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NATIONAL CHERNOBYL REGISTRY OF RUSSIA: XA9745470 RADIATION RISKS ANALYSIS V.K.IVANOV, A.F.TSYB Medical Radiological Research Center (RAMS), Obninsk, Russian Federation 1. CURRENT STATUS OF THE RUSSIAN NATIONAL MEDICAL AND DOSIMETRIC REGISTRY Fig. 1 presents the information on the dynamics of the RNMDR registrant number growth in 1986-1995. As the fig. 1 shows during all these years of its existence the data base of the Federal level of the RNMDR kept accumulating medical dosimetric information and as of 1.09.95 comprises data on 435276 people from throughout the Russian Federation. 435276 370120 324146 251758 226928 206797 190O50 174262 111391 52708 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 Fig. I. DjTiamics of RNMDR registrant number growth in 1986-1995. All the RNMDR registrants are divided into five primary registration groups (PRG): PRG 1 - emergency workers - 152325 (35,0 %); PRG 2 - evacuated and resettlers - 12889 (3,0 %); PRG 3 - residents (persons living or lived in monitoring territories) - 251246 (57,7 %); PRG 4 - children bom of emergency workers of 1986-1987 - 18816 (4,3 %). Fig. 2 demonstrates the distribution of persons registered in the RNMDR on their representation in regional centers (the registry of the Central Region does not include 4 contaminated oblasts - Bryansk, Kaluga, Orel and Tula as each of them has its own regional center). 143 ~~~i 8 - 5888 • ••) 5808-10888 435276 persons -vv3 leeae-aeeae ==sg aeeee-seeee > seaee INDUSTRIAL REGIONS B North H N-West @ Central H Volgo-Vjat [1 C.-Chern. ID Povolzh. H K-Caucas. II Urals 13 W-Siberia 5S E.-Siberia 53 Far East PRG4 4,3 % PRG1 Children 3,9% Adolescents 76,9% PRG2 3,0% Adults Fig. 2. Number of persons recorded in the RNMDR. Sex-age composition of the contingent registered in the RNMDR is the following: men 281775 64,7 %; women 153501 35,3 %. children 83598 19,2 %; adolescents 16906 3,9 %; adults 334772 76,9 %. 2 MORTALITY, MORBIDITY AND DISABILITY OF EMERGENCY WORKERS: FACTUAL DATA AND PROGNOSTICATION Fig. 3 illustrates the distribution density f(D) of external exposure doses for EWs included into the RNMDR system. As it is seen from fig. 3 the distribution of doses is of complicated character which is characterized by presence of several peaks (1, 5, 10 and 20-25 cGy). This distribution is obtained using superposition of distributions differing in dates of beginning the works by each emergency worker in the zone of radioactive contamination. With regard to the age distribution of EWs (the average age at the moment of the accident - 33 years) and dosimetric data, in Table I the prognostication of additional mortality of EWs from malignant neoplasms 20 years after the exposure is given. In particular, the excess radiation-induced mortality (attributive risk) from all malignant neoplasms was found to account for 2,8 %. On leukemia cases the analogous parameter will be equal to 23,6 % [1, 2], 144 f<D). 1/cGy OD). 1/eGy 0.15 0.075 • 0.1 th- 0.05 0.025 0 S 10 15 20 25 30 35 40 45 50 0 S 10 15 20 25 30 35 40 45 50 O. cGy . f(D). 1/cOy 0 5 10 15 20 25 30 35 40 45 50 0 5 10 15 20 25 X 35 40 45 50 D.cGy D.eGy . f(D). 1/cGy . f<D>. 1/cGy "•——y—•-•""T • 0 5 0 S 10 IS 20 25 30 35 40 45 50 D.cGy Fig. 3. Distributions f(D) of external exposure doses D for emergency workers registered in the RNMDR. Distributions f(D) for different dates of arrival in the contaminated territories (1986, 1987, 1988, 1989, 1990) are demonstrated separately. Inside the oval the number of EWs (sample size) is indicated on each picture. TABLE I. PREDICTING LATE EFFECTS OF RADIATION ON MORTALITY FROM MALIGNANT NEOPLASMS AMONG EMERGENCY WORKERS 20 YEARS AFTER THE EXPOSURE Year of employ- Number Mean Collec- Excess cancer death Natural cancer death Attributive risk (%) ment of emer- absorbed tive dose due to the exposure in the gency dose (men'Gy) zone workers (cGy) leukemia all types leukemia all types ~ leukemia all types 1986 46575 15,9 7405,4 22 84 45 1945 32,8 4,1 1987 48077 8,95 4302,9 11 47 45 1952 19,6 2,4 1988 18208 3,3 600,9 2 7 17 768 10,5 1989 5475 3,2 175,2 - 2 6 234 7,4 ^0 1 1986- 118335 10,5 12483,1 35 140 113 4899 23,6 2,8 1989 145 The data of prognostication on mortality from malignant neoplasms are in a good agreement with the rates of mortality (observed in the RNMDR) from these causes for EWs (Fig. 4). Mortality of EWs from malignant neoplasms does not exceed the control rate. Dose dependence of mortality from malignant neoplasms is not revealed by us as well. So, the relative risk of mortality from malignant neoplasms among EWs received the doses higher than 25 cGy amounts to 1,4. However, 95% confidence interval of this estimate is within the range of 0,61-2,16 (i.e. it includes the value of 1,0) and does not allow one to make the conclusion about dose dependence. It should be noted that in spite of significant growth of the rate of mortality among EWs from all causes in 1990-1994 this index does not exceed the control values (Fig. 5). Thus, on mortality rates (from all causes and malignant neoplasms) the health effects actually observed during 9 years after the ChNPP accident are in a good agreement with prognostication estimates. 100 -r 95.4 98.8 £ O 80 a.o o o 60 8 O 60 o 45.1 a. 40 S S 20 + 1990 1991 1992 1993 1994 Fig. 4. Death rate of emergency workers from malignant neoplasms in 1990-1994. It is the more complicated problem related to prediction and interpretation of actual data by morbidity and disability rates for EWs [3]. Table II demonstrates the comparison of morbidity rates per 100 thousand people on general classes of diseases both for population of Russia as a whole and for EWs. It is clear from the Table II that morbidity rates of EWs in a series of cases do repeatedly exceed the analogous ones for population of Russia. Undeniably, level, completeness and quality of prophylactic medical examination of EWs differ much from the All-Russian practice. Really, peculiarities and quality of prophylactic medical examination of EWs are that for their examination the most currently available methods of diagnosis of diseases are applied, in so doing, the works listed are carried out by trained and competent specialists. In such a manner, according to the data of the MRRC of RAMS the establishment of primary registered diseases by specialists of this institution is several times higher than by local physicians. In this situation it is very difficult to choose an adequate review control group of comparison. Thus, on the cohort of EWs registered in the RNMDR two main conclusions may be done: - factual evidence for the period just ended and prognostication of total mortality rate as well as that from malignant neoplasms made on the basis of radiation risk coefficients by ICRP are in a good agreement with observed rates which do not exceed corresponding control values on the Russian Federation; - on morbidity and disability rates the EWs of 1986 and 1987 comprise the group of higher risk. 146 ** t • 4C * t *« t ..,...• IIBIM 1 il li —— 1 m 1 m l 1994 ;• * li t ** * * a ; o ' 33 o • D , L H ...... 1993 & • ** «« • ** 0 • fffMtft L £ . 0 1992 • •:• a ' id 1991 _ 1 i = — •••• 1990 1 2 3 4 5 6 7 8 9 10 11 12 Fig. 5. Death rate from all causes for EWs in economical regions of Russian Federation in 1990-1994. 1 - Russian Federation, 2 - North region, 3 - North-West region, 4 - Central region, 5 - Volgo-Vyatsky region, 6 - Central-Chernozem region, 7 - Povolzhsky region, 8 - North-Caucasus region, 9 - Urals region, 10 - West-Siberia region, 11 - East-Siberia region, 12 - Far East region; * p < 0,05; ** p < 0,01. TABLE II. COMPARISON OF MORBIDITY RATES PER 100000 PERSONS ON GENERAL CLASSES OF DISEASES FOR POPULATION OF RUSSIA AS A WHOLE AND EMERGENCY WORKERS ON 1993 Relationship Population of Emergency Classes of diseases among the Russia workers indices Neoplasms 788 747 0,9 Malignant neoplasmsa 140 233 1,6 Diseases of the endocrine system 327 6036 18,4 Diseases of the blood and blood-forming organs 94 339 3,6 Mental disorders 599 5743 9,6 Diseases of the circulatory system 1472 6306 4,3 Diseases of the digestive system 2635 9739 3,7 All classes of diseases 50785 75606 1,5 a - For malignant neoplasms the standardized index on age distribution of emergency workers as of 1993 is given. 147 3. RADIOLOGICAL CONSEQUENCES DUE TO THE CHERNOBYL ACCIDENT AMONG POPULATION OF BRYANSK AND KALUGA OBLASTS, RADIATION RISKS IN INDUCTION OF THYROID CANCER It is known that among radiological consequences due to the ChNPP accident the thyroid tumours will play a decisive role within the framework of somatic stochastic radiation effects. Despite the fact that malignant thyroid tumours especially among children are of infrequent occurrence as compared with tumours of other localizations, nevertheless, an increasing level in induction of radiation thyroid cancers over spontaneous one would be expected. At the same time it is of importance to estimate the whole spectrum of malignant tumours of different localizations and, in particular, that of tumours being the most radiosensitive malignant neoplasms of hemopoietic system which are characterized by short latent period.