish from Gafarsa Reservior were exposed to Pb, Cd, Cr, and Ni pollution with a
lifetime carcinogenic risk. The result of one-way ANOVA analysis each fish sample showed that
there are statistically significant differences (p˂0.05) in their heavy metal concentration. Since
HQ values was more than one in all organs, therefore there are health effect on humans
