NATIONAL CHERNOBYL REGISTRY OF : XA9745470 RADIATION RISKS ANALYSIS

V.K.IVANOV, A.F.TSYB Medical Radiological Research Center (RAMS), , 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 - , , 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

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. 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 *« ..,...• IIBIM 1 il l ——

m 1 li t m

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. According to the data of the RNMDR as of 1994 no excess tumours and other malignant tumours, induced by the Chernobyl radiation, among population of the oblasts mentioned above were established. Factual data of the RNMDR evidence prognostication in this field. Prognostication on excessive thyroid cancer cases for residents of contaminated districts of Kaluga (105300 persons) and Bryansk (466900 persons) oblasts is given in Table III. The parameter "expected" includes spontaneous and excessive (radiation-induced) morbidity.

TABLE III. ABSOLUTE NUMBER OF EXCESSIVE AND EXPECTED THYROID CANCER CASES AMONG RESIDENTS OF CONTAMINATED RAYONS OF BRYANSK AND KALUGA OBLASTS

Time after exposure (years) Attributive Region Age 10 20 lifetime 10 20 lifetime risk % () groups Morbidity (lifetime) Excessive Expected Bryansk adults 20 42 87 160 250 470 18 children 20 53 185 20 68 350 53 Kaluga adults 1 2 4 20 37 70 6 children 2 5 18 4 8 56 32

As it is seen from the Table III the attributive lifetime risk for children living in these areas of will amount to 53% (i.e. every second cancer will be radiation-induced one), for children of - to 32%. In the cohort of children and adolescents of Kaluga oblast (5694 people) with individual doses of radiation to thyroid estimated on the basis of direct radiometry carried out in 1986 the estimates of radiation risk of non-cancer thyroid diseases are obtained. In particular, the estimate of excess relative risk coefficient at the dose of 1 Gy which is equal to 0,2 (0,06; 0,34) is in a good agreement with the data published based on AHS cohort (Japan). Table IV presents risk coefficients.

TABLE IV. COMPARISON OF RADIATION RISK COEFFICIENTS OF NON-CANCER THYROID DISEASES IN KALUGA COHORT OF CHILDREN AND ADOLESCENTS AS WELL AS IN AHS COHORT

Cohort Excess relative risk (ERR) Attributive risk (AR) AHS 0,3 16,4 (Japanese cohort) (0,16; 0,47) (9,1; 24,2) Kaluga cohort 0,2 12,1 (0,06; 0,34) (4,1; 18,7)

148 At present time 48 thyroid cancer cases in those been children and adolescents at the time of the Chernobyl accident have been registered in Bryansk oblast [4, 5]. The "case-control" technology for determinating the radiation risks of cancer thyroid diseases in children and adolescents, living in Bryansk oblast is first realised (Fig. 6). Relative risk coefficient (Fig. 7) of cancer thyroid diseases in contaminated western districts of Bryansk oblast was demonstrated to be equal to 7,15 (1,52; 33,8) at the dose of 1 Gy.

131

Fig. 6. Reconstruction (20 May, 1986) of 131I ground contamination and cases of thyroid cancer in children and adolescents living in Bryansk oblast after the accident.

65 , . i . i i i . . • . i i • . . i . i S0.2 - I RR 38.9 1 8 i _ 1

1 1 1 1

6

4

2

l

1 i 8 Dose 5-60 60-140 > 140 (cGy)

Fig. 7. Radiation risks of cancer in children and adolescents of Bryansk oblast (case-control study).

149 4. CONCLUSION

10 years have elapsed after the Chernobyl accident. The gravest technogenic accident throughout the human history has attracted considerable attention of the whole world community. At the same time, the problem concerning the estimation of the total integral damage to life and health of people exposed to radiation remains very complicate [4, 5]. A negative influence of the Chernobyl included a spectrum of factors which may reinforce each other. In particular, to date there are no theoretical models or practical recommendations on integral estimating the contribution of social and psycho-emotional factors to the risks of diseases due to radiological accidents. On the other hand, for maximum effective rehabilitation of suffered people the ranging and impartial determination of contribution both of proper radiation and non-radiation components of influence are needed. Therefore, continuation of long- standing investigations within the frame of the National Radiation and Epidemiological Registry along with obtaining new scientific data in the field of radiation epidemiology is of great practical importance to diminish health consequences of the accident.

REFERENCES

[1] IVANOV, V.K., et al., Planning of long-term radiation and epidemiological research on the basis of the Russian National Medical Dosimetric Registry, Nagasaki symposium on Chernobyl update and future, Amsterdam, Elsevier (1994) 203-216. [2] rVANOV, V.K., et al., Information systems and modelling: data and organizational aspects of the Chernobyl State registry, Proceeding of the First Conference of International Simulation Societies, Zurich (1994) 579-583. [3] MOULD, R.F., et al., Chernobyl update on health and the "Sarcophagus", Current Oncology 3 (1994)151-162. [4] TSYB, A.F., et al., Disease indices of thyroid and their dose dependence in children and adolescents affected as a result of the Chernobyl accident, Nagasaki symposium on Chernobyl update and future, Amsterdam, Elsevier (1994) 9-19. [5] IVANOV, V.K., et al., Radiation epidemiology of cancer- and non-cancer thyroid diseases in Russia after the ChNPP accident: prognostication and risk estimate, Radiation and Risk, Bulletin of the National Radiation and Epidemiological Registry special issue 95/1 (1995) 3-29.

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