Nutritional hazards caused by radioactive contamination of foods.

Isotopes that may contaminate crops Fallout may be made up of a hundred or more active isotopes but only a few of them are likely to be harmful as crop contaminants. Iodine. As 1311, it will be a major hazard for a few weeks after fallout arrives. Chamberlain & Chadwick (1953) showed that iodine gas is deposited on grass by diffusion. Chamberlain, Loutit, Martin & Russell (1955) note that, in fresh fission products, the iodine hazard will be increased since the short-lived isotopes 1321, lS3I , and 1351 will make a considerable contribution. The maximum permissible concentration on herbage is well below that needed for external radiation hazards (Parker, 1950). Caesium. Much has been heard about the possible effect of 137Cs but it is difficult to assess the dangers that may be associated with this isotope. Ingested caesium is well absorbed and a high concentration develops in muscles (Hood & Comar, 1953). Thus, apart from possible damage to the health of animals, ingestion of 13'Cs may render the animal useless as a source of meat. On the other hand, caesium is not readily taken up from the soil by plants (Anderson, Schuch, Fisher & Langham, 1957) and its biological half-life is fairly short-140 days in man and 20 days in cattle. It might be wise to regard 137Cs as a hazard of unknown degree. Strontium. There is no doubt whatever about the dangers associated with contamination of crops by 89Sr and 90Sr. Lapp (1955) points out that radiostrontium (a) has a long half-life, (b) is born with a high fission yield, (c) because of its gaseous predecessor, diffuses throughout the fireball of a thermonuclear explosion and 'plates' upon the debris, (d) resembles calcium and is thus subject to uptake in biological systems and (e) is a bone-seeker and, because of it, its p-rays are of considerable biological significance. Lapp also stresses the fact that, weight for weight, sgSr is 180 times more radioactive than 90Sr; this higher activity is associated with its shorter half-life. From published figures, he calculates that a lo-megaton thermonuclear bomb might deposit 2-3 g radiostrontium/sq. mile, and this tiny weight of