40. 每个人在日常生活中都会受到氡的照射，这是一种化学性质不活泼的自然生成的放射性气体，它在空气中无处不在。同一国家内和不同国家之间室内氡的含量差别很大，在中东地区，室内空气中氡（名义上的）几何平均浓度不到10 贝可每立方米（Bq m-3），而在几个非洲国家，这一数字超过了 100 Bq m-3。
40. Everyone is exposed in daily life to radon, a chemically inert radioactive gas that occurs naturally and is present in the atmosphere everywhere. Levels of radon indoors vary widely both within countries and between countries, with (nominal) geometric mean concentrations of radon in indoor air ranging from less than 10 becquerel per cubic metre (Bq m-3) in the Middle East to more than 100 Bq m-3 in several European countries.