Scientists Identify Oldest Remains of Human-Derived Lead Pollution in the World

A recent study conducted at the University of Pittsburgh has discovered the oldest record of human-caused lead pollution. Researchers found that humans had started contributing to environmental lead pollution as early as 8,000 years ago, according to the news release.

The team of researchers identified the oldest remains of human-derived lead pollution in the northernmost region of Michigan. This indicates that lead pollution due to copper mining first appeared in North America rather than Europe, Asia and South America.

"Humanity's environmental legacy spans thousands of years, back to times traditionally associated with hunter-gatherers. Our records indicate that the influence of early Native Americans on the environment can be detected using lake sediments. These findings have important implications for interpreting both the archeological record and environmental history of the upper Great Lakes," David Pompeani, lead author of the research paper, said in a press statement.

For the study, researchers observed the Keweenaw Peninsula in Michigan, since it is the largest source of pure native copper in North America. Surveys conducted in this region in the early 1800s found prehistoric mining activities by humans with the help of tools such as pit mines, ladders and hammerstones.

In the year 2010, the team collected samples of sediments from three various lakes that were located near the ancient mine pits. They then looked at the levels of lead, titanium, magnesium and iron along with other organic matter in the sediment samples collected. The researchers noticed that these cores had layers of lead pollution that had been preserved for centuries.

"These data suggest that measurable levels of lead were emitted by preagricultural societies mining copper on Keweenaw Peninsula starting as early as 8,000 years ago," said Pompeani, who is also a PhD candidate in Pitt's Department of Geology and Planetary Science. "Collectively, these records have confirmed, for the first time that prehistoric pollution from the Michigan Copper Districts can be detected in the sediments found in nearby lakes."

On the other hand, on reconstructing metal pollution of other parts of the world such as Asia, Europe and South America, scientists found the evidence of lead pollution just around 3,000 years ago.

The study is highlighted on the cover of the issue Environmental Science & Technology.