Silver fueled the rise of the Roman Empire. But the ancient process of mining and extracting silver was also making the air thick with lead, scientists found.

A new study turned to Arctic ice core records between 500 BCE through 600 CE to find a link between lead pollution and widespread health decline in the Ancient Roman Empire, which most likely lowered the IQs of 80 million people.

The mass production of silver coins in the Roman Empire had an unintended effect: spewing so much lead into the atmosphere that it may have lowered citizens’ IQs.

"A 2 to 3 points lower IQ doesn't sound like much, but when you apply that to the entire European population, it's quite a lot."

Two thousand years ago, the Roman Empire hummed with activity. Roads stretched like arteries, connecting distant provinces. Mines yielded treasures buried deep in the earth, and smelters worked tirelessly to transform raw silver ore into the coins that fueled an empire.