This cross-sectional study was undertaken in CN Palayam, Naduveerpattu village of Cuddalore district, Tamil Nadu, India from March to May in the year 2014. A total of 35 farm workers were recruited by simple random sampling method based on the inclusion and exclusion criteria and 35 non farm workers were taken as controls. A total of 23 farmers and 26 non-farm workers belong to the age group between 20-40 years of age were recruited. Twelve farmers and 9 non-farm workers fall in the age group between 40-60 years. Among the 35 farmers, 11 were males and 24 were females. Among the 35 non-farmers, 16 were males and 19 were females. The control group does not belong to farming community but were involved in pottery selling business. All 35 farmers and 35 non farmers who entered the study were accounted.

The following formula was used for sample size calculation:

Where p, P1=56%(prevalence of respiratory disease among the farm workers) [14]:

q= 100-p

P2=20%

Zα=1.96

Zβ=0.842 for sample size calculation.

The minimum sample size required was coming around 28 and by adding 10% of failure rate it was coming around 31 so we have took 35 as sample size.

Inclusion criteria: Farm workers of both the sex who work six hours a day (average hours of working in the field per day) for atleast six days a week, age group 20-60 years.

Inclusion criteria for controls was non-farm workers of same age group and not exposed to organophosphorus compounds.

Exclusion criteria: Smokers, known asthmatic, hypertensives and cardiac patients, those who were on regular medications for any medical illnesses, < 6 months of exposure to OP compounds.

After getting the Institutional Ethical Committee clearance, subjects were recruited based on inclusion and exclusion criteria. Informed consent was obtained from all the subjects. Detailed medical history mainly the respiratory symptoms, duration of exposure, use of protective equipments if any (face mask, gloves, eye mask, special clothes, shoes and hat) and cleanliness habits (taking food in between the work without washing the hands, taking bath after working in the field) were noted from the study group. Measurements like height, weight, blood pressure, pulse rate, BMI, PEFR were recorded during 10 am-12 am in the morning for both study and the control group.

PEFR was measured using Wright’s mini Peak Flow Meter [15]. PEFR was measured by asking the subjects to sit comfortably and expire forcefully in to the peak flow meter after making deep inspiration to find the maximum velocity of airflow. The procedure was repeated three times and the maximum of the three readings were taken.

Chi-square test was used to analyse the qualitative data. All values were expressed as Mean±SD. Students unpaired t-test was used to compare PEFR between two groups and to compare the duration of exposure and PEFR using GRAPH PAD PRISM. The p<0.05 was considered to be statistically significant.

From [Table/Fig-1] it is seen that the study and the control group were age and BMI matched. Pulse rate and PEFR show a significant difference between study and the control group.

From [Table/Fig-2] it is clearly seen that there was a significant difference (p<0.05) in PEFR between the farmers who worked for ≤ 20 years (n=23) and those who worked > 20 years (n=12)

[Table/Fig-2]:

Relation between duration of exposure and PEFR among the farmers.

The Chi-square test between respiratory symptoms (cough, chest tightness, breathing difficulty) and duration of exposure did not show any significant difference among the farmers. As a whole 71% of the farm workers used one or more personal protective equipments. Among the 35 farm workers 65% used special clothes for working in the field, 31% used special gloves while working with the pesticides, 20% used face mask when they work in the pesticide sprayed field, 14% used special shoes when they work in the freshly pesticide sprayed field and 5% covered their head with cloth while working in the freshly sprayed field. About 22% of farmers had cough and breathing difficulty, 20% had chest tightness. Nearly 14% were taking food in between the work without washing the hands, 71% had the habit of taking bath after working in the field.

There was a significant decrease in PEFR among the farmers when compared to the control group. This is similar to the results obtained by Jinky Leilanie Del Prado-Lu, and Chakraborty S et al., [16,17]. The PEFR seemed to have an inverse relation with the duration of exposure to pesticides. This could be due to entry of pesticides via inhalation and orally because of various unhealthy practices like not washing the hands immediately after work in the field [3,8]. Turabi A et al., also reported that farmers with mild pesticide poisoning fail to report to the health sector because of the fear of losing employment if they were found to have the disease. He also reported that chronic pesticide exposure was a problem among the poor rural population where they live and work in close proximity to the fields on which the chemicals were applied. He further emphasized that use of empty cans of pesticide as drinking water reservoir and bad hygiene were the expected sources of exposure [2].

Though pesticides can get access into the human body by various routes, it can enter more quickly via the respiratory tract causing impairement of lung function. Thus exposure of pesticides through inhalation among the farmers deserves particular attention [18]. Peiris-John RJ et al., further reported that absorption of pesticide is rapid via inhalation and most of the OP compounds directly enter the systemic circulation by passing the liver where they get metabolized [19].

Jinky Leilanie Del Prado-Lu, Chakraborty S et al., and Kesava-chandran C et al., reported that in developing countries like India, farmers get direct exposure to pesticides due to unsafe work practices like improper handling like spraying against the wind, wiping the sweat off the face, incorrect storage and poor housekeeping of the pesticides [16,17,20]. Chitra GA et al., further emphasized that the farmers had very poor knowledge about the ill effects of pesticides and the importance of personal protective equipments [21].

Volatile chemicals after spraying remain suspended in the air can be inhaled by the workers, producing irritant effect and airway narrowing [6]. This shows that the organophosphorus compounds trigger the bronchospasm and increase the airflow resistance among the agricultural farm workers [22]. These small droplets can also have an access to alveolar space and damage the alveolar capillary membrane and subsequently the diffusion of gases. Our findings are further supported by Eskenazi B et al., that OP pesticides cause respiratory diseases among the children through dysregulation of autonomic nervous system [23].

Reduction in PEFR on chronic exposure to OP compounds could be attributed to irreversibile binding to cholinesterase enzyme and its deactivation [19]. Some authors also reported that effect of OP compounds could also be due to the production of oxygen free radicals [24]. Fareed M et al., found that the cholinesterases levels decrease as the respiratory symptoms among the farmers increase [8]. In contrast Cotton J et al., reported that Erythrocyte Cholinesterase activity (EAChE) was reported as normal for mild to chronic exposure group due to wide reference range for EAChE activity [25]. Various animal studies also reported that vagally mediated broncho-constriction is due to decreased function of inhibitory M2 muscarinic receptors on parasympathetic nerves to the airway smooth muscle [26]. Both acute and subacute exposure of Wister rats to OP compounds increase the muscarinic effect on smooth muscles of the airways and the nicotinic effects on the muscles of respiration along with increase in affinity to acetylcholine (Ach) [27]. Our study was further supported by Kesavachandran C et al., who found that FVC, FEV1, PEFR were lower among the pesticide retailers [28].

Evidence suggests that organophosphorus (OP) compounds being highly volatile affects the dwellers around 25 kms radius from the agricultural field apart from farming community. Hence, control group were selected from urban area which is more than 25 kms from the field [2].

OP compounds are known to cause bradycardia and hypotension [8], but in this study both systolic and diastolic blood pressure did not show any significant difference between the two groups. The cardiovascular effects could be due to entry of pesticides in the blood stream via the respiratory tract or due to increased cholinergic activity in the nerve endings causing prolonged depolarization [29]. However, the pulse rate was decreased among the farmers which might be due to their regular physical activity.

Hoppin JA et al., reported that OP like coumaphos and parathion were associated with allergic asthma and wheeze [30]. Various studies found that respiratory symptoms and the bronchospasm among the farmers could be due to lack of using personal protective equipments like mask, gloves, etc., [10]. About 25% of farmers reported one or more respiratory symptoms compared to that of the controls.

From this study we found that 71% of the farmers were using personal protective equipments, but only 20% were using the face mask which prevents the entry of OP compounds into the respiratory tract. This might be the reason for decrease in PEFR as the duration of exposure increases.

Farmers resisted to give their blood samples for analysis to the researcher outside their social setup. Sample size was limited.

Exposure of farm workers to OP pesticides do affect the cardio respiratory system in long run which can be prevented by educating the farmers to use personal protective equipment and following hygienic practices, because safe working environment will promote the physical, mental and social wellbeing of the workers at work places resulting in effective work output.