:’) The lead poisoning claim emerged some years ago, and has never been accepted, except by various popular media scribblers. Oddly enough, someone just FReepmailed some questions about this just in the past couple of weeks. :’)
Well, lead did infect the denarius and debase it to such an extent that it was almost as worthless as the Federal Reserve Note vs the U.S. Dollar.
Well, as to the overall decline of the empire, it was happening with or without the plague, or the lead. Inevitable.
As far as the lead, it carried water and was used for eating/drinking utensils. That had to screw up the people using it.