Urinary excretion measurements for the assessment of body burden of radiocaesium in man: differences between potassium and creatinine normalisation

Human metabolism of orally administered radioactive cobalt chloride

This study investigated the human gastrointestinal uptake (f1) and subsequent whole-body retention of orally administered inorganic radioactive cobalt. Of eight adult volunteers aged between 24 and 68 years, seven were given solutions of (57)Co (T1/2 = 272 d) containing a stable cobalt carrier, and six were given carrier-free (58)Co (T1/2 = 71 d). The administered activities ranged between 25 and 103 kBq. The observed mean f1, based on 6 days accumulated urinary excretion sampling and whole-body counting, was 0.028 ± 0.0048 for carrier-free (58)Co, and 0.016 ± 0.0021 for carrier-associated (57)Co. These values were in reasonable agreement with values reported from previous studies involving a single intake of inorganic cobalt. The time pattern of the total retention (including residual cobalt in the GI tract) included a short-term component with a biological half-time of 0.71 ± 0.03 d (average ± 1 standard error of the mean for the two nuclides), an intermediate component with a mean half-time of 32 ± 8.5 d, and a long-term component (observed in two volunteers) with half-times ranging from 80 to 720 d for the two isotopes. From the present data we conclude that for the short-lived (57)Co and (58)Co, more than 95% of the internal absorbed dose was delivered within 7 days following oral intake, with a high individual variation influenced by the transit time of the unabsorbed cobalt through the gastro-intestinal tract.

External and internal irradiation of a rural Bryansk (Russia) population from 1990 to 2000, following high deposition of radioactive caesium from the Chernobyl accident

In 1990, a joint Nordic-Russian project was initiated in order to make independent estimations of the effective dose to selected groups of inhabitants in a highly contaminated area around the city of Novozybkov in the western Bryansk region of Russia. The inhabitants were living in six villages with initial contamination levels of (137)Cs between 0.9 and 2.7 MBq m(-2). Some villages had been decontaminated, others not. Both school children and adults participated in the study. The external irradiation of 100-130 inhabitants was determined during 1 month in September-October each year from 1990 to 2000 (except 1999), using individual thermoluminescent dosemeters. The body burden of (137,134)Cs was determined by in vivo measurements in about 500 inhabitants annually from 1991 to 2000, and for a subgroup also with analysis of the (137)Cs concentration in urine. The mean effective dose (E) from external and internal irradiation due to (137,134)Cs deposition varied between 2.5 and 1.2 mSv per year between 1990 and 2000. The total mean E decreased, on average, by 9% per year, while the mean external dose decreased by 16% per year. The dose rate from internal radiation decreased more slowly than the dose rate from external radiation, and also showed an irregular time variation. The contribution from the internal dose to the total E was 30-50%, depending on the village. Predictions for the long-term changes in the effective dose to people living in the areas are presented. The cumulated E for the 70 years following the accident was estimated to be about 90 mSv with the assumption that both internal and external dose decrease by 2% per year after year 2000. The highest E during a life-time received by single individuals living in the area may amount to around 500 mSv considering the individual variations in E.

Ecological half-time of radiocesium from Chernobyl debris and from nuclear weapons fallout as measured in a group of subjects from the south of Sweden

From 1960 to 1980 and between 1987 and 1994 the whole-body content of 17Cs, and when possible also 134Cs, was measured in a group of subjects living in the city of Lund, Sweden (55.7 degrees N, 13.2 degrees E). The results have been analyzed to estimate the effective ecological half-time of fallout radiocesium in humans living in the area. The Lund area (The Province of Skåne) was subjected to a deposition of about 2 kBq m(-2) of pre-Chernobyl 137Cs from nuclear weapons testing and 1 kBq m(-2) of 137Cs from Chernobyl fallout in May 1986. The radiocesium from the nuclear weapons tests in the 1950's and 1960's still gave a significant contribution to the total 137Cs levels in humans in the post-Chernobyl study period (1987-1994) of about 0.4 Bq per kg body weight, which was about 10% of the peak post-Chernobyl concentration level of 137Cs (3.5-4 Bq kg(-1)) in 1987. The effective ecological half-time for 137Cs from Chernobyl was found to be 1.8 +/- 0.2 y. The aggregate transfer factor from deposition to mean activity concentration in man was estimated to be 3.6 Bq kg(-1)/kBq m(-2). These values may be compared with an effective ecological half-time of 1.3 y found in the reference group in the 1960's, and an aggregate transfer factor of 10 Bq kg(-1)/kBq m(-2). This difference is largely explained by the continuous nature of the global fallout leading to contamination on growing crops whereas the Chernobyl fallout occurred just prior to the South Swedish growing season, leading to less efficient transfer to crops and to human diet. The average committed individual effective dose (50 y) from ingested 137Cs from the Chernobyl fallout was estimated to be 0.02 mSv and from the nuclear weapons fallout (1945-1995) to be 0.20 mSv.