Radon migration in the area around the coal mine during closing process

The Upper Silesian Coal Basin (USCB) in Poland is an excellent example of an area affected by an increased migration of radon and by radon penetration into buildings. This occurs due to changes in the geological environment caused by the exploitation of mineral resources. Studies conducted in the past showed that the levels of radon emission, depend to a large extent on the geological structure of the subsurface layers. Mining-induced changes of the rock body are one of the main factors influencing the radon's ability to migrate. Some investigations were made near shafts which were closed many years before, and it was found that physical changes and disintegration of the rock body caused by mining activity (e.g. subsidence) could still influence the environment. Enhanced radon emission was observed even in the case of shafts closed for > 50 years. The Anna coal mine - our study area was opened in 1832, and hard coal was extracted until 2017. In this paper, we present the results of radon emission monitoring within a mine closure context. Measurements started in 2016, when the underground coal mine was still under operation; observations continued during the liquidation process, and more measurements will be taken in the post-closure period. The importance of the hazards related to radon emission has been reported by many organisations. According to the World Health Organization (WHO), a statistically significant increase in the risk of lung cancer occurs as a result of prolonged exposure to radon when the concentration is at 100 Bq/m(3), and increases by 16% per each 100 Bq/m(3) increase. Moreover, the United States Environmental Protection Agency (EPA) stated that radon exposure is the second leading cause of lung cancer after smoking. For these reasons, the Council Directive 2013/ 59/EURATOM of 5 December 2013 established basic safety standards for protection against the hazards related to ionizing radiation in 2013, paying particular attention to issues related to radon exposure. The goal of our work was to collect data on radon migration in an area influenced by mining activity around the Anna coal mine, and to assess the corresponding radon hazard.