There are two types of contamination.
External contamination occurs when the source of radiation comes into direct contact with a person via deposits on the skin. This is caused by:
- the aerosols and radioactive gasses contained in the air when a radioactive cloud passes over;
- radioactive aerosols deposited on the ground (fallout);
It can be eliminated by taking a shower.
Internal contamination is the result of consuming radioactive substances. The radionuclide gets inside the organism, most commonly as a result of ingestion or inhalation, but also through skin wounds or intravenously (for example during a scintigraphy).
These substances attach themselves to tissues or organs and continue to expose them to radiation. Internal contamination decreases in line with the period of radioactivity of the radionuclide ingested and with biological elimination (e.g. via the urine).
In some cases, medication can accelerate the elimination of radioactive substances.