The Deadly Dust: The Unhappy History Of DDT

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The Egyptian work was done under the supervision of the American Brigadier General Léon Fox, a field director of the Typhus Commission headquartered in Cairo. It was Fox who was summoned to newly captured, refugee-swollen Naples in late 1943, where Allied medical authorities saw that a major typhus epidemic was in the making. New typhus cases in the city approached sixty a day, and people were dying by the score everywhere, even in the gutters. If the epidemic followed the age-old pattern, there would be an explosion of death, with perhaps as many as 250,000 fatalities. In mid-December, the general and his men began a systematic dusting of the entire Neopolitan population with DDT. Within a month the number of new cases per day was in sharp decline. By mid-February there were no new cases at all. For the first time in history, in winter (typhus is a winter disease), under filthy, overcrowded conditions perfectly suited to it, a well-advanced typhus epidemic was not only arrested but, in a few weeks, totally eliminated. And this was but the beginning of DDT’s march to glory.

Soldiers and sailors by the million carried small cans of DDT powder to protect themselves against bedbugs, lice, and mosquitoes. They came to love the stuff, especially in the tropics. Millions of DDT aerosol bombs were used to spray the interiors of tents, barracks, and mess halls. Through European refugee camps, along the Burma Road, across jungle battlefields of Southeast Asia, on Saipan and dozens of South Sea isles infested by stinging, biting insects, DDT spread its beneficent mist.

By the war’s end, DDT had become the most publicized synthetic chemical in the world. One American newspaper clipping service accumulated nearly 21,000 items about it in an eighteen-month period in 1944-45. Most were glowingly enthusiastic; only a few questioned the unmixed blessings of DDT.

It was the questions, however, that impressed Rachel Carson.

Her career had prospered since 1936. In 1941 she had published a book, Under the Sea Wind , a blend of science and belleslettres which had won critical acclaim, respectable sales, and its author’s appointment as editor in chief of the Fish and Wildlife Service, a post in which she could happily combine her scientific and literary interests. Her required professional reading in that post naturally included a good deal about the “miracle” insecticide. What she read disturbed her.

For instance, an experiment conducted by the U.S. Department of Agriculture’s Bureau of Entomology on May 23, 1945, was reported not only in scientific journals but also in general-circulation magazines. At the rate of five pounds per acre an oil solution of DDT was sprayed over a gypsy-moth-infcsted i,2oo-acre oak forest near Moscow, Pennsylvania. It was terrifyingly effective. Every gypsymoth caterpillar in the forest died within hours. But so did every bird—at least 4,000 of them within eight days. Nor was this the limit of DDT’s mischief. Annihilation of ladybug beetles by the spraying resulted in a tremendous multiplication of aphids, which are not affected by DDT but are naturally controlled by ladybugs. The forest was on the way to being completely defoliated when rains halted the outbreak; aphids are shortlived in wet weather.

In few if any other tests was the rate of DDI application as high as in the Pennsylvania oak forest. One pound per acre was found sufficient to kill gypsymoth caterpillars in a nearby forty-acre wood—a rate of application that seemed not to harm birds but was still disastrous for aquatic life, a point of special interest to Miss Carson. And when DDT in this lesser amount was sprayed over peach orchards to kill caterpillars of the Oriental fruit moth, it was found to be considerably more destructive of a parasite that attacked the moth than it was of the caterpillars themselves. In other instances, fruit trees were turned literally blood red with spiders, myriad upon myriad of them, after DDT killed the insects that normally fed on them.

 
 

Research reports noted the amazing persistence of DDT’s effectiveness, due to its chemical stability and insolubility in water. Pyrethrum as then used in ordinary household sprays was highly poisonous to insects for the first few hours after application but gradually lost all power within a day or two. But DDT, sprayed upon an interior wall, was fatal to flies and mosquitoes for as long as three months; a treated mattress was a fatal resting place for bedbugs for as long as nine months; a DDT-sprayed blanket could be laundered a half dozen times, even dry-cleaned two or three times, and still kill every moth that touched it. This was an obvious advantage to the Army and Navy as well as to future civilian consumers, but among biological scientists it raised further questions as to the wisdom of releasing DDT for mass sprayings of fields and orchards, forests and pastures, city parks and tree-lined streets, year after year.