Radon: Evaluation 'BEIR VI'
Radon is a naturally occurring, radioactive noble gas. The element is released in the course of the radioactive decay of radium, traces of which are present in the soil and in stony building materials. In dwellings and other living and work spaces, radon can accumulate in the air, resulting in a higher concentration than outdoors. Inhalation of the likewise radioactive decay products of radon is believed to play a role in the incidence of lung cancer.
In 1993 the Health Council of the Netherlands discussed the risks associated with radon exposure in an advisory report about the Basisdocument Radon (Integrated Criteria Document on Radon). The Council’s report drew extensively on a publication by a committee of the US National Academy of Sciences, the so-called BEIR-IV report (BEIR: Biological Effects of Ionizing Radiation). The US Academy recently produced another report on radon: BEIR-VI. At the request of the President of the Health Council, a working group of the Council studied the new report, looking into whether the Health Council’s earlier advisory report would need to be adjusted.
In the BEIR-VI report (as in the past) the risk associated with radon exposure is derived from epidemiological research among mine workers. The conclusion, which is endorsed by the working group, is that the central risk estimate has increased somewhat — namely from 4 to 5 per 10,000 per WLM (the ’working level month’ is a measure of exposure to radon). In view of the margins of uncertainty, this does not constitute a significant change. Based on the latest exposure data, the new findings suggest that for the Netherlands, between 100 and 1,200 cases of lung cancer per annum might be attributable to radon exposure. The central estimate is 800. In absolute terms, it is principally smokers who are at risk. This is because there appears to be a mutually exacerbating effect between smoking and exposure to radon as far as the causation of lung cancer is concerned.
The analyses in the US report and those of the working group are based on a linear relationship between exposure to radiation from inhaled radon decay products and the risk of lung cancer, where a threshold of exposure below which no damage occurs is considered to be absent. The working group not only believes that this approach is the most plausible, but also that it minimises the chance of the risk being underestimated.