Scientists Think Humans Polluted the Arctic With Lead as Far Back as Ancient Roman Times

Scientists who have tracked lead pollution in the Arctic caused by humans over the past 1,500 years say it paints a picture of the economic health of European societies since the Middle Ages.

The authors of the study published in the journal Proceedings of the National Academy of Science studied 13 Arctic samples of ice—or cores—collected from almost half the Arctic, stretching between Greenland and Severnaya Zemlya in the Russian Arctic.

The international team of experts used the resulting data to predict where the lead pollution in the Arctic came from between 500 and 2010.

Between the Early Middle Ages and the 1970s, levels of lead pollution spiked between 250 to 300-fold, according to the authors. In the 1970s, policies such as the Clean Air Act in the U.S. aimed to tackle pollution, and levels of the substance in Arctic ice dropped by over 80 percent. Still, levels of lead in Arctic ice remain around 60 times higher than they were at the start of the Medieval period.

This rise could be explained by industrial processes like smelting silver to make coins from the Roman Empire to burning fossil fuels in more recent decades, the team believes. Meanwhile, drops in pollution appeared to be linked to periods of war, plague, famine and changes in the climate.

In 2018, several of the authors of the current study showed how lead pollution in one ice core in Greenland reflected economic changes in Europe between 1100 BCE and 800 AD.

Joe McConnell, lead author of the study and Research Professor at the Ultra-Trace Ice-Core Chemistry Laboratory at the Desert Research Institute, told Newsweek: "Growth was especially strong during the Early and Late Middle Ages but then stalled for nearly 400 years after the start of the second plague pandemic that began with the Black Death in around 1348."

"What surprised me most was that changes in lead pollution were so similar across the large swath of the Arctic represented by the array, indicating common, large-scale changes in emissions.

"Pollution dropped immediately and then did not recover to pre-Black Death levels for 100 years or more. On the other hand, maybe that shouldn't be too surprising given that roughly 50 percent of the European population died during the Black Death pandemic so both the manpower to mine and smelt, as well as the demand for silver and lead, would have been much reduced for multiple generations," he argued.

"Our new records, combined with a study we published last year on Greek and Roman era pollution in Greenland ice, clearly show that human industrial activities such as mining and smelting have had hemispheric-scale impacts on the environment for at least the past 3,000 years or about 120 human generations.

"Lead is a toxic heavy metal meaning it has no role in metabolism and any level of exposure to ecosystems or people is bad."

He continued: "For greenhouse gases, it is much worse since they stay in the atmosphere far longer, and so will impact temperature and climate around the globe for decades and centuries to come."

Christopher Loveluck, professor of Medieval European Archaeology at the University of Nottingham, who was not involved in the research, critiqued the study, and asked why the authors relied on a single source for the majority of the historical analysis "which has limited the scope of interpretation." He also questioned why the team didn't include sites from northern China in their modeling, as opposed to southern China.

"It is also unclear whether the lead patterns were screened for the influence of volcanoes, which also emit lead," he said.

Dr. Aubrey Hillman, assistant professor in Environmental Science at the University of Louisiana at Lafayette, who was not involved in the study told Newsweek: "What is really interesting about this updated study is the use of multiple different cores sites across the Arctic which really allows the authors to pinpoint how lead pollution travels and which sites are most impacted.

She argued: "The comparison of multiple Arctic sites in this study is very integrative, but could use some additions from locations such as Alaska or Northern Europe.

"This study is very important in identifying those Arctic ecosystems which may be most vulnerable to either modern-day or legacy pollution due to factors such as wind and transport patterns."

Hillman concluded: "I think the biggest takeaway message for readers would be that your actions can have far-reaching consequences. Air pollution knows no political boundaries."