Leaded gasoline was gradually taken off the U.S. market
A combination of health and environmental concerns led to a ban on most uses of leaded gasoline in the United States.
Health hazards associated with lead have been documented since the early 1920s. In 1927, the U.S. Surgeon General set a voluntary standard for lead content in leaded gasoline. In 1970, the U.S. Congress adopted the Clean Air Act and created the U.S. Environmental Protection Agency (EPA). Under the authority of the Clean Air Act, the EPA established standards for the lead allowed in motor gasoline (which changed over time) and standards for automobile emissions of carbon monoxide (CO), nitrogen oxides (Nox), and hydrocarbons. The automobile industry responded to the emissions standards by developing catalytic converters, which convert CO, NOx, and hydrocarbon emissions into water, carbon dioxide, and nitrogen gas. Because leaded gasoline damages catalytic converters, leaded gasoline was banned for vehicles beginning with model-year 1975. Leaded gasoline is still allowed for aircraft, racing cars, farm equipment, and marine engines.