Arsenic levels reaching up to 15 times pre-industrial baselines surged through Arctic ice cores during the Industrial Revolution, tracing back to massive copper smelting operations in Montana.
Researchers examining 10 ice cores collected from Greenland, the Russian Arctic, and northern Canada discovered that heavy metal pollution spanned the second Industrial Revolution. Joseph McConnell of the Desert Research Institute led the analysis alongside colleagues, studying ice layers that preserved airborne particles falling to Earth over centuries. The team found that arsenic concentrations remained notably high from 1870 to 1914.
“The only way you can explain that pattern of deposition is if the emissions are coming from North America,” McConnell told Science News.
Atmospheric circulation patterns carrying material from west to east pointed the team toward North America. By cross-referencing ice core data with historical production statistics, researchers linked the pollution directly to the Anaconda Copper Mining Co.’s operations in southwestern Montana.
At its peak, the facility emitted roughly 30 tons of arsenic into the atmosphere every single day. In an ice core from central Greenland, the team found that arsenic levels rose rapidly to a peak of about 15 times higher than pre-industrial levels around 1914.
By overlapping atmospheric models with American and Canadian census data from 1910 and 1911, investigators determined that roughly 50.5 million Americans and 600,000 Canadians faced elevated arsenic exposure. Populations living in Montana, Wyoming, and Idaho endured nearly 30 years of contamination exceeding World Health Organization thresholds for chronic exposure.
Ranchers and farmers started seeing their livestock die from arsenic poisoning.
Fred Quivik, historian
Montana regulatory policy at the time required companies to install pollution controls only if profitable. Anaconda delayed adopting the technology for about a decade.
The company eventually installed capture devices near its smokestacks beginning in 1919. Ice core records show that arsenic emissions dropped by about 60 percent as a result.
“The parents and grandparents of many Americans alive today were exposed to this heavy metal pollution, so the health impacts are quite recent and close to home,” McConnell said.