Background radiation exposure for a person living in a brick house in Denver, Colorado is approximately three times larger than the exposure of a person living in a wooden home in Palo Alto, California. The factors that contribute to the increased background exposure for the person in Denver include the:
1. High elevation of Denver (more cosmic ray muons reach the ground in Denver)
2. Rock structures in the two areas (more radon in Denver)
3. Bricks in the house contain traces of radioactive elements, whereas wood contains very little.