Smaller general aviation aircraft still use 100LL gasoline (the LL stands for low lead) - and even though there’s lead-free replacement candidates (still going through regulatory approval, at least in the US), it’s been known that areas around airports with frequent GA traffic have higher levels of lead in the air, and children living near said airports may have elevated levels of lead in their blood (https://paloaltoonline.com/news/2021/08/06/new-study-finds-l...)