Oldest record of human-caused lead pollution found

Humans began contributing to environmental lead pollution as early as 8,000 years ago, according to a new study.
University of Pittsburgh researchers detected the oldest-discovered remains of human-derived lead pollution in the world in the northernmost region of Michigan.
The finding suggests metal pollution from mining and other human activities appeared far earlier in North America than in 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," said David Pompeani, lead author of the research paper and a PhD candidate in Pitt's Department of Geology and Planetary Science.

"These findings have important implications for interpreting both the archeological record and environmental history of the upper Great Lakes," Pompeani said.
The team examined Michigan's Keweenaw Peninsula because it is the largest source of pure native copper in North America. Early surveys of the region in the 1800s identified prehistoric human mining activity in the form of such tools as hammerstones, ladders, and pit mines.

The team investigated the timing, location, and magnitude of ancient copper mining pollution. Sediments were collected in June 2010 from three lakes located near ancient mine pits.
They analysed the concentration of lead, titanium, magnesium, iron, and organic matter in the collected sediment cores finding distinct decade- to century-scale increases in lead pollution preserved from thousands of years ago.

"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.
"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," Pompeani added.
By contrast, reconstructions of metal pollution from other parts of the world, such as Asia, Europe, and South America, only provide evidence for lead pollution during the last 3,000 years, he said.
The findings were published in the journal Environmental Science & Technology.