throes keri 292 RUSSELL to iodine 131 as the most significant releases of radioactivity into the environment (93). Both phosphorus 32 and zinc 65 have been detected in grass and milk in pastures irrigated by the Columbia River into which the Hanford cooling water is returned. Zinc 65, together with the induced activities, cobalt 59 and 60 and iron 55, has also been found to be the main source of radioactivity in fish and sea water soon after nuclear explosions (94), The low concentration of the carrier isotopes in water can cause these nuclides to be absorbed and concentrated to a spectacular extent in plants and animals. Plutonium.—Because of its very long half life and high toxicity to animals consideration has been given to the entry into plants of the fissile element plutonium. A very slow rate of absorption is to be expected because it forms high valency (usually 4 or 6) ions; this has been confirmed in sev- eral studies and, over 1.5 years, grass grown in pot culture may absorb less than 10-* per cent of that added to the soil (95, 96). LITERATURE CITED 1. Zuckerman, S., Rept. Comm. Manage- ment Control Res. Develop. (Her Plant Phystol., 28, 594-605 (1953) 10. Russell, R. S., and Squire, H. M., J. Majesty’s Stationery Office, London, 1961) 2. United Nations Scientific Committee on the Effects of Atomic Radiation. Rept. Gen. Assembly (United Nations, New York, 1962) 3. Spiers, F. W., Hasards Man Nucl. Allied Radiations, Cmnd. 1225, Annex D (H.M. Stationery Office, London, 1960) 4. Loutit, J. F., Marley, W. G., Mayneord, W. V., and Russell, R. &., Hazards Man Nucl. Allied Radia- Exptl. Botany, 9, 262-76 (1958) 11. Moorby, J., and Squire, H. M., Agr. Res. Counctl Radiobiological Lab., Rept. ARCRL 8, 63-64 (H.M. Stationery Office, London, 1962) 12. Comar, C. L., Wasserman, R. H., and Nold, M. M., Prec. Sec. Expt. Biol. Med., 92, 859-63 (1956) 13. Martin, R. P., Newbould, P., and Russell, R. S., Radtoisotopes Sci. Res., Proc. Intern. Conf,, Paris, Sept., 1957, 4, 173-90, (1958) 14. Menzel, R. G., and Heald, W. R., Soil Stationery Office, London, 1960) 5. Agricultural Research Council Radiobiological Laboratory, Ann. Rept. 15. Bowen, H. J. M., and Dymond, J. A., J. Exptl. Botany, 7, 264-72 (1956) 16. Gulyakin, I. V., and Yudintseva, E. V., tionery Office, London, 1962) 6. Loutit, J. F., Marley, W. G., and Russell, R. S., Hazards Man Nucl. Allied Radiations, Cmnd. 1225, Annex H (H.M. Stationery Office, London, 1960) 7. Farmer, F. R., and Fletcher, P. T., Proc. Intern. Elec. Nucl. Conf. At. Energy, 2nd, Geneva, 18, 47685 (1958) 17. Asada, K., and Kasai, Z., Mem. Res. Inst. Food Sci.. Kyota Univ., 20, 22-30 (1960) 18. Comar, C. L., Russell, R. S., and Wasserman, R. H., Science, 126, 48592 (1957) 8. Middieton, L. J., and Squire, H. M., Agr. Res. Council Radiobiological Lab., Rept. ARCRE 5, 50-51 (H.M. Stationery Office, HMSO, London, 1961) 9. Rediske, J. H., and Selders, A. A., (1960) 20, Vose, P. B., and Koontz, H. V., Atlgardia, 29, 575-85 (1960) 21. Fredriksson, L., and Eriksson, B., Ann. Kgl. Landwirtschaftlichen Hochschule Schwedens (In press 1962) tions, Cmnd. 1225, Annex F (H.M. 1961-1962, ARCRL 8 (H.M. Sta- oth, 1, pt. 1, 413-37 (1959) Sct., 80, 287-93 (1955) Proc. Intern. Conf. Peaceful Uses 19. Mowat, M. C. H., Nature, 188, 513-14 wie Ryn eRe Ere ‘oo ‘

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