Irradiation is the exposure of an individual to a radioactive source situated outside of the body. The body absorbs either all or part of the ionizing radiation energy emitted by this source. This exposure is dependent on the type of radiation, the distance between the source and the person, the duration of exposure, and the protective shields. It will stop as soon as one leaves the radiation field. The effects on health extend from early effects, ranging from skin burns to irradiation syndrome, to delayed effects such as cancer.
In contrast, contamination corresponds either to the deposit of the radioactive compound on the person’s skin or hair (external contamination), or to penetration by incorporation into the body (internal contamination). The latter can result from ingestion or inhalation of the radioactive material, or by its absorption through a contaminated wound or across the healthy skin.
Inhalation is the most common path for internal contamination in occupationally exposed workers (e.g. industrial and laboratory settings). By contrast, ingestion remains the most common path for public exposure, due to consumption of contaminated foodstuffs. In the case of an internal or external contamination, exposure to ionizing radiation will cease once the radionuclides have been eliminated from the body, either by natural excretion or by radioactive decay (or even by medical treatment). The effects on health are usually delayed, cancer-like effects.
Thus, it is essential to differentiate contamination (either internal or external) from irradiation, in order to put in place specific protective measures and to administer an appropriate treatment to the irradiated and/or radiocontaminated victims.