science

Yeah but the jet stream takes care of any concerning concentrations of exhaust.

Even under 10,000 ft the atmospheric dispersion is orders of magnitude above surface.

The turbulence at the surface on a bad day can 'lock out' the upper atmosphere sometimes, which is extra dangerous for surface car exhaust - but is actually beneficial the higher your altitude vs ground.

So in all ways the ways airplane fuel would expose someone to lead, isnt experienced by the general populace. (minus directly handling the fuel, may have concentrated lead get on someone's hand/food, but thats another situation)