Leaded Gasoline in the United States

Refiners in the united states started adding lead compounds to gasoline in the 1920s to boost octane levels and improve engine performance by reducing engine “knock” and allowing higher engine compression. ¹ Lead was used for boosting octane because it was less expensive than other fuel additives (e.g., ethanol and other alcohol-based additives), and because people were ignorant of the dangers of lead emissions, which include mental retardation and hypertension. The reduction in lead in gasoline in the United States came in response to two main factors: (1) the mandatory use of unleaded gasoline to protect catalytic converters in all cars starting with the 1975 model year, and (2) increased awareness of the negative human health effects of lead, leading to the phasedown of lead in leaded gasoline in the 1980s.