Estimates of cancer incidence in Alaskan natives due to exposure to global radioactive fallout from atmospheric nuclear weapons testing.
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Many generations (1-18) of natural populations of small mammals that inhabited in 1986-1991 areas contaminated by radionuclides, had increased levels of the mutations in somatic cells and gametes. The high frequency of chromosome aberrations in somatic cells of young carps from contaminated ponds was detected in 1988-1992. Radiosensitivity of hereditary structures of animal somatic cells and gametes was increased in subsequent generations as compared with generations that lived in 1986-1988.
The inhalation hazard of fallout particles from a nuclear ground burst has been evaluated with the ICRP Task Group Lung Model and the DELFIC fallout model for the 0.5-kt to 10-Mt yield range. It was found that for the conditions considered in this work, the inhalation of fallout particles does not present a significant radiological hazard.
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After the Chernobyl accident the isotopes of radioiodine in air were detected both in aerosol and gaseous forms. In the ICRP publication, No 30 the committed dose equivalent in thyroid per intake of unit activity of 131I, B(ih), were presented. This value holds true only for aerosols with activity median aerodynamic diameter (AMAD) 1 micron. The radioactivity deposition coefficients in human respiratory tract have another values for molecular and organic forms of gaseous radioiodine. In present work the measured AMAD and the proportion between aerosols, molecular and organic forms of 131I in various regions after the accident are given. The correction factors for B(ih) are calculated for the following cases: 1) the radioiodine concentration in air is measured by means of the aerosol filter only, 2) all forms of radioiodine are sampled. The neglection of the gaseous forms of radioiodine could lead to extremely large errors in the determination of inhaled dose radiation: the real value of dose radiation could exceed calculated one by more than 5 times.
To estimate the level and distribution of fallout attributable to the 26 April 1986 Chernobyl nuclear power station accident in the Ukraine, we sampled several kinds of substances at Korosten, Zhitomir and at Katyuzhanka, Vishgorod, Kiev in the Ukraine, and measured the radioactivity of 137Cs, 134Cs, 90Sr, 129I, 238Pu, 239,240Pu, and the density of 127I (stable). The substances investigated were soil, dry milk, wheat, rye, drinking water, and mushrooms. Except for the mushrooms collected, which were sampled at Katyuzhanka, Vishgorod, and at Kiev, all substances were at Korosten, Zhitomir. The activity of 137Cs, 134Cs, 90Sr, 238Pu, and 239,240Pu were all higher in soil and mushrooms than in the other four substances. The activity of 137Cs was 960 and 1,210 Bq kg-1 in the two soil samples and 6,110 Bq kg-1 in the mushrooms. The activity of 134Cs was approximately 15% of 137Cs in the two soil samples while < 3% of 137Cs in the mushrooms. The activity concentration level of 90Sr as compared to 137Cs concentration was 15-31% in food samples other than mushrooms but only 1.9% in mushrooms and 1.4 and 1.2% in the two soil samples. The radioactivity ratios, 238Pu: 239,240Pu and 239,240Pu: 137Cs, suggested that the proportion of cesium radioisotopes and 239,240Pu in the soil attributable to the Chernobyl accident was approximately 100% and 10-20%, respectively, while approximately 100% of 239,240Pu in the mushrooms was attributable to the accident. The activity of 129I was small but the ratio of 129I: 127I in the two soil samples was 4.3 x 10(-8) and 1.0 x 10(-7), which is approximately 10 times larger than that in the global fallout. These results suggest that the areas where the soil was sampled are iodine-deficient and were contaminated slightly by the Chernobyl accident.
Previous studies reported an association between leukemia rates and amounts of fallout in southwestern Utah from nuclear tests (1952 to 1958), but individual radiation exposures were unavailable. Therefore, a case-control study with 1177 individuals who died of leukemia and 5330 other deaths (controls) was conducted using estimates of dose to bone marrow computed from fallout deposition rates and subjects' residence locations. A weak association between bone marrow dose and all types of leukemia, all ages, and all time periods after exposure was found. This overall trend was not statistically significant, but significant trends in excess risk were found in subgroups defined by cell type, age, and time after exposure. The greatest excess risk was found in those individuals in the high-dose group with acute leukemia who were younger than 20 years at exposure and who died before 1964. These results are consistent with previous studies and with risk estimates for other populations exposed to radiation.
Cancer mortality was compared between a three-county region in southwestern Utah and the remainder of Utah in an investigation of reported excess cancer risks associated with residence in southwestern Utah during the period of above-ground nuclear tests at the Nevada Test Site. Because most of the fallout in southwestern Utah was deposited during 1953-1957, comparisons were limited to persons born before 1958, and deaths from leukemia and bone cancer during 1955-1980 and from other cancers during 1964-1980. There was no excess risk of cancer mortality in southwestern Utah, for single or grouped sites, with the single exception of leukemia which showed statistically significant odds ratios of 1.45 based on 62 deaths at all ages, and 2.84 based on nine deaths at ages 0-14. The finding for childhood leukemia was based on different time periods and geographic comparisons from those of two earlier studies in which no such excess was found. Mortality from all cancer sites combined was significantly lower in southwestern Utah than in the remainder of the state, even after adjustment for the higher proportion of (lower risk) Mormons in southwestern Utah. The present results, including the positive association for leukemia, are inconsistent with the high excess risks reported by Johnson (JAMA 1984;251:230-6) based on an interview survey of cancer incidence among long-term Mormon residents of southwestern Utah.
Radioiodines, particularly 131I, may be released into the environment in breach-of-containment nuclear reactor accidents and localize in and irradiate the thyroid with an attendant risk of neoplastic growth and other adverse health effects. Pharmacologic thyroid blockade by oral potassium iodide (KI) (50-100 mg in adults) can substantially reduce thyroid uptake of and irradiation by internalized radioiodine. In the current analysis, computer modeling of iodine metabolism has been used to systematically elucidate the effects of two practically important but highly variable factors on the radioprotective effect of KI: the time of administration relative to exposure to radioiodine and the dietary level of iodine. In euthyroid adults receiving iodine-sufficient diets (250 microg d(-1) in the current analysis), KI administered up to 48 h before 131I exposure can almost completely block thyroid uptake and therefore greatly reduce the thyroid absorbed dose. However, KI administration 96 h or more before 131I exposure has no significant protective effect. In contrast, KI administration after exposure to radioiodine induces a smaller and rapidly decreasing blockade effect. KI administration 16 h or later after 131I exposure will have little effect on thyroid uptake and absorbed dose and therefore little or no protective effect. The 131I thyroid absorbed dose is two-fold greater with insufficient levels of dietary iodine, 2,900 cGy/37 MBq, than with sufficient levels of dietary iodine, 1,500 cGy/37 MBq. When KI is administered 48 h or less before 131I intake, the thyroid absorbed doses (in cGy/37 MBq) are comparably low with both sufficient and insufficient dietary iodine levels. When KI is administered after 131I intake, however, the protective effect of KI is less and decreases more rapidly with insufficient than with sufficient dietary iodine. For example, KI administration 2 and 8 h after 131I intake yields protective effects of 80 and 40%, respectively, with iodine-sufficient diets, but only 65 and 15% with iodine-deficient diets. In conclusion, whether exposed populations receive sufficient or insufficient dietary iodine, oral KI is an effective means of reducing thyroid irradiation from environmentally dispersed radioiodine but is effective only when administered within 2 d before to approximately 8 h after radioiodine intake.
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Chromosome analysis of peripheral lymphocytes from two Norwegian populations (44 reindeer herding South samis from Røros and Snåsa, 12 sheep farmers from Valdres) exposed to fallout from the Chernobyl accident were made. The doses from caesium through the years 1987-1991 were calculated based on whole-body measurements 134Cs and 137Cs giving a total cumulative mean internal dose of 5.54 mSv for the total group of 56 persons. Chromosome aberrations were within the normal range when compared with historical controls with the exception of dicentrics (0.3% per cell, which is a 10-fold increase) and rings (0.07% per cell). A dose-dependent increase in dicentrics and rings based on caesium exposure was not observed.
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