https://today.duke.edu/2022/03/lead-exposure-last-century-shrunk-iq-scores-half-americans

Leaded gasoline calculation to have stolen over 800 million cumulative IQ points since 1940s

A new study calculates that exposure to car exhaust from leaded gas during childhood stole a collective 824 million IQ points from more than 170 million Americans alive today, about half the population of the United States.