(1/76) Juvenile hypothyroidism among two populations exposed to radioiodine.
We found an epidemic of juvenile hypothyroidism among a population of self-defined "downwinders" living near the Hanford nuclear facility located in southeast Washington State. The episode followed massive releases of 131I. Self-reported data on 60 cases of juvenile hypothyroidism (<20 years of age) among a group of 801 Hanford downwinders are presented, as well as data concerning the thyroid status of approximately 160,000 children exposed to radioiodine before 10 years of age as a result of the 26 April 1986 Chernobyl explosion in the former Soviet Union. These children were residents of five regions near Chernobyl. They were examined by standardized screening protocols over a period of 5 years from 1991 to 1996. They are a well-defined group of 10 samples. Fifty-six cases of hypothyroidism were found among boys and 92 among girls. Body burdens of 137Cs have been correlated with hypothyroidism prevalence rates. On the other hand, the group of juvenile (<20 years of age) Hanford downwinders is not a representative sample. Most of the 77 cases of juvenile hypothyroidism in the Hanford group were diagnosed from 1945 to 1970. However, the ratio of reported cases to the county population under 20 years of age is roughly correlated with officially estimated mean levels of cumulative thyroid 131I uptake in these counties, providing evidence that juvenile hypothyroidism was associated with radioiodine exposures. Because even subtle hypothyroidism may be of clinical significance in childhood and can be treated, it may be useful to screen for the condition in populations exposed to radioiodine fallout. Although radiation exposure is associated with hypothyroidism, its excess among fallout-exposed children has not been previously quantified. (+info)
(2/76) Change in centromeric and acentromeric micronucleus frequencies in human populations after chronic radiation exposure.
Acute radiation exposure of humans was observed to induce various forms of cytogenetic damage, including increased frequencies of micronuclei and chromosomal aberrations. However, the cytogenetic effects of chronic low dose radiation exposure in vivo needs further characterization. Sixteen subjects with chronic low dose rates of gamma-radiation exposure from 60Co-contaminated steel in radioactive buildings were compared with seven non-exposed reference subjects for micronucleus frequencies after they relocated. By in situ hybridization using a digoxigenin-labeled anti-alpha all human centromere probe, the exposed subjects were shown to have a significant increase in cytochalasin B-modulated micronucleus (CBMN) frequencies, as well as a significant increase in centromere-positive (C+) CBMN, centromere-negative (C-) CBMN, total C+signals, single C+ MN signals and multiple C+ signals/1000 binucleated cells (BN). However, decreases in the ratios C+MN/C- MN and C+MN/total CBMN (%) were also noted in the exposed subjects. By mixed effects analysis, considering individuals from the same families, the C- MN and single C+ MN/1000 BN were both positively and moderately associated with previous cumulative exposure. When the time period of relocation post-exposure (relocation time or RT) was considered, total C+MN and multiple C+MN/1000 BN were negatively and significantly associated with RT. Moreover, the C+MN, C- MN, C+MN/C- MN ratio and single C+MN/1000 BN were all negatively and moderately associated with RT, but not with exposure dose. This suggested that acentromeric and single or multiple centromeric CBMN cytogenetic damage seems to disappear differentially in human subjects post chronic low dose radiation exposure. (+info)
(3/76) Biodosimetry results obtained by various cytogenetic methods and electron spin resonance spectrometry among inhabitants of a radionuclide contaminated area around the siberian chemical plant (Tomsk-7).
On April 6, 1993, near the town of Tomsk (Russia) there was an accident at the Siberian Chemical Plant (SCP) which resulted in extensive contamination of an area of 250 km(2) to the north of SCP with long-lived radionuclides such as (239)Pu, (137)Cs and (90)Sr. Cytogenetic methods and electron spin resonance (ESR) spectrometry of tooth enamel were used to estimate the radiation doses received by the population. The ESR signal intensity and the chromosomal aberration frequency in lymphocytes of the tooth donors showed a good correlation. The data showed that 15% of the inhabitants of the Samus settlement received a radiation dose >90 cGy. The exceptions were results of an examination of fishermen, where ESR gave high values (80-210 cGy) but both the chromosome assay and the cytokinesis block micronucleus method gave lower ones (8-52 cGy). A large increase in chromosome damage was observed in people born between 1961 and 1969. It was found that during these years several serious accidents at the Siberian Chemical Plant had occurred causing radiation pollution of the area. The number of cells with chromosome aberrations was significantly less among the people arriving in Samus after 1980. We found good correlations between the level of carotene consumption and a decrease in frequency of both micronuclei in binucleated lymphocytes (r = 0.68, P < 0.01) and chromatid aberrations (r = 0.61, P < 0.01) among the inhabitants. We also examined the inhabitants of Samus for opisthorchis infection, which was present in 30% of the population. The Samus inhabitants affected by Opisthorchis felineus showed significantly increased levels of micronuclei in binucleated lymphocytes and chromatid aberrations as compared with the controls. (+info)
(4/76) The risk linked to ionizing radiation: an alternative epidemiologic approach.
Radioprotection norms have been based on risk models that have evolved over time. These models show relationships between exposure and observed effects. There is a high level of uncertainty regarding lower doses. Recommendations have been based on the conservative hypothesis of a linear relationship without threshold value. This relationship is still debated, and the diverse observations do not allow any definitive conclusion. Available data are contradictory, and various interpretations can be made. Here we review an alternative approach for defining causation and reconciling apparently contradictory conclusions. This alternative epidemiologic approach is based on causal groups: Each component of a causal group is necessary but not sufficient for causality. Many groups may be involved in causality. Thus, ionizing radiation may be a component of one or several causal groups. This formalization reconciles heterogeneous observations but implies searching for the interactions between components, mostly between critical components of a causal profile, and, for instance, the reasons why specific human groups would not show any effect despite exposure, when an effect would be expected. (+info)
(5/76) Summary of the JCO criticality accident in Tokai-mura and a dose assessment.
A criticality accident occurred on September 30, 1999, in a conversion test facility at the JCO Tokai site. The accident was triggered by pouring an 18.8% enriched uranyl nitrate solution into a precipitation vessel beyond the critical mass. The accident continued for about 19 hours before the criticality could be stopped. during which time neutrons and gamma-rays were emitted continuously due to fission reactions. The total number of fission reactions was 2.5 x 10(18), which was estimated by an activity analysis of the fission products in the solution of the precipitation vessel. The accident gave serious radiation dose to 3 employees and fatal dose to 2 of them. Neutrons and gamma-rays emitted by the accident caused meaningful doses to the residents of the surrounding area of JCO. The dominant dose to the residents and JCO employees was brought by neutrons and gamma-rays from the precipitation vessel, while the contribution of radioactive plume was negligible. The individual dose was estimated for 234 resident, 169 JCO employees and 260 emergency personnel. The maximum doses were 21 mSv for the residents, 48mSv for the JCO employees, and 9.4mSv for the emergency personnel, respectively. No deterministic effect, however, has been observed, except for the 3 workers. (+info)
(6/76) Transport calculation of neutrons leaked to the surroundings of the facilities by the JCO criticality accident in Tokai-mura.
A transport calculation of the neutrons leaked to the environment by the JCO criticality accident was carried out based on three-dimensional geometrical models of the buildings within the JCO territory. Our work started from an initial step to simulate the leakage process of neutrons from the precipitation tank, and proceeded to a step to calculate the neutron propagation throughout the JCO facilities. The total fission number during the accident in the precipitation tank was evaluated to be 2.5 x 10(18) by comparing the calculated neutron-induced activities per 235U fission with the measured values in a stainless-steel net sample taken 2 m from the precipitation tank. Shield effects by various structures within the JCO facilities were evaluated by comparing the present results with a previous calculation using two-dimensional models which suppose a point source of the fission spectrum in the air above the ground without any shield structures. The shield effect by the precipitation tank, itself, was obtained to be a factor of 3. The shield factor by the conversion building varied between 1.1 and 2, depending on the direction from the building. The shield effect by the surrounding buildings within the JCO territory was between I and 5, also depending on the direction. (+info)
(7/76) Determination of radionuclides induced by fast neutrons from the JCO criticality accident in Tokai-mura, Japan for estimating neutron doses.
A criticality accident occurred at a uranium conversion facility in Tokai-mura, Japan on September 30, 1999, and fission neutrons were continuously emitted for about 20 hours. Materials of stainless steel or iron, and chemical reagents were collected at places between 2 m and 270 m from the criticality accident site on October 25 and 26, 1999, November 27, 1999 and February 11, 2000. Neutron-induced radionuclides. such as 54Mn and 58Co, in the materials exposed to fast neutrons from the accident were measured to estimate the neutron fluences and energy distributions. Highly sensitive y-ray spectrometry with a well-type Ge detector was performed after radiochemical separation of Mn and Co from the materials. An instrumental neutron activation analysis was mainly applied for determinations of the target elements and chemical yields. The concentrations of 54Mn and 58Co in a mesh screen of stainless steel collected at a location 2.0 m from the accident site were determined. The total number of fission events was evaluated to be 2.5 x 10(18) by Monte-Carlo calculations of neutron transfer by considering the observed values of 54Mn and 58Co. The results presented here are fundamental to estimate the neutron doses at various distances. (+info)
(8/76) The onset of the excess of childhood cancer in Seascale, Cumbria.
BACKGROUND: The objective of this study was to formally investigate the onset of the Seascale cluster of childhood and young person's cancer. This has not previously been attempted. METHODS: A mortality study within the Whitehaven registration district was set up and death records were abstracted for 1906-1970. They were categorized as death from leukaemias, lymphomas, other cancers and all other causes in persons aged 0-14, 0-24 and 25-84. The number of deaths, death rates and standardized mortality ratios were calculated. RESULTS: The mortality of persons aged 25-84 in Seascale civil parish, Gosforth civil parish and the rest of the Whitehaven district was unremarkable compared with national data 1906-1970. There were no cancer deaths aged 0-24 in Gosforth civil parish during 1906-1970. In Seascale civil parish a hitherto unrecorded childhood cancer case was revealed, dying in 1954. No cancer deaths aged 0-24 were found before that date. In the period 1946-1955 three cancer deaths gave a statistically significant excess owing to non-leukaemia cases, whereas in the period 1956-1965 a statistical excess of all types of leukaemia occurred as a result of two deaths. There was no case excess (based on one leukaemia death) in the period 1966-1970. CONCLUSION: We found no clear temporal associations of the case excesses either with the periods of significant nuclear activity on the Sellafield site or with the main periods of population growth in the area. (+info)