Study Reveals Ancient Rome’s Lead Pollution Might Have Reduced Average IQ by Up to 3 Points

New research suggests that pervasive lead pollution during ancient Roman times could have reduced the average person’s IQ by 2.5 to 3 points. Published in the Proceedings of the National Academy of Sciences, the study sheds light on how widespread industrial activities in the Roman Empire impacted human health and raises questions about whether environmental toxins played a role in the empire’s decline.

The researchers traced the lead pollution to Roman silver smelting operations, linking ice core samples from Greenland to key periods in Rome’s economic history. The findings reveal the first clear example of large-scale industrial pollution in history.

“Human or industrial activities 2,000 years ago were already having continental-scale impacts on human health,” said Joe McConnell, lead author of the study and a climate scientist at the Desert Research Institute in Nevada.

Pollution Embedded in Ice
Ice cores from Greenland showed rising and falling lead levels over a millennium, correlating with significant events in Rome’s expansion and economic development. For instance, lead pollution spiked during Rome’s control of present-day Spain, when silver production surged to support the empire’s coinage and economy.

“For every ounce of silver you might produce, you might produce 10,000 ounces of lead,” McConnell explained. Smelting processes released large amounts of lead into the atmosphere, where it attached to dust particles and traveled across Europe before being deposited in Greenland.

Health Effects and Legacy
Using modern data on lead exposure, the researchers calculated how much lead entered Romans’ bloodstreams and its impact on cognitive function. Lead, a powerful neurotoxin, has no safe level of exposure and is linked to learning disabilities, reproductive issues, and mental health problems.

The study underscores that ancient environmental pollution had far-reaching consequences for human health, with potential implications for societal development. McConnell noted that Roman-era pollution marks “the earliest unambiguous example of human impacts on the environment.”

This groundbreaking research highlights the unintended consequences of industrial advancements, drawing parallels to ongoing concerns about pollution and its effects on public health today.