What are the typical sources and annual levels of background radiation exposure?
Annual background radiation has been increasing due to the dramatic rise in medical imaging over the past two decades. In the early 1980s, the total annual background radiation exposure was approximately 3.2 mSv, of which only 15% was from medical imaging. Two decades later, the total annual background exposure is approximately 6.2 mSv, with nearly 50% attributed to medical imaging. Figure 7-3 illustrates the breakdown of annual background radiation, comparing the 1980s to 2006. The largest exposure from medical imaging is due to CT.