DR. LAETITIA KANJA
UNIVERSITY OF NAIROBI
1
Mwangi M. C1, Karuri E. G2 and Kanja L. W3
1Department
of the National Public Health Laboratory Service, Ministry of Health, Kenya
of Food Technology & Nutrition, College of Agriculture and Veterinary Sciences, University
of Nairobi
3Department of Public Health, Pharmacology and Toxicology, College of Agriculture and Veterinary
Sciences, University of Nairobi
2Department
2
INTRODUCTION
Nile Perch in Lake Victoria:
 Largest fresh water lake in Africa and covers a surface area of 68,800km2 and an
average depth of 40m. With Kenya taking up 6%, Tanzania 49%, Uganda 45% of the
total lake area.
 Nile Perch (Lates niloticus) dominates the lake forming about 50% of the entire fish
populations
 About 52% of the total perch fillet produced in Kenya is exported to the European
Union (EU) market and other countries.
 The lake experiences environmental influence from the three riparian states,
where agricultural chemicals and industrial effluents are known to contribute
significantly to the lake pollution
3
•
Previous studies in Kenya had shown cases of organochlorine pesticide residue in fish
from the Lake Victoria and other Kenyan lakes (Koeman et al, 1972, Lincer et al
1981,Mugachia et al 1992, Wandiga et al 2002).
•
Environment pollution and the subsequent water contamination in the Lake Victoria,
and poor sanitary conditions at the landing facilities led fish export bans by the EU
market between 1996 and 1999
 This had a negative effect on the EU market, the fishing community’s livelihoods and
other stakeholders.
4
Objectives of the study:
The objective of this study was to identify and
quantify the organochlorine pesticide residues in Nile
Perch fish tissues.
5
MATERIALS AND METHODS
Sampling
 Fish samples (about 1.5kg each and approximately 6-8 months old) were purchased from
five landing facilities along the Kenyan shore line
 Liver and muscle samples were obtained from each fish and wrapped in foil and kept
frozen.
Sample analysis
 Extraction, clean-up and analysis of organochroline pesticide residues was done as
described by Brevik (1981)
 3g of the sample were extracted with diethylether extracts and 2 aliquots of the extract
treated with concentrated sulphuric acid and methanolic potassium hydroxide, and
analysed by gas liquid chromatography (GLC).
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RESULTS
 A total of 125 fish liver and muscle samples were analyzed for
organochlorine pesticide residues.
 The results are presented in Figures 1, 2 ,3,4 and 5.
 The residue concentrations of the pesticides are presented on wet
weight basis.
 Eleven organochlorine pesticide residues were detected in the liver
tissue and nine in the fish muscle.
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400
350
α =BHC
β =BHC
γ =BHC
Heptachlor
Hept Epox
Aldrin
Dieldrin
Endrin
p,p'-DDE
p,p'-DDT
o,p'-DDD
Mean Values
300
250
200
150
100
50
0
February (n=9)
March (n=17)
April (n=13)
May (n=7)
June (n=5)
Period of Sampling
Figure 1: Mean pesticide residue levels (µg/kg) in Nile perch liver, 2001
8
100
90
α =BHC
80
β =BHC
Mean Values
70
γ =BHC
60
Hept Epox
50
Aldrin
Dieldrin
40
Endrin
30
p,p'-DDE
20
10
0
February (n=11)
March (n=14)
April (n=15)
May (n=9)
June (n=3)
Period of Sampling
Figure 2: M ean pesticide residue levels (µg/kg) in Nile perch muscle, 2001
9
250
Mean Values
200
α =BHC
β =BHC
γ =BHC
150
Heptachlor
Hept Epox
Aldrin
Dieldrin
100
Endrin
p,p'-DDE
50
p,p'-DDT
0
FebruaryJune:Liver (n=51)
FebruaryJune:Muscle
(n=52)
Period of Sampling
Figure 3:M ean pesticide residue levels (µg/kg) in Nile perch liver and muscle samples,
February – June 2001
10
4500
4000
α =BHC
3500
Mean Values
β =BHC
3000
γ =BHC
2500
Heptachlor
Hept Epox
2000
Aldrin
Dieldrin
1500
Endrin
1000
p,p'-DDE
500
0
October:
Liver (n=3)
Muscle
(n=3)
November:
Liver (n=8)
Muscle
(n=8)
Period of Sampling
Figure 4: Mean Pesticide residue Levels in Nile Perch Liver and Muscle–
October and November 2000
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Monthly Rainfall
180
169.7
160
140
Line 1
Mean Values
129.8
120
116.7
104
100
80
77.5
74.7
Poly.
(Line 1)
60
40
36.2
20
0
October
November
February
March
April
May
June
Period of Sampling - Year 2000/2001
Figure 5: Monthly mean rainfall (mm)
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Conclusion
 The study established that the landed Nile Perch fish
investigated were contaminated with organochlorine
pesticide residues.
 The EU concerns over the possible contamination of fish by
poisonous chemicals were justified.
 The levels were high enough for action to be taken by the
relevant authorities.
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Recommendations
1.
Continuous monitoring of chemical residue analysis of the lake
environment would help to determine whether pollution is seasonal
or sporadic.
2.
The source of pollution should be clearly established .
3.
Collaborative studies on lake pollution should be initiated among the
riparian states.
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REFERENCES
Brevik, E. M. (1978) Organochlorines in fish and crabs from the Kristiansand Fjord in Norway, Nord. Vet. – Med. 30, 375- 379.
Kanja L.W. (1988) Organochlorine pesticides in Kenyan mothers’ milk: Levels and Sources. Ph. D. thesis. University of Nairobi.
Koeman, J. H. (1972). Apreliminary survey of the possible contamination of Lake Nakuru in Kenya with some metals and chlorinated
hydrocarbon pesticides. J. Appl. Ecol., 9: 411-416 Bulkley, R. V., Leung, S. Y. T. and Richard, J. J., 1981. Organochlorine insecticide
concentrations in fish of the Des Moines River, IOWA, 1977-78, Pestic. Monit. J., 15, 86.
Lincer, J. L.; Zalkind, D.; Brown, L. H.; Hopcraft, J. 1981 Organochlorine residues in Kenya’s Rift Valley lakes J. Appl. Ecol., 18: 157-171.
Mugachia, J.C, Kanja, L. and Gitau F., 1992. Organochlorine Pesticide Residues in Fish from Lake Naivasha and Tana River, Kenya. Bull.
Environ. Contam. Toxicol.) 49:207-210. 1192 Springer- Verlag New York Inc.
Mwangi C. M. (2003) Quality of Lake Victoria Nile Perch (Lates niloticus) at the Landing Facility as a Potential Microbiological and
Organochlorine Pesticide Residue Hazards Critical Control Point MSc Thesis. University of Nairobi, Kenya
Wandiga, S. O.; Yugi, P.O.; Barasa, M. W.; Jumba, I. O.; Lalah, J.O. (2002) The distribution of organochlorine pesticides in marine samples
along the Indian Coast of Kenya.
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ACKNOWLEDGEMENT
 The authors are grateful to the Swedish International Development
Authority (SIDA) for financial support.
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THE END.
THANK YOU.
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