Thomas Midgley Jr.

Thomas Midgley Jr. (May 18, 1889 to November 2, 1944) was an American mechanical and chemical engineer born in Beaver Falls, Pennsylvania, who died in Worthington, Ohio. He discovered that adding tetraethyl lead to gasoline eliminated engine knock, and General Motors began marketing the additive in 1921 despite early warnings about its toxicity. In the late 1920s he developed the first chlorofluorocarbon refrigerants, marketed as Freon, which replaced earlier toxic and flammable refrigerants and became standard in home refrigeration and air conditioning for decades. Midgley held more than one hundred patents, but both signature inventions were later banned once their environmental and health costs, leaded gasoline's toxicity and CFCs' role in destroying the ozone layer, became clear, and he is now often cited as an example of a scientist whose work caused enormous unintended harm.