Cyanide in the Environment: A webinar on the Eagle Mine disaster
Cyanide in the Environment
A webinar on the Eagle Mine disaster
Compiled by Paula Gomez Villalba | March 31, 2025
In the wake of the Eagle Mine disaster, Yukon Seed & Restoration hosted a webinar with updates on the disaster response and ongoing risks from the toxic cyanide solution. Mark O’Donoghue, retired Biologist and advisor to the First Nation of Na-Cho Nyäk Dun, explained the initial heap leach failure and outlined the response so far, including water treatment, storage capacity, groundwater contamination, and ongoing monitoring. Cyanide, cobalt and mercury are three major contaminants of concern. Dr. Laurie Chan, Canada Research Chair in Toxicology and Environmental Health and University of Ottawa professor, spoke about their chemistry, toxicity, and environmental health risks. These conversations are especially important as the Eagle Mine disaster continues to unfold, with toxic water still seeping into the land.
Mark O’Donoghue on Eagle Mine
“It’s been damage control and it’s been triage… This is all happening very quickly. The emphasis has been on avoiding a catastrophe… If nothing was done to contain the water, we would have had a surface spill of cyanide water and that could still be the case because their ponds are quite full there. It would flow from the creek and the toxins out there would have certainly killed everything down the McQuesten River and it would likely have done so down part of the Stewart River as well.”
“There’s massive contamination that’s gone into the groundwater, both in terms of when it first slid and now it’s been leaking since then… But it is estimated that there’s several hundred thousand cubic meters of contaminated solution in the groundwater. So that’s several hundred million liters. It’s a huge amount of contaminated groundwater in the lower Dublin Gulch area.”
“The plume of contaminated groundwater from the mine site has reached Haggart Creek and is having an increasing effect on water quality in the creek. There’s lots of uncertainties about where the water’s going and whether it’s even reasonable to intercept it.”
“Haggart Creek has huge value biologically and culturally. It’s known as a salmon-spawning stream and a salmon-rearing stream. It also has a hugely important grayling run. This is the most important grayling fishery in the Na-Cho Nyäk Dun traditional territory, right where the Haggart Creek comes into the South McQuesten River. The grayling congregate there in March/April, and people go there and fish through the ice. It is a big community event every year.”
“One of the big problems is that [Victoria Gold’s] water treatment plant was never designed to take cyanide out. It was designed to deal with other water that’s coming out of the mine area where they’re mining [with] high turbidity, other metals in it. This water treatment plant had to be repurposed and basically jury-rigged to try and make it so it could remove the cyanide. Getting this right has taken a lot longer than I expected.”
“Each of these dots is a different water monitoring station within the first four kilometers south of where Dublin Gulch flows into the creek. Water quality stayed quite safe all the way through September and then cyanide started increasing and has increased pretty steadily since then… That’s the case with some other contaminants.
— Mark O’Donoghue with the First Nation of Na-Cho Nyäk Dun
Dr Laurie Chan on Cyanide
“It’s fairly uncommon to have high levels of cyanide in the environment so there is relatively few data and very few studies looking at the impact of cyanide in the environment.”
“Cyanide is a very well-known poison. It’s very toxic, but at low doses, our bodies can handle it. Moose and caribou, all animals have some capacity to detoxify the cyanide and then excrete it. It doesn’t stay in the body for long. It doesn’t bioaccumulate in the body.”
“Cyanide in water does not bioaccumulate in tissues or fish because it gets transformed and released. [When] eating fish the risk of contaminative cyanide is low… If there’s a dead fish, there may be some residual cyanide in the fish, but if the fish is alive and kicking, it shouldn’t be a major risk of cyanide.”
“Fish and plankton, those little animals or plants that fish eat, are very sensitive to cyanide…The Canadian drinking water guideline is 0.2 milligram per litre. The guideline for fish is .005 milligram per litre. So, humans are more resistant to cyanide than fish.”
“Cyanide actually inhibits respiration in the cell and it doesn’t discriminate what cell. So that’s why cyanide has got systemic toxicity. It affects the whole body.”
“We get cyanide usually through breathing in, eating, drinking water, or even contacts from skin absorption. The concern is not just ingesting water. If the creek or the river is contaminated, if kids are swimming there, then we need to worry about thermal absorption as a route as well, not just drinking.”
Dr Laurie Chan on Other Contaminants
“Organic mercury can bioaccumulate unlike cyanide and cobalt. It will accumulate in the body of fish and animals. The bigger the fish is and the older the fish is, the more mercury it will have in the body… Mercury attacks the brain and the heart… If there’s consistent release of mercury in the environment, the sediment will have high levels of mercury in the river or the creek, and if there is the right bacteria it will become organic mercury that goes into fish. The fish will have high mercury and not be fit for human consumption. It’s a long-term effect, the mercury doesn’t go away easily.”
“Cobalt is 50 times less toxic than cyanide. Since it’s a nutrient and not very toxic, we don’t have any drinking water guidelines for cobalt. But in the environment, cobalt released in soil, water, plants and cannot be created or destroyed. Cobalt in water has two different forms, one that binds to particles and one that dissolves. The dissolved cobalt is more bioavailable and toxic.”
“We are still in the early stage of understanding what are the impacts of these chemicals in the environment and to people in the area. So we need, definitely, more monitoring…and then we need to do risk assessment, looking at this information and having a better understanding of what do people use, where do people hang out to actually estimate the dose, to answer the question of what might be the effects.”
There’s a lot of fear and uncertainty surrounding the Eagle Mine disaster and the decades of cleanup ahead. The impacts aren’t just technical, they’re deeply personal too. This disaster will continue to affect life-sustaining waters and how people connect with the land. It threatens health, culture, and future generations—but this isn’t something we simply have to accept. There are ways to push for accountability, protect communities, and stand in solidarity with the First Nation of Na-cho Nyäk Dun.
“Go to the emergency response webpage and fill out the letter to send to your local MP/MLA demanding that we get a public inquiry on this so we get to the bottom of it and it never happens again. ”
— Chief Dawna Hope, First Nation of Na-Cho Nyäk Dun
The webinar was hosted by Yukon Seed and Restoration on Monday, March 10th, 2025 with in-person showings at Ihdzí’ in Mayo and the NNDDC office in Whitehorse, Yukon. Quotes edited for length and clarity. The full webinar recording can be found here.
![Heard in the Courtroom... Consultation was at the “lowest” level of priority, and not needed until only before mining development, not exploration in any case (Yukon government). If this is how the Peel Plan is to be interpreted and applied in the future, it represents “something much less than [we] bargained for” (Tr’ondëk Hwëch’in). The judicial review itself represents a “failure of reconciliation” (First Nation of Na-cho Nyäk Dun). Lawyers cited numerous legal cases which suggested the precedent that provincial and territorial governments do have a treaty obligation to consult before doing something like this (First Nation of Na-cho Nyäk Dun). Note ruling is expected relatively soon, around Feb 2025; stay tuned for more updates!](https://cpawsyukon.org/wp-content/uploads/2025/03/Michelle-Creek-Court-Case-Update-8-819x1024.png "Heard in the Courtroom... Consultation was at the “lowest” level of priority, and not needed until only before mining development, not exploration in any case (Yukon government). If this is how the Peel Plan is to be interpreted and applied in the future, it represents “something much less than [we] bargained for” (Tr’ondëk Hwëch’in). The judicial review itself represents a “failure of reconciliation” (First Nation of Na-cho Nyäk Dun). Lawyers cited numerous legal cases which suggested the precedent that provincial and territorial governments do have a treaty obligation to consult before doing something like this (First Nation of Na-cho Nyäk Dun). Note ruling is expected relatively soon, around Feb 2025; stay tuned for more updates!")
