Indoor radon levels in north-western Poland

Concentrations of indoor 222Rn have been determined in order to locate zones of high radon level, to examine their correlations with geological factors, types of building materials, number of storeys etc., and to estimate the inhalation doses to the population living in the region. The north-west part of Poland was taken into consideration as a geologically homogeneous region, representing 42.3% of the country area and inhabited by 32.1% of the inhabitants of Poland. A sample containing 505 dwellings, which means a measurement density of one detector per 24,287 inhabitants (or 6.8 x 103 dwellings) was exposed to Rn over about a 12 month period. Radon was measured with diffusion chambers containing CR-39 α track detectors, evaluated after chemical etching. Measured indoor radon concentrations varied from 10.9 Bq.m-3 to 231.9 860q.m-3 with a median of 33.4 Bq.m-3. The median extrapolated for one year exposure is equal to 39.8 Bq.m-3, which corresponds to an annual effective dose from radon inhalation equal to 0.68 mSv. About 96% of dwellings under examination showed average radon concentrations below 100 Bq.m-3, only in two houses was an excess of 200 Bq.m-3 observed. Survey results confirmed, as predicted by geologic homogeneity of the terrain, that radon levels are relatively low, and range mainly with statistical dispersion. (author)