It was especially terrible before 2006, which is when NASCAR's exemption to the lead ban finally expired, creating a perfect natural experiment to answer the question: how much did the health of people downwind of NASCAR arenas improve after the ban, and conversely, what was the dollar cost of the health externality of lead. Spoiler alert: more than $1000 / gram (approx. 1 tank of fuel).

https://www.aeaweb.org/articles?id=10.1257/pol.20190654