The paper considers information about cancer incidence (solid tumors) among liquidators of the Chernobyl accident, which occurred in April 1986. The information was accumulated in the Russian National Medical and Dosimetric Registry (RNMDR) in the period from 1986 to early 1996. The RNMDR contains individual dosimetric and annual check-up data on liquidators resident in Russia. This paper presents results for male liquidators who had no oncological diseases before arrival to the 30-km zone and for whom the following information was available: confirmed dose of external radiation, birth date, date of arrival to the 30-km zone, time spent in the 30-km zone, and results of medical check-ups. The number of liquidators under study is 114,504, i.e., about 68% of all those registered in the RNMDR. The average dose of the studied cohort is 108 mGy; the average age at first arrival to the 30-km zone is 34.3 y; the total number of person-y is 797,781. The cohort of liquidators is briefly characterized. Cancer incidence in liquidators is compared to that of the population of Russia as a whole by calculating standardized incidence ratio (SIR). The values of SIR with 95% confidence intervals for all solid tumors and malignant neoplasms of the digestive system were 1.23 (1.15; 1.31) and 1.11 (1.01; 1.24), respectively. Assessment of radiation risks for the same classes of diseases has revealed a statistically significant increase in cancer incidence with external radiation dose. This study also shows that statistically significant excesses in the incidence of malignant neoplasms of the respiratory system have not been observed.
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 work focuses on the results of the analysis of the cancer incidence among the Chernobyl emergency workers residing in Russia during 1991-2001. The analysis is based on the data for the cohort of male emergency workers from 6 regions of Russia including 55718 persons with documented external radiation doses in the range of 0.001-0.3 Gy who worked within the 30-km zone in 1986-1987. The mean age at exposure for these persons was 34.8 years old and the mean external radiation dose 0.13 Gy. In this cohort 1370 cases of solid cancer were diagnosed. Three follow-up periods were considered: 1991-1995, 1996-2001 and 1991-2001. The second follow-up period was chosen to allow for a minimum latency period of 10 years. Risk assessments were performed for two control groups: the first control group ("external") represented incidence rates for corresponding ages in Russia in general and the second control group ("internal") consisted of emergency workers. The estimated standardized incidence ratio (SIR) is in good agreement with that of the control within 95% CI. The values of the excess relative risk per unit dose 1 Gy (ERR/Gy) for solid malignant neoplasms have been estimated to be 0.33 (95% CI: -0.39, 1.22) (internal control) for the follow-up period 1991-2001 and 0.19 (95% CI: -0.66, 1.27) for 1996-2001. The analysis of cancer morbidity was carried out for the cohort of 29003 emergency workers who took part in liquidation of the consequences of the Chernobyl accident from 26 April 1986 to 25 April 1987. It was shown that the excess relative risk of cancer deaths per unit dose 1 Sv (ERR/Sv) is equal to 1.52 (95% CI: 0.20, 2.85).
Cancer morbidity and mortality were studied in areas of the Kaluga oblast contaminated with radionuclides. The main objective of the study was to assess the influence of radiation exposure on existing levels of cancer morbidity and mortality. Time trends and relative population risks were analysed. Based on this analysis, it was concluded that the current levels of morbidity from cancers among the populations residing in the studied areas were primarily a result of a complex of factors which predated the exposure from the Chernobyl accident. However, there seems to be an unfavourable trend concerning malignant neoplasms of the respiratory organs for women residing in the contaminated areas. To date, no statistically significant effect of radiation on cancer morbidity (except for thyroid cancer in women) has been noted. The levels of cancer morbidity and mortality in the contaminated areas generally reflect the changes in cancer incidence in the oblast as a whole. The findings are consistent with international data on latent periods for the induction of radiogenic cancers and the biological effects for similar levels of exposure to populations residing in contaminated territories. Further studies are necessary in order to monitor possible effects that are related to the accident.
We estimated the radiation-induced risk of leukemia in 162,684 Chernobyl accident emergency workers (EWs) using the data of the Russian National Medical and Dosimetric Registry (RNMDR). A system was established for the collection and verification of data in 55 cases of leukemia from 1986 to 1995. The principal analysis included 41 leukemia cases that occurred more than 2 years after the first exposure to radiation. The case-control methodology was used to evaluate the risk of leukemia associated with various factors. Radiation dose, effective exposure dose rate, date of entry into the Chernobyl zone (ChZ), and the duration of stay in the zone were used as risk factors. The relationship between the date of entry and the duration of stay in the zone was investigated. All cases of leukemia, excluding chronic lymphocytic leukemia (CLL), were analyzed. An analysis was also performed on all EWs and on the EWs who worked in the zone from 1986 to 1987 (EWs of 1986 to 1987). No significant association was found between the risk of leukemia and the factors we investigated. Nevertheless, the relative risk estimates for leukemia, excluding CLL, were greater than the value for all leukemia and were greater than one. The estimated excess relative risk (ERR) per Gy was greater for all EWs [ERR = 1.33, 95% confidence interval (CI): -6.25, 8.90 for all leukemia, and ERR = 15.59, 95% CI: -24.92, 56.11 for leukemia, excluding CLL] compared with EWs of 1986 to 1987 (ERR = 0.28, 95% CI: -5.84, 7.41 for all leukemia, and ERR = 9.43, 95% CI: -20.0, 38.86 for leukemia, excluding CLL).
Ten years have elapsed since the Chernobyl accident. The gravest technologically generated accident throughout human history has attracted considerable attention from the whole world community. At the same time, the problem of estimating the total damage to life and health of people exposed to radiation remains very complicated. The negative effects of Chernobyl include a spectrum of factors which may reinforce each other. In particular, to date there are no theoretical models or practical recommendations on estimating the contribution of the social, psychological or emotional factors that surround diseases due to radiation accidents. On the other hand, for maximum effective rehabilitation of the affected population, the impartial determination of the contribution by both radiation and non-radiation components is necessary. Therefore, the continuation of long-standing investigations within the framework of the National and Radiation and Epidemiological Registry along with obtaining new scientific data in the field of radiation epidemiology is of great practical importance in limiting the health consequences of the accident.
A. Tsyb Medical Radiological Research Center - Branch of the Federal State Budgetary Institution National Medical Research Radiological Center of the Ministry of Health of the Russian Federation (A. Tsyb MRRC), 10 Marshal Zhukov Str., Obninsk, Kaluga Region, Russia.
Radiat Prot Dosimetry. 2018 Dec 01; 182(1):163-169
The article describes the activities of the Russian National Radiation-Epidemiological Registry (NRER) as the unified federal information system for research and management of individual medical and dosimetry data of people exposed to radiation as a result of the Chernobyl accident and other radiological events. The NRER was created for long-term registration of lifetime changes in the health status of the registered people. We present medical and dosimetry data management process, which is carried out in compliance with approved protocols. The scope and content of the information to be collected from external resources are defined in the documents approved by the Russian Ministry of Health. As of 2017 reporting year, the NRER contains medical and dosimetry information on 205 044 clean-up workers of the Chernobyl accident (liquidators), collected during the follow-up period from 1986 to 2016. Using special software for management of data from long-term studies of the Russian cohort of Chernobyl liquidators NRER ensures high quality of radiation-epidemiological information. The results of research activities of the NRER make great contribution to understanding biological and health effects of low-level radiation, molecular mechanisms of the effects, development of actions to early diagnostic of radiation-related diseases to respond to the needs of the affected population while minimizing unnecessary anxiety, improvement of targeting treatments delivery to exposed people at high risk, development of measures to reduce health risks from medical radiological procedures. During the post-Chernobyl period, new methods for estimating radiation doses were developed, some of them can be used for express estimation of radiation dose in the event of radiological emergency.
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 article represents data on distribution of liquidators in Russian State Medical Dosimetry Register according to account categories, residing territories (regions of Russia), age, sex, dose groups, coverage by medical examinations and health groups. During 1991-1996 the liquidators demonstrated higher occurrence of endocrine, neurologic and sensory, circulatory, digestive and malignant diseases.
This paper presents an analysis of thyroid cancer incidence in the territories of Russia most contaminated after the Chernobyl accident. In the work, data on incidence in the Bryansk, Kaluga, Orel and Tula regions (5298000 persons) are used. Altogether, 2599 cases of thyroid cancer are considered from 1982 to 1995. Of them, 143 cases were among the population who were children and adolescents at the time of the accident in 1986. The work uses the approach based on comparison of distributions of thyroid cancer cases by age at diagnosis and age at exposure. It has been shown that since 1991 the age structure of the incidence has changed significantly with a growing proportion of cases among children and adolescents. The change in the structure occurred due to the radiation factor, specifically as a result of exposure of thyroid to incorporated 131I. It has been shown that the standardised incidence ratio (SIR) of thyroid cancer among children who were 0-4 years at exposure in 1991-6 was 6 to 10 times higher than among adults. On the average, SIR for children and adolescents at the time of exposure is about three times higher than in adults.