Pesticide Residues in Fish - Pesticides: Evaluation of Environmental Pollution - page 373

were attributed to the long exposure period. At this collection site, the dieldrin level in
fish varied from 18.8 to 40.3 ng/g. At Jalan Bharu, the range for dieldrin was even greater
(8.0-63.8 ng/g). Numerous factors contribute to this variability, but spot application of
pesticide may be the most important one. It is therefore important to examine many sub-
samples from each site in environmental surveys. The average daily intake of pesticide
residues was calculated from these data, assuming an average body weight of 60 kg for the
consumer. The highest observed daily intakes were as follows: aldrin/dieldrin, 44.4 ng/kg
of body weight; chlordane, 55.0 ng/kg of body weight; HCH, β-isomer, 15.6 ng/kg of body
weight and γ-isomer, 8.4 ng/kg of body weight; and DDT, 21.8 ng/kg of body weight. These
findings were compared with the acceptable daily intake (ADI) values recommended for
these compounds by FAO/WHO. This showed that all the observed daily intakes of pes-
ticide residues were below the FAO/WHO ADIs. In fact, the aldrin and dieldrin levels
approach the ADI (0.1 ng/kg of body weight) only if the highest observed concentration in
fish (24.9 ng/g) is multiplied by the highest consumption rate of 205 g/day.
One hundred samples of fish from Karadj and Latian Lake (two of the reservoirs sup-
plying Tehran with potable water) were analyzed for the detection and determination of
pesticide residues. DDT and its metabolites TDE and DDE were the pesticides commonly
found. In the Karadj reservoir, the mean concentration of total DDT found in whole fish
was 0.049 ± SD 0.0032 ppm while that of the Latian reservoir was 0.065 ± SD 0.007 ppm.
The mean concentration of the pesticide in fat was 3.11 ± 0.21 and 4.85 ± 0.13 ppm, respec-
tively. This shows the Latian reservoir to be more contaminated. Extreme concentrations of
pesticides in Latian fish were found in Varicorhinus nikolskii , while in Karadj fish, the high-
est level of the pesticide occurred in Salmo trutta morpha fario and the lowest concentration
in Varicorhinus nikolskii . Samples collected in summer showed the highest concentrations
of the pesticides.
The residues of p,p′-DDE and HCB were detected with a frequency of 100%, in fish sam-
ples from the Sene-Gambian, whereas p,p′-DDT was detected in eight, heptachlor epoxide
in six, and endosulfan sulfate in five of the nine fish samples (Manirakiza et al. 2002).
Some OCP residues in tilapia fish ( Tilapia zillii ), sediment, and water samples from Lake
Bosumtwi (the largest natural lake in Ghana) were determined. p,p′-DDE was the predom-
inant residue in all the samples analyzed and was detected in 82% of water samples, 98%
of sediment samples, and 58% of fish samples at concentrations of 0.061 ± 0.03, 8.342 ± 2.96,
and 5.232 ± 1.30 ng/g, respectively. DDT was detected in 78%, at a mean concentration
0.012 ± 0.62 ng/g, of water samples analyzed. The mean concentrations of DDT in sedi-
ments and fish were 4.41 ± 1.54 and 3.645 ± 1.81 ng/g, respectively. The detection of lower
levels of DDT than its metabolite, DDE, in the samples implies that the presence of these
contaminants in the lake is a result of past usage of the pesticides.
In six fish species, namely Heterotis niloticus , Channa obscura , Hepsetus odoe , Tilapia zillii ,
Clarias gariepinus , and Chrysichthys nigrodigitatus , collected from the sampling towns, Weija
and Nsawam along the Densu river basin in the Greater Accra Region of Ghana, the con-
centrations of OCs ranged from 0.3 to 71.3 μg/kg (correct), which were, however, below the
Australian Maximum Residue Limit (MRL) of 50-1000 μg/kg (correct) for freshwater fish.
The results of this work indicate that OCP residues are present in the Densu basin; how-
ever, the concentrations of the OC residues determined in the fish samples were below the
stipulated Australian MRL. Of all fourteen OCPs, seven are among the banned pesticides
of the Environmental Protection Agency (EPA) of Ghana. The mean concentrations of the
banned OCs detected range from 0.30 to 35.2 μg/kg, with the highest concentration of
35.2 μg/kg recorded for δ-HCH in the Channa obscura sp. sampled from Nsawam. The lowest
mean concentration of 0.30 μg/kg was recorded for endrin, aldrin, and endrin-aldehyde