Comment by treyd

If you do the same comparison of the rates of leaded gasoline during childhood to adulthood crime rates across different countries which have different histories of leaded gasoline usage, you notice that the correlation persists. While of course correlation does not imply causation, it's a link that's fairly well-established in literature, it's not a spurious correlation, and we know that lead has concrete neurological effects, so it's plausible from a pharmacological basis.