Lowering the UK domestic radon action level to reduce radiation-induced lung cancer in general population: when and where is it cost effective?

Case studies have shown that radon gas can be present within domestic properties at sufficiently high levels that it can significantly increase the risk of lung cancer in occupants. Recently, Darby et al. (2006) have shown that this risk exists at radon concentrations as low as 100 Bq·m-3, which is below the UK domestic Action Level of 200 Bq·m-3. As a result, there have been suggestions that national domestic Action Levels should be reduced. This paper considers the benefits and costs of the domestic radon remediation programmes in the UK, when a range of Action Levels from 125 Bq·m-3 to 600 Bq·m-3 are applied. The variations of total cost, cost-effectiveness, dose reduction and lung cancers saved for each proposed action level, and the proportion of houses over the proposed action level, were estimated. The study shows that, for an Action Level above 200 Bq·m-3, a completed domestic radon remediation programme in Northamptonshire, where 6.3% of existing houses have initial radon levels over 200 Bq·m-3, will cost less and will target those most at risk, but will be less cost effective. In addition, a higher Action Level leaves a higher residual dose and greater risk of cancer in the population living in unremediated homes. Reducing the Action Level below 200 Bq·m-3 will prevent more cancers, but at significantly higher cost. It will be less cost-effective, because a significant number of houses with moderate radon levels will be remediated with modest health benefit to occupants. The study suggests that a completed radon remediation programme is most cost-effective with an action level of around 250 to 300 Bq·m-3. The finding appears to be independent of the percentage of houses over the Action Level. This has clear implications for future health policy. (author)