Radon occurs in the environment mainly in the gaseous phase. Consequently, people are mainly exposed to radon through breathing air.

Background levels of radon in outside air are generally quite low, but in indoor locations radon levels in air may be higher. In homes, schools and buildings radon levels are increased because radon enters the buildings through cracks in the foundations and basements.

Some of the deep wells that supply us with drinking water may also contain radon. As a result a number of people may be exposed to radon through drinking water, as well as through breathing air.

Radon levels in groundwater are fairly high, but usually radon is quickly released into air as soon as the groundwater enters surface waters.

Exposure to high levels of radon through breathing air is known to cause lung diseases. When long-term exposure occurs radon increases the chances of developing lung cancer. Radon can only cause cancer after several years of exposure.

Radon may be radioactive, but it gives of little actual gamma radiation. As a result, harmful effects from exposure to radon radiation without actual contact with radon compounds are not likely to occur.

It is not known whether radon can cause health effects in other organs besides the lungs. The effects of radon, which is found in food or drinking water, are unknown.

Radon is a radioactive compound, which rarely occurs naturally in the environment. Most of the radon compounds found in the environment derive from human activities. Radon enters the environment through the soil, through uranium and phosphate mines, and through coal combustion.

Some of the radon that is located in the soil will move to the surface and enter the air through vaporization. In the air, radon compounds will attach to dust and other particles. Radon can also move downwards in the soil and enter the groundwater. However, most of the radon will remain in the soil.

Radon has a radioactive half-life of about four days; this means that one-half of a given amount of radon will decay to other compounds, usually less harmful compounds, every four days.