Municipal Affairs and Environment

Uranium in Well Water

Uranium is a naturally occurring radioactive metal that occurs in low concentrations in nature. It is present in certain types of soils and rocks, especially granites. Uranium has the chemical symbol "U". The interim maximum acceptable concentration (IMAC) of uranium in drinking water in Health Canada’s  Guidelines for Canadian Drinking Water Quality opens new window is 0.020 mg/L (milligrams per litre).

What are the known sources of uranium?

Naturally occurring uranium in groundwater is a result of the dissolution of uranium bearing minerals that have been in contact with groundwater for long periods of time. Elevated concentrations of natural uranium in well water are more likely to be found in drilled wells that obtain their water from the cracks and fractures of bedrock, rather than dug wells or surface water supplies. Uranium can also be found in the environment as a result of human activities such as mill tailings, emissions from the nuclear industry, and the combustion of coal and other fuels.

What are the environmental health concerns of uranium?

Naturally occurring uranium has very low levels of radioactivity. The chemical properties of uranium in drinking water are of greater health concern than its radioactivity. Most ingested uranium is due to food intake with lesser amounts accumulated from water or from the air. Uranium mostly is rapidly eliminated from the body, however a small amount is absorbed and carried through the blood stream. Studies show that elevated levels of uranium in drinking water can affect the kidneys. Bathing and showering with water that contains uranium is not considered a health concern. There is inadequate data available to evaluate the carcinogenicity of ingested uranium.

Where have high uranium levels been found in Newfoundland and Labrador well waters?

Research on uranium is being carried out by the Department of Municipal Affairs and Environment, and the Geological Survey of Newfoundland and Labrador, Department of Natural Resources. There have been a total of 5 exceedances on the island portion of the province. To date, no uranium exceedances in well water have been found in Labrador. A uranium risk map has been created by the Geological Survey using a combination of bedrock geology, lake sediment geochemistry, the Mineral Occurrence database system, and maps of airborne geophysics. Any known occurrences of uranium in well water have also been added to this map. As with arsenic in groundwater, elevated uranium levels in drinking water can be found outside of the areas shown on the map, and water from most wells in the areas indicated as higher risk do not contain elevated uranium. The map shows:

  • areas of the province interpreted to have higher risk of uranium in groundwater
  • locations of wells known to contain elevated uranium.


Areas of Potential Uranium Concentration in Well Water PDF (282 KB)

What can well owners do about uranium contamination of well water?

It is recommended that all wells that provide drinking water be chemically tested for a standard list of parameters including uranium. If uranium is found above 0.020 mg/L, you can:

  • obtain bottled water for consumption.
  • treat the water, two of the most common methods being reverse osmosis and anion exchange.
  • switch to a dug well or surface water supply.

More information on uranium in well water can be found from the following sources.


Uranium in Drinking Water Fact Sheet, South and West Devon Health Authority, January 2001. PDF (38 KB)

Uranium in Nova Scotia’s Drinking Water, Department of Environment and Labour, Government of Nova Scotia. opens new window

Uranium, Guidelines for Canadian Drinking Water Quality: Supporting Documentation, Health Canada, edited May 2004. opens new window

What You Need to Know About Uranium in Drinking Water, Connecticut Department of Public Health, Environmental and Occupational Health Assessment Program, August 2006. opens new window

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