Early car drivers suffered engine "knock," irregular kicks delivered when gas ignites too quickly. A General Motors chemist in 1922 found that adding a lead compound to fuel smoothed the ride.
Tetraethyl lead was good for cars but bad for living things. The compound harms child mental development and can cause nervous system and blood pressure conditions in adults. The Environmental Protection Agency started phasing out leaded gas in 1974, overcoming legal battles with refiners. A federal appeals court ruled in 1980 that the EPA could set standards "to act in the face of uncertainty."
Little-known fact: The GM chemist who came up with leaded gas also invented ozone-destroying CFCs, leaving historian J.R. McNeill to conclude that Thomas Midgley Jr. "had more impact on the atmosphere than any other single organism in Earth history."
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