Internal Exposure

Internal radiation exposure hazards result from radioactive material that gets inside the body when you breathe it or eat it or when it passes through your skin. Internal radioactive materials produce radiation exposure the entire time they are in the body until the material is no longer radioactive (it decays) or is removed naturally by the body. There is a form of potassium found in everyone’s body that is radioactive (potassium 40 or ⁴⁰K). It is a gamma emitter.

It was mentioned that external radiation exposure is unlikely from alpha and beta particles. Internal exposure, however, can come from all types of radioactive materials if they are inside the body. Once inside, much of the radiation energy will get absorbed in cells, tissues, and organs. The extent of an internal radiation dose is related to the amount of material inside the body, where it goes in the body, how long it stays in the body, and the type of radiation it emits.

Unlike the skin on the outside of the body, there is nothing inside us to protect cells and tissues from the potentially damaging effects of alpha and beta particles. Alpha particles can be very hazardous internally because an alpha particle does not travel very far and its energy is deposited within a small volume, increasing the chance of cell death.

Where the radioactive material travels when it is inside the body depends on what organs or tissues in the body use the material—these are called target tissues or target organs. For instance, our bones need calcium and when we eat something high in calcium, like milk, our body takes the calcium to our bones. If the calcium is radioactive, our bones will absorb that, too. If the material isn’t used by anything in our body, our body will get rid of it.