Pesticides

Brief History

As early as the 1300s, arsenic and heavy metals such as lead and mercury were used to kill rats in plague-ridden Europe. These chemicals continued to be applied into the mid-20th century to kill animal and insect pests. Arsenic is still infused into pressure-treated wood to deter fungi and insects in the 21st century.

In 1873, dichlorodiphenyltrichloroethane (DDT) was synthesized by a German scientist, but its insecticidal properties were not discovered until 1939 by a Swiss entomologist, Paul Muller, who won the Nobel Prize in medicine for his discovery. DDT was used in World War II to delouse soldiers to prevent typhus, and it is estimated that DDT saved hundreds of thousands of soldiers’ lives. In the 1930s, DuPont scientists discovered that carbamates, derived from the calabar bean, could be used to kill bugs, and the German chemical cartel I.G. Farben developed organophosphate nerve gases such as sarin to kill people. In 1938, I.G. Farben produced the organophosphate pesticide tetraethyl pyrophosphate (TEPP), which was among the many chemicals tested for toxicity on concentration camp inmates.

After World War II, chemical companies in Europe and the United States that had been granted patent rights to I.G. Farben chemicals had an excess of TEPP, sarin, and other organophosphate nerve gases. Since a neurotoxin has much the same effect on an insect's nervous system as it does on a human's, chemists adjusted the formulas so that these compounds could be sprayed on farms to kill crop-damaging insects. Parathion and malathion, chemically similar to sarin, were developed in the late 1940s by American Cyanamid using I.G. Farben research. Subsequently, hundreds of other neurotoxic pesticides were developed and applied worldwide.

Given its well-known insecticidal benefits during the war, DDT also found a ready market in the postwar United States. Touted as completely safe, DDT was sprayed in homes and on crops across the country. Along with fossil fuel–based fertilizers and other features of industrialized agriculture, such pesticides led to the unprecedented production of high-yielding crops known as the green revolution.

In the mid-1950s, Rachel Carson was among the scientists who saw that the widespread use of pesticides such as DDT posed severe ecological damage. In 1962, Carson argued in her book Silent Spring that DDT and some 200 other pesticides were being used indiscriminately and that many persist in the environment, continuing to harm animals and ecosystems. The agricultural and chemical (agchem) industries invested much time and money to denounce Carson as unscientific. Her book was nonetheless a best seller, and her efforts led to the U.S. ban on DDT in 1972.

Banning a pesticide in the United States does not prevent its sale elsewhere. DDT continues to be sold abroad in the 21st century, mostly in developing countries to fight malaria. Many other chemicals that are illegal in the United States are also still sold abroad, including agricultural pesticides that return to the United States on commercially grown imported produce. In the late 1990s, exports of U.S.-banned pesticides averaged over 26 tons per day.

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