- Thomas Midgley Jr. discovered tetraethyl lead (TEL) in 1921 as an additive to reduce engine knocking, despite its known toxicity since 1854.
- GM chose TEL over ethanol because ethanol couldn't be patented or controlled, while oil companies saw ethanol as a threat.
- Leaded gasoline first sold in 1923, despite early incidents like lead poisoning in Midgley and worker deaths in 1924 raising safety concerns.
- A 1926 public health report downplayed everyday risks of leaded gasoline, allowing its continued use until the EPA phased it out in the 1970s.