The ancient Romans knew all about lead, a byproduct of silver mining. They knew the chemistry needed to get metallic lead, a soft and easily melted metal that could be worked into sheets and pipes. Their name for lead was plumbum, from which the word plumber and the chemical symbol Pb are derived. Lead pipe usage increased as civilization developed over the next two millennia, and well into the 20th century—look up Joseph Bramah, an Englishman who invented the hydraulic press to make lead pipe in 1797. As late as 1946, lead pipe was important enough for a patent to be granted (US 2,409,540) for adding approximately 1% of silver to make it stronger.
The Romans also knew that lead wasn't good for you, and scholars have speculated that so many Romans suffered from lead poisoning that they couldn't offer enough resistance to stop the barbarian invasions (the Goth sieges of Rome in 408 and 537 AD, for example). I've got a simpler explanation, untested by scholarship but interesting nevertheless.