A nationwide survey of outdoor radon concentration in Japan.
Nationwide outdoor radon (222Rn) concentrations in Japan were measured to survey the environmental outdoor 222Rn level and to estimate the effective dose to the general public from 222Rn and its progeny. The 222Rn concentration was measured with a passive-type radon monitor. The 222Rn monitors were installed at about 700 points throughout Japan from 1997 to 1999. The annual mean 222Rn concentration in Japan was estimated from four quarters measurements of 47 prefectures in Japan. Nationwide outdoor mean 222Rn concentration was 6.1 Bq m(-3). This was about 40% of the indoor 222Rn concentration in Japan. The 222Rn concentration in Japan ranged from 3.3 Bq m(-3) in the Okinawa region to 9.8 Bq m(-3) in the Chugoku region, reflecting geological characteristics. Seasonal variation of outdoor 222Rn concentration was also found to be lowest in July to September, and highest in October to December. From the results of this 222Rn survey and previous indoor 222Rn survey program, the effective dose to the general public from 222Rn and its progeny was estimated to be 0.45 mSv y(-1).
Oikawa
Shinji
S
Japan Chemical Analysis Center, Division of Research and Training, 295-3, Sanno-cho, Inage, Chiba 263 0002, Japan. s-oikawa@jcac.or.jp
Kanno
Nobuyuki
N
Sanada
Tetsuya
T
Ohashi
Naoyuki
N
Uesugi
Masaki
M
Sato
Kaneaki
K
Abukawa
Joji
J
Higuchi
Hideo
H
D003625:Data Collection; D004781:Environmental Exposure; D004784:Environmental Monitoring; D055593:Geological Phenomena; D005844:Geology; D006801:Humans; D007564:Japan; D011634:Public Health; D011848:Radioactive Pollutants / Q000032:analysis*; D011886:Radon / Q000032:analysis*; D012621:Seasons
D011848:Radioactive Pollutants; D011886:Radon