One group that has the potential to be exposed to radiation is workers in the nuclear industry. Results of a systematic medical follow-up and dosimetric monitoring of these workers can form the basis for a study of the relationship between cancer incidence and radiation dose. As part of such efforts in Russia, a major institution of the nuclear industry with an established medical care unit, archiving capabilities, and dosimetry department was selected: the Institute of Physics and Power Engineering (IPPE) in Obninsk. In the study, a comparative analysis of cancer incidence rates for the IPPE workers and for the general population of Russia in 1991-1997 was carried out. The subjects were the IPPE workers hired before 1981. This restriction was imposed to reduce the uncertainty associated with the possible latent period in the development of solid cancers. Thus the possibility of including persons who already had the disease at the time when they were hired was minimized. The analysis is based on information about 158 cancer cases, including 24 cancers in persons under individual dosimetric monitoring. A statistically significant excess in cancer incidence was found among the IPPE workers compared with a comparison population (the general population of Russia) for some types of cancers. The SIR values for all cancers (ICD-9: 140-208) is 0.93 (95% CI 0.76, 1.12) for males and 1.42 (95% CI 1.06, 1.87) for females. A statistically significant excess for all cancers was also observed for residents of Obninsk compared to the control comparison population. The corresponding SIR value was 1.20 (95% CI 1.12, 1.28) for males and 1.58 (95% CI 1.49, 1.69) for females. An important reason for the observed excess in cancer incidence compared to the control population may be the higher level of health care in the so-called nuclear cities of Russia which may have resulted in increased diagnosis and registration of cancers. A statistically significant dependence of the cancer incidence on the dose of ionizing radiation was not established. The excess relative risk per gray for all types of cancer was 0.91 (95% CI -2.75, 4.61) for males and 0.40 (95% CI -6.94, 7.83) for females. These estimates should be considered to be preliminary, as the number of cases considered in the analysis of the dose response is small (17 males and 7 females).
The paper discusses the provision of targeted health care to nuclear workers in Russia based on radiation-epidemiological estimates of cancer risks. Cancer incidence rates are analysed for the workers of the Institute of Physical Power Engineering (the first nuclear installation in the world) who were subjected to individual dosimetric monitoring from 1950 to 2002. The value of excess relative risk for solid cancers was found to be ERR Gy(-1) = 0.24 (95% CI: -4.22; 7.96). It has been shown that 81.8% of the persons covered by individual dosimetric monitoring have potential attributive risk up to 5%, and the risk is more than 10% for 3.7% of the workers. Among the detected cancer cases, 73.5% of the individuals show an attributive risk up to 5% and the risk is in excess of 10% for 3.9% of the workers. Principles for the provision of targeted health care, given voluntary health insurance, are outlined.
The paper is concerned with the results of a follow-up over the period of 1986-1989 of function of the hypophyseo-thyroid system in children and adolescents (approximately 6000 persons), residing in the South-West of the Kaluga Region, where radiation fallouts were observed after the Chernobyl accident. The results were based upon the analysis of medical examinations and determination of the blood levels of TSH, T4 and T3. A certain functional activation of the thyroid system was observed in a majority of the examinees. A conclusion has been made of a necessity of a long-term follow-up of the thyroid of persons who received radioactive iodine in childhood.
The paper considers the radiation doses of the thyroid gland in the inhabitants from the Ukrainian SSR areas (Kiev, Zhitomir, Chernigov, and Vinnitsa Regions), which have been obtained by instrumental studies of thyroidal radioactivity in May-June, 1986, and calculated by the most conservative single-dose administration model. A hygienic evaluation has been made of the findings, taking into account the age and residence. The cumulative irradiation doses of the thyroid have been estimated for children and adults. Possible late sequelae for the areas in question may account for 1060 and 300 thyroid carcinoma cases during the whole life for children and adults, respectively.
Thyroid status was examined in 1214 children living in the Ulyanov district of the Kaluga region contaminated with radionuclides. Thyroid size and structure were assessed using ultrasonic examination, its function was characterized based on thyrotropin and free thyroxin measurements. Specific autoimmunity was evaluated from assays of antibodies to microsomal antigen and thyroglobulin. The resultant values were assessed with due consideration for the individual dose of 131I absorbed by the thyroid. Thyroid enlargement was detected in 21.2%, nodular goiter in 0.79% of the examinees. A reliable positive correlation was found between the degree of thyroid enlargement and 131I absorbed dose. Functional parameters (thyrotropin and free thyroxin) were within the normal range, no correlation was detected between hormonal parameters, thyroid size, and 131I absorbed dose. Antibodies to microsomal antigen were detected in 4.3%, to thyroglobulin in 7.2%, to both in 2.8% of the examinees, this being within the normal range in the population; but a relationship was detected between antibody production and absorbed dose of 131I. Hence, though no noticeable changes in the thyroid status were detected 5 years after the accident in the population examined, the revealed correlations between thyroid enlargement, presence of antithyroid antibodies, and 131I dose may be indicative of a possible growth of thyroid morbidity.
The data on the assessment of the radiobiological situation and the results of clinical and epidemiological studies into the population health status, exposed to radiation because of the Chernobyl NPP accident are summarized. Appropriate regularities in soil contamination with 137Cs are ascertained. It has been shown that the disease incidence among the children's and adult population of the controlled areas is associated not only with improvement of the disease revealing but with the influence of the accident consequences.
Eight 'rogue' lymphocyte metaphases containing a large number of aberrant chromosomes were noted during a survey of chromosomal damage in 328 Belarussian children. The study population comprised children of families living in territory contaminated by radiation from the Chernobyl accident. The majority of the sample had been evacuated within 1 week from very heavily polluted territory to areas that had received much less fallout. Two hundred cells were scored per subject and one rogue cell was found in a child exposed in utero; one in a child conceived after the accident and six in the postnatally exposed group. The possibility that the damage was due to exposure to radio-iodine concentrated in the thyroid gland, or to radiation from incorporated 'hot particles' of an alpha or beta/gamma emitter is discussed. It is concluded that the damage to these cells is unlikely to have been caused by radiation.
Ideas about the thyroid gland diseases development in people suffering from the Chernobyl accident explaining the absence of straight dose dependence of pathologies raise from the irradiation were elaborated. It is supposed that the probable reason for a number of these pathologies can be the inadequate and inopportune preventive iodine administration. It is known that significant amount of iodine being incorporated in children or persons with compromised thyroid gland could lead to a number of pathological changes, primarily to autoimmune thyroiditis which is a reason of other consequent pathologies of this organ. The principal mechanism of the process can be presented as following: iodine transformation (oxidation) in the thyroid gland accompanies with the generation of considerable quantities of various radicals imitating the radiation damage. This hypothesis allows to consider the children suffered from the Chernobyl accident with autoimmune thyroiditis as belonging to the group of risk as the literary data testify that the presence of autoimmune thyroiditis rises 75 time the risk of malignant lympho-proliferated diseases appearance. A simple immunological method of autoimmune thyroiditis diagnostics was developed which informativity is comparable with the method of ultrasound diagnostics. Serial production (the antibodies to microsomal fraction of thyroid gland) was organized. This method can be used in screening investigations.