Lead exposure gives you brain damage: https://en.wikipedia.org/wiki/Lead_poisoning https://en.wikipedia.org/wiki/Lead_poisoning. If you damage your frontal lobe

Lead exposure gives you brain damage: https://en.wikipedia.org/wiki/Lead_poisoning https://en.wikipedia.org/wiki/Lead_poisoning. If you damage your frontal lobes, you generally become more impulsive and less measured in your response to things. Ergo, chronic lead poisoning causes populations to become more aggressive and more likely to engage in crime.