110
THE EFFECTS OF INDOOR GAMMA DOSE RATE, PERMEABILITY OF SOIL, SUBSTRUCTURE, AND VENTILATION ON INDOOR RADON CONCENTRATION

Ilona Mäkeläinen, Hannu Arvela, Anne Voutilainen
STUK (Radiation and Nuclear Safety Authority), P.O. Box 14, FIN 00881 Helsinki, Finland
Tel. +358 9 759 881, Fax +358 9 7598 8556, Email ilona.makelainen@stuk.fi

The effect of indoor gamma dose rate, permeability of soil, substructure, and ventilation habits of
inhabitants were studied using data of 84 low rise residential houses collected in an area of
enhanced indoor radon concentration. The radon concentrations varied from 30 to more than 5000
Bqm -3 . Cross-tabulation, comparisons of means and multiplicative models were used to test the
significance of the effects. In this study a quite high percentage of explained variation R 2 - 68% -was
found. It was found that the most important factors were the substructure and the permeability
of the soil. Because of the rather small size and moderate variation in the uranium content of the
bedrock of the area, the effect of the indoor gamma dose rate was not so prominent. The effects of
ventilation habits and sleeping with open windows were not detected in this study.
Key words: indoor radon, geology, substructure, gamma dose rate, model