Human health

Is the water in Mayo safe to drink?

Yes, the drinking water in the Village of Mayo is safe to drink. The drinking water supply wells for the Village of Mayo have not been impacted. Environmental Health Services and the Chief Medical Officer of Health are actively monitoring the situation for any potential health impacts.

Although we believe the risk is very low, we are supporting the Village of Mayo in ongoing water testing to monitor for contaminants. Should the risk level change, we will update our public advice to those impacted.

If you have any questions or concerns about water quality, please contact the Environmental Health Services branch at environmental.health@yukon.ca, or by calling 867-667-8391.

Is it safe for residents downstream of the Victoria Gold Corporation Eagle mine to use or drink water from their wells?

We are committed to sharing information and updates regarding water quality and safety that would be relevant for people using water from private wells downstream of the Eagle Gold mine site.

As we learn more about the presence and distribution of contaminants in both ground and surface water, we will provide updates to affected users. To date, we do not have any concerns about water quality further downstream in the South McQuesten and McQuesten Rivers.

Additionally, we support individuals in completing routine chemical analysis of their private drinking water wells. We can assist with this testing process by providing sample bottles. While the client needs to arrange and pay for lab testing, we are available to help interpret the results.

Learn more about private well water testing.

What are the contaminants from the failure at the Eagle Gold mine? How are they recognized and measured?

Mining uses many chemicals that are safe when handled correctly. However, if these chemicals enter the environment, they can be harmful to people, plants, and animals. These chemicals are referred to as "contaminants of potential concern." At the Eagle Gold mine's heap leach failure, the main contaminants of potential concern are metals like cadmium, arsenic, mercury, and lead, as well as cyanide and ammonia. Cyanide can pose immediate risks to human and ecosystem health, while heavy metals can accumulate in the environment and in animal tissues, posing long-term risks to health.

We collect samples of water and other materials to check if these contaminants are at levels that could harm people or animals. The samples are tested in a lab and compared to safety guidelines to see if they pose a risk.

Can contaminants build up in animals?

Yes, contaminants can build up in animals over time. It happens when animals absorb contaminants faster than they can get rid of them. Contaminant buildup can occur through contact with contaminated soil, water, or air, or by consuming plants or animals that contain these contaminants. The rate and location of buildup vary depending on the contaminant, the type of plant or animal, and environmental factors. For example, some contaminants may build up more in organs like kidneys or the liver, while others, like cyanide, do not build up over the long term in animal tissues.

Built-up contaminants can pose health risks to people who eat affected plants or animals. We are monitoring these contaminants in the water, fish, and wildlife near the mine site.

Is it safe to eat animals harvested in the area of the spill this year?

Current information shows no evidence that the mine failure has made animals unsafe to eat.

The Department of Health and Social Services is working with a contractor to assess the potential human health impacts, including the risks associated with wildlife harvest and consumption.

What are water quality tests telling us about risks to human health?

We recommend that people using the Haggart Creek area, immediately downstream of the site, avoid drinking the water or eating fish from the area. Signs have been posted to inform the public about this advisory.

We continue to review water quality data from areas near the Eagle Gold mine and downstream. Based on our analysis of the current data, we believe the risk to human health for users downstream, specifically along the South McQuesten and McQuesten Rivers, is very low.

How are groundwater and surface water connected?

Water moves by taking the easiest path downhill, often flowing on the surface in streams, rivers, and lakes. Water moving underground through soil and rocks is called groundwater. It often moves between surface and groundwater, with groundwater seeping into rivers and lakes. Contaminants can move with the water, and in surface water, contaminants can travel far from where they were released. Following a release of contaminated source water, contaminants of concern may be found in both surface and groundwater.

How do contaminant concentrations change as they travel downstream?

Contaminants change as they move through the environment. Physical, chemical, and biological processes can reduce or change them. For example, cyanide naturally breaks down in water over time, although the rate of breakdown depends on factors like water temperature, acidity, microorganisms, and exposure to sunlight. Other contaminants, such as metals, can settle on the bottom of water bodies or build up in plants or animals. These processes help lower the levels of contaminants in the water over time. Contaminants, including metals, can also become less toxic with changes in water conditions or from the actions of microorganisms. As contaminants move downstream and mix with clean water, their levels usually decrease.

What is cyanide? Where does it come from?

Cyanide is a chemical that can be a gas, liquid, or solid. It can occur naturally or be man-made, and it’s used in mining and metal cleaning. At the Eagle Gold mine, heap leaching was the method used to recover gold from ore. Heap leaching involves stacking metal-bearing ore into a heap and spraying the heap with a solution containing sodium cyanide. The gold-containing solution leaches out of the heap and is collected, but this solution also contains cyanide and other contaminants.

In the environment, cyanide exists in several forms, each with different characteristics. “Free cyanide” refers to cyanide either by itself or combined with hydrogen, which is potentially the most harmful form.

What happens to cyanide when it enters water?

Free cyanide doesn’t remain in water for long. In fast-moving rivers and streams, it evaporates or changes into less harmful forms through chemical reactions or by microorganisms. Cyanide in groundwater breaks down very slowly because of a lack of sunlight and oxygen. Cyanide in solid form can dissolve and turn into free cyanide. Cyanide does not build up in plants or animals. However, if large amounts of cyanide enter water, it can take longer for the cyanide to break down, and it can travel further downstream. Large cyanide releases increase the potential risk to human and ecosystem health. Fish are especially sensitive to cyanide, even at low concentrations, and cyanide spills can lead to significant fish deaths.

What forms of cyanide are measured in water samples?

Several types of cyanide can be measured in water samples. The main forms usually measured include:

• Free Cyanide: This includes the cyanide ion (CN-) and hydrogen cyanide (HCN). Free cyanide represents the form of cyanide that is most readily available and has a higher potential to cause harm to organisms.
• Weak Acid Dissociable (WAD) Cyanide: This includes cyanide compounds that can be broken down under mildly acidic (i.e. low pH) conditions to release free cyanide. It generally measures the cyanide that is more easily released into the environment, such as from weak metal-cyanide complexes.
• Strong Acid Dissociable (SAD) Cyanide: Strongly bound or strong metal cyanide complexes are cyanide compounds that are tightly bound to metals and are less likely to release free cyanide under normal environmental conditions.
• Cyanate and Thiocyanates: These compounds are much less toxic to living organisms as compared to free cyanide.

Could the level of risk increase for people using the area in the future?

Some contaminants can build up in animal tissues and pose a risk to human health. Ongoing efforts to assess human health risks related to the mine failure will guide further monitoring.

Not all contaminants will build up in wildlife tissues or reach levels that pose risks to human health from consumption. Technical experts from the Yukon government, the First Nation of Nacho Nyak Dun, and other partners will update sample data, risk assessments, and reassess the risks of consuming wildlife from this area.

What was done following the failure to help contain contaminated water?

Shortly after the failure, mine operators built dams to hold back contaminated water and began pumping water into storage ponds. The dams appear to have contained the visibly flowing solution. We will know more as water monitoring results become available.

What are the health impacts of the contaminants, specifically cyanide, that were released in the incident?

Cyanide is toxic to humans at high enough levels. The Canadian Drinking Water Guidelines have set the maximum acceptable concentration of free cyanide in drinking water at 0.2 mg/L (200 μg/L or 200 ppb). We are also monitoring for other contaminants of concern, such as heavy metals. Current water samples do not show elevated levels of contaminants.

We have assessed that the risk of cyanide or other contaminants being released outside of the mine site at harmful concentrations is low at this time. However, this risk could change as we learn more.

What can someone do if they suspect they have been exposed to cyanide or have consumed contaminated material?

If you experience symptoms of concern, contact your health professional or visit the nearest health centre or hospital. The Chief Medical Officer of Health advises that people seek immediate medical attention if they believe they have been exposed to cyanide or contaminated water.

What are the risks for anyone using the land in the area?

Based on current information, there is no risk to people using the area for recreation. Different activities, however, may carry different levels of risk. Drinking surface water immediately downstream of the site poses the highest risk. Harvesting wildlife or gathering plants is not considered a health risk at this time. Out of an abundance of caution, we recommend not eating fish from the immediate area of the mine. Ongoing monitoring will provide more information about long-term risks.

We will have a better understanding of potential long-term impacts as environmental monitoring continues.

 

Department of Energy, Mines and Resources: emr-info@yukon.ca

Department of Environment: env-comms@yukon.ca

Employment Standards Office: eso@yukon.ca or 867-667-5944

Environmental Health Services: environmental.health@yukon.ca or 867-667-8391

Workers’ Safety and Compensation Board - work.safe@wcb.yk.ca or 867-667-5645

 

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