Radon exposure and its influencing factors across 3,140 workplaces in Spain

Indoor radon exposure increases the risk of lung cancer. Radon concentration in workplaces is regulated in EU countries, including Spain, based on a reference level of 300 Bq/m³. The objective of this study is to describe workplace radon exposure in Spain and its influencing factors. To do this, we collected long-term radon measurements with alpha track detectors in 3140 workplaces mainly located in radon prone areas. Radon concentration exceeded 300 Bq/m³ in 1 out of 5 workplaces. Median radon concentration was 107 Bq/m³ in radon prone areas, 28 Bq/m³ off radon prone areas, and 101 Bq/m³ globally for the complete sample. Our results indicate that excessive radon concentrations can be expected in radon prone areas at all floor levels, especially below ground. Floor level, working sector, and location significantly influence radon concentration. The highest radon concentrations were found in the Education & Culture sector, comprising schools, universities, libraries, or cultural centers. These results indicate that radon should no longer be considered a risk for marginal occupations, but a risk everyone has if located in a radon prone area. Immediate action, including radon testing and mitigation, is needed to protect workers in Spain against radon exposure. This is already mandatory since EU regulation for radon has been recently transposed in Spain. Competent authorities should enforce this regulation without further delay, and employers must address their responsibility and communicate with workers about this risk.