Benefits from Pesticides

Because of the productivity demanded in modem agriculture to feed the millions of increasing world population, the use of different pesticides has become a necessity to contain a host of crop and household pests. A major benefit of pesticides is their ability to contain hosts of pests on commercial crops, food crops, lawn, and turf in and around household surroundings. Hop destruction by locust infestation in Africa is an example. Insecticides also are used for control of vector-bome diseases such as typhus and malaria. 

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One reason for the rapid growth in the use of pesticides worldwide has been the "Green Revolution" (5), Although there have been some benefits from pesticide use in agriculture, they also cause significant environmental and public health problems. The same is true in public health where Insecticides have been used to control malaria. However, today Increased resistance to insecticides in mosquitoes and Increased resistance to drugs by the malarial parasite are resulting in an explosive increase of malaria worldwide (5). 

Hayes (5) has also reviewed the contribution of pesticides to the control of human diseases spread by arthropods and other vectors. Outbreaks of malaria, louse-borne typhus, plague, and urban yellow fever, four of the most important epidemic diseases of history, have been controlled by use of the organochlorine insecticides, especially DDT. In fact, the single most significant benefit from pesticides has been the protection from malaria. Today malaria eradication is an accomplished fact for 619 million people who live in areas once malarious. Where eradication has been achieved it has stood the test of time. An additional 334 million people live in areas where transmission of the parasite is no longer a major problem. Thus, about 1 billion people, or approximately one-fourth of the population of the world, no longer live under the threat of malaria. 

However, Silent Spring , Rachel Carson s challenge to the perceived abuse of synthetic pesticides, published in 1962, initiated the a movement toward strict agrochemical regulation and the far more rigorous assessment of risks and benefits from pesticide use. 

As well as these major application fields, biosensors and analytical techniques should also benefit from the technology. Some examples have already been described. The detection of formaldehyde by a formaldehyde dehydrogenase coated onto a piezoelectric crystal has been performed at the ppm level. Detection of pesticides and organophosphorus compounds at the ppb level has been rendered... 

So although there is no doubt that the presence of pesticide residues and food additives is significantly different between organic and conventional foods, there are no generally accepted volumes of data showing that the difference in composition makes a difference to the health of consumers. However, a more precise estimate of the magnitude of risk from pesticide residues or food additives may not make much difference to the view of many consumers, who do not want to take any risk, no matter how small, when not associated with clear benefits for themselves (Torjusen et al. 2004). 

Appendix B provides brief case studies of two pesticides, glyphosate and permethrin, for which a pre-existing risk assessment can help to put biomonitoring results into perspective. In both cases, the Environmental Protection Agency (EPA) has evaluated risks for a wide array of exposure scenarios as part of the reregistration process, and there are biomonitoring data whose interpretation could benefit from these risk assessments. 

The agricultural use of pesticides such as insecticides, herbicides, and fungicides has clearly reduced crop losses due to insects, weeds, and plant diseases in the US and throughout the world. The benefits from agricultural pesticides include improved crop yields, greater availability of fruits, vegetables, and grains, and lower consumer costs (Ecobichon, 1996). 

This system of integrated crop production places high demands on all aspects of crop production, including the controlled use of pesticides. Development and benefit from integrated pest management systems depend upon the combined efforts of the researcher, development and scouting persons and a highly trained farmer. 

One of the major benefits of pesticides is the protection of crop yields. According to the National Research Council (2000), removing pesticides from U.S. agriculture would cause crop production to decline as much as 50%, depending on the crop species. Moreover, farm exports would decrease by 50%, and consumer expenditures for food would increase— and be accompanied by an increase in inflation—as food prices increase. In the United States, we will spend 30-40% of our income on food as opposed to 8.7% currently. It was concluded that chemical insecticides should remain part of a larger toolbox of diverse pest management tactics in the foreseeable future. 

Compared with the occupational exposnre of applicators and workers following pesticide application in the field, post-application residential exposure to pesticides used in and around the home is lower in level, but encompasses a wider variety of scenarios, such as age distribution, activity patterns and product use. Typically, few data are available on residential exposure, while a large body of data does exist for occupational exposures. Residential exposure assessment and modeling may benefit from the new data requirements under the United States Food Qnality Protection Act of 1996 (Lewis et al, 1994 Hill et al., 1995 Lu and Fenske, 1998 USEPA, 1990 Whitmore et al., 1994). In occupational exposnre assessment, a database approach is favored, while in residential exposure assessment a mechanistic and statistical modeling approach is dominant. 

Unfortunately, PPE used for protection from pesticides can increase the potential for heat stress. The PPE features that keep pesticides out also serve to prevent body heat from escaping. People cannot work as long or as hard when the PPE they are wearing reduces the body s ability to maintain its thermal balance. Under some enviromnental conditions, certain activities cannot be performed withont jeopardizing the health of the worker unless auxiliary cooling is provided. The risk that PPE may aggravate heat stress must be balanced with the PPE s potential worker protection benefits. 

Of most immediate interest to gardeners, however, are the thousands of species of predatory insects that attack pests. They are common worldwide and most numerous in gardens where pesticides are not used. Although they are often unseen, we reap immeasurable benefit from their presence. Sometimes the bcnc-ficials are difficult to distinguish from the pests. See Insect Impostors on page 260 for hints to help you see the difference tietween these two groups of insects. 

The interaction between the needs of agriculture, environmental protection and concerns for human health is complex, and is depicted in Figure 1.1. Human health implications cannot be simply regarded as negative and restricted to the potential risks associated with the presence of pesticide residues in foods. It is also essential to take into account the undoubted benefits from the control of infectious diseases vectored by pests and the contribution to health from a varied and safe food supply. 

Exposure to pesticides may occur in a variety of different ways including worker exposure during manufacture, during transport, and exposure to residues in edible crops, soil and water. Adverse effects on man may result from the compound itself, its mammalian metabolites, plant and soil metabolites or, possibly, from breakdown products in the environment. Pesticides are often dispersed widely in the environment as stable materials, such as DDT, which may remain as virtually permanent contaminants, though at detectable concentrations. This, together with the fact that pesticides are highly biologically-active molecules, requires a fine balance to be set between the benefits of pesticides and their possible hazard to man or the environment. 

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