A lot of them depend on the area you're in and the age of the property you're interested in purchasing. Please contact the EPA for further, more specific information and recommendations regarding testing of various environmental issues.
Radon enters a home through cracks and holes in the foundation and can also be found in well water.
The main concern is radioactivity which becomes trapped in your lungs through normal breathing. It is the second leading cause of lung cancer in the United States. Although smoking by itself is the leading cause of cancer, when it is combined with elevated Radon levels, a person may be 10 to 20 times more likely to develop lung cancer than from smoking alone. EPA estimates that 1 out of every 15 homes in the United States has an elevated level of radon gas. Any home can have a radon problem, new or old, with or without a basement.