Risk assessment of exposure of tobacco farmers to pesticide in Swabi, Pakistan.

Risk assessment of exposure of tobacco farmers to pesticide in Swabi, Pakistan
Background and issue identification
Use of pesticides is much common in developing countries. It is used extensively to protect the crops from insect-borne and other endemic diseases for their increase production (Ecobichon, 2001; Khan, Bhatti, Khan, Naqvi & Karam, 2008; Khan, Shabbir, Majid, Naqvi & Khan, 2009). About 30% of worldwide serious health issues, related to the improper use of pesticides, have been reported in several developing countries (Khan et al., 2009). According to WHO (1990), about three million incidences of acute, severe poisonings and 220 000 deaths have been documented in developing countries (Ecobichon, 2001). Besides, a significant number of mild to moderate intoxication cases remain unreported.
Like other developing countries, significant amount of pesticides are used in Pakistan (Khan et al., 2009). The few studies, conducted on the health effects of pesticides among cotton and fruit farmers in Pakistan, indicate high incidence rate of pesticides poisoning.
Tobacco, a significant cash crop of Pakistan, is cultivated mostly in Swabi district of North West Frontier Province (NWFP) (Khan et al., 2009). Pesticides are used in tremendous quantities in tobacco cultivation as it is prone to many insect-borne and other types of diseases. The two mostly used pesticides in Pakistan tobacco farming are Organophosphate (OP) and Carbamate (CM). Though, there is significant role of pesticides in the high production of the crop, however, its relatively frequent and improper use makes the tobacco farmers susceptible to adverse health effects.

Health effects of pesticides have been reported in other countries. For example, high incidence rate of pesticides poisoning had been documented in tobacco farmers of Malaysia and Greece (Khan et al., 2009). Moreover, health effects of pesticides use have been reported in other farmers of Pakistan but not studied in tobacco growers. Hence, risk assessment study of exposure to pesticides is necessary to determine its acute health hazards and incidence of pesticides poisoning in tobacco farmers of Swabi, Pakistan.
Risk assessment methodology
Presence of pesticides in air, soil and water is an environmental hazard which puts the tobacco growers at the risk of adverse health effects. Hence, the “Environmental Health Guidelines for assessing human health risks from environmental hazards (2012) will be used for this risk assessment study. It is a comprehensive tool for the risk assessment of environmental hazards.
Hazard assessment
Hazard identification
Classification of pesticides on the basis of WHO guidelines
The toxicity of the pesticides, used by tobacco farmers, can be classified according to the WHO guidelines (khan et al., 2009). Types of pesticides and percentage of the user farmers are given in the table 1.
Table 1. Classification of pesticides on the basis of WHO guidelines
Name of pesticide WHO class Class description Percentage of the users
Methomyl class Ib Highly hazardous 63 %
Methamidophos Class Ib Highly hazardous 62 %
Thiodicarb Class II Moderately hazardous 56 %
Cypermethrin Class II Moderately hazardous 36 %
Thiodan Class II Moderately hazardous Rarely
Confidor Class II Moderately hazardous Rarely

Health effects of pesticides
Health effects vary in accordance of level of exposure. High level exposure to pesticides is associated with acute toxicity and low level exposure is attributed with chronic toxicity.
Acute toxicity
High level of exposure to the majority of pesticides can cause neurotoxicity in acute phase (Alavanja, Hoppin, & Kamel, 2004). Response to exposure can be observed instantly within minutes; however, symptoms of toxicity vary for mild and severe cases. Manifestations of mild cases are nausea, vomiting, headache, dizziness, eye watering, excessive perspiration, salivation and constriction of pupils. Sever cases result in muscle jerks and weakness, heart rate changes, bronchospasm, and later can lead to seizures and comma.
Sub-chronic toxicity
An intermediate syndrome can occur afterward which is characterized by sensory abnormalities, muscle spasm and weakness which can progress to paralysis (Alavanja et al., 2004).
Chronic toxicity
Chronic exposure to pesticides is linked with several non-specifics symptoms (Alavanja et al., 2004). These include fatigue, headache, dizziness, nausea, weakness, chest congestion, confusion, insomnia and concentration difficulty.
Other forms of manifestations of chronic toxicity include deficits of cognitive and psychomotor functions, changes in mood and affect.
Moreover, chronic exposure may increase risk for some neurological diseases like Parkinson’s disease and dementia.
Summary
Health effects of pesticides exposure depends on the level of exposure and the toxicity of the pesticides. Some of the associated health effects are acute, sub-chronic and chronic, each with different clinical manifestations. Chronic exposure is toxic to body systems and is associated with different diseases and some types of cancers.
Dose–response assessment
The relationship of adverse health effects and dose-response were determined by both the exhibited symptoms and the level of plasma cholinesterase (PChE) (Khan et al., 2009). However, Plasma cholinesterase (PChE) levels are more accurate indicators as compared to the clinical symptoms.
Classification of poisoning
The severity of poisoning was classified by reduction in the levels of plasma cholinesterase (PChE). Pre-exposure baseline plasma cholinesterase (PChE) levels of all subjects were tested and recorded. Details of the classification are given in the table 2.
Results
The clinical signs and symptoms of acute poisoning were recorded within 1-4 hours after spraying pesticides; however, most of the symptom occurred within one hour of exposure which was consistent with the established toxicology of pesticides (Khan et al., 2009).
Table 2. Classification of poisoning on the basis of post-exposure reduction in the PChE
Reduction in the PChE level from the base line levels Classification of poisoning
< 20 % Normal poisoning 20-40 % Mild poisoning >44 % Moderate poisoning
Clinical manifestations
Majority of the farmers suffered from many symptoms of the gastrointestinal, central nervous systems and respiratory systems. These include headache, dizziness, nausea, vomiting stomach cramps, diarrhea, breathing difficulty, eye redness, skin rash and muscle weakness.
Prevalence of symptoms of mild and moderate poisoning
Farmers who suffered from moderate poisoning showed higher prevalence of clinical symptoms which include headache, dizziness, nauseas, vomiting, diarrhea, stomach cramps, breathing difficulty and eye redness as compared to those who experienced mild poisoning.
Incidence rate of poisoning on the basis of reduction in PChE
Significant decrease in the PChE levels was found after exposure, which was associated with the clinical symptoms in the farmers. The incidence rate of poisoning types is given in the table 3.

Table 3. Incidence rate of poisoning types on the basis of reduction in PChE
Reduction in the PChE levels Severity class Number of affected farmers Percentage of total number of farmers
< 20% Normal 58 55.23 % 20-40% Mild 35 33.33 % >44% Moderate 12 11.42 %

Summary
Plasma cholinesterase (PChE) level was used as an indicator of severity of poisoning. The post-exposure results were compared to the pre-exposure PChE levels for the determination of incidence rate. Significant reduction in the PChE levels was found which was associated with the clinical manifestations of the types of poisoning, i.e. mild or moderate poisoning.
Exposure assessment
Data of subjects and their exposure to pesticides
A total of 105 potential pesticides sprayers were selected. All subjects were male, with mean age less than 30 years and were working full time in the tobacco fields. Only 36 % of them were literate but majority of them (40 %) were illiterate. Their activities included storage, preparation and spraying of pesticides for at least 30 hours per month
Farmers’ factors of exposure to pesticides
Most of the farmers didn’t have training of safe handling of pesticides. Half of them were working in tobacco fields for the last 11-20 years but only 12 workers had gotten formal training. Majority of farmers were careless about the handling, storage and discarding of the left over pesticides. Only 36% farmers stored pesticides in an appropriate storage area, however, most of them (64%) did not store properly.
Majority of the farmers were exposed to the pesticides through many ways. Most of them, for example, did not use personal protective equipments (PPEs) while handling pesticides. Gloves and face masks were not used while preparing, refilling of tanks, spraying and transferring pesticides. Many of them wore traditional clothes while working in the field and spraying, and covered their mouth with cotton cloth which does not provide proper protection against inhalation or ingestion of pesticides. In addition, some tanks, which are mounted on the back, were found leaking which made the farmers’ back in direct contact with pesticides.
Furthermore, empty pesticides containers were not disposed properly. Most of the farmers (62%) discarded empty containers in the fields openly or in irrigating water channels. Only 38% farmers disposed the empty containers properly, i.e. burnt them or buried in the soil.

Use of PPEs minimizes exposure to pesticides. However, most of the farmers did not use PPEs which predisposed them to pesticides exposure through inhalation, oral ingestion and direct skin contact. This is consistent with the results of this study. Analysis of the results showed that reduction in the PChE levels was significant in those farmers who used PPEs less frequently as compared to those who used them regularly, in addition to other safety measures.
Summary
Most of the farmers were predisposed to pesticides exposure, owing to their lack of knowledge and practice of safe handling of pesticides. Majority of them did not use PPEs which put them exposed to the pesticides entry into their bodies through inhalation, oral ingestion and direct skin contact. This resulted in pesticides toxicity as showed by the post exposure reduction in PChE levels of the non-users of PPEs.
Risk characterisation
Effects of prolong exposure
Data analyses of different studies show that chronic exposure to pesticides is associated with severe consequences for human health. It affects multiple systems of the body and associated with many types of cancers.
Effects on central nervous system (CNS)
Neurological manifestations associated with of chronic toxicity include deficits of cognitive function, changes in mood and affect, and psychomotor function deficits (Alavanja et al., 2004).
Moreover, chronic exposure may increase risk for some neurological diseases like Parkinson’s disease and dementia.
Effects on endocrine system
A study conducted on effects of pesticides exposure on reproductive and thyroid hormones in agricultural workers concluded that there is a strong association between pesticide exposure and interruption in thyroid and reproductive hormone levels (Khan, Ahad, Ansari & Khan, 2013).
Effects on reproductive system
Study of pesticides production workers, who were infertile, revealed that sperm count of almost 50% workers were lower than normal level as compared to non-exposed workers (Sharp, Eskenazi, Harrison, Callas & Smith, 1986).
Types of associated cancers
A study reviewed and analysed literature to find out association between pesticide exposure and cancer (Bassil, Vakil, Sanborn, Cole, Kaur & Kerr, 2007). Majority of studies indicated positive association of pesticide exposure with non-Hodgkin lymphoma and leukaemia. A positive association of cancer prevalence with pesticides exposure was found in children and pregnant women. Many studies indicated links with solid tumours, like brain tumours and prostate cancers. Incidence of kidney cancer was reported by some studies in children whose parents was exposed to pesticides at job. However, these links were found more consistent with high level and long term exposures.
Summary
Chronic exposure to pesticides is associated with grave health consequences for humans. It is linked with adverse effects on multiple body systems such as CNS, endocrine system, reproductive system and may cause some type of cancers. Effects on other body systems need to be evaluated.
Conclusion
Pesticides are used extensively in developing countries where high incidence of associated health issues has been reported. It is associated with severe acute, sub-chronic and chronic health effects on human body including some types of cancers.
This study identified many factors which put Pakistani tobacco farmers at risk of exposure to pesticides and ultimately to adverse health outcomes, such as their low level of literacy, lack of knowledge and training on safe handling of pesticides, unavailability of PPEs. The incidence rate of pesticides poisoning in them was confirmed by linking their clinical manifestations with reduction in their post exposure level of PChE.
Results of this study show that pesticides toxicity is prevalent in the tobacco farmer of Pakistan which necessitates safety measures on the part of farmers. They need to be trained for the safe handling of pesticides and use of PPEs.

References
Alavanja, M. C., Hoppin, J. A., & Kamel, F. (2004). Health Effects of Chronic Pesticide Exposure: Cancer and Neurotoxicity* 3. Annu. Rev. Public Health, 25, 155-197.
Bassil, K. L., Vakil, C., Sanborn, M., Cole, D. C., Kaur, J. S., & Kerr, K. J. (2007). Cancer health effects of pesticides Systematic review. Canadian Family Physician, 53(10), 1704-1711.
Ecobichon, D. J. (2001). Pesticide use in developing countries. Toxicology, 160(1), 27-33.
Khan, D. A., Ahad, K., Ansari, W. M., & Khan, H. (2013). Pesticide exposure and endocrine dysfunction in the cotton crop agricultural workers of southern Punjab, Pakistan. Asia-Pacific Journal of Public Health, 25(2), 181-191.
Khan, D. A., Bhatti, M. M., Khan, F. A., Naqvi, S. T., & Karam, A. (2008). Adverse effects of pesticides residues on biochemical markers in Pakistani tobacco farmers. International journal of clinical and experimental medicine, 1(3), 274.

Khan, D. A., Shabbir, S., Majid, M., Naqvi, T. A., & Khan, F. A. (2009). Risk assessment of pesticide exposure on health of Pakistani tobacco farmers. Journal of Exposure Science and Environmental Epidemiology, 20(2), 196-204.

Sharp, D. S., Eskenazi, B., Harrison, R., Callas, P., & Smith, A. H. (1986). Delayed health hazards of pesticide exposure. Annual Review of Public Health, 7(1), 441-471.