DDT

Monsanto and 14 other companies manufactured DDT for the U.S. government beginning in 1944. The highly toxic dioxin was effective in eradicating malaria from most of the southern Europe and was widely used in the 1950s and 1960s as a cheap form of mosquito control, but in 1972, the government banned DDT after evidence showed the chemical eradicated entire populations of fish and birds.