The FAA did finally approve unleaded fuel for all piston aircraft this past year. It will probably take a minute to get all the refueling infrastructure switched over but it's finally happening. They haven't outright banned 100LL (the current leaded fuel) but lots of pilots have been wanting the FAA to approve unleaded fuel forever. Hopefully the switch comes sooner rather than later.

The other regulatory piece of this is that if we knew for so long that leaded fuels caused health problems, why was the land so close to airports zoned for residential use (or schools)? A huge amount of the time, the airport was built away from everything in the 40s or 50s (or earlier), and then much later people started building houses next to them, then complaining about the noise and the potential health risks, and in some cases getting the airports shut down. Case in point, Santa Monica airport. Opened in the 20s, one of the busiest general aviation airports in the country, and now set to shut down later this decade.