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Water Talk: Radionuclides in drinking water

We have developed guideline values for radionuclides in drinking water to protect the health of people in Canada. Learn about the health effects of radionuclides and how to reduce your exposure if they are present at high levels in your drinking water.

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Radionuclides in drinking water

All people in Canada are exposed regularly to natural background sources of ionizing radiation. On average, the inhalation of radon gas is the largest contributor to this exposure. Ingestion of radionuclides in drinking water typically represents a very small percentage of the total background exposure or dose.

Most radionuclides in drinking water are naturally occurring and enter source water through natural processes such as the erosion of radionuclide-bearing minerals in rock and soil. To a much lesser extent, they can also enter water sources through human activity such as mining or nuclear industry processes, but these releases are highly regulated.

Levels of radionuclides in drinking water are generally low but can vary across Canada. Levels tend to be higher in groundwater than in surface water.

The only way to know radionuclide levels in your drinking water is to have the water tested. The first step of testing is to perform gross alpha and gross beta screening to see if radioactivity is detected above a threshold level. If it is above the threshold level, more specific testing can be conducted to identify and quantify the radionuclide(s). If you are interested in testing your drinking water for the presence of radionuclides, you should contact your municipality or local public health authority for advice and assistance.

Health effects of radionuclides in drinking water

When ionizing radiation is absorbed in a human cell, it can cause damage to the DNA molecule. The body’s natural response mechanisms will often deal with the damage before it becomes a problem. However, when damage is repaired incorrectly, this may lead to abnormal cell growth, or cancer. Cancer is the main health effect associated with chronic radiation exposure. The risk of cancer at the guideline level is very low. Short-term exposure above the guideline level will not significantly increase this risk.

If you have concerns about your drinking water or health, contact your public drinking water authority or public health authority for more information.

How to reduce your exposure to radionuclides in drinking water

The radionuclides Lead-210, Radium-226, and Radium-228 will not enter the body through the skin or by breathing in vapours while showering or bathing and as such, exposure by these routes is not a health risk.

You may wish to remove radionuclides from drinking water in your home if the levels are above the guideline values, which is more likely in water from a private well. There are certified treatment devices to remove radionuclides from your drinking water.

Residential treatment devices include:

These are installed either where the water comes into your house (point-of-entry) or directly at the tap (point-of-use). Consult a qualified water treatment specialist for advice.

Any unit or system you use should meet one of the following NSF/ANSI Standards:

To make sure the treatment unit is working properly, you should regularly test:

Your treatment unit should be installed and maintained according to the instructions from the manufacturer.

If you are pregnant or breastfeeding, these same actions will protect your health,  you are not at higher risk of becoming ill from radionuclides in drinking water.

Preparing infant formula

If you are preparing infant formula with drinking water that exceeds the screening criterion for gross alpha or gross beta, you may wish to use an alternate drinking water source while more testing is done to identify and quantify the specific radionuclide(s). You can compare the test results to the individual radionuclide threshold level. This will help you decide if you should:

Radon

In most circumstances, radon in a drinking water supply is not a problem, the bigger health risk is from radon in indoor air. Radon is a radioactive gas that can enter a home through many avenues, including outgassing from well water. Exposure to high levels of radon in indoor air increases your risk of lung cancer. The only way to know if radon is an indoor air issue is to test the air and compare the results to the Canadian guideline for radon in air.

Guideline values for radionuclides in drinking water in Canada

We worked with provinces and territories to establish maximum levels for three of the radionuclides that are the most important contributors to the radiation dose received from Canadian drinking water. We also established screening criteria at a lower level to measure radioactivity in general. These also help water utilities optimize water treatment and distribution system operations. The guideline values are

These levels protect the health of all people in Canada, including those at highest risk, such as infants and children.

Related information

Guidelines for Canadian Drinking Water Quality for Radiological Parameters

If you have questions about the guidelines or radioactivity in drinking water, you can contact us at:

For questions on radon contact radon@hc-sc.gc.ca.

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2025-12-05