Studies have associated x-ray exposure with thyroid, breast, and lung cancer and leukaemia. We are exposed to a small amount of radiation all the time. Cosmic rays from the heavens, radioactive elements in the soil and air (radon), stone or brick from your house, for example. And you get even more if you fly in jets a lot. The average person receives about 3 mSv of background radiation per year.
But how much radiation exposure is there with standard imaging tests?
| Test | Dose (mSv) | Years of background radiation / test |
| Chest x-ray | 0.1 | 10 days |
| Pelvis x-ray | 0.1 | 10 days |
| CT Head | 2 | 8 months |
| CT Cervical spine | 3 | 1 year |
| Plain C-Spine | 0.2 | 3 weeks |
| CT Chest | 7 | 2 years |
| CT Abdomen/pelvis | 10 | 3 years |
| CT T&L spine | 7 | 2 years |
| Plan T&L spine | 3 | 1 year |
| Millimetre wave scanner (that hands in the air thing at the airport) | 0.0001 | 15 minutes |
| Scatter from chest x-ray in trauma bay when standing one meter from patient | 0.0002 | 45 minutes |
Human exposures to radiation should follow the ALARA principle; that is, be As Low As Reasonably Achievable. This ensures that the benefits balance the risks.