Lead Astray

Lead pollution is often seen as a modern-day problem.

But new research suggests that widespread pollution in the form of airborne lead was affecting health and lowering IQs during the Roman Empire, according to a new study.

“Human or industrial activities 2,000 years ago were already having continental-scale impacts on human health,” Joe McConnell, lead author of a new study, told NBC News. “Roman-era lead pollution is the earliest unambiguous example of human impacts on the environment.”

For roughly two centuries starting in 27 B.C., Europe, the Middle East, and North Africa had a period of relative stability and prosperity, known as the Pax Romana, fueled by huge mining operations that produced silver for the empire’s currency.

The problem is that this type of mining creates a lot of lead – one ounce of silver produces about 10,000 ounces of lead, researchers said.

And lead is a powerful neurotoxin and exposure is associated with learning disabilities, reproductive problems, mental health issues, and increased risk of hearing loss, among other effects.

McConnell and his team discovered the ancient lead pollution after detecting it in ice layers collected in Russia and Greenland that date back to the Roman Empire, according to the Desert Research Institute. The lead was released into the atmosphere from mining operations for silver, traveled on air currents, and became part of snow in the Arctic, the researchers hypothesized.

While the levels of lead detected in the Arctic were low, the lead concentrations would have thinned out over the long journey from the southern European mines.

The researchers, meanwhile, used powerful computer models of the planet’s atmosphere and made assumptions about the location of the mining sites to estimate the amount of lead originally emitted by Roman mining operations.

“This is the first study to take a pollution record from an ice core and invert it to get atmospheric concentrations of pollution and then assess human impacts,” McConnell said in a statement. “The idea that we can do this for 2,000 years ago is pretty novel and exciting.”

The researchers calculated that between 3,300 to 4,600 tons of lead were being emitted into the atmosphere each year by the mining operations. The researchers then used modern-day data to estimate how much lead would have entered the bloodstreams of those in ancient Rome.

The researchers believe that in ancient Rome, toxic lead was so pervasive in the air that it most likely dropped the average person’s IQ by 2.5 to 3 points.

“Lead is known to have a wide range of human health impacts, but we chose to focus on cognitive decline because it’s something we can put a number on,” study co-author Nathan Chellman, said in a statement. “An IQ reduction of 2 to 3 points doesn’t sound like much, but when you apply that to essentially the entire European population, it’s kind of a big deal.”