Protection against radon-222 at home and at work. A report of a task group of the International Commission on Radiological Protection.

The Commission has used an epidemiological basis for the assessment and control of radon exposure in this report. Since all the available epidemiological studies use the quantity inhaled potential alpha energy, this has been used as the primary quantity in this report. The Commission does not recommend the use of the dosimetric human respiratory model (ICRP, 1994) for the assessment and control of radon exposures. The Commission sees practical advantages in the delineation of radon-prone areas where more buildings than usual have elevated radon levels. For dwellings, it is suggested that areas with more than 1% of buildings with radon concentrations exceeding ten times the national average concentration might be designated as radon-prone, but the choice will depend on local conditions. A similar approach might be adopted in non-residential areas. Action against radon should be focused on such radon-prone areas. The imperatives of intervention against adventitious exposure to radon in buildings are clear. Above appropriate action levels, intervention is practicable and usually more cost-effective than other investments in radiological protection. Two types of building need to be considered, dwellings and workplaces. In both cases, radon concentrations are most likely to be elevated by the ingress of soil gas from the subjacent ground. Preventive and remedial measures to avoid this circumstance are recommended. The action levels adopted should fall within the recommended range of values given in Table 7. Proven measures against radon are readily available. For remedial work, the technical procedure that is most likely to maintain the radon level to a value well below the action level should be adopted from the outset. Intervention should take place soon after the discovery of elevated levels, especially if the concentrations are substantially above the action levels adopted by the competent authority. For preventive work, construction codes and building guides should be devised that will consistently achieve low concentrations of radon in the completed buildings. In workplaces, both in buildings and underground, where the radon concentrations remain above the recommended action level after any appropriate remedial measures have been taken, the Commission's system of protection should be applied and radon should be treated in the same way as any other radioactive material at work. The relevant data on conversion coefficients are given in Table 6 and the main quantitative recommendations are summarised in Table 7. Corresponding values in historical units are given in Table 8.