Wildfire arsenic release study is an ‘alarm bell,’ says author

The author of a new study on the potential for wildfires in the Yellowknife area to release arsenic says its findings should be “a wake-up call” to other scientists and policymakers.

The study was published last month in the journal Environmental Research Letters as an accepted manuscript – the version approved for publication after review by other scientists.

Using publicly available data, researchers estimated that between 1972 and 2023, wildfires near Yellowknife potentially caused the release of 141 to 562 megagrams of arsenic. One megagram is equivalent to 1,000 kilograms.

Of that, they estimated 61 to 381 Mg of arsenic could have been emitted into the atmosphere and 39 to 109 Mg mobilized as water-soluble.

By comparison, Yellowknife’s Giant and Con gold mines are estimated to have released 22,000 Mg of arsenic as dust into the surrounding landscape during their lifetimes.

“We were quite shocked when we put all the numbers together,” said Colin McCarter, one of the study’s authors and Canadian Research Chair in Climate and Environmental Change at Nipissing University.

McCarter said the results suggest that just four of 2023’s NWT wildfires, burning approximately 250,000 hectares north of Great Slave Lake, accounted for somewhere between 15 and 59 percent of the world’s atmospheric arsenic emissions from wildfires that year. He estimates those fires accounted for two to nine percent of global arsenic emissions from natural sources, a category that includes the likes of volcanoes.

More research is needed to refine the study’s findings, McCarter said, acknowledging that scientists had little data to rely on and research on arsenic release from wildfires in the area is lacking.

While there are relatively good estimates of how much arsenic exists in the area, he said, “we do provide relatively large ranges because there’s a lot of uncertainty in our estimates.”

For example, McCarter said the amount of arsenic released from burning wetlands depends on the density of the peat and temperature of the fire.

The study calls for more collaborative research from wildfire and soil scientists, biochemists, atmospheric chemists and health scientists, noting climate change is expected to increase the size and severity of wildfires.

“This paper is really an alarm bell,” McCarter said.

“It’s really trying to bring light to this issue and to try to come together to solve it, or at least figure out ways to mitigate these risks, particularly in the industrial-impacted region.”

He said the study also highlights the importance of limiting exposure to wildfire smoke and wearing masks.

NWT launches study of its own

A spokesperson for the NWT’s Department of Environment and Climate change said it is “aware of the relationship between wildfire and arsenic remobilization” and the new study “presents an interesting concept of the risk from wildfire to contaminated areas.”

“We appreciate the interest in northern issues and the research to address them,” department spokesperson Thomas Bentham wrote in an email to Cabin Radio.

“We continue to encourage researchers investigating northern issues to collaborate whenever possible and publish results so they may inform northern decisions.”

Bentham said the study notes an absence of data, particularly regarding the area’s soil minerology and the different chemical forms of arsenic.

He said the territory is funding its own three-year project to investigate the impacts of wildfire on arsenic in the Yellowknife area, adding a public announcement will be made soon. He said the project is in its first year and being led by a northern researcher.

The Giant Mine Oversight Board, in its latest annual report, called for research into the potential risk of arsenic release from forested areas around Yellowknife during a fire.

Arsenic has accumulated in the soil and sediment surrounding Yellowknife through gold-mining operations like Con and Giant. Historically, gold processing involved roasting the ore, which produced arsenic trioxide dust.

Soils in the region also have naturally high arsenic levels from the underlying bedrock.

While Con Mine installed a scrubber in 1949 that limited its effect on the surrounding environment, Giant Mine – the source of most arsenic emissions – did not install pollution control equipment until the end of 1951.

That was after a two-year-old Dene child died of acute arsenic poisoning and reports of widespread sickness among residents on Latham Island, as well as livestock dying in Yellowknife.

In 1951, Giant Mine began storing highly toxic arsenic trioxide dust underground. Today, 237,000 tonnes of that dust remains in chambers beneath the site. A $4.38-billion federally led remediation project intends to freeze the bedrock around those chambers to stop the dust being released.

Federal officials said wildfires in 2023 posed a low risk to the arsenic stored underground as well as materials from the deconstructed roaster, which are stored in shipping containers in a tailings pond.

Natalie Plato, deputy director of the remediation project, stated in an email to Cabin Radio that assessing contamination on the former mine site is part of the team’s closure and reclamation plan. She said that plan aims to reduce risks at the site, including from arsenic-contaminated soil.

“The project team will continue to monitor and manage the risks on and to the site, considering all information, research and expertise available to them, to keep the public and environment safe,” she wrote.

Plato said the project team has taken steps to reduce wildfire risks at the site, including clearing brush and moving materials from recent construction away from structures and onto tailings ponds, where fires have little if any fuel they can burn.

“In the event of area wildfires, the greatest and most immediate risk is the fire itself,” she wrote.

Arsenic monitoring

Bentham said the NWT’s Department of Health and Social Services, which monitors drinking-water supplies across the territory, performed additional testing following last year’s wildfires. He said no abnormal change in Yellowknife’s drinking water has so far been noted.

He said the NWT government has long funded research on the potential effects of arsenic contamination on water, fish, the landscape and human health.

A federally funded program researches levels of arsenic and other contaminants among residents in Yellowknife, Dettah and Ndılǫ. So far, that program has found contaminant levels among Yellowknife-area residents are comparable to those among other Canadians, and those arsenic levels were not related to any identified health problems.

Clarification: June 10, 2024 – 8:21 MT. This story previously listed measurements in mg. A megagram is denoted by Mg.