Irradiation is exposure to radiation from a source at a distance, and it leaves no radioactive material on or in the person, who is therefore no hazard to anyone else. Contamination is radioactive material on or in a person or object, which keeps irradiating and can be spread to others on skin, clothing, vehicles and dust; washing removes contamination and does nothing for a dose already absorbed.
Part of Radiation Safety
Irradiation is something done to a body from outside; contamination is something carried on or in it. Almost every practical mistake in radiation safety comes from confusing the two.
The Two Situations Side By Side
| Irradiated only | Contaminated | |
|---|---|---|
| What happened | Radiation passed through the body from a source | Radioactive material is on skin, hair, clothing or inside the body |
| Is the person radioactive? | No | Yes, the material on or in them is |
| Hazard to others? | None | Yes, until washed or the material is removed |
| Does washing help? | No: the dose is already absorbed | Yes, for surface contamination |
| What helps | Supportive care for the effects of the dose | Remove clothing, wash, treat any wound |
| Ongoing exposure? | Stops when they leave the field | Continues until the material is removed |
The parent article, Nuclear Safety, states the key distinction: a person exposed to gamma radiation from a distance is not radioactive and cannot harm others, while a person with radioactive dust on skin or clothes can expose others until decontaminated. This determines whether you need to isolate the patient or just treat them.
Contamination Travels On Everything That Touched It
Contaminated material spreads like dust, because it is dust. It moves on boots, hands, hair, clothing, tools, vehicles, animals and wash water, and indoors it settles on floors, bedding and food. The things that matter are therefore the ones nobody thinks of as people: the coat hung by the door, the cart wheels, the dust tracked into a clean room. Surfaces can be decontaminated; see Decontamination. How material reaches food and water is in Contamination Pathways.
Contamination can also be internal: swallowed, inhaled, or entering through a wound. Internal contamination cannot be washed off. That is the setting in which alpha and beta emitters do most harm; see Types of Radiation.
A Real Case Of Contamination Spreading Through Handling
In 1987 in Goiania, Brazil, scavengers broke open a discarded radiotherapy source containing caesium-137 and the powder was passed from hand to hand, carried home and shared. People died, and many more were contaminated, and homes had to be cleaned or demolished. This account is from general knowledge and not from the corpus; it illustrates how a sealed source becomes a contamination problem the moment it is opened. See Waste Site Identification.
Worked Example: Same Person, Two Different Responses
A survivor arrives from a district hit by fallout, coated in grey dust and vomiting. Treat the two problems separately. The dust is contamination: remove outer clothing outdoors, bag it, wash the person with soap and water, and wash your own hands. The vomiting suggests a dose: it needs fluids and rest, and no amount of washing will change it. If the same survivor had been far from any fallout but had stood near a strong source, nothing needs washing: the person can be sat among others and nursed.
Common Mistakes
- Isolating an irradiated patient from the family. Isolation does nothing for them and deprives them of care.
- Washing an irradiated patient and thinking it reduced their dose. It did not.
- Skipping decontamination because “they were only exposed”. If you do not know which it was, assume contamination until you have checked.
- Forgetting the clothes. A patient washed and re-dressed in contaminated clothes is contaminated again.
Safety
Treat the helper's skin and breath as part of the problem
Anyone handling a possibly contaminated person should cover skin, wear gloves, cover nose and mouth, and wash afterwards; see Personal Protection. Do not eat, drink or smoke while handling contaminated people or objects.
What’s Next
- Learn next: Decontamination — how to clean people, equipment and areas
- Combine with: Personal Protection — keeping contamination off yourself