Deposits of radium and uranium are common in the rock and soil. Studies have shown that exposure to radon gas and its decay products can increase the risk of lung cancer. The risk of developing lung cancer is related to the concentration of radon in the air and the length of time an individual is exposed. While neighboring homes can vary dramatically in radon levels, the fact that neighbors have high levels is a good reason to test.
Tests are cheap and easy to do.
I recommend doing the test in winter, when radon levels are likely to be highest, the ground is frozen, your home is closed and your heating system is operating. For more information on radon testing, contact your county UW-Extension office or your local public health office. The real problem is that radon continues to decay, producing other radioactive materials and emitting radiation. The new materials produced by the decay of radon are solids which readily attach to dust particles in the air, they then can be inhaled. These radon decay products are also radioactive and continue the decaying process producing new solids and emitting additional radiation.