Organochlorine pesticides residues in fish and sediment from lake Naivasha

Abstract

The main objective of this study was to identify and determine the levels of organochlorine pesticides residues in fish and sediment from Lake Naivasha and to evaluate the toxicological implications of their presence. A total of 82 fish samples and 24 samples of sediment were analyzed using a Packard gas liquid chromatograph fitted with a 63Ni electron capture detector. The fish samples comprised of liver, eggs and muscle tissues. Out of 82 samples of fish analyzed 93.9% had detectable levels of at least one of the organochlorine compounds. Hexachlorocyclohexanes were the most frequently detected pesticides residues, α ‐HCH showing in 93.9% of the samples, β‐HCH in 60.9% of the samples and lindane in 6% of the samples. The cyclodienes were also detected with 50% of fish samples having heptachlor which had a mean of 0.004mg/kg, dieldrin was detected in 26 samples with a mean of 0.023 mg/kg, heptachlor epoxide in 25 samples with a mean of 0.0052mg/kg, aldrin was detected in only one liver sample of a female black bass and endrin was also found in only one liver sample of a male Tilapia fish. The 24 sediment samples analyzed, 62.5% showed presence of α ‐HCH with a mean of 0.003mg/kg, 37.5% samples had β‐HCH with a mean of 0.00315mg/kg, 12 samples had lindane with a mean of 0.00175mg/kg; Heptachlor epoxide was detected in only one sample with a value of 0.0012mg/kg, dieldrin was found in one sample with a value of 0.0033mg/kg and aldrin in one sample with a mean of 0.0025mg/kg. No DDT or its analogue was detected in fish and sediment samples. This showed that there has not been any recent use of the pesticide in the surrounding areas. The presence of α ‐HCH, β‐HCH and γ‐HCH in both fish and sediment samples indicate continuous use of these chemicals in the numerous flower farms around Lake Naivasha. The organochlorine pesticide residues found in the present study are generally below the maximum residue limits (MRL) set by FAO/WHO bodies. This indicated that the organochlorine pesticide residues do not pose a health risk to the consumers of the fish from Lake Naivasha. However emphasis should be laid on a continuous monitoring programme to safe guard the consumer of fish and animal products from Lake Naivasha