In any case, I agree you can't do this properly with humans. And lead is definitely a factor in many deceases including mental ones so it could well be one of the causes of increased violence.
It's still widely available (and in use) for small piston aircraft as avgas. And it seems like tetraethyl lead is still available for people to mix their own leaded gas to put in very old cars.
In any case, I agree you can't do this properly with humans. And lead is definitely a factor in many deceases including mental ones so it could well be one of the causes of increased violence.