Mining in North America Contributed to Lead Pollution about 8,000 Years Back: Study

Lead pollution from human activities existed about 8,000 years back, a new study has reported.

The study was conducted by researchers at the University of Pittsburgh and colleagues who found the earliest evidence of humans' contribution to environmental lead pollution. According to the researchers, lead pollution first occurred in North America - around Michigan - due to copper mining.

For the study, researchers examined Michigan's Keweenaw Peninsula because it is known to be the largest source of copper in North America. Previous research has shown that mining took place in this region much before it began anywhere else in the world.

"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," said David Pompeani, PhD candidate in Pitt's Department of Geology and Planetary Science and lead author of the study.

The study was based on sediments that were collected in June 2010 from lakes near ancient mines. Researchers looked at the levels of lead, titanium, magnesium and iron along with organic matter in the sediment cores. These cores have layer-by-layer account of lead pollution preserved for many 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. 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," said Pompeani.

Studies on metal mining from other regions such as Asia and Europe have shown that lead pollution from these sources occurred about 3,000 years ago, Pompeani said in a news release.

The study paper, "Lake Sediments Record Prehistoric Lead Pollution Related to Early Copper Production in North America", is published in Environmental Science and Technology.

The industrial age substantially increased lead pollution and according to a new study, lead levels even today are about 100 times higher than the natural background level. Developing countries such as China and India are the largest contributors of lead in the environment.