Pesticide into Pest

Few chemicals concocted by man have been so widely used and so thoroughly applauded as dichlorodiphenyltrichloroethane, more commonly known as DDT. It has proved its unmatched power in the worldwide battle against those pestborne killers, typhus, encephalitis and, particularly, malaria. Its mastery over the mosquitoes that carry malaria has undoubtedly spared millions of people from death and debilitating infection. Equally potent in saving crops, it has almost doubled the yield from U.S. cotton fields in the past two decades by controlling the boll weevil. Even the Swedes, who have decided to ban the chemical, readily acknowledge its effectiveness. In 1948 they awarded the Nobel Prize for chemistry to Swiss Chemist Paul Mueller for his discovery of its "miraculous" capacity for destroying insects.

Now, growing numbers of scientists and politicians are convinced that Mueller's miracle is more curse than cure. Long after exterminating the bugs at which it is aimed, DDT goes on performing its lethal work, washing from fields into rivers, lingering on the leaves of trees, floating about in the atmosphere for years--and contaminating everything it touches. There are some scientists who estimate that as much as two-thirds of the 1.5 million tons of DDT produced by man may still be adrift.

Poisonous Broth. More widespread than radioactive fallout, DDT is found in every kind of aquatic life and in almost every animal. Even mother's milk exhibits traces of DDT two or three times as high as the maximum standard for cow's milk set by the Food and Drug Administration. In any other container, a current quip has it, mother's milk would be prohibited from crossing state lines.

It is also in trouble within the states. Arizona has already banned DDT spraying. Michigan recently imposed a similar ban after the FDA condemned some 700,000 coho salmon from Lake Michigan because they had unacceptably high concentrations of DDT. Stringent controls are now being considered in the states of Massachusetts, New York and Wisconsin.

Europeans have taken even more decisive action. Following discovery of the chemicals in their herring catch, the Swedes ordered a two-year ban on DDT, as well as the related pesticides lindane, aldrin and dieldrin. The Netherlands decided to stop using DDT. So did Denmark. West Germany limits spraying so severely that only 192 tons of the substance were used throughout the country last year. France and Britain are keeping a watch on pesticide levels within their borders. The Russians, too, are concerned, as Premier Aleksei Kosygin indicated when he offered to join with the Swedes in cleaning up what Europeans call the "poisonous broth" conditions in the Baltic Sea.

The Deadly Seven. That will be no easy task, considering DDT's extraordinary durability and mobility. The chemical belongs to a family of organochlorine pesticides--the "deadly seven" as ecologists call them.-Like the other organochlorines, DDT does not dissolve in water. Thus it accumulates in rivers, lakes and seas for years after the original contamination. Moreover, its unusually long half-life of ten to 15 years means that it retains 50% of its effectiveness for more than a decade after it is first used.

Despite its resistance to water, DDT is easily soluble in fats and highly susceptible to "biological magnification" as it makes its way up the food chain. A typical case of this kind of metabolic mayhem occurred in Long Island Sound. After some mosquito-infested marshes were sprayed, the DDT was found in the nearby water in a "safe" concentration of .000003 parts per million. Nonetheless, the DDT quickly accumulated in more concentrated form in the

Sound's tiny Zooplankton (.04 ppm), then built up further in the fatty tissue of plankton-eating fish (.5 ppm). These small fish, in turn, were devoured by larger fish with yet another increase in DDT concentration (2.0 ppm). By the time the chemical had passed into the bodies of such fish-eating birds as cormorants, mergansers and ospreys its concentration (25 ppm) had increased an astounding 10 million times over the original amount (see diagram).

DDT also interferes with the reproductive cycle. Adult fish, for example, are able to tolerate relatively high levels of DDT. The fish embryo, on the other hand, dies almost immediately when it begins to absorb the pesticide through the fatty yolk sac. In birds, DDT kills off the young by interfering with the female's egg-laying process. Though the exact chemistry is still obscure, the pesticide apparently sends the mother bird's liver into a frenzy of enzyme production. The excess enzymes break down such steroids as estrogen that are essential to the manufacture of calcium. Lacking adequate calcium, the bird's eggs emerge thin-shelled and flaky, offering scant protection for the embryo. In at least one instance, reports the National Audubon Society, which has just joined the public crusade against DDT, a bald-eagle egg was found on the shores of Lake Superior with no shell at all--just a fragile membrane. According to University of Wisconsin Ecologist Joseph Hickey, DDT has caused a disastrous decline in the population of the bald eagle, which is the U.S. national symbol--and the emblem of next week's Apollo 11 flight. Other predators, such as the osprey and peregrine falcon, are gradually vanishing, as are the brown pelican and the extremely rare Bermuda petrel.

Airborne Cats. Beyond the danger to fish and birds lies DDT's threat to the whole ecological system. Concentrations of DDT no larger than a few parts per billion in plankton, says Biologist Charles F. Wurster Jr., chief scientific adviser to a New York conservationist group called the Environmental Defense Fund, can substantially hinder the photosynthesis process. On a larger scale, such interference could have a devastating effect, since phytoplankton produces 70% of the earth's oxygen.

A bizarre case of ecological damage from DDT occurred in Borneo after the World Health Organization sprayed huge amounts of the pesticide. The area's geckos, or lizards, feasted on the houseflies that had been killed by DDT. The geckos, in turn, were devoured by local cats. Unhappily, the cats perished in such large numbers from DDT poisoning that the rats they once kept in check began overrunning whole villages. Alarmed by the threat of plague, WHO officials were forced to replenish Borneo's supply of cats by parachute.

Since DDT's effects are so severe in nature, many scientists think that it will inevitably exact a toll of man. The National Cancer Institute in Bethesda, Md., has produced evidence incriminating DDT and related pesticides as the cause of tumors of the liver and lungs in mice. When men are consistently exposed to such chemicals, adds the University of Colorado's Dr. David R. Metcalf, there is deterioration of memory and reaction time.

Impaired Effectiveness. The pesticide's defenders consider the dangers vastly exaggerated, although DDT poisoning can cause tremors and convulsion in man. "There isn't anything that doesn't have some toxic effect," insists Vanderbilt University Toxicologist Wayland J. Hayes, a former Public Health Service official and DDT's stoutest supporter. "The toxic effect of mashed potatoes," he adds rather irrelevantly, "is obesity." As proof of DDT's innocence, Hayes and others often point to studies of workers at the Montrose Chemical Corp., the world's largest DDT producer, and federal prisoners who voluntarily accepted daily doses of DDT in Atlanta. In both cases, they say, there was no damage. But other scientists, including Stanford Molecular Biologist Joshua Lederberg, a Nobel laureate, explain that far too little is known about how DDT reacts with other body chemicals to acquit the pesticide so readily.

In spite of its defenders, the use of DDT has already declined sharply. In 1962, when Rachel Carson published Silent Spring, the U.S. produced 167 million Ibs. Last year production slipped to 138 million Ibs., nearly 80% of which was exported. Not only has adverse publicity curtailed the chemical's use; its efficiency has been impaired by the resistance developed by many strains of insects. One scientist estimates that 150 pests formerly controlled by DDT are now immune to it. Nor do scientists expect to produce a new all-purpose bug killer. Instead they are emphasizing more subtle and selective methods of pest control--among them, the breeding of new insect-resistant crops, trapping pests with light and sound, and eliminating insects through sterilization. None of these methods pose anything like the dangers of DDT. The problem is that neither do they promise anything like its effectiveness.

-The others: dieldrin, aldrin, endrin, heptachlor, chlordane and lindane. They are

also sometimes called chlorinated hydrocarbons.

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