Humans began contributing to environmental lead pollution as early as 8,000 years ago, according to a new study published in the journal Environmental Science & Technology (paper in .pdf).

University of Pittsburgh researchers have found the world’s oldest remains of human-caused lead pollution in Lake Manganese and Copper Falls Lake, the Keweenaw Peninsula of the Upper Peninsula of Michigan.

“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,” explained study lead author Dr David Pompeani.

“These findings have important implications for interpreting both the archeological record and environmental history of the upper Great Lakes.”

The findings also suggest metal pollution from mining and other human activities appeared far earlier in North America than in Europe, Asia, and South America.

Dr Pompeani and his colleagues 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.

They 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 analyzed 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. 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,” Dr Pompeani said.

“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.”

“We’re hopeful that our work can be used in the future to better understand past environmental changes,” concluded study co-author Dr Mark Abbott.

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Bibliographic information: David P. Pompeani et al. 2013. Lake Sediments Record Prehistoric Lead Pollution Related to Early Copper Production in North America. Environ. Sci. Technol., 47 (11), pp. 5545–5552; doi: 10.1021/es304499c