Thomas Midgley, Jr. (May 18, 1889 - November 2, 1944), was a clever American mechanical engineer turned chemist, but from the viewpoint of 2002 his achievements in preventing internal combustion engines from "knocking by adding tetra-ethyl lead to the gasoline they burn, and making refrigerators safer by synthesizing chloro-fluorocarbon (CFC) compounds (also called "Freons") and substituting them for the variously poisonous or explosive substances previously used, look less impressive.

In medicine one of the major uses of CFCs is as safe inert propellants in metered dose inhalers (Asthma Inhalers) for the treatment of asthma. Since the adoption of the Montreal Convention, by which major countries agreed to no longer produce CFCs, health services and pharmacological companies have been replacing these inhalers with devices that do not contain CFCs, and training patients in their use.

Thomas Midgley Jr. was a holder of over 170 patents. Midgley suffered from lead poisoning due to his work with tetra-ethyl lead, a fact he kept hidden from the public. In 1924 Midgley took a prolonged vacation from working to cure himself of lead poisoning. One historian remarked that Midgely "had more impact on the atmosphere than any other single organism in earth history."