In 1921, General Motors engineer Thomas Midgley Jr. discovered that tetraethyl lead eliminated engine knocking — a noisy inefficiency that made early cars intimidating. His boss Charles Kettering had spent a decade chasing the fix. Ethanol worked equally well as an anti-knock agent, but it couldn't be patented, and Du Pont viewed it as a threat to their control of the internal combustion engine. TEL offered the same octane boost without competing with gasoline itself.

The toxicity was no secret. A Du Pont executive described TEL in 1922 as "very poisonous if absorbed through the skin." Midgley himself suffered severe lead poisoning before the first tank was sold in February 1923. The next year, five workers died at the Standard Oil Refinery in New Jersey. Yet the 1926 Public Health Service report concluded there was "no reason to prohibit the sale" if factory workers were protected, dismissing trace lead in drivers' blood and garage dust as tolerable — "another generation's problem."

That precedent held for half a century. The EPA didn't begin its legal phase-out until the mid-1970s. Research since links childhood lead exposure from gasoline fumes to lower IQ, behavioral disorders, learning disabilities, and violent crime. The lead persists in soil and dust decades after the last leaded pump closed.