Another similar epidemic to lead poisoning we've been sleeping on is lithium deficiency. Look at the quantum of improvement on suicide and all kinds of violent crime, including rape and murder per this study[1]. Image of results table:
It's hard not to conclude that it's immoral to not chuck lithium in the water supply, if the natural variance is associated with a doubling of murder. The study has been replicated on suicide in Japan[2] and on Dementia in Denmark[3].
We don't even know that lithium deficiency is definitively a thing, it's not like there's an established RDA. There could be any number of reasons why it's correlated with lower violent crime.
https://imgur.com/p6p886e
It's hard not to conclude that it's immoral to not chuck lithium in the water supply, if the natural variance is associated with a doubling of murder. The study has been replicated on suicide in Japan[2] and on Dementia in Denmark[3].
[1] https://www.ncbi.nlm.nih.gov/pubmed/1699579
[2] https://www.ncbi.nlm.nih.gov/pubmed/19407280
[3] https://www.ncbi.nlm.nih.gov/pubmed/28832877