Researchers analyzing Arctic ice cores have traced elevated arsenic levels from the late 19th and early 20th centuries to a Montana copper mining and smelting operation.

Ice cores extracted from the Arctic contain elevated levels of heavy metals, including arsenic and lead, dating back to the U.S. Industrial Revolution. Researchers analyzing 10 ice cores collected across Canada, Greenland, and Russia determined that the pollution was likely emitted by the Anaconda Copper Mining Company in southwestern Montana.

Tracing Pollution to North America

Joseph McConnell, an environmental scientist at the Desert Research Institute, and his collaborators analyzed ice cores containing material deposited as early as 210 BCE, focusing in particular on the interval from 1870 to 1914. During this period, arsenic concentrations in some ice cores reached up to 15 times higher than pre-Industrial Revolution levels. Because the largest increases in arsenic appeared in Greenland ice cores, researchers deduced the source must be in North America, as atmospheric circulation patterns move from west to east. The team concluded the primary source was the Anaconda Copper Mining Company, which processed ore containing heavy metals like arsenic and lead.

Emissions and Mitigation Efforts

Using ice core concentrations and atmospheric dispersion models, researchers estimated that the Montana smelter emitted roughly 30 tons of arsenic per day into the atmosphere in the late 19th and early 20th centuries. By comparison, Chile, the world's largest copper producer today, collectively emits about one quarter as much arsenic currently. In 1919, the company installed capture devices near its smokestacks, causing arsenic emissions to drop by about 60 percent. Researchers suggest that combining these findings with census records could help epidemiologists investigate the health impacts on human populations exposed during that era.