RK. L. BLANCHARD and J. B. MOORE 133 Table 5, A comparison of the “1°Pb content in old and recent caribou bones Latitude Concentration in recent (1965-1966) caribou bones ( pCi 2p b/ajy Concentrauion in pre-1951 caribou bones from Table + ( pCi 29Pb/e} <60°N Range: 2.1-5.6 (1-1) 2.1 (fawn) 60°-65°N Range: 2.1-7.5 (26) 5.4 ~63°N Mean: 3.1 -+ Oot Mean: 4.5 + O.F Range: 4.9-13.1 (15) Mean: 15.4. 8.1 7.0 - 0.6 1.5 {(fawn) \ Note: (a) The numberof caribou are given in parentheses (b) The uncertainties are the standard deviations of the mean. ‘The next step in the arctic food chain is caribou, which should also reflect higher levels of *!°Pb after 1951 if nuclear testing contributed substantially to the #®Pb levels in the aretic environment. ‘UVhe *!°Pb results for the pre-1951 caribou bone samples given in ‘Table 4 are compared in ‘Table 5 to adult caribou bone samples which were collected during 19651966.Due to a possible increase in the 74°Pb bone concentration with increasing latitude,’ the results in Table 5 are arranged in three groups according to latitude. Except for sample OC-05, a fawn, the results of the pre-1951 samples are within the range of values reported for the recent samples. As it has been reported that the *"Pb skeletal burden of fawns is only about one-half that found in the skeleton of the adult,{the two samples from fawns, OC-04 and OC-05, are undoubtedly low relative to adult caribou from the same areas. As in the case for lichen samples, there does not appear to be any substantial increase in the #°Pb skeletal burden of caribou following the advent of nuclear testing in the arctic. Consequently, it scems unlikely that arctic testing of nuclear weapons has had any significant effect on the amountof #!°Pb in the arctic ecosystem. SUMMARY Although there were relatively few tissue samples available for study, the results indicate that caribou or reindeer meat is the principal source of 219Po for Alaskan residents, and that, in general, the intake of ?Pb and #!°Po by inhalation is about the same as in the conterminous United States. In addition, it was illustrated in the case of these subjects that consumers of caribou meat may ingest large quantities of “10Po unsupported by its parent, 7Pb. ‘This produces high “Po bedy burdens only as long as the subject continues to eat caribou or remdeer meat, and when the meat is climinated fromthe dict the 2!°Po will be excreted within a relatively short period and the body burden will approach that of an unexposed person. Phe Pb concentrations in lichen and caribou bone samples collected belore 1951 were comparable to concentrations in similar samples recently collected. “Whe data tend to discount the iinportance of nucleartesting in the arctic as a significant source of 24°Pb. Acknowledgement—TVhe authors thank Perer JArLow, Alaskan Native Mcedicul Center, Anchorage and Db. J. Werner, Alaskan Native Hospital, Kotzcbue, for supplying the tissue samples; Mason Hate, Smithsonian Institution, Washington, D.C., for the pre-1951 lichen samples; P. M. YouncMman, National Museum of Canada, Ottawa, for the pre-1951 caribou samples; and B. Kaun, ofthis laboratory, for helpful suggestions during the preparation of this paper. REFERENCES 1, A. R. Scnuert, Science 136, 146 (1962). 2. D. G. Watson, W. C. Hanson and J. J. Davis, Science 144, 1005 (196-4). 3, W. C. Hanson and Hi. I. Parmer, Trans. M. Am. Wildl. Conf. 29, 215 (1901). 4, W. C. Hanson and H. E. Patmer, Health Phys. iE, 1401 (1935). 5. W. C. HANson, Science 153, 525 (1966). 6. R. L. BrancHarp and J. W. Kearney, Znviron. Set. Technol. 1,932 (1967). 7. R. B. Hottzman, Nature Lond., 210, 1094 (1966),