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Organochlorine Pesticides Residue in Cocoa Beans (Theobroma Cacao) and Soils of Cocoa Plantationsin Ondo State, Nigeria

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Organochlorine Pesticides Residue in Cocoa Beans (Theobroma Cacao) and Soils of Cocoa Plantationsin Ondo State, Nigeria.


The study investigated the levels of organochlorine pesticide residues in both cocoa beans and soils of cocoa plantations in selected farms in Ondo State. Soil samples and cocoa pods were collected from four major farms in the State.

The pesticide residues were extracted, cleaned up, and analyzed using Gas Chromatography-Electron Capture Detector (GC-ECD).

In the analyzed cocoa samples, the ranges of the mean concentrations of the organochlorine pesticides were: α-HCH (ND-0.094 mg/kg), β-HCH (ND-0.371 mg/kg), γ-HCH (ND-0.032 mg/kg), δ-HCH (ND-0.032 mg/kg), heptachlor (ND-0.272 mg/kg).

Heptachlor-epoxide (0.040-0.185 mg/kg), aldrin (ND-0.117 mg/kg), dieldrin (0.052-1.110 mg/kg), endrin (0.297- 1.516 mg/kg), endosulfan I (1.719-10.689 mg/kg), endosulfan II (0.028-0.570 mg/kg), endosulfan sulphate (ND-3.865 mg/kg), p,p’ DDT (ND-0.100 mg/kg), cis-permethrin (0.078- 0.662 mg/kg), trans-permethrin (0.085-0.927 mg/kg).

However, the levels of aldrin, dieldrin, endrin, and endosulfan in the cocoa samples analyzed were found to be high and above Maximum Residual Limits (MRLs) established by WHO/FAO (HCH isomers, heptachlor, heptachlor-epoxide, aldrin, endrin and dieldrin (0.020 mg/kg) and endosulfan I, II and sulfate (0.100 mg/kg)).

European Union (α-HCH, β-HCH and δ-HCH isomers, heptachlor, heptachlor-epoxide, and dieldrin (0.020 mg/kg), γ-HCH (1.000 mg/kg), p,p’- DDT, aldrin (0.050 mg/kg) and endosulfan I, II, cis- and trans-permethrin (0.100 mg/kg)) .

In the soil samples analysed, the ranges of the mean concentrations of the organochlorine pesticides were: α-HCH (ND-0.064 mg/kg), heptachlor-epoxide (0.059-1.384 mg/kg), aldrin (ND-0.450 mg/kg), dieldrin (0.041-0.066 mg/kg), endrin (0.136-0.567 mg/kg), endosulfan I (0.319-1.451 mg/kg), endosulfan II (0.033-0.113 mg/kg), endosulfan sulphate (0.764-1.711 mg/kg), cis-permethrin (0.077-0.259 mg/kg), trans-permethrin (0.079-0.151 mg/kg).

The mean concentration of aldrin, dieldrin, endrin, endosulfan (I and II) in the soil sample analysed were above the MRLs of the analytes established by Netherlands aldrin(0.0025mg/kg), dieldrin(0.0005mg/kg), endrin (0.001mg/kg), endosulfan(0.050mg/kg), en dosulfanII(0.050mg/kg). p, p’ DDT was below the detection limit (10-4 mg/kg) in 50% of the analyzed cocoa and all the soil samples.

Similarly, HCH isomers and p,pp DDT were below the detection limit (10-4 mg/kg) in the soil samples analyzed except Oluji-1 where α-HCH was detected.

The results of the bioaccumulation factors showed that endosulfan, dieldrin, endrin heptachlor, heptachlor-epoxide, cis- and trans-permethrin were bioaccumulated in the cocoa samples from the selected farms.

The high bioaccumulation factors of endosulfan I (7.367 in Oluji-1, 3.084 in Oluji-2 and 14.525 in idanre), Dieldrin (27.073 in Oluji-2, 7.477 in Owena), and cis- and trans-permethrin (1.8 and 11.734 in Owena, 8.597 and 8.429 in Idanre respectively) give cause for concern considering the adverse health hazards posed by high accumulation of these pesticides on man.

This indicated the recent use of these pesticides despite the ban imposed on their use. The results of ANOVA showed that there was no significant difference between the mean concentrations of the pesticide residues in all the cocoa samples (p<0.05).

Similarly, no significant difference was observed between the mean concentrations of the analytes in all the soil (p<0.05).


Title page i
Certification ii
Dedication iii
Acknowledgment iv
Abstract vi
Table of Content vii
List of Tables x
List of Figures xi
List of Abbreviations xiii


1.0 Introduction 1
1.1 Statement of problem 5
1.2 Objective of study 7
1.3 Justification of study 8


2.0 Literature review 10
2.1 Pesticides 10
2.1.1 History of pesticides 11
2.1.2Organochlorine pesticides 13
2.1.3Toxicology of organochlorines 24
2.2 Pesticides used by cocoa farmers in Nigeria 26
2.3 Nature of samples 40
2.4 Methods of samples collection 41
2.5 Methods used for sample preparation 42
2.5.1 Extraction techniques 43
2.5.2 Clean-up techniques 46
2.5.3 Instrumental analysis 47


3.0 The Study Area 50
3.1 Reagents and Apparatus 52
3.2 Sample collection and processing 53
3.2.1 Cocoa Sampling 53
3.2.2 Soil Sampling 53
3.3 Extraction and Clean-up of organochlorine pesticide Residues
From Cocoa Beans And Soil Samples 54
3.4 Gas Chromatographic Analysis of cocoa and soil samples 56
3.5 Quality Assurance 59
3.6 Determination of soil physicochemical parameters 60
3.6.1 Soil Organic Matter / Total Organic Carbon 60
3.6.2 Particle Size Analysis (% Silt, % Sand and % Clay) 63
3.6.3 pH 65
3.7 Bioaccumulation Factor 66
3.8 Statistical Analysis of the data 66


4.0 Socio-Economic Characteristics of the farmers in
the selected farms 67
4.1: Results of Soil pH, % Particle Composition, % Organic Carbon
and %Organic Matter Analyses 70
4.2 Pesticide residues level in cocoa samples from the selected farms 71
4.3 Pesticide residues level in soil samples from the selected farms 87
4.4 Result of Bioaccumulation Factor of the OCPs 95
4.5 Statistical analysis 96


5.1 Conclusion 97
5.2 Recommendations 98
References 99


Cocoa is an important tropical tree crop that does not only provides farmers with much-desired income to meet their basic family needs1 but also serves as a foreign exchange earner for many West African countries like Nigeria, Ghana, Côte d’Ivoire, Cameroon, and Togo.

Its botanical name, Theobroma Cacao, given by Swedish natural scientist Carl Von Linne denotes its rich taste and high nutritional value which make it irresistible to both young and adult especially when processed into diverse products.

These include; chocolate, sweet, cocoa drink, cocoa biscuit, cocoa bread, cocoa cake, cocoa flakes, cocoa popcorn, cocoa jam, cocoa jelly, cocoa cream, cocoa wine, and spirit, etc.2-4.

Cocoa was believed to have originated in the hot, humid region near the source of the River Amazon in South Africa and was introduced into Nigeria in 1874.1,5In Nigeria, Cocoa is grown mostly in the Southern States such as Ondo, Oyo, Ogun, and Osun.

It is a tropical lowland crop that flourishes best where the annual rainfall is at least 1140mm with a mean temperature below 170C.

It requires shade to reduce moisture evaporation especially at the nursery and the early stages of its establishment in the field. It also requires deep, fertile, and well-aerated loamy soil which must be loose and friable.

The cocoa plant when mature reaches a height of 7.5 to 10.5m. Before 1960, the exportation of cocoa accounted mainly for agricultural export, which made over 80% of the Gross National Product (GNP) of the Nigerian economy.

This showed that cocoa was the chief source of foreign exchange earnings for Nigeria before the discovery and exploration of crude oil.


Mossu, G. (1992): Cocoa. Macmillan Press Limited, London and Basingstoke, 103p

Ojeh, O.A. (1979): Uses of Cocoa. Text of a lecture delivered to Cocoa and Tree Crop Development UnitsField Staff at the Annual In-Service Training organized by Cocoa Research Institutes of Nigeria(CRIN), 28th September 1979.

Soleye, W.A. (1971): Processing of Cocoa for the Markets. Progress in Tree CropResearch in Nigeria, CocoaResearch Institutes of Nigeria (CRIN), Ibadan. P 7-9.

Adeyemi, S.A.O. (1992): Current status of insecticides in controlling cocoa pests in Nigeria. Annual Report of Cocoa Research Institutes of Nigeria, Ibadan.

Ayoola, B., Fasina, K.B. and Aikpokpodion, P. (2000): Development of Nigeria cocoa industry, Current 149 issues and challenges for research and production. Conference Sabah: Malaysia. pp: 1367-1373.

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