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Emerging Infections: Microbial Threats to Health in the United States
small part of the pesticide market. The committee feels strongly, however, that pesticide development in this area needs to be given some priority. Pesticide development is now driven mainly by the demands of agriculture. Moreover, as pesticide development has become ever more specialized, there are fewer compounds available that have both agricultural and public health uses.
Agricultural applications account for about 75 percent of pesticide use in the United States. Approximately 407,000 tons of pesticide were used in 1987, of which about 89,500 tons were insecticides. Public health use accounts for about 10 percent of all pesticides globally; the major public health uses are for control of malaria, filariasis, schistosomiasis, onchocerciasis, and trypanosomiasis (Moses, 1992).
Dichlorodiphenyl trichloroethane (DDT), one of the most effective and economical pesticides ever developed, was first marketed in 1942, three years after Swiss chemist Paul Mueller discovered that the compound had insecticidal properties. In 1972, all agricultural use of DDT in the United States was banned because of its adverse environmental effects. Its use is now restricted by the EPA to public health emergencies, as defined under FIFRA. DDT is still used in many developing countries for public health purposes, particularly malaria control. Currently, aldrin, benzene hexachloride, chlordane, chlordimeform, DBCP, diazinon, dieldrin, dinogeb, ethylene dibromide, andrin, EPN, heptachlor, lindane, mirox, nitrofen (TOK), 2,4,5-T/silvex, and toxaphene also are banned, suspended, or severely restricted in their use as pesticides within the United States (Moses, 1992).
The use of insect growth regulators (so-called biorational or third-generation pesticides) to control vector populations is being investigated. These compounds affect certain biological processes of insects, such as metamorphosis, that are not present in mammals and other vertebrates. Biological control agents (the use of one organism to control another) are also considered biorational pesticides. Once licensed, many such materials will be used to control the immature stages of a number of insect vectors. They are likely to be of limited value as adulticides, however, since compounds used to control adult insects usually must produce mortality quickly. So far, only conventional broad-spectrum pesticides possess this characteristic. Resistance to biorational pesticides has recently been demonstrated in laboratory settings, even in the case of microbial pesticides.
The lack of a sufficient stockpile of effective pesticides, which might be required in the event of a major epidemic, continues to be a serious problem. The public health community has played a minor role in the formulation of pesticide use policy, which is mainly influenced by agricultural and environmental lobbying efforts. Until there are adequate alternative means for controlling disease-carrying vectors, it is critical that public health requirements for pesticides be considered when pesticide policy is being