How did restrictions on leaded gasoline reduce airborne lead pollution?

Leaded gasoline contained an antiknock additive called tetraethyl lead, which, upon combustion in an engine, released lead particulates into the atmosphere through vehicle exhaust.12

Restrictions on leaded gasoline significantly reduced airborne lead pollution by eliminating this primary source of emissions. In the United States, the phase-out began in the 1970s, driven partly by the need to protect catalytic converters—which were rendered ineffective by lead—and to mitigate the severe public health risks associated with lead exposure.2

Following the implementation of these regulations and the eventual complete ban on leaded gasoline for road vehicles, lead concentrations in outdoor air dropped by more than 90 percent in the United States. This transition represents a major success in air pollution control, as it removed a toxic particulate from the environment that is linked to learning disabilities and other serious health conditions.13