Increased lead in crops grown within a few miles of airports has been noticed.[1].
As had reduced IQ's in children living near airports. [2]
[1]: https://core.ac.uk/download/pdf/344932499.pdf
[2]: https://www.newscientist.com/article/2353962-children-living...
Imagine if 100 years from now, Brazil is an up and coming economic powerhouse, and economists figure out that they are doing so well because their strategists, businesspeople, scientists and engineers are all smarter because their food contains less lead than ours does. We'd quickly start outlawing high lead food, which in turn might make big swathes of our cropland unusable for food.
https://qz.com/africa/2053227/leaded-gasoline-is-now-banned-...
Luckily lead is very heavy and chemically active which makes it much easier to remove from soils than some of the nastier contaminants. You can essentially break it down with sulphur amendments to acidify the soil and then let the plants do the rest of the work. Eventually dilution does the rest of the work until it reaches background levels.
This is why the FAA wasn't in a huge hurry but at the same time they were WAY too slow. It should have been a crash priority honestly.