Radon surveys and effectiveness of remedial actions in spas on the Ischia island (Italy)

: The possible damaging effects on human health of inhaled radon and its decay products are of interest to workers and the public. In particular, radon in thermal environments often occurs in high concentrations. Therefore, investigations and remedial actions are important to reduce activity concentration values and associated risk. This work concerns the analysis of two surveys of radon gas activity concentration carried out in 2006/2007 and 2019/2020 at twenty thermal spas on the island of Ischia (Italy). Annual measurements were carried out in workplaces located in the basement and ground floor using passive CR-39 detectors. In the spas involved in both surveys, the effectiveness of the remedial actions, implemented by the owners, was assessed obtaining an average percentage reduction of 74%. Considerations were made about the annual effective dose, and the location of the spas taking into account the geological setting of the volcanic nature of the island.