Naturally-occurring “Background” Radiation Exposure

We are exposed to radiation from natural sources all the time. According to recent estimates, the average person in the United States receives an effective dose of about 3 milliSieverts (mSv) per year from naturally occurring radioactive materials and cosmic rays, which is radiation that comes from outer space. These natural “background” doses vary throughout the country.

Altitude plays a role in the amount of cosmic radiation, so people living on the plateaus of Colorado or New Mexico receive about 1.5 mSv more per year than those living near sea level. The added dose from cosmic rays during a coast-to-coast round trip flight in a commercial airplane is about 0.03 mSv. However, the largest source of background radiation comes from radon gas in our homes (about 2 mSv per year). Like other sources of background radiation, exposure to radon varies widely from one part of the country to another.

In simple terms, the radiation exposure from one chest X-ray is equivalent to the amount of radiation exposure one experiences from our natural surroundings over three days.