Radon and Building: preventive action for risk reduction.

The World Health Organization identifies radon as the second cause of lung cancer in the general population, after smoking. Epidemiological studies have provided convincing evidence of an association between indoor radon exposure and lung cancer, even at the relatively low radon levels commonly found in residential buildings. Radon is a natural gas produced from uranium and thorium decay; soil is generally the main source of radon accumulating in indoor environment. Thus the knowledge of gas potential release from soil is a powerful tool to make new buildings with low level of indoor radon: a preventive action with a specific field survey can be more effective and economic if compared with later mitigation practices. The knowledge of potential radon emission from soil can have different addresses according to the investigation scale. If applied to large scale survey, it can provide useful data for urban planning and lead to a territory zoning, with location of areas where a significant proportion of homes exceed the reference level (radon-prone areas). In case of small scale investigation (construction site scale), it is possible to collect more detailed information on potential radon release from soil. Here, a protocol for the evaluation of radon hazard factor is proposed in order to promote a practical approach to exploit in any single construction site. This protocol provides a set of indications whose core is the contemporaneous measurements of soil radon concentration and intrinsic permeability. Using these two parameters, a numerical index is calculated, whose value allows to characterise the site on the basis of hazard classes. Mapping soil radon and radon hazard can be a further investigation tool, useful to define the spatial distribution of parameters. Furthermore, the protocol provides suggestions on the protection degree of a new building, in terms of proper construction techniques to prevent gas transport from the soil to the indoor environment. It also gives indication on the permeability features of the ground surrounding the building with the aim of preventing a focused radon flow towards the building foundations. It is important to keep in mind that different methods can be used to measure the parameters. Consequently, it is useful and necessary to validate the method through intercomparison exercises in test-sites. Caffarella Valley (Rome) represents a well-consolidated reference site to study soil radon variability and intercomparison work took place there. Actually, this kind of events are regularly organised in different European countries with the participation of universities, research centres and private firms.