Measurements of indoor radon concentrations in the Santiago de Compostela area

Galician soils are among those with the highest 222Rn exhalation rates in Spain. A year-round study of the indoor 222Rn concentration in buildings in the Santiago de Compostela area (Galicia, Northwest of Spain) was performed. The study is based on systematic samplings with active charcoal canisters, following a modified EPA 520/5-87-005 protocol. These measurements were complemented by others obtained using etched track dosimeters. Each data set follows a log-normal distribution, with a geometric mean of (253 ± 3) Bq m−3 for charcoal canisters and (285 ± 2.5) Bq m−3 for etched track detectors. After correcting for the different measuring conditions, the mean value of both methods differed by only 2%. A careful analysis of the seasonal dependence of our measurements did not reveal any significant seasonal variations in the 222Rn concentration. Parallel to these measurements, different meteorological parameters were recorded, which revealed a direct correlation between the indoor radon concentration and the outdoor temperature derivative with respect to time.