| dc.description.abstract | Organochlorine pesticides persist in the environment and
accumulate in aquatic organisms. Although the chemicals have
been used in Kenya since the 1940's, information on the occurrence
of their residues in fish is still scanty. The main objective of the
present study was to identify and quantify organochlorine residues
in freshwater and estuarine fish from selected areas in Kenya and
evaluate the toxicological implications of the findings.
A total of 275 fish samples were collected from five locations
in Kenya between October, 1988 and October, 1989. The samples
were obtained from Tana River at Masinga Darn, Garsen and
Tarasaa, the estuary of Athi (Sabaki) River at Malindi and Lake
Naivasha in the Great Rift Valley. The fish were caught with gill
nets, line and hook or fishing baskets. The liver, eggs and fillet
(muscle) from each fish were analysed separately using a Packard
gas liquid chromatograph, fitted with a 63Ni electron capture
detector. Nine· organochlorine pesticide residues were detected in
22.5% of the samples in the following order of frequency: p,p' DOE
(20.4%), p,p' DDT (12.7%), Lindane (4.7%), o,p'DOT (4%), p,p' ODD
(3.6%), f3-HCH (2.5%), a-HCH (1.8%), heptachlor (0.7%) and o.p'
DDD (0.4%). Polychlorinated biphenyls (PCB's) and
hexachlorobenzene (HCB) were not detected in the fish.
The residues with the highest levels were p,p'DDE and
p,p'DDT with ranges of 0.027 to 1.241 and 0.011 to 2.674mg/kg on
wet weight basis respectively. Sum DDT levels ranged from 0.03 to
3.148mg/kg. The range for residue levels of lindane and o.p' DOT
were 0.004 to 0.295 and 0.031 to 0.133mg/kg respectively.
The results showed locational differences in the occurrence of
the pesticide residues in the fish but no significant difference
(p> 0.1) in the means of the residue levels. Out of the 67 samples
from Malindi and 40 samples from Masinga Darn, 72.7% and 39.5%
respectively had one or more of the 9 pesticide residues detected.
Only one out of the 65 samples from Garsen had p,p' DOE at a low
level of 0.033mg/kg. No residues were detected in the 65 samples
from Tarasaa and 40 samples from Lake Naivasha.
There was a difference in the distribution of organochlorine
pesticide residues in the fish body. Cornman carps obtained from
Masinga Darn had lindane, p.p' DDE and p,p' DOT in fillet while
fish from Malindi rarely had the pesticide residues in fillet. Lindane
was only detected in fish from Masinga Darn and was more
common than DDT and its metabolites in the fish. p,p' DOT was
more frequent than p,p' DDE and other DDT metabolites in the
fillet of common carps. This indicated a recent exposure of the fish
to p,p' DDT or a slow degradation rate of the compound in this
species. Common carps had significantly higher residue levels of
lindane (p= 0.008) than catfish in Masinga Darn.
There was a positive correlation (r= 0.74) of sum DOT to
weight in the seven species of fish with detectable levels of the
residue. Sharks had significantly higher mean level of sum DDT
(p< 0.0001) than catfish, common carps and breams. No difference
was observed between males and females of various fish species
and betwen different organs in the levels of the various pesticide
residues detected in the fish. Nonetheless, the residues were most
common in the liver and eggs (ovaries).
The residue levels found in the present study are generally
below the maximum residue limits (MRL), for the respective
organochlorine pesticide residues, set by the National Food
Administration (NFA) of Sweden. This indicates that the pesticide
residues do not pose a health risk to the consumers of fish from the
areas studied. | en |
