Intake of lead by the aristocracy may have been as much as 1 mg/day. The resultant mental incompetence and especially the rapidly declining birth rate among the ruling class are now believed to have been major factors in the decline of the Roman Empire.
Rome during it’s fall was eerily similar to the modern US.
For one, a lot of people were brain damaged by lead.
https://today.duke.edu/2022/03/lead-exposure-last-century-shrunk-iq-scores-half-americans
https://pubmed.ncbi.nlm.nih.gov/6395049/#:~:text=Intake of lead by the,decline of the Roman Empire.