* March 2022 - https://www.pnas.org/doi/full/10.1073/pnas.2118631119 - "Half of US population exposed to adverse lead levels in early childhood"
* October 2011 - https://ehp.niehs.nih.gov/doi/10.1289/ehp.1003231 A Geospatial Analysis of the Effects of Aviation Gasoline on Childhood Blood Lead Levels
The two papers (plus others) taken together suggest that the impact is measurable (paper 2), perhaps to the tune of one or two IQ points on average per person exposed (me drawing a line from paper 1).
Granted, the latter point is my extrapolation, but there's enough of a foundation now for policy decisions to be made in advance of explicit research connecting these dots.
From this paper[1], "An increase in blood lead from 10 to 20 micrograms/dl was associated with a decrease of 2.6 IQ points". So while there is an impact on lead levels, it is not nearly large enough to lead to the loss of 1-2 IQ points.
I'm not saying we shouldn't get rid of leaded avgas, but it accounts for about 0.1% of gasoline used in the US so the impact will be much smaller than banning leaded fuel for cars was.
You're right that from a environmental/health standpoint, it's not a giant issue. Lead emissions from general aviation are highly localized, and generally within air quality limits - with peaking areas limited to within airport limits themselves (https://www.epa.gov/regulations-emissions-vehicles-and-engin...).
But this rant is more about bureaucracy cockups. The FAA is launching another lead-free fuel initiative while sitting on approvals for an existing lead-free fuel. That's a waste of money, and it's not a sign of the competence/lack of corruption that we should expect from the FAA.
At my school, we have ~10 aircraft flying every day, 8-12 hours a day depending on the weather. Most of these flights happen over prime, in production farmland, or on the edges of the nearby town which has 8 schools at a minimum.
Now we're one of probably 5 aviation schools within a 50 mile radius, all of whom are operating at similar or greater profiles.
I'm sure the individual impact is small, but for every jumbo jet there's something like 3-5 piston aircraft in operation.
https://www.faa.gov/air_traffic/by_the_numbers/
But the key number is there 25,506,000 GENERAL AVIATION FLIGHT HOURS PER YEAR, which is almost exactly the amount of 100LL used a year (technically some GA flights are jet).
This Excel(!) document breaks GA hours down between types of aircraft: https://www.faa.gov/data_research/aviation_data_statistics/g...
From that document, here are the estimated total hours flown by type of general aviation aircraft:
Fixed wing piston: 12.9 million
Fixed wing turbine (turboprop + turbojet): 5.6 million
Helicopter (turbine): 1.8 million
Helicopter (pison): 0.6 million
Aside, if you compare Chart4 and Chart5 in that document, you can see that although piston aircraft are far more numerous, on average they spend a lot more time on the ground than turbine powered aircraft.
If you want to be angry about government inaction on lead, the “hear no evil, see no evil” respect to lead paint and soil contamination is the thing.
There are so few aircraft running leaded gas I can't imagine that environmental lead concentrations, could ever be at the right order of magnitude to be a problem for anyone(except probably AT airfields near fueling stations and maintenance areas). These aren't typically areas where children get exposed.