> Sources outside the home include avgas which is the largest source for lead in the atmosphere
In the atmosphere, sure (as it is not naturally occurring in the air). But how large is this source? And what harm does it actually cause?
There are indications that the levels of lead around airports are very low - even the article linked said that ~2.5% of children around the airport had "detectable" levels of lead. But it doesn't provide enough data to tell if the contamination came from the air. If this was significant, wouldn't many more children around the airport have high (not only detectable) levels of lead? Everyone has to breathe, but not everyone has the same contamination sources.
From Wikipedia:
> Final results from EPA's lead modeling study at the Santa Monica Airport shows off-airport levels below current 150 ng/m3 and possible future 20 ng/m3 levels.[108] Fifteen of 17 airports monitored during a year-long study in the US by the EPA have lead emissions well below the current National Ambient Air Quality Standard (NAAQS) for lead.[109]
To be safe, obviously we want to reduce all exposure to zero.
Avgas was changed in formulation to reduce lead.
There are alternatives to avgas - in Europe, avgas is already hard to find. Automotive gasoline conversions are available for some widely used engines. The problem is that you can't just take it to a shop and covert it - the airplane was originally certified with one engine type. If it is changed, it is no longer certified. No company is willing to eat the costs to re-certify - for the planes that are still in production. Let alone planes made by companies that no longer exist.
In the 'experimental' category, there are many types of engines that can directly burn either avgas or "mogas".
Some manufacturers, like Diamond, can use "jet fuel" (essentially, diesel) in their piston engines (as they have their own engines, based on diesel car engines). But even they will have avgas-burning versions (with Lycoming engines) for the US market.
Then you have competing agencies dragging their feet. There's the EPA, which should be issuing regulations. Then there's the FAA that needs to come up with a solution with the certification issue - they are pretty underfunded so it's unlikely they will. One agency points the finger to the other, none take action. I'm probably missing other agencies. There are alternatives in development - without a full government push, progress is slow.
Meanwhile, planes (and many helicopters) in the US keep spewing lead. Many of which provide important services.