This paper estimates the social cost of air pollution due to lead in gasoline at a whopping $1,100/g Pb. The authors do not study the 1986 US ban on leaded gasoline, whose breadth creates too many confounding variables, but instead they look at the intense and geographically localized use of lead fuel at NASCAR races prior to the ban in 2006, which allows for more focused analysis. They conclude that elderly people in racetrack counties experienced 1.7% higher all-cause mortality, and that the externality of the continued use of leaded aviation fuel is massively underpriced.
Summary by the authors here:
https://hollina.github.io/hollingsworth_rudik_social_cost_of...