A French engineer trying to improve gasoline accidentally invented smog control

Eugène Houdry developed catalytic cracking to boost wartime fuel supplies, then turned the same chemistry toward car exhaust in the 1950s after air pollution alarmed him. His catalytic converter design — using a catalyst to convert exhaust pollutants into less harmful gases — became mandatory on new US cars by 1975.

— Eugène Houdry, Biographical and patent record — Catalytic converter patented 1956