Inhalation accounts for approximately 2.28 millisieverts of annual natural radiation exposure.

“Uh and you have some from the internal by ingestion, .29 millisieverts.”

“So, 2.2 millisieverts every year from background radiation, radiation from sources like sun, radioactive earth, rocks, uh small amounts passed up in the food chain, um and one chest x-ray is .02 millisieverts.”

“and just living on Earth you're getting about 1 to 2 millisieverts a year.”