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。

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This is called natural background radiation.

这称为自然环境辐射。

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Radiation doses to humans may be characterized as low-level if they are comparable to natural background levels.

对人类的放射剂量如果与自然环境辐射水平相比属低水平。

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Dr. GERBER: It's approximately four times the natural radiation dose that we all receive annually in the Unites States, as a result from background radiation due to radon and other materials.

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