Lead is a neurotoxicant and is especially problematic for young children. There is no safe level of lead.
Although leaded automobile fuel was last used in 1995, piston-engined aircraft still run on leaded aviation fuel (avgas). They are the number one source of lead pollution in America while 75% of them can fly safely without lead in the fuel.
Lead particles from airplane exhaust are concentrated close to airports and are emitted during flight. About 16 million people live and 3 million children go to school within a half-mile of an airport where leaded avgas is sold.
The rate of autism has steadily been increasing in US. While we are trying to eliminate the lead paints from our walls or lead coating on the toys, small airplanes continue to still spray lead on our children.