You can't see radon. And you can't smell it or taste it. But it may be a problem in your home. Radon comes from the natural breakdown of uranium in soil, rock and water. Radon is the second leading cause of lung cancer in the United States. There are low levels of radon outdoors. Indoors, there can be high levels. Radon can enter homes and buildings through cracks in floors, walls or foundations. Radon can also be in your water, especially well water. Testing is the only way to know if your home has elevated radon levels. It is inexpensive and easy. You can buy a test kit at most hardware stores or hire someone to do a test. Radon reduction systems can bring the amount of radon down to a safe level. The cost depends on the size and design of your home.