Lead and Schizophrenia
By I’ve linked to articles before connecting the protection of people from lead poisoning through environmental regulations and drops in crime over the last few decades. Here is a scientific study reinforcing these connections, with lead poisoning leading to schizophrenic symptoms in mice. Interesting stuff.
More broadly, the lead-crime nexus shows the unexpected payoffs of potentially expensive environmental regulations and remediation. Protecting people from pollutants creates healthier, happier, and more productive people. It also helps make them mentally healthy and helps prevent them from committing crimes. These are huge payoffs.