The newest international trend about regulation of indoor radon.

On the basis of recent epidemiological findings, many international and national organisations have revised their recommendations and regulations on radon exposure in dwellings and workplaces, or are in the process to do it. In particular, new recommendations and regulations were recently published (or are going to be) by World Health Organization, Nordic Countries, International Commission on Radiological Protection, International, Atomic Energy Agency (and the other international organisations sponsoring the International Basic Safety Standards), European Commission. Although with some differences, these new documents recommend lower radon concentrations in indoor air, especially in dwellings, compared with previous ones. Moreover, preventive measures in all new buildings are more and more considered as one of the most cost-effective way to reduce the radon-related lung cancers, compared with previous approach restricting preventive measures in radon-prone areas only. A comprehensive national action plan, involving several national and local authorities, is generally considered a necessary tool to deal with the many complex actions needed to reduce the risk from radon exposure in an effective way.