物理phy~~~~~~~~~~!

Radon(氡氣) in the open air is usually of low concetration and doesn't give any significant hazard to people. Most hazard from radon arises from indoor air.

Radon is a decay product of radium. It is an alpha emitting radionuclide. Because alpha particles have a high ionization power and very short range in tissue, thus radon, if inhaled into the lung, would give significant radiation exposure to the lung. The result is the possible development of lung cancer.

Radon may come from the soil, due to presence of natural radium, or from building materials. In villages, where houses are ususally one or two storeys high, radon from soil is the major source of environmental hazard, especially in cold countries where most houses are air-tight in order to preserve heat in winter. This causes much radon exposure to occupants.

In Hong Kong, most buildings are high-rise, builing materials become the major source of indoor radon. Staying in high radon concentration buildings increases the risk of comitting lung cancer.