This page provides answers to questions about the drinking water advisory related to Trihalomethanes (THMs) issued on December 22, 2025. It applies to residents of the Hamlet of Fort Liard.

Why was this advisory issued?

The recent laboratory testing has identified levels of THMs in the community drinking water consistently above the Health Canada set guideline values for total THMs. This is a precautionary advisory to notify the public and provide information on steps people can take to protect their health.

Is the water safe to use?

Yes, the water is safe for general use. Although the total THM level is above the guideline, the main THM present, chloroform, is well below Health Canada’s health‑based value. The advisory is being issued as a precaution while the Hamlet of Fort Liard works to reduce levels long-term.

While this work is being carried out, you can take the steps listed below to reduce your risk and protect your health and the health of your loved ones.

Long-term exposure to high levels of THMs (over 70 years) may increase the risk of serious illness.

No illnesses have been reported that are related to THMs exposure.

Steps you can take to reduce your exposure to THMs in drinking water

While the Hamlet of Fort Liard and the GNWT work to lower the level of THMs. You can take steps to lower your exposure to THMs by:

• Using a pour-over water filter (e.g., Brita rated to remove THMs) or a filter certified to remove THMs (NSF/ANSI 53) AND is designed to remove THMs
  • Follow manufacturer instructions for installing and replacing filters
• Using bottled water
• Filling a pitcher with tap water and leaving it uncovered in the fridge for 24 hours

Cooking, preparing baby formulas and cleaning

• Use filtered or bottled water for cooking
• Ventilate your kitchen when boiling or steaming tap water
• Tap water is safe for washing fruits, vegetables, dishes, and hands
• Tap water is safe for household cleaning

Bathing and household use

• Keep showers under 10 minutes and baths under 30 minutes
• Open windows or use a fan to ventilate the bathroom
• Tap water is safe for brushing teeth and doing laundry

Note: When showering or bathing, a very small amount of THM’s may evaporate out of the water into the air, so shortening baths/showers and turning on a fan will help reduce your exposure.

What are THMs?

THMs are a group of chemicals that form when the disinfectant (chlorine) used to treat water reacts with organic material naturally present in water. There are over 100 different kinds of THMs, but the most common THMs in drinking water are chloroform, bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform. Health Canada has set a Maximum Acceptable Concentration (MAC) of 100 µg/L for THMs in general. This refers to the total amount of the four most common THM types.

What type of THM is high for Fort Liard?

The sum of all four THMs (Total THMs) is above the Health Canada set Maximum Acceptable Concentration for Fort Liard drinking water. Among the four THMs, chloroform is the major contributor.  

What is the health concern with chloroform?

The health-based value – meaning the level that is likely to cause human health effects for chloroform is 1400 µg/L. Fort Liard’s drinking water has never reached this threshold for chloroform. The most recent 2025 average of chloroform is around 120 µg/L.

Why does the water have THMs?

THMs are formed when disinfectants used to treat water react with natural organic material present in lakes and rivers, like decaying plants and other organic matter. Even clear water contains tiny bits of organic material from plants and soil.

When water is disinfected, THMs are formed.

Why are THMs higher than usual?

Due to the changing nature of the river and well water, higher amounts of organic material are entering the Fort Liard water treatment plant. The current treatment plant is not designed to remove all the organic materials. Because some organic material remains after initial treatment when chlorine is added, THMs are formed.

Why does the water need to be disinfected

Disinfectants are used to make water safe to drink. In the NWT and in many other parts of Canada and the world, chlorine is used to disinfect drinking water. This kills germs, like bacteria and viruses, found in the natural environment, including lakes and rivers, that can make people very sick. The health risk from these germs is much higher than the health risk from THMs.

What is being done to lower THM levels at the water treatment plant?

The Department of Municipal and Community Affairs (MACA) is committed to working with the Hamlet of Fort Liard to take mitigation measures.

The Hamlet of Fort Liard has also increased sampling for THMs moving forward. This testing will continue to monitor THM levels and ensure water quality remains safe.

The advisory will remain in place until THM levels are lowered to below the Maximum Acceptable Concentration, and consistent testing confirms the water meets drinking water safety standards. Residents will be informed when the advisory is lifted.

What changes are being considered at this point to reduce THM levels in Fort Liard?

Since October 2025, the community has been in consultation with MACA to identify the best steps to reduce THM levels. In the interim, the plant is taking water from a well that has lower organic materials. This has shown to reduce the THM levels.

In the short term, the plan is to add an aeration device to remove THM from water.

In the long term, there are plans to upgrade the whole treatment plant to add anion exchange to improve water filtration and remove the organic materials.

If you have questions or need help

For questions or concerns, contact an Environmental Health Officer.