Chen Jing, Moir Deborah, Sorimachi Atsuyuki, Tokonami Shinji
Radiation Protection Bureau, Health Canada, 775 Brookfield Road, Ottawa, ON, Canada.
Radiat Environ Biophys. 2011 Mar;50(1):85-9. doi: 10.1007/s00411-010-0338-5. Epub 2010 Sep 25.
Naturally occurring isotopes of radon in indoor air are identified as the second leading cause of lung cancer after tobacco smoking. Radon-222 (radon gas) and radon-220 (thoron gas) are the most common isotopes of radon. While the radon equilibrium factor is well established, the equilibrium factor between thoron progeny and thoron gas is still not well known. Thoron gas and progeny concentrations were determined in the lowest floors of 138 Canadian homes simultaneously. While thoron gas was only detectable in about 52% of the homes, thoron progeny concentrations were measured in every home surveyed. Thoron concentrations, thoron progeny concentrations, and the equilibrium factors varied widely and were log-normally distributed. With a 3 months simultaneous measurement of thoron and thoron progeny concentrations, the equilibrium factor was determined to be 0.024 with a geometric standard deviation of 2.7.
室内空气中天然存在的氡同位素被认为是仅次于吸烟的第二大肺癌致病因素。氡-222（氡气）和氡-220（钍射气）是最常见的氡同位素。虽然氡平衡因子已得到充分确立，但钍射气与其子体之间的平衡因子仍不太清楚。同时测定了加拿大138户家庭最低楼层的钍射气及其子体浓度。虽然仅在约52%的家庭中检测到钍射气，但在所调查的每个家庭中都测量了钍射气子体浓度。钍射气浓度、钍射气子体浓度和平衡因子差异很大，呈对数正态分布。通过同时对钍射气及其子体浓度进行3个月的测量，确定平衡因子为0.024，几何标准差为2.7。
