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Human data are used to obtain (MPC)wvalues for continuous occupational exposure to Sr90, Sr89and Sr85. A three-exponential model is found to give an empirically adequate representation of the data on retention and excretion of strontium by grossly normal adults for a period of 200 days following intake. The third exponential is selected to be roughly consistent with the data on stable strontium in diet and in bone of adults, as well as in fair agreement with the estimates of bone turnover rates by ROWLAND. The use of a power function to describe retention is summarized. Also, MPC values are estimated for Sr90by the use of the observed ratio, O.R., and from the diet-bone data on stable strontium. These various models are discussed briefly as to their adequacy for applied health physics. It is found that all these models indicate an (MPC)wfor Sr90which is higher by a factor of 4 or more than that recommended currently by ICRP and NCRP.

The extent of individual variation of the concentration of certain elements in human tissue has been studied. The data were obtained from emission spectrographic studies of human tissue which have been a joint research project between the Health Physics Division, Oak Ridge National Laboratory, and the Physics Department. University of Tennessee. Dr. ISABEL H. TIPTON of the University of Tennessee has directed the spectrographic work. There is strong evidence that within a homogeneous population group the fraction of the population exceeding the sample mean by a factor of three will not exceed 5 per cent of the population. This was true in nearly all cases where the sample size was sufficiently large to permit the estimation of 5 per cent of the population at the 95 per cent confidence level. Elements studied include Cd, Cu, Zn and Al in the kidney, liver and lung. These tests indicate that for such elements and under continuous exposure to radionuclides in the environment, only a small fraction of a homogeneous population group will receive a dose in excess of three times the mean dose for the group. This tends to validate the assumption of the Federal Radiation Council in its Report No. 1 concerning the distribution of the dose in such a group.

The dose rates and annual doses of individuals continuously exposed to radioactive material in the environment will be approximately proportional to the concentration of the radionuclide in the various tissues of these individuals. A stable isotope of the same element should have a similar distribution in these tissues, and thus the form of the distribution of the annual dose or dose rate may be inferred from studies of the distribution of concentrations of stable isotopes in human tissues. Statistical methods given by BRUNK and MASSEY have been applied to data for normal isotope distribution in human tissue as reported by TIPTON et al., BRYANT et al. and KULP et al. The method by BRUNK determines a band such that at each concentration value one may assert with 95 per cent confidence that the true distribution function lies below (above) the upper (lower) boundary of the band. The method by MASSEY has been applied to obtain a 95 per cent confidence band for the entire cumulative distribution curve. In the majority of cases studied one may assert with 95 per cent confidence that not more than 5 per cent of the population groups sampled have concentration values above three times the sample mean, thus providing some quantitative interpretation of the assumption used in the reports of the Federal Radiation Council.

The introduction of eight alkoxy or eight alkyl substituents onto the phthalocyanine (Pc) nucleus at the non-peripheral (1,4,8,11,15,18,22,25) positions produces derivatives which are soluble in a variety of organic solvents. However, other physico-chemical properties of the two series differ. Octa-alkyl derivatives, R8 Pcs, pack as more ordered molecular assemblies in the solid state and show thermotropic liquid crystal behaviour with transition temperatures dependent upon substituent chain length and the central metal atom. In contrast, octa-alkoxy materials, (RO)8 Pcs, melt directly into the isotropic liquid. The latter can be deposited as Langmuir-Blodgett films whereas the former cannot. Experiments with examples of the two series in which one or two of the chains are functionalized at the terminal positions with a hydrophilic moiety show that these amphiphilic analogues deposit well by the Langmuir-Blodgett method. A number of the films show a high degree of molecular ordering, as judged by X-ray reflectivity methods, transmission infrared, RAIRS and polarized optical spectroscopy. Results indicate that the type of ordering is controlled by the type of substituent and the length of the chain.