Jan Bartek – AncientPages.com – Lead exposure has been linked to various health issues, particularly affecting children’s cognitive development, even at low levels. Researchers from DRI (Desert Research Institute) have previously utilized atmospheric pollution records found in Arctic ice cores to trace lead pollution during the Roman Empire.
Recent studies build on this by examining three ice core records to determine lead pollution in the Arctic from 500 B.C. to 600 C.E., covering the rise and fall of the Roman Empire and focusing on its peak period, known as Pax Romana.
The study used lead isotopes to trace mining and smelting activities across Europe as probable sources of pollution during this time. By employing advanced computer models of atmospheric movement, researchers created maps showing lead pollution levels across Europe. This research also correlates with findings that link lead exposure to cognitive decline, suggesting a potential reduction in IQ levels by at least 2 to 3 points among Europeans due to historical lead exposure.
“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,” says Joe McConnell, research professor of hydrology at DRI and lead author of the study. “The idea that we can do this for 2,000 years ago is pretty novel and exciting.”
Records Of The Past Preserved In Ice
The McConnell Ice Core Laboratory at DRI has studied ice cores from Greenland and Antarctica for decades. Using large drills, the team extracts ice columns up to 11,000 feet long to explore Earth’s history. Analyzing volcanic eruptions in the ice helps construct precise timelines as historical markers. Gas bubbles reveal past atmospheric conditions, while pollutants like lead indicate historical mining and industrial activities.
Ice in the core barrel while drilling on the Greenland ice sheet. Credit: Joseph McConnell
Over twenty years ago, McConnell developed methods for detailed lead records in ice cores. Archaeologists and historians have since collaborated with him to study the Roman period using these advanced techniques to resolve historical questions.
“The resulting research changed our understanding of the era by finding precise linkages between the lead pollution records and historical events such as population declines associated with periodic plagues and pandemics,” adds co-author and ancient historian Andrew Wilson of Oxford University.
A Growing Understanding Of The Harms Of Lead Pollution
Ancient lead pollution primarily originated from silver mining, where the lead-rich mineral galena was processed to extract silver. This method released thousands of ounces of lead into the atmosphere for every ounce of silver produced. In contrast, during the 20th century, vehicle emissions from burning leaded gasoline became a major source of lead pollution. Implementing the Clean Air Act in 1970 in the U.S., which limited leaded gasoline use, led to a significant decrease in human blood lead levels. This reduction has allowed researchers to understand better how exposure affected health and cognitive development, particularly among children born between 1950 and 1985.
As McConnell notes, “The decline in lead pollution over the last three decades has highlighted its detrimental effects on human development.” In adults, high levels of exposure have been associated with infertility, anemia, memory loss, cardiovascular disease, cancer, and weakened immune response. For children, even minimal exposure can result in lower IQ scores, difficulties with concentration, and decreased academic performance.
While the U.S. Centers for Disease Control and Prevention (CDC) considers a blood lead level of 3.5 µg/dl the point for medical intervention for children, they have stated that there is no level of lead exposure without risk.
Ice sample on the melter during continuous ice core chemical analyses at the Desert Research Institute. Credit: Sylvain Masclin
“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,” says study co-author Nathan Chellman, assistant research professor of snow and ice hydrology at DRI.
“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.”
The study reveals that atmospheric lead pollution began during the Iron Age, reaching its peak in the late 2nd century B.C. at the height of the Roman Republic. This pollution level declined significantly during the 1st century B.C. amid the crisis of the Roman Republic but rose again around 15 B.C. with the rise of the Roman Empire. Lead pollution remained elevated until it was impacted by the Antonine Plague from 165 to 180s C.E., severely affecting the Roman Empire.
It wasn’t until the High Middle Ages in the early 2nd millennium CE that Arctic lead pollution surpassed these levels sustained during Rome’s peak. The research indicates that over 500 kilotons of lead were released into Earth’s atmosphere throughout nearly two centuries at Rome’s zenith.
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Although ice core records show Arctic lead pollution was up to forty times higher during its historical peak in the early 1970s, this study highlights how industrial activities have affected human health for millennia, as noted by McConnell.
The study was published in the journal Proceedings of the National Academy of Sciences
Written by Jan Bartek – AncientPages.com Staff Writer
