The U.S. Environmental Protection Agency (EPA) announced its final determination that emissions of lead from aircraft that operate on leaded fuel cause or contribute to air pollution which may reasonably be anticipated to endanger public health and welfare under the Clean Air Act.
There are alternatives:
https://en.m.wikipedia.org/wiki/Antiknock_agent
MMT looks like it could be substituted, directly. Still nasty, but small usage, and removing lead & cadmium from our ecology should be high priority.
And, of course, replacing avgas engines with diesels would do it, as they can run on Jet-A or whatever.
This is all no-brainer territory.
The established aviation-engine manufacturers won’t develop diesels,
& the upstarts keep going broke…
the LiquidPiston X-Engine is the brilliantest aviation engine I’ve ever considered, turning a Wankel rotary inside-out,
and the Astron Omega is … insane ( I couldn’t understand how the hell ANYBODY could even think of that …
… then I found out the inventor wasn’t a piston-engines guy, he was a turbine-engines guy…
… which explains it! )
I’d expect the IQ & life-potential of lives who grew-up near avgas-centric ( little ) airports to be damaged, consistently, by the lead.