Objectives as stated in the project proposal:

1. To assess the occupational and environmental hazards of pesticides in rural farmers engaged in agricultural practices.
2. To assess the susceptibility of DDT and other persistent pesticides commonly used in agricultural practices among the rural farmers of different age group, dietary habits and duration of exposure.
3. To determine the concentration of pesticides in circulating blood and placenta/umbilical cord of pregnant women farmers undergoing full term, pre term and abortion cases.
4. To critically examine the symptoms of acute and chronic exposure to pesticides in farmers occupationally exposed to pesticidal spray, especially the pregnant ones.
5. To collect the base line data on the actual and potential number of farmers belonging to the weaker section of the society engaged in agricultural spray of pesticides and evaluation of their vulnerability to the harmful effects of pesticides.

The widespread use of pesticides by agricultural farmers and the consequent passage of these pesticides into the food chain as well as in the human tissues has become a serious issue of public health. The increasing reports of Indians carrying the highest body burned of pesticides in the world has intensified governmental and non governmental affords to elucidate the potential harmful effects that could be rendered to human, especially the farmers who has been occupationally exposed to varying concentration of pesticides as sprayers. While aiming at generating a baseline data on the occupational and environmental hazards of pesticides, series of experiments were designed and conducted over the years as detailed in the preceding section. The following evaluations have been found to emerge from these studies, which may constitute vital base line data from this important agricultural sector involving several million farmers.

1. The study of farmers occupationally exposed to pesticides as sprayers over long and short duration was to monitor their health and assess the harmful effects, if any. In addition to recording the general health status, estimated of the concentration of organochlorine pesticides were made in the serum of farmers and in control group having no accidental or occupational exposure.

A survey of 144 spray men associated with malaria control of India by the World Health Organization revealed that blood levels of DDT were 7.5 - 15.0 times those in controls and were at least as high as those reported for workers who manufacture and formulate DDT elsewhere in the world. However, on examination they sprayers showed brisker knee reflexes an slight tremor was more often present. In the present study confined to only twenty spray men with different exposure periods. Total DDT residues were about ten times those in control. Workers did not report any untoward signs on clinical examination. DDT sprayers having total DDT residues of 478.107 and 249 ppb in their serum showed abnormal nerve conduction i.e. 58.8 and 38,   46.6 and 29 as well as 70 and 38.2 m/s respectively. However, this abnormality can not be solely attributed to DDT because the subjects with 791.633 and 510 ppb also showed normal nerve conduction.

Zielhuis suggested levels below 200 ppb of total DDT in the blood as No Effect Level (NEL). It was, however, recommended that when the range is 200-500ppb the worker should be temporarily removed from his occupation.

Further according to Poland an average levels of 573 ppb DDT in blood of the exposed workers corresponds to an average daily intake of about 18 mg/man/day. Since in the present study the average was 409 ppb of DDT equivalent in the occupationally exposed workers, their average daily intake is about 10.3 mg/man/day against 0.25 mg/man/day, the acceptable daily intake (ADI) recommended by WHO/FAO.

DDT has been shown to cause the induction of hepatic drug metabolizing enzymes (HDME) in man. Increased metabolism of drugs and steroid indicative of induction of hepatic microsomal enzymes have been reported in workers exposed to DDT. Therefore, considerably low levels of BHC in DDT exposed workers as compared with controls assume a great significance. High levels of DDT in occupationally exposed workers in the present study might have resulted in the induction of HMDME and led to a rapid biodegradation of BHC in the exposed workers.

A significant increase in the serum lactic dehydrogenase(LDH) activity (<0.05) and a more substantial decrease in serum creatine phosphokinase (CPK) activity (<0.05) in workers with 16-167 ppb of p,p' DDT in their serum has been reported. A range of 9-548 ppb of p,p' DDT was observed in the present study.

Morgan and Lawrence showed a negative relationship between serum bilirubin and serum (DDT + DDE) and suggested a continuous reduction in serum bilirubin as a function of serum (DDT+DDE) level over the range which was less than the present study. As an inducer of xenobiotic metabolizing enzyme of the liver, DDT (and probably DDE) stimulate the activity of glucuronyl transferase which is responsible for the excretion of bilirubin. It is this effect of DDT which plays as important role in the clinical control of jaundice due to congenital deficiency of hepatic glucuronyl transferase.
 

2. The placenta serves as a barrier between mother and foetus for the large number of exogenous and endogenous substances. It contains appreciable concentrations of fat and hence can function as a carrier for lipophilic xenoboitics including organochlorine pesticides. Transfer of organochlorine pesticides from mother to the developing foetus through the placenta as influenced by age, dietary habit and ethnicity of the mother was described in these studies, on biological monitoring of pesticides.

 

 
 
 

It is obvious from the results that a longer life span of the mother results in a greater excretion through the placenta at the time of delivery. Mothers in the age group 26-34 years were found to dispose of mean of 31.47 µg of total 1,1,1-trichloro-2,2-bis (p-chlorophenyl) as against 21.24 µg in mothers of 18-25 years of age. Similarly, the older group excreted 25.11 µg of benzene hexachloride (BHC) against 17.28 µg in younger group. Differences were also found in quantitative excretion of lindane. 1.1-dichloro-2-2-bis (p-chlorophenyl) ethylene (p,p' DDE) and p,p' DDT. The amount of aldrin and 1.1-dichloro-2-2-bis (p-chlorophenyl) ethane (p,p' DDD) excreted through the placenta were almost similar in two age - groups of mothers.

The effect of dietary habits on the phenomenon of pesticide excretion through the placenta was suggested by the observation that non vegetarian mothers excreted relatively higher amount of chlorinated pesticides compared with vegetarian mothers. The mean amount of total DDT excreted through the placenta at the time of delivery was found to be 32.63 µg in non vegetarian and 25.02 µg  in vegetarian mothers. The mean concentration of BHC was 23.36 and 16.68 µg respectively.

The area of living of the mothers during pregnancy was also found to influence the pesticide excretion the mean removal being 31.23 µg of total DDT and 19.80 µg  of BHC in rural subjects as against 26.83 µg  of total DDT and 26.81 µg  of BHC in urban subjects. Thus, urban mothers excreted more BHC than rural mothers.
 

3. Oragnochlorine insecticides estimated in the maternal blood, placenta, and foetus of pregnant women, undergoing preterm lobar or spontaneous abortions, were compared with those obtained from an equal number of women undergoing full-term labour.

 

 
 
 

The statistical outcome of the data, representing range of observation and mean values with standard deviation, are summarized. Average levels of organochlorine insecticides, viz. BHC, aldrin, p,p' DDD, p,p' DDT and total OCI, estimated in the maternal blood, placenta, and foetus of preterm, spontaneous abortion and full-term labour followed the trend:

Spontaneous Abortion > Preterm > Full-term Employing the usual significance tests, the findings of preterm and spontaneous abortions differed significantly from controls (p<0.001).

The ratios of values of all the detected insecticide in the maternal blood, placenta, and foetus were also computed for each individual pair and their mean ± S.D. The ratio for p,p'-DDE and DDTR (total DDT equivalent) was found to be the highest in abortive subjects, followed by preterm, and the lowest in full-term cases. The ratio for other insecticides did not differ significantly in control, preterm, or spontaneous abortive subjects.

A rise in the level of oestrogen before parturition has been reported, suggesting is role in labour. Synthesis of the contractile proteins actin and myocin, and the deposition of glycogen and the enzymes concerned with deriving chemical energy from glucose are some functions of oestrogen. The ability of DDE and DDT to exert an oestrogen effect and to disturb the progesteroneestrogen metabolism assumed significance while discussing their role in the initiation of labour.

Higher levels of organochlorine insecticides detected in the maternal blood, placenta and foetus of pregnant women undergoing preterm labour and spontaneous abortions as compared with those of full-term labour, can tentatively be related to the possible involvement of OCI in facilitating the onset of labour. It has been shown that the presence of prostaglandins in the decidua is closely associated with the initiation of labour, and they are known to be released at the time of labour. The biosynthesis of prostaglandin is governed by phospholipase-A₂, present in the lysosomes through the release of arachidonic acid - a precursor of prostaglandin. A study has revealed that DDT and DDE cause labilization of lysosomes. It can, therefore, be presumed that higher level of DDT and DDE observed in cases of spontaneous abortion and preterm labour may cause the lysis of lysosomal membrane, thereby releasing the phospholipase-A₂, a rate limiting factor in the biosynthesis of prostaglandin and thus, may help affect the onset of labour.

A ratio between the maternal blood, placenta and foetus for p,p'-DDE and DDTR (total DDT equivalent) was found to follow the trend:

Full-term < Preterm < spontaneous Abortions.

This signifies minimum transfer of organochlorine insecticides across the placenta among the abortive subjects. However, it would be difficult to assign these compounds as a contributory factor for preterm or abortion unless some experimental or theoretical evidence is available to implicate them.

O' Leary et al reported that the ability of organochlorine insecticides to stimulate the hepatic microsomal enzymes can theoretically cause premature labour. However, in a follow-up study they failed to correlate DDE and DDT, detected in all the cases, with abortions. Our study has shown that the highest levels of total ICI are found in the maternal blood, placenta, and foetus of abortive subjects, followed by preterm and full-term cases. This order can be used as a base to speculate regarding the possibility of organochlorine insecticides acting as antagonists to pregnancy, either directly or indirectly.
 

4. Human milk is a primary and potent source of infant nutrition. It is rich in fat and stands at the end of the food chain. In view of their lipophilic nature pesticides could accumulate in milk in alarming concentrations. In India, although per capita consumption of agrochemical is much less than that in other developing countries, the tendency to accumulate them in body issues is relatively high.

The mean residue levels of total BHC (sum of it a, b and c-isomer) and total DDT (p,p' DDT, p,p' DDD and p,p' DDE) in milk are 0.107 ± 0.012 and 0.12 ± 0.002 ppm; in maternal blood, 0.022 ± 0.001 and 0.02 ± 0.002 ppm, respectively. BHC level in milk is, thus, five times more than that present in maternal blood, while the factor for DDT is about six. Aldrin concentration was also correspondingly higher in milk.

Accumulation of less biodegradable OCP in blood of women and then subsequent transfer to the foetus, through placenta during pregnancy and then their excretion through breast milk and its consumption by the neonates pose various problems of management of neonatal nutrition and health.

The residue detected in the active circulation in blood breast milk, and in umbilical cord blood represents the pesticides burden of breast feeding mothers and then their transfer from maternal to prenates and neonates.

Milk from older nursing mothers contains more DDT than dose that of younger mothers. In the present study 25 cases have been examined; out of them 21 subjects are between 19 and 23 years of age and others are 26.28, and 35 years, therefore, no sufficient information emerge  to make any assumption in relation to age.

The average amount of milk excreted daily is about 854 ml for breast feeding mothers with one child and 950 ml for a mother with twins. If is assumed that the entire milk produced daily is consumed by the neonate, the present study suggested a daily intake of about 198.628 ppm of total DDT and 91.975 ppm of BHC by the neonates. However, this neonatal intake is lower in case of mothers with twins, but that is an exception.
 

5. There is now general agreement that toxic action of organophosphates  and carbamtes, upon insects as well as vertebrates, is caused by their ability to inhibit acetyl cholinesterase in various parts of the nervous system, and thereby disrupt nervous transmission at that location.

 

 
 
 

Acetyl cholinesterase is widely distributed in the body viz. RBC, ganglia and brain at myoneural junctions. Earlier workers have reported the level of enzyme during exposure to organophosphate pesticides which are replacing the less toxic but more persistent chlorinated hydrocarbons such as DDT. This has resulted in new class of occupational hazards for the agricultural industry, chronic pesticides toxicity.

The results of our study shows a range and mean level of enzyme  activity in red blood cells of normal subjects, having good health and did not report any past accidental or occupational exposure to pesticides, to be 8.33-19.36 and 12.31±1.16 respectively.

As a biological indicator of exposure to organophosphates acetyl cholinesterase activity in RBC, of field workers spraying pesticides was found to be inhibited at the level of 16% (10.30±0.29) as compared with activity of enzyme in normal subjects.
 

6. There is a significant fall in plasma cholinesterase activity in healthy young women in the first trimester of normal pregnancy which returns to normal (pre pregnancy) levels in later stages of pregnancy. Acetyl cholinesterase (AchE) activity of blood has become a diagnostic tool in the pesticide poisoning of organophosphorus and carbamate compounds, and hence several studies on AchE in blood of normal subjects and in pesticide exposed persons as well as in different age groups of children have been conducted. Determination of AchE levels was done in red blood cells of human volunteers a few days before delivery and also in the cord blood which will furnish information about the same in foetus red blood cells. Determination of enzyme activity has also been conducted one day after delivery in RBC of mother. 

A change in activity of acetyl cholinesterase(AchE) in red blood cells(RBC) of mother after delivery in women subjects (25-30) years is not significant. A significant increase was observed, about 20% in age group between 20-25 years. About 55% of material RBC AchE levels are noticed in the foetus in 20-30 years group, while in 30-35 years group it is about 80%.
 
7. Education, training and skill development programme in the safe and judicious use of pesticides by farmers in 510 villages of six blocks of Lucknow and Sitapur district were undertaken through audio-visual aids in local hindi language under this study. This programme was carried out in different batches ranging from 25-50 farmers. The curriculum for this training included categorization of pesticides, non target toxicity, safety measures, anti dotes for pesticide poisoning and the understanding of warning symbols displayed on different category of pesticides with a view to minimize the occupational and environmental hazards of pesticides in farmers. In all 2380 farmers were trained through this study.

Based on the findings of the project on the assessment of occupational & environmental hazards of pesticides in rural farmers of weaker section of the society, the following inferences may be drawn:

1. The farmers, especially those engaged in the spray of pesticides have been found to be maximum susceptible to higher levels of less degradable pesticides and may, thus, be posed with help hazards.
2. Pregnant women of rural areas have been found to have higher body burden of pesticides and a statistical correlation may exist between the onset of premature labour and levels of DDT and its metabolite p,p' - DDE.
3. Significant depletion in the acetyl cholinesterase activity of pesticide sprayers has been observed which may lead to irreparable damage to central nervous system.
4. Breast milk of rural women farmers has been found to contain higher toxic residues posing a serious health hazards to the normal growth and development of suckling neonates from rural areas.
5. There a virtual non-existence of formal or non formal education among the farmers regarding the potential hazards associated with pesticides & there is no system to impart training on this line.

As the farmers, especially the sprayers of pesticides, belonging to the weaker section of the society, are widely distributed through out the country, having different crop pattern & accordingly exposed to different category of pesticides. They should be focussed on an all India basis for which these findings may be used as base line data!