# Arctic Ice Cores Reveal Industrial-Era Arsenic Emissions From Montana Smelter

> 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.

- Published: 2026-11-10T10:00:00.000Z
- Category: science
- Source: [Science News](https://www.sciencenews.org/article/toxic-secrets-hiding-arctic-ice-harm)
- Canonical URL: https://manypress.com/article/arctic-ice-cores-reveal-industrial-era-arsenic-emissions-from-montana-smelter
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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.

### Key numbers

- **15 times** — increase in arsenic concentrations compared to pre-Industrial levels
- **30 tons** — estimated daily arsenic emissions from the Montana smelter
- **60 percent** — drop in arsenic emissions after pollution-abatement devices were installed

**Why it matters:** The study links historical industrial emissions from a Montana copper smelter to toxic heavy metal fallout trapped in Arctic ice. Researchers hope epidemiologists will use these findings and census records to investigate the long-term human health impacts, such as higher rates of certain cancers and declines in IQ, among populations exposed during the 19th and 20th centuries.

## 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.

**Key points**

- Researchers analyzed 10 ice cores collected across Canada, Greenland, and Russia.
- Arsenic concentrations in some ice layers were up to 15 times higher than pre-Industrial levels during the 1870 to 1914 interval.
- The Anaconda Copper Mining Company emitted an estimated 30 tons of arsenic per day into the atmosphere.
- Arsenic emissions dropped by about 60 percent after the company installed pollution-abatement devices beginning in 1919.
- The findings were published November 3 in Nature Sustainability.