How it began
Paul Hermann Müller, a Swiss chemist born in Olten in 1899, was a research chemist at the J.R. Geigy company in Basel from 1925. In 1935 he began a search for an ideal insecticide: fast and potent against many insect species, of little harm to plants and warm-blooded animals, chemically stable and cheap to make. Four years later, in 1939, he tested dichlorodiphenyltrichloroethane, DDT, and found that it met these requirements. The compound itself had first been synthesized in 1874 by the chemist Othmar Zeidler, who did not recognize its value as an insecticide. The Nobel Foundation gives 1942 for Müller's finding.
Before it existed
Several serious diseases are spread by insects. Malaria is carried by mosquitoes, and typhus fever by lice in clothing. Typhus epidemics broke out where hygiene was neglected, particularly in connection with wars. Müller himself had begun his career on dyes and tanning agents before turning to the search for a synthetic insecticide.
How it works
DDT acts as a contact poison: an insect does not have to eat it, and landing on or touching a treated surface is enough. It kills by interfering with nerve cells. It keeps sodium channels from closing properly, so that nerves fire repeatedly and uncontrollably, which leads to spasms, paralysis and death. The compound is highly stable and does not dissolve easily in water, but it dissolves readily in fats.
How it spread
After World War II, DDT became popular because it was inexpensive, long-lasting and effective against many pests. It was applied heavily in agriculture, in homes and in mosquito control through the late 1940s and 1950s. With its derivatives it was the most widely used insecticide for more than 20 years and a major factor in higher world food production and the suppression of insect-borne diseases. Use in the United States peaked in 1959 and world production in 1963.
Who pushed back
DDT lingered in soils for years and built up in animal tissues, becoming more concentrated at each step up the food chain. It caused eggshell thinning in birds such as eagles and falcons, whose populations fell sharply, and many insect species evolved resistance. Public concern grew in the 1960s, fueled in part by Rachel Carson's book Silent Spring of 1962. By the 1970s many countries, including the United States, had banned or heavily restricted it.
What changed first
In 1939 the Swiss government tested DDT successfully against the Colorado potato beetle, and the United States Department of Agriculture did the same in 1943. In January 1944 it was used to stop an outbreak of louse-borne typhus in Naples, the first time a winter typhus epidemic had been halted. Müller received the Nobel Prize in Physiology or Medicine in 1948.
Where it stands today
DDT is still used in some parts of the world against the mosquitoes that spread malaria. Under World Health Organization guidelines it may be applied indoors in regions where malaria remains a major public health threat. That continued use remains controversial because the chemical persists in the environment and harms wildlife.
