2000 年 35 巻 2 号 p. 203-209
It is important to understand 222Rn concentrations in dwellings precisely for dose assessment. 222Rn concentrations were continuously measured in a reinforced-concrete house in Tokyo with three stories above ground and one basement for seven years, from October 1988 to September 1995. In the basement, temperature and humidity were also measured, which were used for analyzing the seasonal variation of the 222Rn concentration and its relationship with environmental factors. 222Rn concentrations on the 2nd and 3rd floors showed a statistically significant seasonal variation, i. e., higher in winter and lower in summer, but those on the 1st floor did not show any significant seasonal variation. The 222Rn concentration in the basement showed a reverse seasonal variation, i. e., higher in summer and lower in winter. The 222Rn concentrations on each floor showed a drastic decrease after the renewal of the dehumidifier in the basement, which suggests that the 222Rn concentration in the basement has an influence on that in the rooms above ground. A multiple regression analysis suggested that the 222Rn concentration in the basement and its seasonal variation can be expressed with statistical significance by the linear combination of temperature, humidity and atmospheric pressure. It was also revealed that the 222Rn concentration on the 1st floor can be expressed by the linear combination of the concentrations in the basement, 2nd and 3rd floors.