Dr. Tsubokura's Radiation Lecture Vol.16
Author: Masaharu Tsubokura
Editors: Akihiko Ozaki M.D., Yuki Senoo
31. The exposure dose determines the impact on the body
External exposure occurs when your body is exposed to radiation from an external source, and internal exposure occurs when you are exposed to radiation from radioactive substances that you have taken into your body. The total amount of this external and internal exposure determines its health effects on your body.Although internal radiation exposure is often assumed to be much more dangerous than external exposure is, the influence of radiation exposure is determined not by the type of exposure but by its total dose.
To compare the influence of "internal" and "external" radiation on the same measurement, we use a unit called the sievert. The magnitude of radiation as measured using this unit enables us to predict its impact on our body.When the doses of external and internal radiation exposure are 100 and 1 millisievert, respectively, as the values indicate, the level of external radiation exposure is higher.