“…The only known health effect associated with long-term exposure to elevated radon levels in indoor air is an increased risk of developing lung cancer. Several large joint analyses of residential radon exposure and lung cancer incidence in Europe (Darby et al, 2005(Darby et al, , 2006, North America (Krewski et al, 2005(Krewski et al, , 2006 and China (Lubin et al, 2004) provided strong evidence that exposure to indoor radon can increase the risk of lung cancer in the general population. Radon and its decay products have been identified as the second leading cause of lung cancer after tobacco smoking (WHO 2009, IARC 2004, 2012a, 2012b.…”