DR. LAETITIA KANJA

UNIVERSITY OF NAIROBI

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Mwangi M. C1, Karuri E. G2 and Kanja L. W3

 1Department of the National Public Health Laboratory Service, Ministry of Health,

Kenya2Department of Food Technology & Nutrition, College of Agriculture and Veterinary

Sciences, University of Nairobi3Department of Public Health, Pharmacology and Toxicology, College of Agriculture

and Veterinary Sciences, University of Nairobi

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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

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• 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.

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Objectives of the study:

The objective of this study was to identify andquantify the organochlorine pesticide residues in

NilePerch fish tissues.

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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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RESULTSA 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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8

0

50

100

150

200

250

300

350

400

Mean V

alu

es

February (n=9) March (n=17) April (n=13) May (n=7) June (n=5)

Period of SamplingFigure 1: Mean pesticide residue levels (µg/kg) in Nile perch liver, 2001

α =BHCβ =BHCγ =BHCHeptachlorHept EpoxAldrinDieldrinEndrinp,p'-DDEp,p'-DDTo,p'-DDD

9

0

10

20

30

40

50

60

70

80

90

100

Mea

n V

alues

February (n=11) March (n=14) April (n=15) May (n=9) June (n=3)

Period of SamplingFigure 2: Mean pesticide residue levels (µg/kg) in Nile perch muscle, 2001

α =BHC

β =BHC

γ =BHC

Hept Epox

Aldrin

Dieldrin

Endrin

p,p'-DDE

10

0

50

100

150

200

250

Mean V

alu

es

February-June:Liver (n=51)

February-June:Muscle

(n=52)

Period of SamplingFigure 3:Mean pesticide residue levels (µg/kg) in Nile perch liver and muscle samples,

February – June 2001

α =BHC

β =BHC

γ =BHC

Heptachlor

Hept Epox

Aldrin

Dieldrin

Endrin

p,p'-DDE

p,p'-DDT

11

0

500

1000

1500

2000

2500

3000

3500

4000

4500M

ean V

alues

October:Liver (n=3)

Muscle(n=3)

November:Liver (n=8)

Muscle(n=8)

Period of SamplingFigure 4: Mean Pesticide residue Levels in Nile Perch Liver and Muscle–

October and November 2000

α =BHC

β =BHC

γ =BHC

Heptachlor

Hept Epox

Aldrin

Dieldrin

Endrin

p,p'-DDE

Monthly Rainfall

77.5

169.7

36.2

116.7

129.8

104

74.7

0

20

40

60

80

100

120

140

160

180

October November February March April May June

Period of Sampling - Year 2000/2001Figure 5: Monthly mean rainfall (mm)

Mea

n V

alues

Line 1

Poly.(Line 1)

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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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