The method of processing and the results of measurements of 131I content in the thyroids of Russian people performed in May-June 1986 are presented. The contribution of radiation from Cs radionuclides in the human body was taken into account in the processing of measurement data with an SRP-68-01 device. The greatest individual 131I content was found in the thyroids of inhabitants of the Bryansk region, up to 250-350 kBq, and in the Tula and Orel regions, up to 100 kBq. The average 131I thyroid activity in the middle of May 1986 reached 80 kBq for inhabitants of some settlements in the Bryansk region, 5-8 kBq in the Tula region and 5 kBq in the Orel region.
The level of radiation exposure in children in Belarus caused by the Chernobyl accident was investigated on the basis of whole body 137Cs count. The subjects were 10,062 children (4,762 boys and 5,300 girls) in Mogilev and Gomel, Belarus, who received Chernobyl Sasakawa Health and Medical Cooperation Project health examinations from May 1991 to December 1992 and who were 5-16 y old at the time of examination. The median whole body 137Cs count per body weight varied from 21-48 Bq kg-1 and from 28-126 Bq kg-1 in Mogilev oblast and Gomel oblast, respectively. (The "oblast" is the largest administrative district constituting the country. Belarus consists of 6 oblasts). Corresponding annual effective dose equivalents were all less than the public dose limit of 1 mSv y-1, but the observed levels in the children were considerably higher than the average level of 2.3 Bq kg-1 reported in the past for the former Soviet Union.
Comment In: Health Phys. 1995 May;68(5):733-57730075
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.
Dosimetry studies in Zaborie, a territory in Russia highly contaminated by the Chernobyl accident, were carried out in July, 1997. Studies on dosimetry for people are important not only for epidemiology but also for recovery of local social activity. The local contamination of the soil was measured to be 1.5-6.3 MBq/m2 of Cs-137 with 0.7-4 microSv/h of dose rate. A case study for a villager presently 40 years old indicates estimations of 72 and 269 mSv as the expected internal and external doses during 50 years starting in 1997 based on data of a whole-body measurement of Cs-137 and environmental dose rates. Mean values of accumulated external and internal doses for the period from the year 1986 till 1996 are also estimated to be 130 mSv and 16 mSv for Zaborie. The estimation of the 1986-1996 accumulated dose on the basis of large scale ESR teeth enamel dosimetry provides for this village, the value of 180 mSv. For a short term visitor from Japan to this area, external and internal dose are estimated to be 0.13 mSv/9d (during visit in 1997) and 0.024 mSv/50y (during 50 years starting from 1997), respectively.
We reviewed histopathologically 19 cases of childhood thyroid cancer occurring between 1991 and 1994 among 14,396 screening subjects in Gomel, Republic of Belarus, the region most severely radio-contaminated by the Chernobyl nuclear power plant accident in 1986. The patients were 13 girls and 6 boys with a mean age of 10.6 years. The mean age at the time of the accident was 3.2 years. Mean tumor diameter was 16 mm, and all cases were papillary carcinoma with various amounts of solid component. Psammoma bodies and stromal fibrosis were encountered to some extent in almost all cases. The tumors were highly prone to local invasion and regional lymph-node metastasis. No morphological evidence for radiation-induced cancer was obtained in these cases. 137Cs levels were relatively high in the patients' bodies and in the soil at the places of domicile. However, there was no dose-response relationship between cancer prevalence and radioactivity. These facts suggest that the incidence of aggressive pediatric thyroid cancer is extremely high in Gomel, where most of the children were exposed to a low level of radioactivity over a long time after the accident. At present, however, no definite conclusion can be drawn on the relationship between cancer occurrence and radioactive contamination.
The prevalence of goiter among children living in areas affected by the Chernobyl accident was investigated by analysis of data on approximately 120,000 children examined at five medical diagnostic centers in Belarus, Russia, and the Ukraine. Examinations of thyroid gland were conducted with an arch-automatic ultrasonographic instrument at the five centers under the same protocol. The diagnosis of goiter was established when the thyroid volume exceeded a limit calculated from age, height, and body weight of a child. A considerable variation by region was noted in the prevalence of goiter. Highest in the Kiev region, the prevalence in the five regions was 54% in Kiev, 38% in the Zhitomir regions of the Ukraine, 18% in Gomel, 22% in the Mogilev regions of Belarus, and 41% in the Bryansk region of Russia. Urinary iodine content was measured in approximately 5700 children, and an endemic iodine deficient zone was confirmed in the Bryansk, Kiev, and Zhitomir regions. A significant negative correlation was observed between the prevalence of goiter and the median level of urinary iodine content (Spearman's rank correlation coefficient was -0.35, P = 0.025).
Measurements of 137Cs body burden were carried out in 1991-1996 for children residing in the western part of Bryansk Oblast (Russia) where area contamination with 137Cs following the Chernobyl accident varied from 0.03-3.7 MBq m(-2). The mean and median values of 137Cs specific activity (SA) in the bodies of children 5-15 y old for the whole period of surveillance averaged for 26,029 measurements was 85 Bq kg(-1) and 49 Bq kg(-1), respectively. Mean values in different places of residence varied from 30-342 Bq kg(-1) for the settlements where the number of examinees was not less than 50. There is a moderately strong relationship between mean SA in the settlement and the level of area contamination with 137Cs. A strong seasonal effect on 137Cs body burden was found. The ratio of average SA values is 1:1.75 for spring to autumn 1992-1995 in the settlement where the largest number of children was examined. This effect might be attributed to a seasonal change in diet. Based on questionnaire information on individual consumption of locally produced foods, the descending rank of contribution of food items to 137Cs intake by children was found to be: meat-mushrooms-milk-vegetables. Assuming that the dose distribution would follow the distribution of SA values, internal doses to the whole body from ingested 137Cs were assessed. The mean value of annual internal dose averaged for the whole set of measurements is 0.21 mSv, and the median of the individual dose distribution is 0.12 mSv y(-1) For 2% of the total sample the annual dose exceeded 1 mSv, with the highest individual dose being 9 mSv in 1994 for a 7-y-old girl.