Radioactive material reaches people by four routes: it settles on skin and clothing, it is inhaled as dust, it is swallowed in contaminated food and water, and it enters through wounds. In food the path runs from air to plants and soil, through grazing animals into milk and meat, and some isotopes concentrate in particular foods, such as iodine-131 in milk and caesium-137 in mushrooms.
Part of Radiation Safety
A contamination pathway is a route by which radioactive material gets from where it was released to where it can irradiate a person from inside or on the surface.
Four Ways In
- Surface contact: dust on skin, hair and clothing, carried from place to place. This is the pathway that makes a person a hazard to others; see Contamination vs Irradiation.
- Inhalation: dust and, for some isotopes, vapour, breathed in. The parent article, Nuclear Safety, names plutonium as a lung hazard if inhaled.
- Ingestion: contaminated food, water, soil and hands.
- Wounds: material entering broken skin.
Surface contamination is the one decontamination removes; the other three put the material inside, where washing cannot reach. See Decontamination.
The Food-Chain Route
The parent article describes it this way: particles settle on plants, dissolve in water and are absorbed by soil; animals eat contaminated plants and concentrate radioactivity in their tissues; humans eat the animals and plants. It calls this bioaccumulation, with each step up the chain concentrating the contamination. The picture is more varied than “each step concentrates”: some isotopes concentrate in particular foods or organs, and others do not build up at every step (recalled general knowledge, not from the corpus). The reliable statements are the specific ones below.
| Pathway (parent article) | Why it matters |
|---|---|
| Milk | Iodine-131 concentrates in milk within hours; avoid milk from animals grazing contaminated pasture for at least 90 days |
| Leafy vegetables | Large surface area collects fallout; wash thoroughly or avoid |
| Mushrooms | Efficient at concentrating caesium-137 from soil; avoid in contaminated areas for decades |
| Freshwater fish | Concentrate contamination from water; safer than plants short-term, dangerous long-term |
| Root vegetables | Relatively safe if peeled, as contamination concentrates in the outer layer |
Worked Example: Why 90 Days For Milk
Iodine-131 has an 8-day half-life (parent table). Ninety days is 90 / 8 = 11.25 half-lives, a fraction of 2^-11.25 = 0.04 percent of the starting activity. The parent’s “10+ half-lives” is consistent with this. The waiting period applies only to iodine; caesium-137 at 30 years and strontium-90 at 29 years do not fade in 90 days. See Half-Life.
Isotopes Behave Like The Elements They Resemble
Strontium-90 mimics calcium and deposits in bones, as the parent says; caesium behaves like potassium and spreads through soft tissue and plants (recalled, not from the corpus). That is why a fertile, well-watered field is not a safe field: the isotopes ride the same routes as nutrients.
Breaking The Pathways
- Keep it off: cover stored food and water; see Water Storage.
- Keep it out of the house: leave outer clothing and boots at the door; see Personal Protection.
- Keep it out of the diet: choose foods by Safe Food Selection.
- Keep dust down: wet-clean, do not sweep dry.
Common Mistakes
- Treating healthy-looking crops as clean. Contamination does not show.
- Letting children play in dirt or put hands in mouths. Soil is a direct ingestion route (recalled).
- Feeding contaminated forage and eating the animals.
- Assuming one pathway was blocked and all were.
Safety
Internal contamination cannot be washed off
Anything swallowed or inhaled remains until it decays or leaves the body. Do not eat, drink or smoke in contaminated areas, and keep children from soil, puddles and drains in affected districts. Potassium iodide blocks thyroid uptake of radioiodine and protects nothing else; see Treatment Protocols.
What’s Next
- Learn next: Safe Food Selection — what to eat and what to avoid
- Combine with: Food & Water Safety — keeping water clean