Exposure to indoor radon and natural gamma radiation in public workplaces in north-western Greece

Measurements of indoor radon levels and gamma dose rates were performed in 42 workplaces in Ioannina, north-western Greece. Radon concentrations followed a log-normal distribution with an arithmetic mean of 95 ± 51 Bq m^?3. In all cases, radon levels were below 400 Bq m^?3, which is the action level implemented by the Greek Regulation for Radiation Protection, in accordance with the European Commission recommendation. Comparing summer and winter measurements, no statistically significant seasonal variation was established. However, radon concentrations measured in basement and ground floor workplaces were significantly higher (p < 0.01) than those measured in the first and upper floors. Annual effective dose rates from inhalation of radon and its decay products were estimated to be in the range from 0.13 to 1.36 mSv y^?1 with a mean value of 0.62 mSv y^?1. Indoor exposure to natural gamma radiation entailed an average effective dose rate of 0.13 mSv y^?1, of which approximately 62% was due to terrestrial and the rest due to cosmic sources. The reported data contribute to the assessment of radon distribution and dose estimate at the national level.