The article presents the results of radon research, carried out in the area of the mining commune in the Upper Silesian Coal Basin (USCB), Poland. Past investigations in the 1990s on radon concentrations in buildings, located within the mining area, showed that the indoor radon concentrations measured in the area affected by mining were higher than in buildings located outside that area. Currently, all underground hard coal mines within the boundaries of the observed commune have been closed. In 2020, after the closure of the last active mine, radon measurements were started again. The current results of indoor radon concentrations were compared with the archival results from the 1990s. It was found that the radon concentration increased significantly in the basements of buildings where measurements were made in 1990, 2020, and 2021: the maximum values were 260 Bq/m3, 644 Bq/m3, and 1041 Bq/m3, respectively. Therefore, these questions were posed: Do the mine closure processes increase radon migration? How long is the period of the occurrence of changes in radon concentrations in buildings after the cessation of mining operations?
Keywords: abandoned coal mines; coal mining; doses to inhabitants; indoor radon concentration; radon migration.