Dear Osujieke Donald,

The term pesticide covers a wide range of compounds including insecticides, fungicides, herbicides, rodenticides, molluscicides, nematicides, plant growth regulators and others. Among these, organochlorine (OC) insecticides, used successfully in controlling a number of diseases, such as malaria and typhus, were banned or restricted after the 1960s in most of the technologically advanced countries. The introduction of other synthetic insecticides – organophosphate (OP) insecticides in the 1960s, carbamates in 1970s and pyrethroids in 1980s and the introduction of herbicides and fungicides in the 1970s–1980s contributed greatly to pest control and agricultural output. Ideally a pesticide must be lethal to the targeted pests, but not to non-target species, including man. Unfortunately, this is not the case, so the controversy of use and abuse of pesticides has surfaced. The rampant use of these chemicals, under the adage, “if little is good, a lot more will be better” has played havoc with human and other life form.

 The high risk groups exposed to pesticides include production workers, formulators, sprayers, mixers, loaders and agricultural farm workers. During manufacture and formulation, the possibility of hazards may be higher because the processes involved are not risk free. In industrial settings, workers are at increased risk since they handle various toxic chemicals including pesticides, raw materials, toxic solvents and inert carriers.

C compounds could pollute the tissues of virtually every life form on the earth, the air, the lakes and the oceans, the fishes that live in them and the birds that feed on the fishes . The US National Academy of Sciences stated that the DDT metabolite DDE causes eggshell thinning and that the bald eagle population in the United States declined primarily because of exposure to DDT and its metabolites . Certain environmental chemicals, including pesticides termed as endocrine disruptors, are known to elicit their adverse effects by mimicking or antagonising natural hormones in the body and it has been postulated that their long-term, low-dose exposure is increasingly linked to human health effects such as immune suppression, hormone disruption, diminished intelligence, reproductive abnormalities and cancer . A study on workers (N=356) in four units manufacturing HCH in India revealed neurological symptoms (21%) which were related to the intensity of exposure . The magnitude of the toxicity risk involved in the spraying of methomyl, a carbamate insecticide, in field conditions was assessed by the National Institute of Occupational Health (NIOH) . Significant changes were noticed in the ECG, the serum LDH levels, and cholinesterase (ChE) activities in the spraymen, indicating cardiotoxic effects of methomyl. Observations confined to health surveillance in male formulators engaged in production of dust and liquid formulations of various pesticides (malathion, methyl parathion, DDT and lindane) in industrial settings of the unorganised sector revealed a high occurrence of generalised symptoms (headache, nausea, vomiting, fatigue, irritation of skin and eyes) besides psychological, neurological, cardiorespiratory and gastrointestinal symptoms coupled with low plasma ChE activity .

Data on reproductive toxicity were collected from 1,106 couples when the males were associated with the spraying of pesticides (OC, OP and carbamates) in cotton fields .A study in malaria spraymen was initiated to evaluate the effects of a short-term (16 week) exposure in workers (N=216) spraying HCH in field conditions .

For determining the extent of pesticide contamination in the food stuffs, programs entitled ‘Monitoring of Pesticide Residues in Products of Plant Origin in the European Union’ started to be established in the European Union since 1996.

Pesticides can contaminate soil, water, turf, and other vegetation. In addition to killing insects or weeds, pesticides can be toxic to a host of other organisms including birds, fish, beneficial insects, and non-target plants. Insecticides are generally the most acutely toxic class of pesticides, but herbicides can also pose risks to non-target organisms.

Pesticides can reach surface water through runoff from treated plants and soil. Contamination of water by pesticides is widespread

Groundwater pollution due to pesticides is a worldwide problem.

A large number of transformation products (TPs) from a wide range of pesticides have been documented .Not many of all possible pesticide TPs have been monitored in soil,

Heavy treatment of soil with pesticides can cause populations of beneficial soil microorganisms to decline. “If we lose both bacteria and fungi, then the soil degrades. Overuse of chemical fertilizers and pesticides have effects on the soil organisms that are similar to human overuse of antibiotics.

Pesticide sprays can directly hit non-target vegetation, or can drift or volatilize from the treated area and contaminate air, soil, and non-target plants.

 Regards,

Prem Baboo

i am in full conformity with Sir prem baboo

decline number of soil microbes fungi, yeasts,bacteria,actinomycetes,nematoes, earthworms,other soil inhabiting fauna  

all due to application of pesticides and excess chemical fertilizers

An excellent response from  Dr Prem Babo. Of late , there has been increasingly greater realisation about the effect of excessive application of pesticides on soil fertility , primarily induced through vast decline in microbial load of soil  ( in terms of structural and functional microbial diversity ), thereby , soil not only loose nutrients contributing to intensity factor , but turns soil unresponsive to applied fertilizers . This aspect , we hardly look at , rather we start looking pesticide resistance as one of the causes of decline in productivity/unsustainability. Regarding chemical fertilizers , i have my own reservation that it will induce any reduction in microbial population of the soil  , as long as , fertilization is balanced . 

Yes I agree with Dr Srivastava. Impact of pesticides on soil microbial community is more serious than the chemical fertilizers. 

But , i feel , such scenario , one can observe in any region , where intensive agriculture is followed with higher cropping intensity , more so in arid/semi-arid than tropical soils.?

Here are some attachments  analysing this important issue...

excellent approach !!!