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Người đàn ông sử dụng thuốc trừ sâu như các chất gây ô nhiễm môi trường có mục đích để cải thiện chất lượng môi trường cho bản thân và vật nuôi và cây trồng của mình. Trong nông nghiệp, thuốc trừ sâu được sử dụng để tăng tỷ lệ lợi ích chi phí ủng hộ của người nông dân và người tiêu dùng cuối cùng của sản phẩm thực phẩm và chất xơ, các công dân. Nó đã được ước tính rằng các nông dân Mỹ nhận được một lợi nhuận trung bình ròng khoảng $ 4 cho mỗi. | PESTICIDES INTRODUCTION Man employs pesticides as purposeful environmental contaminants in order to improve environmental quality for himself and his domesticated animals and plants. In agriculture pesticides are used to increase the cost benefit ratio in favor of the farmer and of the ultimate consumer of food and fiber products the citizen. It has been widely estimated that the U.S. farmer receives an average net return of about 4 for every 1 invested in pesticides PSAC 1965 Pimentel and Levitan 1986 . In our present era of managed ecology of monocultures of farm mechanization and of the complex system of food harvesting processing distribution and storage the use of pesticides often represents the slender margin between crop production and crop failure and between economic profit and economic loss. In the developing countries where food supplies are marginal pesticide use may represent the margin between survival and starvation. In public health pesticides often provide the only feasible means for the control of the invertebrate vectors of human and animal diseases. It is difficult to place monetary values on human health but for malaria in India the World Health Organization has estimated that an investment of 200 million in malaria control by DDT residual house spraying during 1956-66 saved 179.5 million man days of labor or an estimated saving of 490 million. The cost benefit ratio has thus been about 2.7 return for every 1 invested. In addition during this period the annual number of cases of malaria has decreased from 75 million to 150 000 and deaths from about 750 000 to 1500 World Health 1968 . In surveying the role of pesticides in environmental quality it must be remembered that pests themselves generally affect adversely the quality of the environment. The spectrum ranges from a mosquito in the bedroom or a cockroach in the pantry to a plague of locusts or the tsetse flies Glossina spp. which as vectors of trypanosomiasis have effectively prevented the
