Relatedly I often think about the Lead–Crime Hypothesis: https://en.wikipedia.org/wiki/Lead%E2%80%93crime_hypothesis https://en.wikipedia.org/wiki/Lead%E2%80%93

Relatedly I often think about the Lead–Crime Hypothesis: https://en.wikipedia.org/wiki/Lead%E2%80%93crime_hypothesis https://en.wikipedia.org/wiki/Lead%E2%80%93crime_hypothesis While tough to ever formally prove, the hypothesis posits that the major problems in the 70s/80s with urban crime that trailed off quickly in 90s was as much caused/worsened by leftover lead in urban environments from the mistakes of leaded gasoline as any other factor. Pollution has been a great "unseen" evil in a lot of the 19th and 20th Centuries, and its amazing given how many secondary effects we can point to that there's any debate at all remaining on efforts to fix pollution issues.