Radon is a naturally occurring radioactive gas and is the product of Uranium decay. It is found in a wide range of rocks and soils and in turn building materials derived from these rocks. Outdoors radon gas dissipates harmlessly into the air but in buildings it is known to build in concentration and thus radioactive potency.
Quantative relationships between residential radon levels and health risks are difficult to show due to the nature of low dosage exposure over a long time. However research into the rates of lung cancer amongst workers in Uranium mines has shown linear relationship between exposure and radon levels.
Investigations carried out in South West England and Germany have all displayed significant positive relationships between exposure to radon and lung cancer rates. It was also found that those that smoked were at an even greater risk.
It is well known that the greatest exposure to radon occurs in the indoor environment where people spend the majority of their time especially at nights where domestic radon levels are known to increase slightly. As a result of this there has been a lot of effort made in identify area at risk and remedial measures to counteract the risk of health problems.
The action level for radon in residential properties was set by the National Radiological Protection Board (NRPB), which is now part of the Health Protection Agency at an annual average concentration of 200 Becquerel’s per cubic metre and where more than 1 percent of the housing stock is predicted to have radon concentration greater than the action level.
The effectiveness of both Action Levels and radon remediation programmes has been subject to debate. One question concerns the extent to which the Action Levels, based on the assumption of a linear relationship between radon levels in the home and actual exposure and typically expressed in terms of the mean annual radon concentration, reflect actual exposures.
If this assumption does not hold, then actual exposures may depart from the estimated exposure levels.
