in india , more than 1 billion people are engaged in agricultural activities and a large quantity of pesticides is used to protect their crop against pests to get more yields . india is the largest producer of pesticides in asia and the third largest consumer of pesticides in the world . pesticide consumption has been increasing steadily in the past few years and there has been a distinct shift from organochlorine to organophosphorous ( op ) and carbamate pesticides . these pesticides interfere with or inhibit the activity of cholinesterase ( che ) enzymes in nerves and muscle tissue , which results in accumulation of the neurotransmitter acetylcholine ( ach ) in the nervous system . acute toxicological effects of op pesticides are a result of the inhibition of acetylcholinesterase ( ache ) in the nervous system , which can cause respiratory , myocardial , and neuromuscular transmission impairment . chronic effects of op exposures are not well documented ; however , several recent reports indicate that certain birth outcomes ( e.g. , decreased gestational age , decreased birth length ) and abnormal reflex functions in infants may be associated with low level environmental exposures to op pesticides.[46 ] ache inhibition causes clinical features due to overstimulation of cholinergic synapses in the parasympathetic system , neuromuscular junction , and central nervous system . decrease in che activity by 1525% , 2535% , and 3550% is caused by low , moderate , and severe intoxication with pesticides , respectively . people are directly exposed to these pesticides through dermal contact and inhalation , and indirectly through the food chain . annually , about 3 million people worldwide are intoxicated with organophosphates ; out of this , 300,000 either die or are severely injured . a most economical blood test for the monitoring of farm workers who are exposed to op insecticide is measurement of plasma butyrylcholinesterase ( bche ) activity . monitoring of plasma bche has been recommended in the op - exposed population , as this could be a useful biomarker to predict and prevent health hazards of pesticides . it is recommended that the workers che level should be assessed before they start working at a pesticide applied region . in view of this , the present study was aimed to evaluate the ache and bche activities among agriculture workers occupationally exposed to pesticide . the study was conducted in the neighboring villages of chikkaballapur town , rural bangalore , south india , from december 2010 to march 2011 . this study included 28 rural people who were agriculture workers , engaged in floriculture , and cultivation of cabbage , potato , and grape . a control group consisting of 13 unexposed workers , who never had any exposure to op pesticides , was taken as the reference group . a detailed history , including the personal and occupational details , was recorded through a questionnaire . a written informed consent was taken from all study subjects after explaining the importance of the study in their local language . five milliliters of venous blood was collected in dried heparinized tubes and transported in ice box to the laboratory . blood samples of voluntarily participated agriculture workers ( n = 28 ) who have been involved mainly in pesticide spraying activities in vegetable and grape gardens were collected . a control group consisting of 13 male subjects who belonged to a similar age group and socioeconomic status and were not exposed to any kind of pesticides was selected for the study from the same localities . blood was centrifuged at 4000 rpm for 10 min at 4c to separate the plasma . che activity was determined by the method of ellman et al . as modified by chambers and chambers . three milliliters of 0.25 mm of 5,5-dithiobis ( 2-nitrobenzoic acid ) ( dtnb ) prepared in 0.05 m phosphate buffer was pipetted out into a cuvette , in which 20 l of thoroughly mixed plasma sample and 100 l of 1 mm substrate ( acetylthiocholine iodide for ache assay ) were added . the sample was placed on a uv - vis spectrophotometer set at a wavelength of 410 nm . the change in absorbance with a light path of 1 cm width was recorded following time drive kinetic spectrophotometric method for 5 min to ensure that the linear phase of the reaction was measured at a time lag of 30 sec . a nonenzymatic blank was included to assess the background levels of hydrolysis of the substrate . t - test was used to compare the significance of the mean differences in che activity between exposed and control subjects . the study was conducted in the neighboring villages of chikkaballapur town , rural bangalore , south india , from december 2010 to march 2011 . this study included 28 rural people who were agriculture workers , engaged in floriculture , and cultivation of cabbage , potato , and grape . a control group consisting of 13 unexposed workers , who never had any exposure to op pesticides , was taken as the reference group . a detailed history , including the personal and occupational details , was recorded through a questionnaire . a written informed consent was taken from all study subjects after explaining the importance of the study in their local language . five milliliters of venous blood was collected in dried heparinized tubes and transported in ice box to the laboratory . blood samples of voluntarily participated agriculture workers ( n = 28 ) who have been involved mainly in pesticide spraying activities in vegetable and grape gardens were collected . a control group consisting of 13 male subjects who belonged to a similar age group and socioeconomic status and were not exposed to any kind of pesticides was selected for the study from the same localities . blood was centrifuged at 4000 rpm for 10 min at 4c to separate the plasma . che activity was determined by the method of ellman et al . as modified by chambers and chambers . three milliliters of 0.25 mm of 5,5-dithiobis ( 2-nitrobenzoic acid ) ( dtnb ) prepared in 0.05 m phosphate buffer was pipetted out into a cuvette , in which 20 l of thoroughly mixed plasma sample and 100 l of 1 mm substrate ( acetylthiocholine iodide for ache assay ) were added . the sample was placed on a uv - vis spectrophotometer set at a wavelength of 410 nm . the change in absorbance with a light path of 1 cm width was recorded following time drive kinetic spectrophotometric method for 5 min to ensure that the linear phase of the reaction was measured at a time lag of 30 sec . a nonenzymatic blank was included to assess the background levels of hydrolysis of the substrate . students t - test was used to compare the significance of the mean differences in che activity between exposed and control subjects . the values of p < 0.05 were considered significant . the demographic data of lifestyle habits , type of crop cultivation , pesticides used , and frequency of application collected on both exposed and control subjects are summarized in table 1 . the average age of exposed subjects and controls were 34.6  8.22 and 28.1  9.33 years , respectively . about 53.6% of study subjects were using pesticides weekly once and 21.4% were using weekly thrice for their crop protection . the majority of the workers did not use any protective equipment and a normal cloth was used to cover their face as a mask while spraying . about 6871% had complained having the symptoms of headache and eye irritation [ table 1 ] . characteristics of agricultural workers ( n=28 ) table 2 shows the list of commonly used pesticides in the study locations and world health organization ( who ) classification . majority of the pesticides used were in the categories of moderately hazardous to highly hazardous . pesticides used were in the chemical group of op , organochlorine , carbamates , and synthetic pyrethroids . list of commonly used pesticides in the study area ache and bche activities measured in the blood plasma of exposed and control subjects are given in table 3 . ache activity among exposed subjects ranged between 1.65 and 3.54 moles / min / ml , with a mean concentration of 2.51 moles / min / ml , whereas in the control group it ranged between 2.22 and 3.51 moles / min / ml . the bche activity in agricultural workers ranged between 0.16 and 5.2 moles / min / ml , with a mean concentration of 1.66 moles / min / ml , whereas in the control group it was 2.195.06 moles / min / ml , with a mean concentration of 3.87 moles / min / ml ( p < 0.05 ) . the measured levels of ache and bche activities in exposed subjects were comparatively less than in the control subjects [ figure 1 ] . cholinesterase activity ( moles / min / ml ) among exposed and control group subjects variation in cholinesterase activity between exposed and control groups ( p<0.05 , t - test ) the finding suggests that the ache activity in agriculture workers was decreased ( 14% ) when compared to that of controls due to the inhibition of ache activity by pesticides . the inhibition of ache might have resulted in the accumulation of ach at the synaptic junctions , which may lead to cytotoxicity . occupational exposures to che inhibiting pesticides used in india for agricultural pest control can impair the respiratory health of agricultural workers who work in the field . in agreement with the present study , california agricultural pesticide applicators showed considerable changes in ache inhibition and low ache activities due to exposure to pesticides during the high exposure period . their study also demonstrated that relations exist between change in che inhibition and symptoms , especially respiratory symptoms , symptoms of the cns ( analysis including controls ) , and eye symptoms ( internal analysis ) . studies by hillman and clarke et al . indicated that there was a significant decrease in activity of ache and bche found among the op pesticide sprayers as compared to the controls . reduction in plasma bche activity ( 56% ) in the present study supports similar findings observed by various researchers . the use of che inhibiting pesticides in the agricultural activity caused the depletion of ache and bche activities among workers . from earlier reports and the present results , it can be speculated that decreased plasma che activity is due to prolonged exposures to op pesticides among the study subjects as compared to controls [ figure 1 ] . this study was carried out as part of the academic dissertation and a large number of people could not be included . however , the data generated highlights the effects of pesticide exposures and it would help conduct further studies . this study was carried out as part of the academic dissertation and a large number of people could not be included . however , the data generated highlights the effects of pesticide exposures and it would help conduct further studies . the ache and bche activities measured were significantly lesser due to multiple exposures to different groups of pesticides used for agricultural activity . unscientific way of pesticide mixing , improper way of handling pesticides , and entering agriculture field immediately after pesticide application play significant roles in reducing plasma che activity . preventive measures coupled with biomonitoring of pesticide exposure using che inhibition as a marker are very much important . this will create awareness among the agriculturists , pesticide manufacturers , agriculture department , etc .