All soil used anywhere for agriculture contains radionuclides to a greater or lesser extent.
The ingestion of radionuclides in food is one of the pathways leading to internal retention and contributes to human exposure from natural and man-made sources. Excessive contamination of agricultural land, such as may occur in a severe accident, can lead to unacceptable levels of radionuclides in food. The radionuclide contaminants of most significance in agriculture are those which are relatively highly taken up by crops, have high rates of transfer to animal products such as milk and meat, and have relatively long radiological half-lives. Direct deposition on plants is the major source of contamination of agricultural produce in temperate regions. While the caesium isotopes and strontium-90 are relatively immobile in soil, uptake of roots is of less importance compared with plant deposition.