Radium, which is naturally present in many building materials, decays to the radioactive gas radon, which is exhaled from the surface of concrete block and is a major source of human exposure to ra...

中文翻译：

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评估覆盖层对建筑材料氡排放的影响

天然存在于许多建筑材料中的镭会衰变成放射性气体氡，从混凝土块表面呼出，是人类暴露于辐射的主要来源。