After the Chernobyl accident in 1986, about 150,000 monitoring measurements were performed in Ukraine. From this data base, 40,000 measurements were selected for which the results of the reference-source measurements could be analyzed by statistical means. The majority of these measurements are of high quality. In this paper, the uncertainties introduced due to the variabilities of anatomic parameters and the measurement geometry are quantified by measurements using a thyroid-neck phantom. Parameters considered are the thyroid mass, the thickness of the tissue overlying the thyroid as well as the detector-neck distance, the orientation, and the horizontal and vertical position of the detector. The uncertainty introduced due to the variability of these factors corresponds to a coefficient of variation in the range of 25-40% for the measured activity.

Based on the results of 131I thyroid activity measurements in three districts of the Chernigov region (Ukraine), individual doses were calculated and an approach of the age dependence of the average thyroid exposure was derived. Using the relationships between the thyroid doses and the 137Cs deposition as well as the location relative to the Chernobyl Nuclear Power Plant (NPP), age-dependent average thyroid doses were extrapolated also for those settlements of this region where no monitoring measurements have been carried out. The highest doses were found in the west of the region with the lowest distance to the Chernobyl NPP. In this part, the highest mean of the thyroid dose in a settlement was 3.3 Gy for infants and 0.5 Gy for adults. The collective thyroid dose was 31,000 and 27,000 person-Gy for children and adults, respectively. Based on this assessment, 140 and 21 excess thyroid cancer cases are predicted for children and adults, respectively. In the years 1989 to 1991, in the whole contaminated territory of the Ukraine 0.4-1.2 cases per 100,000 children were observed. Although the absolute numbers are very small, this indicates the possibility of an increase in thyroid cancer morbidity among children. The same trend also seems to be indicated in the Chernigov region. A careful epidemiological study in the future is necessary to enable a final evaluation of radioinduced cancers in this region.

One of the consequences of the Chernobyl reactor accident in 1986 was a comparatively high contamination of foodstuffs in Southern Federal Republic of Germany. In order to test radioecological models predicting the radiological consequences of such accidents, several thousand measurements were performed to determine Cs body burdens in members of the public. For the interpretation of these data and as a contribution to the improvement of the available database on the biokinetics of Cs isotopes in humans, we followed a small group of volunteers after their consumption of highly contaminated venison. Intakes, excretion rates and total body activities were measured during a period of more than 200 d. The data obtained were evaluated in terms of a compartment model to derive gastrointestinal uptakes, biological half-lives and dose conversion factors. The resulting uptake factors range from 65-90%, the half-lives of the long-term retention from 45 to 200 d. The majority of the resulting dose conversion factors lie below the values recommended by the ICRP, showing that the ICRP model is a reasonable and safe description of the Cs biokinetics in our study group, while the great variability of the results shows that it is not an accurate representation of the individual Cs retention.

The age-dependence of the radiation dose absorbed in a target organ or the total body is determined by the mass, size, shape and separation of the organs as well as by the metabolic behaviour of the radionuclide compound. Using values of the specific absorbed dose for adults, the age-dependent effective dose equivalents for 28 radiopharmaceuticals (62 radionuclides) were calculated by modifying the above mentioned values, considering radiation type, organ mass and source-target separation. From the results, the currently used mathematical models for the modification of values of specific absorbed doses in the adult prove to be of sufficient accuracy. In comparison with the few available values calculated by Monte Carlo-techniques, our method overestimates the specific absorbed fractions by a factor of four in the least favourable case. For practical radionuclide dose estimates, these deviations are of minor importance as long as the availability of reliable information on the metabolic behaviour of radionuclide compounds and radiopharmaceuticals as a function of age is extremely limited. Considering, however, both the parenteral administration and the short half-life of radionuclides used in paediatric nuclear medicine, this uncertainty in regard to the gastrointestinal absorption and the biological half-lives is of little consequence for the results of absorbed dose calculations.

The transfer in cattle of the radionuclides 137Cs, 60Co, 54Mn, 22Na, 131I and 95mTc was studied experimentally to determine transfer coefficients from feed to milk and meat. Special interest was kept on normal feeding and maintenance conditions used in Germany. The radionuclides were incorporated into fodder plants through root uptake and thus available in a chemical form resulting from the contamination of agricultural soil. This permitted realistic simulation of the soil-plant-animal food chain. The equilibrium transfer coefficients for milk were calculated to be 22Na: 0.016 +/- 0.002 d/l, 60Co: less than or equal to 0.0002 d/l, 54Mn: less than or equal to 0.0005 d/l, and 137Cs: 0.0022 +/- 0.0002 d/l. The equilibrium transfer coefficients for meat were calculated to be 22Na: 0.01 +/- 0.002 d/kg, 60Co: less than or equal to 0.00013 d/kg, 54Mn: less than or equal to 0.0005 d/kg, and 137Cs: 0.0062 +/- 0.0006 d/kg. A single dose of 131I was orally administered three times in the chemical form of iodide. Models were applied to obtain parameters for a quantitative description of the iodine metabolism. The equilibrium transfer factor for 131I in this chemical form to milk was calculated to be 0.009 +/- 0.0014 d/l. For 95mTc only an upper limit of the transfer factor of 1.7.10(-4) d/l could be estimated because of the small amount of radioactivity available.