Smokers are at higher risk of developing radon-induced lung cancer.
Radiation is a natural part of the environment and all persons receive some exposure from naturally occurring radioactivity. Most of that exposure comes from radon. One pCi is equal to the decay of about two radioactive atoms per minute. In constructing a house with a basement, a hole is dug, footings are set, and coarse gravel is usually laid down as a base for the basement slab. Then, once the basement walls have been built, the gap between the basement walls and the ground outside is filled with material that often is more permeable than the original ground.