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This paper presents indoor radon concentrations and specific activities of natural radionuclides measured in soils of Kosovo and Metohija. The measurements of radon concentration were performed during two consecutive 6-month periods in two rooms of 63 houses using CR-39 detectors. The annual radon concentration ranged from 30 to 810 Bq m(-3) with the average value of 128 Bq m(-3). Almost 15% of the houses had radon concentration higher than 200 Bq m(-3). The difference between radon concentrations measured in the two 6-month periods was analyzed, showing, as expected, a slightly higher radon concentration in the winter period than in the summer period. The variation between different rooms of the same houses was also analyzed, showing that 20% of the dwellings had a significantly higher radon concentration ( GT 100 Bq m(-3)) in one room compared to the other (the coefficient of variation ranged up to 96%). The specific activities of natural radionuclides in the nearby soil were determined by gamma spectrometry. The estimated average value (and standard deviation) of Ra-226, Th-232, and K-40 specific activities were 32 (13), 35 (16), and 582 (159) Bq kg(-1), respectively. The correlation between indoor Rn-222 and Ra-226 content in soil was investigated. Only a weak correlation was found (Spearmans rho = 0.220) indicating that other factors might affect diffusion and accumulation of radon indoors, as confirmed also by the high variability between the rooms of the same houses.

Some previous studies on radon concentration in dwellings of some areas of Kosovo and Metohija have revealed a high average radon concentration, even though the detectors were exposed for three months only. In order to better design a larger study in this region, the annual measurements in 25 houses were carried out as a pilot study. For each house, CR-39-based passive devices were exposed in two rooms for the two consecutive six-month periods to account for seasonal variations of radon concentration. Furthermore, in order to correlate the indoor radon with radium in nearby soil and to improve the knowledge of the natural radioactivity in the region, soil samples near each house were collected and Ra-226, Th-232, K-40 activity concentration were measured. The indoor radon concentration resulted quite high from the average (163 Bq/m(3)) and generally it did not differ considerably between the two rooms and the two six-month periods. The natural radionuclides in soil resulted to be distributed quite uniformly. Moreover, the correlation between the(226)Ra content in soil and radon concentration in dwellings resulted to be low (R-2 = 0.26). The annual effective dose from radon and its short-lived progeny (5.5 mSv, in average) was calculated by using the last ICRP dose conversion factors. In comparison, the contribution to the annual effective dose of outdoor gamma exposure from natural radionuclides in soil is nearly negligible (66 mu Sv). In conclusion, the observed high radon levels are only partially correlated with radium in soil; moreover, a good estimate of the annual average of radon concentration can be obtained from a six-month measurement with a proper choice of exposure period, which could be useful when designing large surveys.