2·For most people more than half of their natural background radiation dose comes from radon, a radioactive gas that can accumulate in homes, schools and workplaces.
对大多数人来说，他们自然环境辐射剂量的一半以上来自氡—一种可聚集在家庭、学校和工作场所的放射性气体。
3·These sources of water normally have much higher concentrations of radon than surface water from rivers, lakes and streams.
这些水源通常比河流、湖泊和小溪的地表水具有高得多的氡浓度。
4·When inhaled, the radiation exposure from radon may lead to lung cancer.
当吸入之后，来自氡的放射暴露可导致人们罹患肺癌。
5·Due to dilution in the air, outdoor radon levels are usually very low.
鉴于在空气中的稀释，室外的氡水平通常很低。