ABSTRACT
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 analysed using Gas Chromatography-Electron Capture Detector (GC-ECD).
In the analysed 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 analysed 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
sulphate (0.100 mg/kg)) and 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),endosulfanI(0.050mg/kg),en
dosulfanII(0.050mg/kg). p, p’ DDT was below detection limit (10-4 mg/kg) in 50% of the
analysed cocoa and all the soil samples. Similarly, HCH isomers and p,p’ DDT were below
detection limit (10-4 mg/kg) in the soil samples analysed 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 pose by high
accumulation of these pesticides on man. This indicated 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).
TABLE OF CONTENTS
Title page i
Certification ii
Dedication iii
Acknowledgement iv
Abstract vi
Table of Content vii
List of Tables x
List of Figures xi
List of Abbreviations xiii
CHAPTER ONE: INTRODUCTION
1.0 Introduction 1
1.1 Statement of problem 5
1.2 Objective of the study 7
1.3 Justification of the study 8
CHAPTER TWO: LITERATURE REVIEW
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
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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
CHAPTER THREE: MATERIALS AND METHODS
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
CHAPTER FOUR: RESULTS AND DISCUSSION
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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
CHAPTER FIVE: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 97
5.2 Recommendations 98
References 99
Appendix I Chromatograms of cocoa samples 114
Appendix II Chromatograms of soil samples 119
Appendix III Chromatogram of certified reference material 123
Appendix IV Results of statistical analysis 124
Appendix V Triplicate concentrations of analytes in the cocoa samples
from the selected farms 125
Appendix VI Triplicate concentrations of analytes in the soil samples
from the selected farms 126
Appendix VII Certificate of certified reference material 127
CHAPTER ONE
1.0 INTRODUCTION
Cocoa is an important tropical tree crop which does not only provide farmers with
much desired income to meet their basic family needs1 but also serves as aforeign 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 such as 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 introduced into Nigeria in 1874.1,5In Nigeria, Cocoa is
grown mostly in Southern States such as Ondo, Oyo, Ogun and Osun. It is a tropical lowland
crop which flourishes best where the annual rainfall is at least 1140mm with 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 a deep, fertile and
well aerated loamy soil which must beloose and friable. The cocoa plant when mature
reaches a height of 7.5 to 10.5m.6
Before 1960, exportation of cocoa accounted mainly for the agricultural export, which
made over 80% of the Gross National Product (GNP) of the Nigerian economy.7This showed
that cocoa was the chief source of foreign exchange earnings for Nigeria before the discovery
and exploration of crude oil. Despite the oil boom experienced in Nigeria, cocoa still serves
as the major agricultural export crop and accounted for about 38% of agricultural export in
1997.8Being an important agricultural produce, cocoa provides employment for the farmers
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in the remote villages and millions of individuals all over the world involved in its
processing, marketing and distribution. It is imperative to note that large scale production of
cocoa can solve the problems of unemployment in Nigeria. This is because the world demand
for cocoa and its derived products is ever increasing and remains insatiable. Eighty-five
percent (85%) of the cocoa demand of the European Nations is from West Africa where
Nigeria is one of the major exporters5. This showed that the final destination of West African
cocoa is Europe.
Although, the cocoa producing Nations in West Africa derive revenue from the export
of cocoa to Europe, much more revenue could be derived if the exported cocoa is being
processed within the West African region and the finished products is exported for the
consumption of the European nations after the satisfaction of the local demands. This could
only be achieved if laws are enacted and necessary provisions are made to provide a very
conducive environment for the farmers and the local processing industries to strive.However,
the discovery of abundant natural resources, such as crude oil in Nigeria, gold in Ghana,
probably led to the reduction in effort of most African Governments to make available these
required provisions. Consequently, cocoa farming is now left mostly to smallholder farmers
(with farm size less than 5 hectares) who rely on the crop as the primary source of income.8
Many of these farmers are geographically isolated, illiterate, poorly informed and have very
limited resources for proper crop management. This development has caused a sharp decline
in cocoa production as many of the farmers still adopt the traditional methods of farming
which is very inefficient and pose high risk to the farmers8.
Unfortunately, the enormous effort of these farmers at sustaining production under
high risk conditions was not most often reflected in their output as pests and diseases largely
contributed to decline in cocoa production.9In Nigeria, decline in cocoa production started in
1971 and 1972 with yield of 255,000 and 241,000 metric tonnes respectively5. The lowest
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yield in the 70’s was recorded in 1978 with output of 137,000 metric tonnes5. Yields declined
further from a peak of about 350,000 metric tonnes in the mid 80’s to about 58,700 metric
tonnes in 19865. According to THISDAYLIVE Newspaper report issued on 21st January, 2014,
the cocoa production in Nigeria was 250, 000 metric tonnes in 2011, 300, 000 metric tonnes
in 2012, and 350, 000 metric tonnes in 2013. This showed an annual increase in production
by 50, 000 metric tonnes but when compared to the annual cocoa production from other West
African countries in the same period (Ghana cocoa production was between 850, 000 – 1,
000, 000 metric tonne per annual and Cote d’Ivoire cocoa production was in the range 1.2 –
1.4 million metric tonnes per annual), it would be obvious that the growth rate was not only
insignificant but also the annual output was too small for the most populated black Nation
(Nigeria) that is expected to champion the course of self sustenance in food production in
Africa.
Major contributors to this decline were pests as 25-30% loss in yield of cocoa was attributed
to the cocoa mired, Sahlbergella singularis while about 17% was lost through the feeding of
the cocoa pod borer Characoma strictigrapta10, 11. The collective efforts of minor pests (such
as the shield bug, Bathycoelia thalassina, the pod miner, Mamara species, the root-feeding
termites, Macrotermes bellicosus,Mesohomotoma tessmanniand the cacao thrips,
Selenothrips rubrocinctus)could become significant especially under suitable conditions in
young cocoa or ageing cocoa plantations.
It is important to note that several concerted research efforts have been made to
develop various control techniques (such as cultural, biological and chemical) which could be
adopted for integrated management of the major and minor pests of cocoa in Nigeria. It is
however quite unfortunate to note that many of the findings of such research hardly reached
the local farmers and when they did eventually, the inability of the farmers to read and write
often hindered the proper interpretation of those findings. Despite the various mechanisms
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developed for pest management, the farmers rely greatly on the use of pesticides (chemical
control technique) because it provides immediate and quicker remedy in the periods of
serious pest outbreaks.11
There are over seven hundred (700) chemicals in use as pesticides, which are
formulated into about thirty-five thousand products classified as insecticides, herbicides,
fungicides and rodenticides.12Although, pesticides are known to be very efficient in pest
control, reliance and prolonged application of thesesynthetic chemicals had given rise to
numerous problems which affected the food chain and posed negative impact on biological
diversity. It has been established that pesticides application could lead to serious health
hazard ( such as epilepsy, stroke, respiratory disorders, leukemia, convulsion, brain and liver
tumors ) and environmental pollution as it is often manifested in the disturbance of the
ecosystem,which include destruction of some natural vegetation, pollution of the important
water bodies (ground water, river water, drinking water), soil and air as well as reduction and
extinction of some aquatic species and wildlife population.13-15
In Nigeria, cocoa farmers use different insecticide formulations including the very
notorious organochlorine types. Due to their bioaccumulation throughout the food chain and
prolonged persistence in the environment coupled with numerous associated health risk, food
and environmental regulatory bodies in many developed and developing nations,including
National Agency for Food and Drug Administration and Control (NAFDAC) in Nigeria,
place ban on the use of most pesticides especially those with organochlorine formulations in
line with the new European Union Legislation on pesticide use.16 Despite, the ban on these
chemicals, the hazards associated with them still remain for long period as many of them
possess extended half-life especially the organochlorines which are very stable and persist for
a long period of time.The problem is further complicated as these compounds have many
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derivatives which are very soluble in body fat and can move with relative ease through the
food chains.
It is therefore very expedient to provide adequate quantitative and qualitative
information on these banned pesticidesand their derivatives in soil, farm produce (e.g. cocoa)
and water. This is to assist; the farmers (who use these pesticides), government (in the
formulation of policy)and the general public (to make the consuming populace aware of the
associated danger inherent in consumption of farm produce and water contaminated
withpesticides). These can only be achieved through concerted research effort tailored and
targeted towards acquiring this much important information.
1. 1 STATEMENT OF PROBLEM
Use of Pesticide in Nigeria has been on the increase since its introduction in early 50s
for cocoa production. To attain acceptable levels of crop production, Nigerian cocoa
production is strongly dependent on pesticides. The campaign against mired attack on cocoa,
which followed the recommendation of Lindane in 1957, lead to highly significant increase in
cocoa production from an average of 103,000 tons per annum in 1961- 67 periods to 212,000
tons per annum in 1961-65 periods.16 This shows to a large extent that the use of some
pesticides is of significant importance to the production of cocoa. Since cocoa is one of the
major cash crops that contribute towards the Gross Domestic Product (GDP) of Nigeria
through foreign exchange, increasing the productivity of cocoa is tantamount to an indication
of economic development. However, most recently, the developed nations discovered
increase in the case of cancer among their citizens. This prompted the European Union to be
conscious of the quality of food products meant to be consumed among her citizens. This
development is in connection to pesticide residue observed to be high in most imported
agricultural produces and products. Thus, within the European Union (EU), as in many parts
of the world, legislation regulates the supply and use of pesticides. It has two important
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components: Directive 91/414, which defines active substances permitted for use in the EU;
and Regulation 396/2005, which defines the maximum levels of residues (MRLs) permitted
in food and feedstuffs in the EU. Regulation 396/2005 came into force on 1st September,
2008 and has significant implications.17 From 1st September 2008, any foodstuffs, including
cocoa as an imported commodity, containing pesticide residues above the temporary
maximum levels of residues (tMRLs) is considered illegal in the EU. In the new legislative
framework, tMRLs have been set on beans but also apply to cocoa and chocolate products. In
the light of this development, it is imperative for cocoa exporting countries like Nigeria to
make concerted effort to ensure their cocoa produce meet up with the set standards as Europe
is the final destination of cocoa produce in most developing nations.
Since cocoa produce that has its pesticide residue far above the minimum required
level stated by EU are restrained in the foreign exchange market, this implies that those local
farmers that are not aware of this legislation are only producing for themselves. Knowing
well that the market of cocoa is not only situated within the country but extends outside this
country, hence farmers that are still using the banned chemicals will definitely be running at a
loss. Information available at theFederal Environment Protection Agencyindicated that the
Federal Government of Nigeriarecognizes the problems of pesticides use andhas put in place
legal and administrativeprocedures aimed at regulating and monitoringpesticide manufacture,
importation, distribution,use and disposal so as to protect users as well as the nation’s
environment from the effects of thesepesticides.16 However, the marketing of pesticides in
Nigeria is very much unorganized and lacks proper legislative control. This has made it
difficult to determine the various market sizes, types, and shares of pesticides in use. Hence
there is no dependable official statistics on the type and amount of pesticides imported into
the country.18This is indeed a pathetic situation that requires immediate attention, which can
only come from well structured and organized research.
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1. 2 OBJECTIVE OF THE STUDY
The intensive use of pesticides leads to environmental problems such as
contamination of soil, farm produce and underground water. On application of pesticides to
destroy pests and pathogens, only 15% of the applied amount hits the targeted pests, with the
remaining 85% being distributed in the soil and air.19 The soil is the main matrix for pesticide
disposition and the bulk of pesticide residues are generally confined to the upper 20cm of the
top soil.20 Pesticide residue in the soil can move from the surface when they dissolve in
runoff water, or percolate down through the soil, and eventually reach the groundwater.
Plants take up pesticides dissolved in water. These pesticides are distributed in most part of
the plants especially in fruits rich in fat like cocoa beans. Most farmers are only interested in
protecting their crops from pests in order to get good harvest but have little concern for the
detrimental effects of these pesticides on the soil, environment and their health.20 In order to
comply with the maximum residue limit regulation and produce high quality cocoa beans for
exportation, it becomes expedient to assess organochlorine – α-HCH, β-HCH, γ-HCH,
Heptachlor, Heptachlor-epoxide (B), Aldrin, Dieldrin, Endrin, Endosulfan (I, II and
sulphate), DDT, cis- and trans-Permethrinresidue in cocoa beans and soil from selected
cocoa plantations in Ondo State, Nigeria.
The general objective of the study is to determine organochlorine pesticides residue
in both cocoa beans and soil of cocoa farm, and assess the pesticide management practices
among farmers in selected cocoa plantation in Ondo state, Nigeria. The specific objectives
are to:
(i) Identify pesticide management practices adopted by the farmers in the study area
(ii) Determine the level of organochlorine pesticides residue in the cocoa beans from the
selected farms
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(iii) Determine soil physicochemical parameters (soil organic matter / total organic carbon,
particle size analysis and pH)andthe level of organochlorine pesticides residue in the top soil
of the selected cocoa farms
(iv) Evaluate the bioaccumulation factor
(v) Compare the values of the organochlorine pesticides in cocoa and soil with the accepted
Maximum Residual Limits (MRLs) established by international organisations
(vi) Provide required suggestions and make useful recommendations based on the findings of
this research to both the farmers and the Government.
1. 3 JUSTIFICATION OF THE STUDY
Until recently, environmental pollution monitoring and control have not received
much attention in most part of cocoa producing States in Nigeria. One important aspect of
this is the availability of adequate and reliable data on the levels of key pollutants resulting
from applications of pesticides. The occurrence, persistence, and consequences of
organochlorine pesticides in the environment will continue to represent an environmental
issue for contemporary and future generations. To address this issue, it is necessary to
determine the levels of organochlorine pesticides in some areas of likely predominance. This
informs the choice of the selected study area, Ondo State. This is a major cocoa producing
area in Nigeria where large cocoa plantations are situated. Thus, the findings of this research
can serve as a basis on measure of the presence and persistence of organochlorine pesticides
in major cocoa farms in Nigeria.
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