Indoor Radon Concentrations in Portugal - A National Survey

Abstract

A programme for the evaluation of indoor radon concentrations in Portugal was implemented by the Radiological Protection and Safety Department in 1987. This Programme was started in dwellings in zones of technologically enhanced natural radioactivity and it was later enlarged to the whole country. The survey was performed with the cooperation of the local high schools. The dosemeters were personally delivered to the teachers, who managed their distribution, on a statistical basis of one dosemeter for 2000 inhabitants. The total recovery of the distributed dosemeters was about 55%. Passive track detectors, LR-115s, were used and exposed for 1–3 month periods. Whenever possible, measurements were performed twice in each house. More than 4000 dwellings were surveyed and the observed individual concentrations range from 6 Bq.m-3 (detection limit) to about 3 × 103Bq.m-3. The geometric mean per county values (the administrative division considered) range from about 7 to 200 Bq.m-3. The results obtained in the 276 Portuguese counties are presented in the form of a map. It is shown that the highest mean values correspond to the zones of technologically enhanced radioactivity and, also, to the granitic regions. Significant seasonal variations were observed and are also presented. The dose to the Portuguese population due to the inhalation of indoor radon has been calculated.