RESUMEN
Indoor and soil radon concentrations were measured in the villages of Ayn-Jana, Ishtafena, Samta and Umm-Yanabe' in the district of Ajloun, Jordan. Several factors that are strongly related to the radon concentrations are considered whether in soil such as its type or indoors such as room occupation type, floor level and building materials. In the village of Ayn-Jana, our results showed that the average radon concentration decreases gradually as the floor level increases. The highest concentration was found to be in the ground floor (35.5 ± 5.0 Bqm(-3)) and the lowest was in the second floor (22.9 ± 3.2 Bqm(-3)). Regarding the effect of ventilation rate in the same village, storage rooms revealed the highest concentration (38.8 ± 5.4 Bqm(-3)) while the lowest concentration was in living rooms (33.8 ± 4.4 Bqm(-3)). In the four villages, it was found that the highest radon concentration was in the dwellings made of clay (45.7 ± 6.7 Bqm(-3)) and the lowest was in dwellings made of brick (33.9 ± 6.4 Bqm(-3)). In general, the average indoor radon concentration in these villages was 36.3 ± 2.3 Bqm(-3) and it corresponds to an average effective dose rate of 0.92 ± 0.06 mSvyr(-1). These indoor radon concentrations as well as the annual effective dose are below the action level recommended by ICRP. The average radon concentration in soil of these villages was about 2.55 ± 0.20 kBqm(-3), and it ranges from 2.08 ± 0.12 kBqm(-3) in the village of Ayn-Jana to 3.62 ± 0.13 kBqm(-3) in the village of Ishtafena.