Earlier quoted context omitted.
Sources outside the home include avgas which is the largest source for lead in the atmosphere https://www.nbcnews.com/business/business-news/leaded-gas-wa...
> 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…
IQ damage of any amount is extremely significant and has subtle effects on society which are difficult to economically quantify, and given that many avgas burners basically do it for fun, seems mostly unjustifiable.