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PubMed1995

Thyroid abnormalities among children in the contaminated area related to the Chernobyl accident.

Gradual increases of various radiation-related diseases including thyroid cancer following the Chernobyl accident have been recently reported. We have carried out systematic thyroid surveys in school children aged 10-15 years in the highly contaminated area and compared the results with a similar survey in a nonaffected neighboring area as a control. Systematic examinations of the thyroid gland were performed in 888 schoolchildren (408 males and 480 females) in the districts of Chechelsk city with 5 to over 40 Ci/km2 of radiation level for 137Cs. In the control area (Bobruisk city), 521 children with the same age range (229 males and 292 females) were examined. Thyroid surveys were carried out as follows: palpation, ultrasonography, blood examinations of thyroid function, and measurements of daily urinary excretion of iodine. Certain thyroid abnormalities were observed in the high radioactive fallout area more frequently than in the control region. In particular, the prevalence of multiple micronodular lesions in diffuse goiter in the contaminated area was significantly higher than in the control area. However, endemic goiter due to iodine deficiency was present in both districts. The environment factor of iodine deficiency might have resulted in the early occurrence of ultrasonographic thyroid abnormalities attributed to radioactive contamination.

Adolescent↗
PubMed1995

Childhood thyroid diseases around Chernobyl evaluated by ultrasound examination and fine needle aspiration cytology.

Screening by ultrasound examination and fine-needle aspiration cytological biopsy (FNA) was conducted in five regions in Belarus, Ukraine, and Russia to investigate the prevalence of childhood thyroid diseases around Chernobyl. Gomel, Zhitomir, Kiev, and the western area of Bryansk are the administrative regions where severe radioactive contamination occurred. The subjects from Mogilev, where contamination was relatively low, served as controls. Among 55,054 subjects (26,406 boys and 28,648 girls), the prevalence of ultrasonographic thyroid abnormalities such as nodule, cyst, and abnormal echogenity was significantly higher in the regions with severe contamination than in Mogilev. Of the 1,396 children showing echographic thyroid abnormalities 197 were selected for FNA, and a sample was successfully obtained for diagnosis from 171 (51 boys and 120 girls) of the 197 subjects. The aspirate was insufficient for diagnosis in the remaining 26 subjects. Thyroid cancer was encountered in four children (2.3%) from the contaminated regions, two children being from Gomel. The other thyroid diseases were follicular neoplasm, 6.4%; adenomatous goiter, 18.7%; chronic thyroiditis, 31.0%; and cyst, 24.0%, suggesting that a major cause of thyroid nodularity is nonneoplastic changes, mainly chronic thyroiditis and cysts. These results will serve as an important data base for further analyses and suggest that childhood thyroid diseases, including both neoplasms and immunological disorders, are consequences of radioactive fallout.

Adenocarcinoma, Follicular↗
PubMed1997

Lessons from Chernobyl: the event, the aftermath fallout: radioactive, political, social.

The accident at the Chernobyl nuclear power station on April 26, 1986, released about 300 MCi of radioactive substances, including about 40 MCi of 131I and 100 MCi of short-lived radioiodines. In the immediate surroundings there were 143 cases of acute radiation syndrome, 34 deaths, and hundreds of thousands of people displaced from their homes, many permanently. The social and psychologic stresses that followed have been enormous and long-lasting. This article focuses on the rising incidence of thyroid cancer in exposed children. Radiation-induced thyroid cancer following external radiation is well documented but there is little evidence in humans of thyroid cancer from internal radiation and the risk coefficient for radioiodine exposure is known. To achieve this, thyroid dose reconstruction and prospective follow-up of about 50,000 persons who were children in 1986 will be required. Thyroid cancer in children of southern Belarus began to increase in 1990 and there now are about 1,000 cases in Belarus and northern Ukraine. These aggressively growing tumors, almost all variants of papillary thyroid cancer, are typical for thyroid cancer in children not exposed to radiation, and a low mortality rate is to be expected. It also is expected, however, that malignant as well as benign thyroid neoplasms will continue to arise in these exposed children well into their adult life.

Adult↗
PubMed2000

Molecular alterations involving p53 codons 167 and 183 in papillary thyroid carcinomas from chernobyl-contaminated regions of belarus.

After the Chernobyl accident in 1986, there was a significant increase in the incidence of papillary thyroid carcinoma in fallout-exposed children from Belarus. We studied the p53 gene from 24 papillary thyroid carcinoma cases presenting in 1996. All subjects lived in contaminated regions of Belarus at the time of the accident and were under age 20 when exposed to fallout. Exons 5 through 9 of p53 were amplified from genomic tumor DNA using the polymerase chain reaction (PCR). The PCR products were analyzed by direct DNA sequencing using an automated sequencer. Five cases each exhibited two molecular alterations within exon 5. Alterations were confirmed by sequencing in both directions. One alteration, involving codon 167 (CAG-->CAT) in all five cases, resulted in the substitution of HIS for GLN. The second alteration, involving codon 183 (TCA-->TGA) in all five cases, resulted in a premature termination codon. Leukocyte DNA from each of the positive cases was analyzed and found to contain only wild-type p53 sequence. These results suggest that mutations involving codons 167 and 183 in the p53 locus are important in the pathogenesis of a subset (21%) of radiation-induced papillary thyroid carcinomas from Belarus.

Adolescent↗
PubMed2004

Thyroid cancer incidence trends in Belarus: examining the impact of Chernobyl.

BACKGROUND: While prior studies of thyroid cancer incidence within Belarus have increased since the 1986 Chernobyl reactor accident, the magnitude of increase is not well quantified. METHODS: Using Belarussian national cancer registry data, trends in average annual age-adjusted thyroid cancer incidence rates were examined by calendar year and gender. Incidence rates were also examined across specified time intervals, for specific age groups at diagnosis, and in 'higher exposure' regions compared with 'lower exposure' areas. RESULTS: Age-adjusted thyroid cancer incidence rates (adjusted to the WHO 2000 world population) have increased between 1970 and 2001 from 0.4 per 100 000 to 3.5 per 100 000 among males (+775%) and from 0.8 per 100 000 to 16.2 per 100 000 among females (+1925%). The relative increase among males (+1020%) and females (+3286%) in 'high exposure' areas exceeded increases among males (+571%) and females (+250%) in 'lower exposure' areas of Belarus. Dramatic increases in thyroid cancer incidence rate ratios were noted among both males and females and in all age groups. The highest incidence rate ratios were observed among people from 'higher exposure' areas ages 0-14 yr at time of diagnosis. CONCLUSIONS: Marked increases in the incidence of thyroid cancer have occurred over a relatively limited period of observation in all areas of the Republic of Belarus and among all age categories. The greatest increases have occurred among children, suggesting that a high prevalence of pre-existing iodine deficiency in combination with unique susceptibility among younger people might have contributed to potential carcinogenic exposures to the thyroid.

Adolescent↗
PubMed1992

Birth defects in Norway by levels of external and food-based exposure to radiation from Chernobyl.

In Norway, external doses of radiation resulting from fallout from the Chernobyl nuclear accident were estimated from detailed measurements, including soil deposition patterns. Internal doses were estimated from measurements of radioactive cesium in meat and milk supplies. The doses were calculated as average monthly doses for each of 454 municipalities during 36 consecutive months after the accident in spring 1986. Prospectively collected data on all newborns listed in the Medical Birth Registry of Norway who were conceived in the period May 1983-April 1989 were used to assess possible dose-response relations between estimated external and food-based exposures and congenital malformations and some other conditions. A positive association was observed between total radiation dose (external plus food-based) and hydrocephaly, while a negative association was observed for Down's syndrome. However, an important conclusion of the study was that no associations were found for conditions previously reported to be associated with radiation, i.e., small head circumference, congenital cataracts, anencephaly, spina bifida, and low birth weight. Potential sources of bias, including exposure misclassification and incomplete ascertainment of cases, are discussed.

Abnormalities, Radiation-Induced↗
PubMed2003

Uncertainties in thyroid dose reconstruction after Chernobyl.

The most significant impact of the Chernobyl accident of 26 April 1986 is the increased incidence of thyroid cancer among Belarusians, Russians and Ukrainians who were exposed as children to radioiodines in fallout resulting from atmospheric releases. The US National Cancer Institute (NCI), in cooperation with the ministries of health of Belarus and Ukraine, is involved in epidemiological studies of thyroid diseases related to the accident. Individual thyroid doses, as well as uncertainties, have been estimated for the members of the cohort studies (approximately 13,000 Ukrainians and 12,000 Belarusians). The cohort subjects, who were selected from the large group of children whose thyroids were monitored for gamma radiation within a few weeks of the accident, provided personal information on their residence history and dietary habits during interviews. Thyroid dose estimates range from 1 mGy to more than 20 Gy. The uncertainties are found to be approximately log-normally distributed, with geometric standard deviations ranging from 1.6 to 5.0. The medians of the geometric standard deviations are 1.7 for the Ukrainian subjects and 2.1 for the Belarusian subjects. The major sources of uncertainty in the thyroid dose estimates are found to be those related to the thyroid mass of the subject and to the estimation of the thyroidal content of 131I at the time of thyroid monitoring.

Adolescent↗
PubMed2003

Limitation of individual internal exposure by consideration of the confidence interval in routine personal dosimetry at the Chernobyl Sarcophagus.

In view of the probabilistic nature and very wide uncertainty of internal exposure assessment, its deterministic ('precise') assessment does not protect against not exceeding established reference levels or even the dose limits for a particular individual. Minimising such potential risks can be achieved by setting up a sufficiently wide confidence interval for an expected dose distribution instead of its average ('best' estimate) value, and by setting the limit at the 99% fractile level. The ratio of the 99% level and the mean ('best' estimate) is referred to as the safety coefficient. It is shown for the typical radiological conditions inside the Chernobyl Sarcophagus that the safety coefficient corresponding to the 99% fractile of the expected internal dose distribution varies within the range from 5 to 10. The maintenance of minimum uncertainty and sufficient sensitivity of the indirect dosimetry method requires measurement of individual daily urinary excretion of 239Pu at a level of at least 4 x 10(-5) Bq. For the purpose of reducing the uncertainty of individual internal dose assessment and making dosimetric methods workable. it is suggested that the results of workplace monitoring are combined with the results of periodic urinary and faecal bioassay measurements.

Body Burden↗
PubMed2001

Contribution of different foodstuffs to the internal exposure of rural inhabitants in Russia after the Chernobyl accident.

In a large village, Veprin of the Bryansk region of Russia contaminated with radionuclides as a result of the Chernobyl accident, 137Cs concentration in food products of agricultural produce and natural origin was regularly measured, local inhabitants were polled on the composition of their diet, and the 137Cs content in their bodies was measured at the same time. These results were used as the basis for calculation of annual effective doses of internal exposure to inhabitants and for reconstruction of the dose during the entire period after the accident (1986-1996). The efficiency of countermeasures performed for reduction of the internal dose was assessed. The internal dose in inhabitants during the 10 years after the accident was shown to be reduced by countermeasures by a factor of 2, namely down to 35 mSv instead of the expected 70 mSv. The dose of external gamma radiation during the same time period is close to the obtained dose of internal exposure. The presence of peat and water-meadow soils in the vicinity of this village that are characterised by high transfer factors for radionuclides from soil to vegetation causes a high contribution of internal exposure to the total dose of population exposure. The contribution of natural products to the internal dose increased from 6% in 1987 increased to 25% in 1996. The individual content of 137Cs in the body of inhabitants reliably correlates with consumption of milk in the initial period after the accident and with consumption of forest mushrooms in the subsequent period.

Adult↗
PubMed2001

Retrospective dosimetry for Latvian workers at Chernobyl.

Between 1986 and 1991 approximately 6500 Latvian inhabitants were recruited for clean-up work at the Chernobyl nuclear power plant. Their absorbed doses are usually unknown, because less than half of them had their external exposure officially documented. Clinical investigations show a high morbidity rate for these clean-up workers when compared with that of the general population. In order to understand the causes of their diseases and the impact of ionising radiation, electron spin resonance (ESR) has been used to measure the absorbed doses in human tooth enamel. The doses estimated by ESR were between two and three times higher than previously documented and are in accord with the results of immunological and biological tests. The results may be explained by considering the effects of irradiation caused by long-lived incorporated radionuclides.

Adult↗
PubMed2002

The influence of caesium-137 distribution in Poland's north-eastern ecosystem on effective dose 10 years after the Chernobyl disaster.

A comparison is presented of particular methods of exposure in the first year after the Chernobyl disaster and ten years later. This comparison shows that the population exposure due to the presence of radiocaesium in the environment results from the presence of caesium contained in the soil, which provides 68% of the dose (as compared to 32% in 1987) while the influence of diet has been reduced to 32% (from 68%). The exposure from caesium-137 contained in the air has dropped from 14% to 0. The effective dose from caesium has been 50 times smaller than that from environmental sources of the natural radiation estimated for the region under study to be 1.61 mSv x y(-1).

Accidents↗
PubMed2004

Thyroid dosimetry in the western trace of the Chernobyl accident plume.

According to World Health Organization guidelines (WHO/SDE/PHE/99.6), the reference level for consideration in stable iodine prophylaxis is based on the inhalation exposure pathway. In the western trace of the Chernobyl accident, the measurement of airborne (131)I fractions (aerosol-associated, gaseous reactive and gaseous organic) indicates that airborne gaseous reactive and, especially, organic (131)I fractions were the major contributors to thyroid exposure due to inhalation. The contribution of inhaled short-lived radioiodines was negligible. To attain more precise thyroid exposure evaluation, (131)I dose factors were determined as a function of age and prevalence of stable iodine deficiency. The results demonstrate that children with a stable iodine deficiency experienced at least two times higher thyroid doses than did children with a dietary iodine sufficiency. The results of these investigations demonstrate that in thyroid dosimetry it is important to know the stable iodine status as well as to have a standardised method for airborne radioiodine measurements, especially for consideration of stable iodine prophylaxis based on the inhalation exposure pathway.

Adolescent↗
PubMed2006

Using total beta-activity measurements in milk to derive thyroid doses from Chernobyl fallout.

Following the Chernobyl accident, more than 200 childhood thyroid cancer cases have been observed in Brest Oblast of Belarus in territories slightly contaminated with 137Cs, but with suspected relatively high 131I fallout. The most helpful measurements available that can be used to estimate thyroid doses for the population of Brest Oblast are the total beta-activity measurements in cow's milk performed using DP-100 device within a few weeks after the accident. The 131I concentrations in milk were derived from the total beta-activity measurements on the basis of (1) a radioecological model used to estimate the variation with time of the radionuclide composition in milk and (2) the determination of the calibration factors of the DP-100 device for the most important radionuclides present in milk. As a result, 131I concentrations in milk were reconstructed for territories with different levels of 137Cs deposition. A non-linear dependence of the 131I concentration in milk on the 137Cs deposition density was obtained; it was used to estimate the thyroid doses from the consumption of 131I-contaminated cow's milk by the population of Brest Oblast. The average individual thyroid doses have been estimated to be 0.15, 0.18, 0.12, 0.06, 0.04 and 0.03 Gy for newborn, children aged 1, 5, 10 and 15 y and adults, respectively. The collective thyroid dose for the entire population of Brest Oblast is estimated to be 64,500 man Gy, the contribution from the adult population being about one half of the total. The methodology that is described could be applied in the framework of epidemiological studies of the relationship between radiation exposure to the thyroid gland and thyroid cancer in areas where numerous total beta-activity measurements in cow's milk were performed within a few weeks after the accident.

Adolescent↗
PubMed1988

Estimates of radiation dose and health risks to the United States population following the Chernobyl nuclear plant accident.

Estimates of both individual and collective doses received by the United States population following the Chernobyl accident have been made by using the data obtained from the U.S. Environmental Protection Agency's Environmental Radiation Ambient Monitoring System. Radionuclides associated with the debris first were measured in precipitation and surface air particulates at Portland, OR and Olympia, WA on 5 May 1986. Iodine-131 was the most consistently measured nuclide in all media, although several Cs and Ru isotopes also were observed. Strontium and any actinides notably were absent from the samples at the lower level of detection. The highest calculated individual-organ dose due to intake during May and June 1986 was 0.52 mSv to the infant thyroid in the state of Washington. This was predominantly (98%) from the ingestion of milk. The maximum U.S. collective dose equivalent to any organ was calculated to be 3,300 person-Sv to the thyroid. Risk estimates project three excess lung cancer deaths and an additional four deaths due to cancers of thyroid, breast and leukemia in the U.S. population over the next 45 y from exposure during the May-June 1986 interval. The only long-lived radionuclide measured in milk samples following the accident was 137Cs. We estimate 20 excess fatalities from the ingestion of 137Cs in milk during all subsequent years, with six of these due to lung cancer and the majority of the remainder distributed approximately equally among cancers of the thyroid, breast, liver and leukemia. A total of 100 excess fatalities from all dietary components was estimated. Because of the uncertainty of risk estimates from data such as those available for this study, all calculated values carry a range of uncertainty from a minimum of one-half the calculated value to a maximum of two times the calculated value. The estimated excess fatalities given above may be compared with corresponding projected cancer mortality from all other causes: 41,000 fatalities from thyroid cancer and 3,800,000 fatalities from lung cancer are estimated to occur within the U.S. population during the next 45 y.

Accidents↗
PubMed1988

Monitoring of 131I in milk and rain water in Japan following the reactor accident at Chernobyl and estimates of human thyroidal dose equivalents.

Iodine-131 in milk and in rain water in Nagoya, Japan, (a location 8,000 km from Chernobyl) was monitored between May and July 1986. The 131I concentration in rain water ranged from 43.1 Bq L-1 on 4 May to 15 mBq L-1 on 12 July, and that in milk ranged from 21.8 Bq L-1 on 19 May to 11 mBq L-1 on 14 July. Iodine-131 concentrations in milk were estimated to be 4 to 6 times greater than those in rain water during the first few weeks after the accident. Both concentrations decreased with approximately the same effective half-life of 5.9 +/- 0.3 d for rain water and 5.0 +/- 0.2 d for milk. The 131I concentration in milk sold in markets varied from dairy to dairy and ranged from 0.07 to 0.2 times that in fresh milk. The maximum thyroidal dose equivalents estimated for an adult man and for a baby were far lower than the population annual dose equivalent to the thyroid from natural radiation.

Accidents↗
PubMed1988

The environmental behavior of 131I in northwestern Greece following the nuclear reactor accident at Chernobyl.

A three compartment (air-grass-milk) milk contamination model for 131I has been applied to atmospheric, grass and milk data, following the April 1986 nuclear accident at Chernobyl. Samples of ovine and bovine milk collected daily by a large dairy company in Ioannina (northwestern Greece), throughout the month of May 1986 have been employed. The contamination impulse in the area, which provides the input to the model, has been approximated by a first order gamma-variate curve. Transfer rates and decay constants have been extracted by fitting predictions of the model independently to each set of data (air, grass and milk). All model parameters obtained from more than one set of data show remarkable consistency. These parameters are used to calculate the transfer coefficients fm for the transport of radioiodine at equilibrium for sheep and cows. The results are also employed for the extraction of radiation dose estimates sustained through ingestion and inhalation by the population in the area.

Accidents↗
PubMed1988

Radiocesium concentration in migratory birds wintering in Spain after the Chernobyl accident.

Levels of 137Cs and 134Cs resulting from the Chernobyl nuclear accident were studied in 195 birds that winter in two regions of Spain. Only five of the 12 species examined were contaminated. The average values for 137Cs vary between 1.6 and 41 Bq kg-1 fresh. In particular, the contamination for song-thrushes (Turdus philomelos) are compared between the regions of Extremadura and Valencia, 350 km east of Extremadura at the same latitude. The results show that the contamination of birds wintering in Spain decreases from east to west. The whole-body dose commitment for humans consuming these contaminated birds was calculated. The values are well below the established ICRP guideline.

Accidents↗
PubMed1989

Chernobyl fallout on Alpine glaciers.

Measurements of the gross beta activity of snow samples from four Alpine glaciers contaminated by radioactive fallout from the Chernobyl nuclear accident and a gamma-spectrum analysis of selected samples are reported. The results are discussed with respect to possible risks to the population from using meltwater from these glaciers as drinking water.

Accidents↗