Uranium is a common element found in rock and soil that can be present in drinking water. Consuming too much uranium has harmful health effects.
Public drinking water supplies and private wells should be tested for uranium to ensure the water is safe to drink.
What is uranium?
Uranium is a metallic gray element found naturally in rock and soil. A result of volcanic activity, it is radioactive, meaning that the atoms in uranium spontaneously break down to form new atoms, releasing energy in the process. The mineral also has chemical toxicity. It has no taste, colour, or smell.
Uranium is common, being present in soil at an average concentration of two parts per million (“About Uranium,” uraniumsa.org). It is mined for energy, industry, medicine, and weapons, among other things.
Uranium in drinking water
Uranium is present in greater quantities in certain types of rock such as granite, shale and sandstone. Wherever groundwater flows through rock formations containing uranium, the mineral can dissolve into the water. Drilled wells that draw water from underground sources where it flows through bedrock are more likely than other wells to contain too much uranium for safe consumption.
Health Canada defines the maximum safe level of uranium in drinking water as 0.02mg/L (20µg/L or 0.02 parts per million) (“The Drop on Water: Uranium,” gov.ns.ca). Water that contains more uranium than this should not be consumed, although it may be used for washing and other purposes, depending on the quantities of uranium present.
The World Health Organization has been working to determine safe levels, and a 2011 document offering a provisional guideline suggests that 0.03mg/L (30µg/L or 0.03 parts per million) may be conservative. The WHO points out, however, that “the guideline value for uranium remains provisional because of the difficulties in identifying an exposure level at which effects might be expected from the scientific data” (“Uranium in Drinking Water,” who.int).
Because uranium is naturally occurring in the environment, people who rely on drilled wells for their water supply are advised to have their well water tested. Other possible sources of uranium in drinking water include mining, industry, and agricultural fertilizers.
Uranium health risks
The Nova Scotia Department of the Environment reports that health risks resulting from uranium in water arise only from consumption of the water. Uranium is not absorbed through the skin and is not inhaled in aerosols in amounts great enough to be harmful. Ingesting excessive amounts of uranium can lead to kidney damage (“The Drop on Water.”)
However, when uranium breaks down, radon gas is produced. Radon has a tendency to collect in homes and increases the risk of lung cancer when inhaled. Exposure to water in areas where uranium is present can result in radon gas exposure; therefore, even when home interiors are protected from radon gas infiltration, well water can bring the gas into the home and expose occupants, particularly during activities of intense water use, such as showering (“Radon in Water and Air,” University of Maine).
Homeowners who find that they have high levels of uranium in their well water are well advised to have their home tested for the presence of excessive amounts of radon gas (EPA, “Radiation Protection: Radon” epa.gov).
Both uranium and radon can be physically removed from household water supplies with specially designed filtration systems.
- Nova Scotia Environment Website. “The Drop on Water: Uranium”
- WHO Guidelines for Drinking Water Quality. “Uranium in Drinking Water”
- University of Maine. “Radon in Water and Air”.
- EPA. “Radiation Protection: Radon”.