According to Radon tests analyzed by Air Chek Labs, the average radon gas levels in Frederick, MD are among the highest in the state, being measured at 12.3 pCi/L. More than half of the tests conducted (55.2 %) measured over the EPA's action level of 4.0 pCi/L. Following closely behind was Carroll Co averaging 10.1 pCi/L and Washington Co at 10 pCi/L.
Check out www.radon.com/maps/ to see how your county measured on average. You can click on any county in the United States and learn their average tested radon exposure. (note these values are only based on levels tested by Air Chek Labs, overall average could be higher or lower overall.)
The only way to truly know your exposure to radon gas is to conduct a test. Conduct a test every 2-5 years as the ground shifts effecting your exposure to radon gas.
Sources:
https://hawkenvironmental.com/