Indoor radon concentration and gamma dose rate in dwellings of the Province of Naples, South Italy, and estimation of the effective dose to the inhabitants

The indoor radon concentration was measured in 471 dwellings in the Province of Naples. Radon concentration measurements were carried out using LR-115 passive alpha track detectors (SSNTDs) that were exposed for two consecutive semesters. The annual average radon concentration in the dwellings was found to vary from 21 to 722 Bq m(-3) with an average value of 107 +/- 75 Bq m(-3). In about 93% of the dwellings the radon concentrations were found to be below 200 Bq m(-3), which is the recommended level by Italian law for new buildings. Simultaneously with the radon concentration measurements, indoor gamma dose rates were measured in 388 dwellings. Indoor gamma dose rates were measured using Thermoluminescent Dosimeters (TLDs) exposed in each dwelling for six months. The arithmetic mean value was found to be 327 +/- 102 nGy h(-1), after the subtraction of the cosmic ray contribution. A weak correlation between the indoor radon concentration and gamma dose rate was found. The correlation between indoor radon measurements and gamma dose rates and the same building characteristics was also studied.