¥y isomer (2:9 yr) of rhodium, which we have ignated 1emRh, are quite prominent (Fig. 3) along with the “Co, 188b and '7Ca Also ceaily identifiable areAm, seu, 11Rh, '*Rh, 14Ge end “Zn. - All of the isotopes identified in Fig. 3 along with Eu and *‘Mn were present in of soil samples from blast areas. Insoils from non-blast, low fallout areas we usually found only trace amounts of ‘Am, 128Eu and 14Ku along with the major:ceritributers, ¥*Os, Co and 14Sb. We also de BL ~ int aol paamrple frocathe Bravo crater on the northwestern veef_and have tentatively identified '*Ba in w-soilsamplefrom Nam Island. Although most ofthe i which we found contribut- ing to the radiation fields on the atoll are familiar long- lived fission products, such as "Ca (36 yr), '**8b (8-7 yr), *Ru-Rh (367 days) and Ce (284 days) or frequently observed activation products sach as “Mn (303 days) and “Zn (245 days), other isotopes such as “Co, *’Bi, Eu,Eu and ™Rh are rarely detected with such prominence in environmental samples. Many of the weapons tests were conducted on barges, and the resulting activation of **Co and “Ni in the steel ofthe barges accounts for the large amount of “Co activity. ‘Eu (12-7 yr), an apparent activation product, has been found previously’ in trinitite, an artificial mineral produced in the first nuclear explosion in New Mexico in 1945. '*“Rh (3 yr) and ***Rh (206 days) are also activation products. '*Rh is known to have been used as a tracer material in several weapons tests. © **tAm indicated theexpected presence of plutonium isotopes. The measured external exposure rates along with the fractional contributions due to various short and longlived components were used in estimating time integrated doses from external radiation to a returning population. Account wae taken of the time breakdown of inhabitation of various areas of the islands. Beoause of the low cosmic-ray and negligible natural radioactivity levels, and the radioactive decay of the large fraction of shortlived components, these estimates rapidly become comparable with or, in some cases, as for Eneu Island, much lower than integrated doses from natural radiation i: the United States. In addition to cur measurements of external radiation at Bikini, intensive sampling by other investigators of flora, fauna, marine life, birds, soils and ground water was carried out in 1964 ag well as in 1967. All these data were considered carefully by governmentofficials and a special scientific committee of consultants in arriving at the recent decision to allow reeettlament ‘of certain i-lands of the atoll. The radiation situation on Bikini newed 3 unique intense rtunity for. investigating.an fallout field. atively We were able to relate exposure rates on the atoll to test locstians an@ ‘environmental conditions at and subsequent tothe times of the teste. A large number of radionuclides, including several unusual for environmental samples, were found contributing to the wide range of external y-radiation levels.. Utilization of the combination of ionization chamber and field spectro- metric measurementa with laboratory Ge(Li) spectrometry of soil samples proved to be a very effective method of analysing this complex radiation environment. The 1967 Bikini environmental survey was sponsored by the Division of Biology and Medicine of the US Atomic Energy Commission. We thank Edward Held, University of Washington marine radiobiologist; the survey leader; his assistant, Robert Erickson; Tommy McCraw, USAEC Division of Operational Safety; Arnold Joseph, USAEC Division of Biology and Medicine; Jack Tobin, former Trust Territory district anthropologist; James Hivane, Trust Territory district agricultarist; and Francis Tomnovek and Edward Jones, US ‘NavalI Radiological Defence Laborstory. Reosived May 27; revised July 21, 1969. 3 Lowder, W. M., Beck, H. L., and Condon, W. J., Nature, 208, 745 :164). : BerkBe Condon,W.J., and Lowder, W. M., USABC Report, HA>L-150 * Beck, H. L., Lowder, W. M., Bennett, B. G., and Condon, W. J. 'N4EC Report, HASL-170 (1966). ��� Glasstone, 8., The Effecis of Nuclear Weapons (USAEC, 1962). s Bede L., Bennett, B. G., and McCraw, T. F., USAEC Report, H.1> 1-190 ) * McGowan, F. K., and Stelson, P. H., Pays. Rev., 128, 2181 (1961). 7 Salter, L. P., and Harley, J. H., Science, 148, 954 (1065). Printed in Great Britain by Fisher, Knight & Co. Ltd., St. Albans. x. 127Cg, Therelatively large “Co and?"Sb activities relative to Cs contrast with the BikiniIsland situation. The peaks characteristic of the recently identified* long-lived