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. For many years it has been recommended that, if the
concentration of radon in indoor air exceeds the Action Level of 200
becquerels per cubic meter, steps should be taken to reduce it. It
is now recognized that some private water supplies contain levels of
radon which should also be controlled. However, it is important to
recognize that radon in water almost certainly presents a smaller
public health hazard than radon in air, both in term of the numbers
of people exposed to high levels, and in terms of the risks to the
most exposed individuals.
The European Union (EUW) is considering a draft
recommendation on the protection of the public against exposure to
radon in water supplies. The EU is proposing:
-
for private water supplies that are part of a
commercial or public activity (e.g.
hotel or bed and breakfast) remedial action should always be
taken when the
radon concentration exceeds an Action Level of 1000 becquerels
per liter.
-
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 liter.
This Action Level of 1000 becquerels per liter 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 meter. 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)
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).