The Economics of Poisoning

Although the use of poisons on fellow human beings has the longer recorded history, man has seldom scruple to poison any insects, rodents, plants, or fungi that he felt were threatening his health, safety, livelihood, or comfort. By the end of the eighteenth century lye, lime, soap, turpentine, tobacco, pyrethrum powder, mineral oil, and arsenic had all, in various compounds, been tried against insects. Commercial use of pesticides, however, did not really begin in the United States until just after the Civil War when Paris green was used against the Colorado beetle. The success of Paris green led to experiments with other arsenic compounds, of which lead arsenate and calcium arsenate came into commercial use. All of these were used primarily in agriculture, largely on fruits, vegetables, cotton, and a few other high-value crops.

In 1945 DDT, a synthetic organic pesticide developed during the war for the military establishment, was released for civilian use. It is the best known of a large group of chemicals, the chlorinated hydrocarbons. Some of them are highly toxic to insects. They are also persistent. From the standpoint of killing insects this is a desirable quality, for (unlike aphids, a whole generation of which can be killed in the egg state by relatively simple means) many pests can be controlled only by a persistent chemical or by repeated doses of one that is not persistent. But from the standpoint of hazard to human beings and useful insects and animals, the quality of persistence is most undesirable. Another group of chemicals—the organic phosphates—have more recently come into use as pesticides, and new compounds are continually being tested and synthesized. An advantage of this class, which includes parathion and malathion, is the wide range of properties that can be developed in the various compounds. Some, such as tetraethyl phosphate, hydrolyze and leave no residue after use. Others affect the whole bodily systems of growing plants or animals.

Recently there has been something of a trend to a new class of chemicals—the carbamates—caused partly by the fact that insects quickly began to develop resistance to the chlorinated hydrocarbons and the organic phosphates. Another stimulus has been the search for control agents that are relatively harmless to warm-blooded animals and do not accumulate as residues in animal tissues. One of the carbamates, Sevin, has these desirable properties, although some of the others inhibit production of cholinesterase, a substance essential to the functioning of the nervous system in mammals. Some of the carbamates, have growth-regulating effects on plants, which makes them useful as herbicides, but for this reason they are unacceptable as agricultural insecticides.

With the development of the new synthetic pesticides, spraying and dusting operations have spread from the few intensive crops that used to be treated with the arsenic compounds to field crops, pastures, and forests, and to homes and gardens. Insecticides also are widely used to protect stored foods and to control insects that carry diseases or are simply nuisances. The use of herbicides, following the introduction of new compounds like 2,4-D and 2,4,5-T, has increased greatly and become more diversified. Aside from control of weeds in crops, pastures, and lawns, they have been used extensively for controlling vegetation along roadsides, clearing land, and controlling weeds in irrigation and drainage canals.

As a consequence, the annual use of commercial chemical pesticides has been increasing steadily. By 1962 an estimated one acre out of every twelve in the contiguous 48 states was being treated with either an insecticide, an herbicide, or both. Use of the older insecticides—the arsenic compounds and the poisons derived from plants, like pyrethrum and rotenone—has fallen rapidly, often to negligible amounts. But consumption of the new synthetics, pound for pound, has far more than made up for the decline, and each pound of the new materials goes a lot farther than the old ones in killing power.

This shift has taken place in the face of a stubborn technical obstacle—increased resistance on the part of the insects to the substances designed to kill them. This is not a new problem, but it is one that has been greatly intensified by the very effectiveness of the newer chemicals. The high rates of kill enormously accelerate the process of selection for resistance. With the older types of pesticide the emergence of immune strains usually took several decades; now it usually takes only a few years, and the resistance often applies not only to a specific chemical, but to others in the same group. Thus the effort to replace obsolete agents is continuous. Like the Red Queen, the chemical pesticide industry has to do a great deal of running to stay in the same place.

Many persons believe—and their viewpoint has been put forward eloquently—that the known hazards and still unknown risks of large-scale use of chemical pesticides may well outweigh the gains to agriculture and specific public health campaigns; that the long-range results of upsetting the balance of nature could be disastrous; and that, consequently, alternatives to chemical pesticides (perhaps biological controls through introduction of parasites, predators, and pathogens) must be found if there is even any doubt of the side effects of the chemicals. Others maintain that the obvious dependence of modern agriculture on chemical pesticides is sufficient reason for doing nothing to restrict their use; that the gains in agricultural productivity clearly more than balance losses of other values.

Neither of these uncompromising viewpoints seems convincing. The real problems and issues that arise from adding large quantities of pesticides to the environment cannot be resolved either by resorting to panaceas or by treating the question as if it were independent of other elements of technology.

Even now, with much still to be learned on the scientific side about direct and indirect side effects of pesticides and their technical relationships to agricultural production, health, and natural resources, the sober techniques of economic analysis can make a contribution to responsible decisions of public policy. A complete appraisal of the social costs and benefits of chemical pesticides may still be a long way off, but a useful beginning can be made now in comparing costs and benefits in economic terms as a help in deciding in what ways the largest net gains to society can be realized. The problem of pesticides is largely and inescapably economic in nature.