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.

In ancient Rome, lead was widely used in glazed table wares, paints, cosmetics, and was intentionally ingested as well as being present in air pollution from mining and smelting.

It was during the period known as the Pax Romana, a time of stability in the Roman Empire that lasted for about two hundred years between 27 BC and 192 AD. Mining and smelting operations throughout Europe were likely a a source of lead contamination,

"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."