If my maths is correct, general aviation emits 380 tons of lead per year into the atmosphere.
If just 0.1% of that eventually ends up in a human (remembering many plants humans eat, like potatoes, bioaccumulate lead. Also, some lead may be consumed multiple times, since biosolids are used to fertilize crops, allowing the same lead to be consumed twice), the dose is still 100x the daily max consumption for every single american.
The NIH study I linked elsewhere shows less than 5% of the lead in the highest risk populations can be attributed to leaded AVGAS. It's waaay lower for everyone else. Those are young children within 500m of a piston/GA airport. The other 95% isn't going anywhere after this.
Good to get rid of it? Yes. A serious factor in society wide human lead exposure? No.
If just 0.1% of that eventually ends up in a human (remembering many plants humans eat, like potatoes, bioaccumulate lead. Also, some lead may be consumed multiple times, since biosolids are used to fertilize crops, allowing the same lead to be consumed twice), the dose is still 100x the daily max consumption for every single american.