The Environmental Protection Agency (EPA) considers 4 Pc/L of radon as a cutoff point between acceptable and not acceptable level of radon. If your house has more than 4 Pc/L of radon in the air, you and your family are continuously being bombarded by alpha particles. If you live in that property for a long time, you are increasing your chances to acquire lung cancer. I would strongly recommend installing a radon removal system in your house if the level of radon is measured around and above 4 Pc/L.
Based on EPA statistics, Radon is found in all of the 50 states. About 1 out of 15 homes in the US has high radon levels.
The largest misconception about Radon is that only old houses have high concentration of Radon.