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The article is titled “Yellowknife’s Giant Mine: Canada downplayed arsenic exposure as an Indigenous community was poisoned.” It was originally published on July 22, 2025 and is authored by Arn Keeling, Professor, Department of Geography, Memorial University of Newfoundland and John Sandlos, Professor, Department of History, Memorial University of Newfoundland.

Decades of gold mining at Giant Mine in Yellowknife, Northwest Territories, has left a toxic legacy: 237,000 tonnes of arsenic trioxide dust stored in underground chambers.
As a multi-billion government remediation effort to clean up the mine site and secure the underground arsenic ramps up, the Canadian government is promising to deal with the mine’s disastrous consequences for local Indigenous communities.
In March, the minister for Crown-Indigenous relations appointed a ministerial special representative, Murray Rankin, to investigate how historic mining affected the treaty rights of the Yellowknives Dene First Nation.
We document this history in our forthcoming book, The Price of Gold: Mining, Pollution, and Resistance in Yellowknife, exposing how colonialism, corporate greed and lax regulation led to widespread air and water pollution, particularly affecting Tatsǫ́t’ıné (Yellowknives Dene) communities.
We also highlight the struggle for pollution controls and public health led by Tatsǫ́t’ıné and their allies, including mine workers.
Sickness from Giant Mine
The story begins when prospectors discovered a rich gold ore body at Giant Mine in the 1930s. While mining started at the nearby Con Mine in the late 1930s, Giant’s development was interrupted by the Second World War. Only with new investment and the lifting of wartime labour restrictions in 1948 did Giant Mine start production.
Mining at Giant was a challenge. Much of the gold was locked within arsenopyrite formations, and to get at it, workers needed to crush, then roast the gold ore at very high temperatures.
This burned off the arsenic in the ore before using cyanide treatment to extract gold. One byproduct of this process was thousands of tonnes per day of arsenic trioxide, sent up a smokestack into the local environment.
In addition to being acutely toxic, arsenic trioxide is also linked to lung and skin cancers, though scientific understanding of environmental exposures was inconclusive at the time.
Archival records show that federal public health officials recommended the roaster be shut down until arsenic emissions could be controlled. But the company and federal mining regulators dragged their feet, fearing the economic impact.
The result, in 1951, was the poisoning death of at least one Dene child on Latham Island (now Ndilǫ), near the mine; his family was compensated a paltry $750. Many Dene in Ndilǫ relied on snow melt for drinking water, and there were reports of widespread sickness in the community. Local animals, including dairy cattle and sled dogs, also became sick and died.
Only after this tragedy did the federal government force the company to implement pollution controls. The control system was not terribly effective at first, though as it improved, arsenic emissions dropped dramatically from nearly 12,000 pounds per day to around 115 pounds per day in 1959. Thousands of tonnes of arsenic captured through this process was collected and stored in mined-out chambers underground.
Fighting back against pollution
Throughout the 1960s, public health officials continually downplayed concerns about arsenic exposure in Yellowknife, whether via drinking water or on local vegetables.
By the 1970s, however, latent public health concerns over arsenic exposure in Yellowknife became a major national media story. It began with a CBC Radio As it Happens episode in 1975 that unearthed an unreleased government report documenting widespread, chronic arsenic exposure in the city. Facing accusations of a cover-up, the federal government dismissed health concerns even as it set up a local study group to investigate them.
Suspicious of government studies and disregard for local health risks, Indigenous communities and workers took matters into their own hands. A remarkable alliance emerged between the Indian Brotherhood of the Northwest Territories and the United Steelworkers of America (the union representing Giant Mine workers) to undertake their own investigations.
They conducted hair samplings of Dene children and mine workers — the population most exposed to arsenic in the community — and submitted them for laboratory analysis.
The resulting report accused the federal government of suppressing health information and suggested children and workers were being poisoned. The controversy made national headlines yet again, prompting an independent inquiry by the Canadian Public Health Association.
The association’s 1978 report somewhat quelled public concern. But environmental and public health advocates in Yellowknife continued their fight for pollution reduction through the 1980s.
Giant’s toxic afterlife
As Giant Mine entered the turbulent final decade of its life, including a violent lockout in 1992, public concern mounted over the growing environmental liabilities. Most urgently, people living in and near Yellowknife began to realize that enough arsenic trioxide had been stored underground over the years to poison every human on the planet four times over.
Without constant pumping of groundwater out of the mine, the highly soluble arsenic could seep into local waterways, including Yellowknife Bay. When the company that owned the mine, Royal Oak Mines, went bankrupt in 1999, it left no clear plan for the remediation of this toxic material, and very little money to deal with it.
The federal government assumed primary responsibility for the abandoned mine and, in the quarter century since, developed plans to clean up the site and stabilize the arsenic underground by freezing it — an approach that will cost more than $4 billion.
Public concern and activism by Yellowknives Dene First Nation and other Yellowknifers prompted a highly contested environmental assessment and the creation of an independent oversight body, the Giant Mine Oversight Board in 2015. Under the current remediation strategy, the toxic waste at Giant Mine will require perpetual care, imposing a financial and environmental burden on future generations.
The long history of historical injustice resulting from mineral development and pollution around Yellowknife remains unaddressed. In support of calls for an apology and compensation, the Yellowknives Dene First Nation recently published reports that include oral testimony and other evidence of impacts on their health and land in their traditional territory.
Hopefully, the Canadian government’s appointment of the special representative means the colonial legacy of the mine will finally be addressed. Giant Mine serves as a warning about the current push from governments and industry to ram through development projects without environmental assessments or Indigenous consultations.
Extractive projects may generate short-term wealth, but they also compromise the national interest if they saddle the public with enormous costs and long-term consequences.

Yellowknife’s Giant Mine: Canada downplayed arsenic exposure as an Indigenous community was poisoned

July 22, 2025 • My Project Name

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