INTRODUCTION:- Tremendous benefits have been derived from the use of pesticides in forestry, public health and the domestic sphere – and, of course, in agriculture, a sector upon which the Indian economy is largely dependent. An area of 169 million hectares consists of permanently cropped land. Food grain production, which stood at a mere 50 million tonnes in 1948-49, had increased almost fourfold to 198 million tonnes by the end of 1996-97. This result has been achieved by the use of high-yield varieties of seeds, advanced irrigation technologies and agricultural chemicals1. The term pesticide covers a wide range of compounds including insecticides, fungicides, herbicides, rodenticides, molluscicides, nematocides, 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 1970s – 1980s contributed greatly in pest control and agricultural output. Ideally a pesticide must be lethal to the targetted pests, but not to non-target species, including man. Unfortunately, this is not 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 forms. In India, the first report of poisoning due to pesticides was from Kerala in 1958, where over 100 people died after consuming wheat flour contaminated with parathion2. This prompted the Special Committee on Harmful Effects of Pesticides constituted by the ICAR to focus further attention on the problem3. Further, Carlson in 1962 warned that OC 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 fishes4. Later, 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 metabolites5. 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 are increasingly linked to human health effects such as immunosuppression, hormone disruption, diminished intelligence, reproductive abnormalities and cancer(6-8).
The pesticide industry in India The production of pesticides started in India in 1952 with the establishment of a plant for the production of BHC near Calcutta, and India is now the second largest manufacturer of pesticides in Asia after China and ranks twelfth globally9. There has been a steady growth in the production of technical grade pesticides in India, from 5,000 metric tonnes in 1958 to 102,240 metric tonnes in 1998. In 1996-97 the demand for pesticides in terms of value was estimated to be around Rs. 22 billion (USD 0.5 billion), which is about 2% of the total world market. The pattern of pesticide usage in India is different from that for the world in general. As can be seen from Figure 1, in India 76% of the pesticide used is insecticide, as against 44% globally9. The use of herbicides and fungicides is correspondingly less heavy. The main use of pesticides in India is for cotton crops (45%), followed by paddy and wheat. Figure 1. Consumption pattern of pesticides
BENEFITS OF PESTICIDES:- Improving Productivity:- Similarly outputs and productivity have increased dramatically in most countries, for example, wheat yields in the United Kingdom. Corn yields in the USA Increases in productivity have been due to several factors including use of fertiliser, better varieties and use of machinery. Pesticides have been an integral part of the process by reducing losses from the weeds, diseases and pests that can markedly reduce the amount of harvestable produce. Warren (1998) also drew attention to the spectacular increases in crop yields in the United States in the twentieth century. Webster et al. (1999) stated that “considerable economic losses” would be suffered without pesticide use and quantified the significant increases in yield and economic margin that result from pesticide use. Protect Crop losses/yield reduction:- In medium land rice even under puddle conditions during the critical period warranted an effective and economic weed control practice to prevent a reduction in rice yield due to weeds that ranged from 28 to 48% based on comparisons that included control (weedy) plots. Weeds reduce yield of dry land crops by 37-79%. Severe infestation of weeds particularly in early stage of crop establishment ultimately accounts for a yield reduction of 40%. Herbicides provided an economic and labour benefit. Suspicion about chemicals in food is fuelling sales of organic crops (MAF, 2006) but it is by no means certain whether organic production could sustain the world’s growing population (Oerke, 2004). Vector Disease Control:- Vector-borne diseases are most effectively tackled by killing the vector. Insecticides are often the only practical way. Insecticides are used to control the insects that spread deadly diseases such as malaria that results in an estimated 5000 deaths each day (Ross, 2005). Bhatia (2004) wrote that malaria is one of the leading causes of morbidity and mortality in the developing world and a major public health problem in India. Quality of Food:- Increasing evidence (Dietary Guidelines, 2005) shows that eating fruit and vegetables regularly reduces the risk of many cancers, high blood pressure, heart disease, diabetes, stroke, and other chronic diseases. Lewis et al. (2004, 2005) discussed the nutritional properties of apples and blueberries in the US diet and concluded that their high concentrations of antioxidants act as protectants against cancer, heart disease. Lewis attributed doubling in wild blueberry production and subsequent increases in consumption chiefly to herbicide use that improved weed control. Other area-Transport, Sport Complex, Building:- The transport sector makes extensive use of pesticides, particularly herbicides. Herbicides and insecticides are used to maintain the turf on sports pitches, cricket grounds and golf courses. Insecticides protect buildings and other wooden structures from damage by termites and wood boring insects.
HAZARDS OF PESTICIDES:-
Human Being:- If the credits of pesticides include enhanced economic potential in terms of increased production of food andfibre, and amelioration of vector-borne diseases, then their debits have resulted in serious health implications to man and his environment. There is now overwhelming evidence that some of these chemicals do pose potential risk to humans and other life forms and unwanted sideeffects to the environment (17-19). No segment of the population is completely protected against exposure to pesticides and the potentially serious health effects, though a disproportionate burden is shouldered by the people of developing countries and by high risk groups in each country20. The world-wide deaths and chronic illnesses due to pesticide poisoning number about 1 million per year21.
Potential Risk in Occupationally Exposed Subjects:- The high risk groups exposed to pesticides include the production workers, formulators, sprayers, mixers, loaders and agricultural farm workers. During manufacture and formulation, the ossibility of hazards may be more because the processes involved are not risk free. In industrial settings, the workers are at increased risk since they handle various toxic chemicals including pesticides, raw materials, toxic solvents and inert carriers. Workers exposed to HCH:- A study on workers (N=356) in four units manufacturing HCH revealed neurological symptoms (21%) which were related to the intensity of exposure22. Formulators exposed to combination of pesticides:- 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 generalized symptoms (headache, nausea, vomiting, fatigue, irritation of skin and eyes) besides psychological, neurological, cardiorespiratory and gastrointestinal symptoms coupled with low plasma holinesterase (ChE) activity 23. Health effects of methomyl on sprayers:- The magnitude of the toxicity risk involved in the spraying of methomyl, a carbamate insecticide, in field conditions was assessed by the NIOH 24. Significant changes were noticed in the ECG and the levels of serum LDH and ChE activities in the spraymen indicating the cardiotoxic effects of methomyl. Reproductive performance in sprayers:- 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 fields25. Studies in malaria spraymen:- Study was initiated to evaluate the effects of a shortterm 16 week exposure in workers (N=216) spraying HCH in field conditions26. Food Commodities:-The UK Pesticide Residue Committee annual report (2002) showed that over 70% of the food in the UK contained no pesticide residues at all and only 1.09% contained residues above the statutory maximum residue levels (MRLs). It concluded that -none of these residues caused concern for people’s health-. John Bell, Head of the UK Food Standards Agency, a body that was set up to restore public confidence in food said (2005) that -Maximum residue levels are generally set well below safety limits. There are no safety concerns or we would take action immediately.” Yet these very small quantities of chemicals in our food, detected at ever lower levels due to increasingly sensitive laboratory equipment, are now easy targets for the media, despite overwhelming evidence that residues pose a very tiny risk to the people who eat farm food (Brown, 2004, US EPA), a risk that is anyway far outweighed by the benefits of a diet that includes fresh produce. Impact on Environment:-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. Soil Contamination:- Pesticides have various characteristics that determine how they act once in soil. Mobility refers to how much a pesticide will move around in the soil. The half life of a pesticide refers to the length of time it takes for half of the pesticide to degrade. Persistence refers to the length of time until all measurable residues of a pesticide are gone. Surface Water Contamination:- Pesticides can reach surface water through runoff from treated plants and soil. Contamination of water by pesticides is widespread. The results of a comprehensive set of studies done by the U.S. Geological Survey (USGS) on major river basins across the country in the early to mid- 90s yielded startling results. More than 90 percent of water and fish samples from all streams contained one, or more often, several pesticides. Pesticides were found in all samples from major rivers with mixed agricultural and urban land use influences, and 99 percent of samples of urban streams28. The USGS also found that concentrations of insecticides in urban streams commonly exceeded guidelines for protection of aquatic life. Twenty-three pesticides were detected in waterways in the Puget Sound Basin, including 17 herbicides. According to USGS, -in general more pesticides were detected in urban streams than in agricultural streams.- 29.
Ground Water Contamination:- Pesticides, including herbicides, can and do leach to contaminate ground water. According to the USGS, at least 143 different pesticides and 21 transformation products have been found in the ground water, including pesticides from every major chemical class. Over the past two decades, detections have been found in the ground water of more than 43 states30. Contamination of ground water is of concern because ground water supplies 50 percent of the U.S. population with Drinkingwater31. Once ground water is polluted with toxic chemicals, it may take many years for the contamination to dissipate or be cleaned up. Cleanup may also be very costly and complex, if not impossible(32-34). Contamination of Air, Soil, and Non-target Vegetation:- 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. Some pesticide drift occurs during every application, even from ground equipment35. Drift can account for a loss of 2 to 25% of the chemical being applied, which can spread over a distance of a few yards to several hundred miles. There are thousands of reported complaints of off target spray drift each year in the U.S. 36. Many pesticides can volatilize (that is, they can evaporate from soil and foliage, move away from the application, and contaminate the environment.) 37, 38. As much as 80-90 percent of an applied pesticide can be volatilized within a few days of application39. Despite the fact that only limited research has been done on the topic, studies consistently find pesticide residues in air. According to the USGS, pesticides have been detected in the atmosphere in all areas of the nation sampled40. Nearly every pesticide investigated has been detected in rain, air, fog, or snow across the nation at different times of the year41. Many pesticides have been detected in air at more than half the sites sampled nationwide. Harmful Effects of Pesticides on Non-target Organisms:- Pesticides are found as common contaminants in soil, air, and water, and on non-target vegetation in our urban landscapes. Once there, they can harm plants and animals ranging from beneficial soil microorganisms and insects, non-target plants, fish, birds, and other wildlife. Beneficial Soil Microorganisms:- One spoonful of healthy soil has millions of tiny organisms including fungi, bacteria, and a host of others. These microorganisms play a key role in helping plants utilize soil nutrients needed to grow and thrive. Microorganisms also help soil store water and nutrients, regulate water flow, and filter pollutants38. The heavy treatment of soil with pesticides can cause populations of beneficial soil microorganisms to decline. According to soil scientist Dr. Elaine Ingham, -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. Indiscriminate use of chemicals might work for a few years, but after awhile, there aren’t enough beneficial soil organisms to hold onto the nutrients.- 40.
CONCLUSION:- Pesticides are often considered a quick, easy, and inexpensive solution for controlling weeds and insect pests in urban landscapes. However, pesticide use comes at a significant cost. Pesticides have contaminated almost every part of our environment. Pesticide residues are found in soil and air, and in surface and ground water across the nation, and urban pesticide uses contribute to the problem. Pesticide contamination poses significant risks to the environment and non-target organisms ranging from beneficial soil microorganisms, to insects, plants, fish, and birds. Contrary to common misconceptions, even herbicides can cause harm to the environment. In fact, weed killers can be especially problematic because they are used in relatively large volumes. The best way to reduce pesticide contamination (and the harm it causes) in our environment is for all of us to do our part to use safer, nonchemical pest control (including weed control) methods.
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