“From this analysis, the EPA estimates that approximately 5.2 million people live within 500 meters of an airport runway, 363,000 of whom are children aged five and under.”
Piston planes emitted about 470 tons of lead in 2017, 70 percent of all lead put into U.S. air that year. Since 1930 they have burned 38.6 billion gallons of leaded avgas and dumped about 113,000 tons of lead. In 1,140 counties they are the only airborne lead source. The finding itself sets no new rules, and it only obliges the FAA to start writing them.