Especially given that I have read that Romans were aware of the toxicity of lead around the time of Julius Caesar's rule - Vitruvius wrote about it in Book VIII of De Architectura.
Hi, I'm guessing that you might be talking about the idea "lead contributed to the fall of the Roman Empire", and if so, you may be interested in a couple of earlier posts
On Cosmos Neil Degrasse-Tyson said: "Some historians believe the widespread use of lead was a major cause of the decline and fall of the Roman Empire" - What's the evidence? - /u/talleyrayand addresses this claim
Were Roman engineers aware of water chemistry, specifically that certain water sources would corrode lead pipes? - /u/XenophonTheAthenian cites various Roman authors' comments on health concerns about lead