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Radon in Private Drinking Water Supplies

Radon is a natural radioactive gas, originating from uranium which occurs in many types of rock. All water and air contains some radon, though levels are normally much too low to be of concern. Although some private water supplies contain levels of radon which should also be controlled, this almost certainly presents a smaller public health hazard than radon in air.

The European Union (EU) has proposed that

  • for private water supplies that are part of a commercial or public activity (for example, a hotel or bed and breakfast) remedial action should always be taken when the radon concentration exceeds an Action Level of 1000 becquerels per litre.
  • for individual water supplies (no commercial or public activity) consideration should be given to remedial action when the radon concentration exceeds an Action Level of 1000 becquerels per litre.

This Action Level of 1000 becquerels per litre is set so that the risk to a typical person drinking such water is similar to, but probably a little lower than, the risk which would arise from breathing air which contains radon at the Action Level of 200 becquerels per cubic metre. This comparison takes account of the different way that radon affects the body if swallowed, compared to being breathed in.

All exposures to radiation are assumed to carry some risk, though the risks from very low doses are very small. The Action Level does not mark a boundary between safe and unsafe, but rather a level at which action will usually be justified. Some people may choose to take action when the Action Level is approached.

Information from the Committee on Medical Aspects of Radiation in the Environment (COMARE) ( www.comare.org.uk) on radon contamination of UK private water supplies is available.

Further information

NRPB/Faculty of Public Health Medicine/Chartered Institute of Environmental Health. Health risks from radon. NRPB, Chilton (2000).

NRPB. Estimates of late radiation risks to the UK population. Doc. NRPB, 4, No. 4, (1993).

NRPB. Risk of radiation-induced cancer at low doses and low dose rates for radiation protection purposes. Doc. NRPB, 6, No. 1, (1993).

National Research Council. Risk assessment of radon in drinking water. National Academy Press, Washington, DC (1999).

National Research Council. Health effects of exposure to radon: BEIR VI. National Academy Press, Washington, DC (1999).


Last reviewed: 30 October 2009