Recently, Smithsonian.com published a brief article on the history of leaded

Dr. Robert Kehoe, Kettering Laboratory, UC, date unknown
gas. The article, seen here, http://www.smithsonianmag.com/smart-news/leaded-gas-poison-invented-180961368/, is informative though by no means exhaustive. The story begins in 1920, 55 miles up I-75, in Dayton, Ohio, at the General Motors Research Corporation. An engineer there, Thomas Midgely, and his boss, Charles F. Kettering, had developed an anti-engine knock additive called TEL or tetraethyllead.
At the time, “engine knock,” which was due to a malfunction between the fuel, air, and ignition explosion in a car’s cylinder, was at best a mild annoyance causing a light knocking sound and at worst a problem capable of destroying an automobile engine. Midgely’s solution was to add TEL to gasoline which would raise the combustability, or octane, of an engine lessening its chances of malfunctioning.
It worked. Which was all well and good, but TEL contained lead, and as people have known for ages, lead isn’t particularly good for us. In fact it’s rather deadly. The author goes on to discuss the outcry that erupted after several workers died after being exposed to TEL on a regular basis. A federal study was authorized in 1925 and it was decided that the amount of risk associated to every day exposure for most people was minimal and the production of leaded gasoline continued. It was not until the 1970s that growing evidence over leaded gas’s danger became evident. In January, 1996, the U.S. Clean Air act, officially banned the sale of leaded fuel for use in vehicles. Continue reading