Understanding the behaviour of indoor radon to prevent health issues.

The increase in the incidence of lung cancer among non-smoking individuals is triggering lines of research to explore other potential contributing factors. Radon has been identified as a cause of respiratory disease and lung cancer in workers, but lack of sufficient information on radon concentration in private houses may distort the real danger of this gas. An in-depth study is necessary to assess the impact of this gas, which displays highly heterogeneous behaviour depending on parameters such as temperature, atmospheric pressure, humidity… An experiment carried on in a family house, using basic equipment (e.g., RadonEye counter) has shown that although it is published that low atmospheric pressures cause an increase of radon indoors, during the experiment, heavy storms produced a drop in the concentration of indoor radon. This behaviour should be further studied, as heavy storms seem to be more frequent due to climate change. Also, the humidity produced by capillary absorption was responsable for the increase on radon concentration, both in a basement and in the floor above. Although ventilation has been proved to be the more effective method to decrease the radon concentration to very low levels, some geographic characteristics, due to weather, make this measure uncomfortable for the domestic comfort. Structural measures such as Active Soil Depressurization (ASD) Systems have been invoked as potential solution, and impermeabilization of walls is also an implemented measure giving acceptable results. Impermeabilization of the most affected walls of the house used for the pilot project derived in a sustainable decrease of radon concentration (both downstairs and upstairs). Epoxy resins were used to cover an inside wall to stop capillary raise of water derived not only from rain, but from watering gardens of houses around. The process of impermeabilization is easy to implement, somehow expensive but less invasive than other structural measures (e.g., ASD), and the achieved level of radon concentration is acceptable for European standards (i.e., below 300 Bq/m³). Now the debate should be if this level is acceptable in terms of health concerns, as the United States of America Environmental Protection Agency recommends values below 148 Bq/m³ and the World Health Organization recommends levels below 100 Bq/m³.