Some substances contributed more than others to the radiation dose a person received. This module discusses how exposure to radiation occurs, how the body handles internal radiation exposure, and which tissues and organs received the main dose from radioactive materials released from Hanford. I n addition to Hanford radiation, radiation exposure comes from a variety of sources. This module, however, focuses on internal exposure from radionuclides released from Hanford.
Radiation exposure can be either external or internal.
External exposure occurs when the radiation source is outside the body. Examples of this kind of exposure include standing in a cloud of radioactive gas, swimming in radioactively contaminated water, or being subjected to X-rays. Internal exposure occurs when a radionuclide is ingested, inhaled, or enters the body through breaks in the skin. For most people exposed to Hanford's radioactive releases, the main route of exposure was internal for most of the radionuclides listed in Tables 1 and 2 in this section. Five radionuclides are estimated to account for most of the dose a person may have received from the river pathway.