It's complicated. Overall it's better to do most anything to protect kids' development, but doing so is tough.

Leaded avgas mainly benefits turbines, which are a minority of GA planes but the majority of avgas users, because they're the always-running commercial subset.

The benefit is in time between overhauls. Every replacement fuel has resulted in more engine deposits and more maintenance -- essentially requiring $20K overhauls at 1,500 hours instead of 3K. For non-turbine GA, typically age catches up to the engine before hours, but for commercial turbines it can be a make-or-break decision, since a company might own only one or two.

Reid-Hillview airport in San Jose is an example of an airport closed over leaded fuel concerns, because they reportedly found an increase in lead in children's blood in a few who lived right next to the airport. That increase was minimal compared to elevated levels found in Oakland and elsewhere due to ingestion of 60+-year-old leaded paint, but it's essential to remove whatever sources there are.

The EPA has often complained, but the FAA has persisted. This particular move is noise before the next election (timed for the just-approved FAA appointee). It's unclear if it will result in anything faster than the decades-delayed process already in play, but it does give communities huge leverage in their lawsuits.

Local airports often have a lot of land being used for essentially nothing. When local communities take federal money to develop or maintain airports, they legally agree that the airport is to remain in near-perpetuity. It can take decades of refusing federal money to get out from those obligations. The redevelopment opportunity presented by closing an airport in San Jose or Santa Monica is in the billions of dollars. So there are strong economic interests supporting anything that turns a community against the local airport. And since few people want to have planes overhead, those neighborhoods are typically lower-income and often under-represented politically, raising environmental justice concerns and making for concealed politics as monied interests fund advocacy campaigns and scientific research.

Commercial turbine operators, GA owners, and local businesses using general aviation typically have fixed assets that commit them to protecting the airport.

The price of avgas runs 50-150% over automotive fuel. For refiners, it's a production shift and a run that lasts 1-2 weeks per year (and hence some storage costs as well). They also have fixed assets, though distribution networks have in some cases been outsourced in anticipation of moving in or out of the avgas market. They do it mostly to keep people happy, since it's not a big profit maker.

A big issue is ethanol. It's seasonally mixed into automotive fuel almost everywhere, but it attacks most of the current fuel systems. With engine re-certification for avgas, there are only 1-3 manufacturers running a few engines through time on test beds and some pilot programs. That's much, much easier than retrofitting fuel systems of many, many models of planes. In most cases, the manufacturer is no longer in operation, or they would love to see the old planes die so they can sell new ones (often having bought minimal name and assets out of bankruptcy).

Electric is unlikely to replace turbine ICE unless the energy density improves in ways that would transform the entire world. It's more likely smaller jet engines could replace them, but it's not clear who would do that engineering for a relatively small market.

So a pessimistic prediction is that this might help some local land grabs, but is not likely to help a lot of kids. Let's hope for more than that.