In the eight years since Silent Spring was published, Rachel Carson’s warnings about DDT as a universal contaminant have been vindicated by scientists on both sides of the Atlantic Ocean. A number of nations (including Russia) have banned this chemical insecticide, and at the end of 1969, the American public concluded that an imminent ban on DDT was assured in this country as well. But such was not the case.
The U.S. Department of Agriculture announced in November of last year that it was “canceling” the registration of DDT for certain purposes, including use on tobacco, shade trees, aquatic environments, and around the home. Under the complex federal pesticide regulations, however, such a cancellation provides the manufacturer with an appeal procedure that may take several years to complete. DDT’s leading manufacturers have already embarked on an appeal. Conservationists argue that if USDA were really serious about restricting DDT, it would have resorted to an alternative procedure, “suspending” DDT’s use until the appeals procedure definitely established the extent of the pesticide’s hazard. Conservation organizations are now in court seeking a suspension of DDT’s sales. But unless they succeed, the United States is likely to remain for some time in the position of permitting the use of a suspected carcinogen in the open environment.
The appearance of DDT during World War II seemed to offer a solution to the pest-control problem that had plagued man for ages. It was developed as a pesticide from an old formula by the Swiss chemist Dr. Paul Mueller, and named for the first letters of its complex components, dichloro-diphenyl-trichloroethane. During the war it worked wonders in smothering large-scale attacks of typhus and malaria. In 1948 Mueller was awarded a Nobel Prize in chemistry for his work on DDT.
Competent scientists were confused at first by DDT’s special assets, which served to mask its defects. Its persistence, in fact, seemed to be a blessing (or at least a convenience) for the farmer or forester who could get by with only an occasional application of it to his crops.
At the same time, in small doses, DDT seemed to be relatively harmless to living things aside from insects. Few birds, fish, or mammals are killed outright by DDT, if it is used with restraint, in contrast to the effect of age-old pesticides such as arsenic. DDT and its chemical relatives also have a remarkably good safety record among people who work with them. The tragedies we hear of among farm workers, and even among children who find and swallow pesticides, are usually caused by the nonpersistent yet highly toxic varieties.
But the chemists made a fundamental mistake when they turned loose in the world, without adequate tests, a poisonous substance. Instead of pursuing alternate methods of cultural and biological controls which attack only pest insects, the chemists took the line of least resistance pointed out by DDT. They formulated similar chemicals, close relatives to DDT, but many times more toxic. These newer persistent pesticides include aldrin, dieldrin, endrin, chlordane and heptachlor— substances which do not break down in the environment for many years. No one is quite sure even today exactly how they kill, but they are known to affect the central nervous system.
DDT and its chemical relatives work in an insidious way. Many small organisms ingest them in minute amounts without harm, storing them in their tissues. This innocuous start sets off a poisonous train of events; it is this sort of process which has caused communities to lose, for example, their robins. Here is how it works:
A local park department sprays its trees with DDT to control certain insects. The leaves, still carrying residues of DDT, eventually fall to the ground, where they are eaten by earthworms. The earthworms are among the smaller organisms not particularly vulnerable to DDT. They concentrate large quantities of the poison in their tissues. Later robins feed on the DDT-laden earthworms, building up residues in their own bodies until they reach fatal level.
Even more insidious are DDT’s effects on reproduction. Once more, birds serve as a frightening example of how these poisons work. DDT poisoning contributes to the increased production of liver enzymes, leading to the breakdown of estrogen in a bird’s body. Since estrogen helps to mobilize calcium, one result is the production of eggshells deficient in calcium. Thinner, more fragile shells become the norm.
In California, pelicans now crush their eggs simply by sitting on them in the nest. Other large birds, such as hawks and eagles, produce eggshells which are too thin to protect the embryo. Scientists fear that many of our most magnificent birds, including the bald eagle and the peregrine falcon, may be wiped out in the United States within a few years.
And what of the effect of these poisons on human health? DDT causes cancer in laboratory rodents and in trout. Though scientists are not yet willing to extrapolate these results to man, they do urge great caution.
Pesticide residues have been detected in unborn babies and in mother’s milk. DDT levels in mother’s milk ingested by American infants average four times the maximum daily intake recommended by the Food and Drug Administration. And these levels are five times the DDT content permitted in the interstate shipment of cow’s milk. It is a measure of our degraded environment that some doctors suggest infants should no longer drink their mother’s milk.
Teratology, the study of birth defects, is concentrating increasingly on the role that chemicals play in the fact that 7 percent of all babies born alive today suffer from some defect. Doctors warn women not to spray their rooms with pesticides during pregnancy.
In a sea
We live in a sea of pesticides. Less than half of the chemicals sprayed from planes reach their target crops. The rest remains suspended as particles in the air, to be blown about at the wind’s will. Samples of air from even such large industrial cities as Pittsburgh contain DDT. These airborne-pesticide levels increase in towns and cities adjacent to heavily sprayed farmlands or in areas where pesticides are manufactured.
Among farmers, as among the general population, the whole story of long-term effects of exposure to pesticides is not yet known. But more intensive study of the pilots who fly crop-dusting planes has turned up information. Their lengthy exposure to even nonpersistent pesticides brings on mental disturbances of considerable duration. The Federal Aviation Agency reports that “recovery from schizophrenic and depressive symptoms requires from six to twelve months following removal from further contact with toxic agents.”
The planes we fly in, the theaters we visit, often are sprayed regularly with persistent pesticides. Pesticides are added to our clothes by dry cleaners. The rugs we buy have been treated with long-lasting pesticides by the manufacturers. The food we eat contains pesticide residues—what former Interior Secretary Stewart L. Udall has called “the uninvited additive.” Since persistent pesticides are fat soluble, they are most often retained in the fatty parts of animals or in oily fish. Fish oils, including that of tuna, and even refined cod liver oil, contain especially high pesticide residues. Similarly high residues caused many cases of Lake Michigan salmon to be taken off the market.
Another study that uncovered important data was carried out by scientists at the University of Miami. Terminal cancer patients were shown to have a far higher pesticide content in their tissues than victims of natural deaths. Interviews with the former’s next of kin revealed that almost invariably they had been heavy users of pesticides around the house and garden. Like many other Americans, they had treated these dangerous poisons as casually as if they were cough drops.
These data are consistent with the belief that pesticides inhaled or absorbed through the skin cause far more damage than those we ingest with our food. Despite warnings by the Public Health Service and the American Medical Association that they may be hazardous to health, the U.S. Department of Agriculture until recently authorized the use of vaporizing devices to kill insects in restaurants and other public places. These devices often contain lindane, one of the persistent pesticides. Several manufacturers have filed appeals against USDA’s decision to cancel the registration of their lindane vaporizers.
Even more serious doubts were raised recently about “no-pest” strips which are widely sold for use in the home. These paper strips, when hung in a room, release pesticide vapors to the atmosphere. The Public Health Service has disapproved of one of these products for home use, Vapona, which is manufactured by the Shell Chemical Company. PHS insists that the residues could contaminate food and be harmful to infants and elderly persons.
Yet these products are still registered for home use by the Department of Agriculture. Congressional hearings in 1969 disclosed that employees of Shell, acting simultaneously as consultants for the Department of Agriculture, testified to the safety of these strips. Under a recent ruling, labels on the “no-pest” strips must carry this warning: “Do not use in nurseries or rooms where infants, ill or aged persons are confined.”
Even before the government said it planned to phase out most uses of DDT, its importance had declined. According to a recent chemical trade magazine: “DDT’s marketing problems began in earnest with the publication of the late Rachel Carson’s Silent Spring. In ‘57 the U.S. Department of Agriculture sprayed 4.9 million acres with pesticide; in ‘67, USDA sprayed only 100,000 acres with it. Last year the figure was zero.”
Nevertheless, in 1969, 120 million pounds of DDT were produced in the United States; only 20 million pounds were used domestically, the rest exported. (DDT, moving freely in the environment, is, of course, returned to us in the world-circling currents of sea and air.) Meanwhile, DDT’s more potent relatives—dieldrin, endrin, and the others—are manufactured in ever-increasing amounts.
What other chemicals, besides its relatives, are replacing DDT? Here the picture is a little brighter, but still hazardous. Many of the less persistent pesticides, such as parathion, do not exhibit DDT’s long-term effects, but they are extremely toxic to all kinds of life, including human life. It is little wonder, since they are closely related to the deadly nerve gases synthesized by German scientists during World War II. Carelessly used, they can and do kill farm workers both here and abroad. The United Farm Workers Organizing Committee has sought to outlaw their use.
Until very recently, the most widely used chemical weed-killers were thought to be harmless to human beings when applied as directed. But doubts have arisen since the discovery that the herbicide 2,4, 5-T, forty million pounds of which have been used in Vietnam as a defoliant, causes birth defects in animals, and consequently may be a hazard to pregnant women. The federal government has taken steps to prohibit its sale for use around the home, although it is still widely available in retail stores.
Recent research in Sweden proves that the use of mercury as a fungicide on cereal seeds presents enormous hazards to wildlife. Ultimately, scientists fear, its hazard to human beings may prove equally great. The Swedes solved their problem by banning the use of one extremely pervasive compound, methylmercury, and shipping it to the United States, where it is now used to treat wheat seed.
The chemical industry has challenged HEW’s order to phase out DDT. The federal government has taken no vigorous steps against the other persistent pesticides. Clearly, the end of the contamination is not in sight.
-FRANK GRAHAM, JR.