"Radiation & Risk", 1996, issue 7 Scientific Articles
Thyroid doses for the population of Russia as a result of the Chernobyl accident (retrospective analysis)
Stepanenko V.F., Tsyb A.F., Gavrilin Yu.I.*, Khrushch V.T.*, Shinkarev S.M.*, Skvortsov V.G., Kondrashov A.E., Yas’kova E.K., Ivannikov A.I., Parshkov E.M., Shakhtarin V.V., Moskovko L.I., Petin D.V., Chebotareva I.V., Proshin A.D.**, Rozhko Yu.N.**, Dorokhov V.V.**, Rivkind N.B.**, Kvitko B.I.**, Kuz’min P.S.**, Leshakov S.Yu.***, Omel’chenko V.N.*** Medical Radiological Research Centre of RAMS, Obninsk, Russia; * Institute of Biophysics, Russia; ** Department of Health, Administration of Bryansk region; *** Department of Health, Administration of Kaluga region. The paper discusses a methodological approach developed for re- construction of thyroid doses from internal exposure to 131I and prospects of future work in this field. Estimated levels of thyroid irradiation for the population of Russia after the ac- cident are presented. These results have been obtained based on the retrospective analysis using the developed approach. Also, long-term health consequences of thyroid irradiation in the population of Russia have been predicted. Retrospective esti- mates have been made for individual thyroid doses for children and adolescents with the diagnosis of thyroid cancer living on the contaminated areas.
Introduction 1. Key characteristics of available ar- rays of dosimetric data The recent data are indicative of an increase in the frequency of detection In essence, three classes can be of malignant neoplasms of thyroid on the identified in individual internal doses territories contaminated after the Cher- of thyroid exposure to radioactive io- nobyl accident [1, 2]. This enhances the dine: importance of the studies to comprehen- Class 1 includes individual doses sively assess the factors of thyroid ex- calculated from measurements of 131I con- posure to radiation. In this respect, tent in thyroid (people examined in May- based on available results of measure- June 1986). With all reservations con- ments of radioiodine in thyroid and cerning errors in measuring radioiodine various characteristics of the environ- in thyroid and uncertainties in calcula- ment and using additional data which can tion models used for estimation of indi- be obtained in the near future, it is vidual doses, these data should be re- necessary to bring the accuracy of dosi- ferred to as most reliable and objec- metric evaluations of thyroid exposure tive. to the level required by practical medi- Class 2 consists of estimates of in- cine and epidemiological studies, ide- dividual doses for those population ally, to the accuracy which would allow points for which sufficient amount of adjustment of dose coefficients of risk data of Class 1 are available. Based on of thyroid diseases in irradiated per- results of Class 1, parameters of dis- sons. This problem should be first ap- tributions of individual internal doses proached from the standpoint of total for corresponding age groups (mean value absorbed dose, namely internal radiation and deviation from it) are determined dose resulted from intake of radioactive and then for a specific individual for isotope 131I. whom data of Class 1 are not available, an individualised dose is estimated af- ter additional information on life style, milk intake and other information
62 "Radiation & Risk", 1996, issue 7 Scientific Articles is provided. While this additional in- In May-June 1986 in Belarus, Russia formation is missing, as a personal and Ukraine an unprecedented dosimetric characteristic of thyroid internal irra- survey was undertaken which produced re- diation mean values for a corresponding sults of direct measurements of the ra- age group are taken. The objectivity of dioiodine content in the thyroid in more such characteristics is quite high, as than 400 thousand people. The survey was they were derived on the basis of direct performed by numerous groups of special- measurements of radioiodine in the thy- ists of differing training, working in roid. different conditions (from specialised Class 3 includes estimates of indi- establishments to field conditions in vidual internal thyroid doses for resi- the contaminated areas) and having at dents of the rest populated points their disposal different types of meas- (which are the majority) for which the urement equipment (from energy-selective required amount of Class 1 data are not specialised devices to -radiation dose available and it is not possible to de- rate detectors of DF-5 type). As a re- rive estimates of Class 2. In this case sult, a variety of factors influenced the group characteristics of internal the reliability of results of direct exposure of thyroid can be estimated measurements. Some of these factors have from data on characteristics of the ra- been identified and corresponding ad- diation situation and its formation in justments have been made, as, for exam- each populated point of interest using ple, was the case with measurements in one of the calculation models. Belarus which were distorted because of The problem is that the existing data the wrong measurement procedure used and on the radiation situation are rather conversion of measurement units without limited and they are not sufficient for indication of the type of device used application of the known well-developed [6]. multi-parameter models. The most realis- One of the issues which are still de- tic way to solve the problem is to use a batable is a possible distortion of re- large volume of data of Class 1 avail- sults of determination of 131I in thyroid able for the contaminated areas for de- due to “ glow” of detectors because of veloping a semiempirical model of ex- external radioactive contamination of trapolation-interpolation type which body and clothes and as a result of in- would be rather general, but reflect the take of other radionuclides and, first knowledge of the basic processes respon- of all, radioisotopes of cesium (134Cs, sible for thyroid exposure and be based 137Cs). It should be emphasised that the on available empirical material. At the contribution of -radiation of incorpo- same time, it would be desirable that rated radiocesium in the detector read- such a model be quite simple, i.e. would ings (not -spectrometric), when measur- require only available information on ing 131I content in thyroid, changes de- formation of thyroid doses or informa- pending on the date of measurement: from tion that can be obtained by the exist- insignificant in early-middle May 1986 ing methods. to predominant in middle June and later. The features of large-scale measure- The Class 1 data bank on residents of ments of radioiodine in thyroid in May - Kaluga region [3, 13] contains informa- early June 1986 on the contaminated ar- tion of May 1986 only. The Class 1 data eas of Belarus, Russia and Ukraine and bank for the population of Belarus has main aspects of the following verifica- only individual doses determined based tion of measurements, models used and on measurements made not later than 6 individual internal thyroid doses have June 1986. The data on residents of Bry- been described in detail in national and ansk, Tula and Orel regions based on the international publications and discussed difference in detectors readings with at scientific conferences [3-13]. In the measurement geometry of “ thyroid” general, it can be said that separate and “ thigh surface” [8] can signifi- subsets of Class 1 data formed by now by cantly underestimate the true values of different investigation groups differ individual internal thyroid doses for either by the method of obtaining pri- those for whom external radioactive con- mary data of radioiodine measurements in tamination of thigh surface was not thyroid or by schemes for calculating eliminated. individual internal thyroid doses. By far, factors influencing the reli- ability of the determination of 131I con-
63 "Radiation & Risk", 1996, issue 7 Scientific Articles tent in thyroid can not all be quanti- “ per os” intake of 131I with local milk, fied. That is why, at this stage we use which is primarily characteristic of ru- an approach based on conventional clas- ral residents and a model of inhalation sification of results of 131I content intake with consideration of documented measurements in thyroid into several protection measures (such as evacuation certainty groups. Each of these groups or relocation to relatively “ clean” are assigned a relative error by ex- areas). The minor differences in the perts. The data on more than 200 thou- used values of calculation parameters sand residents of Belarus were first di- (constants of thyroid cleaning from 131I vided into three groups of certainty of for separate age groups, cleaning of 131I determinations in thyroid with al- pasture grass and leaf vegetables) lowance for conditions of measurements should be taken into account at the next and devices used with relative errors of stage. The assumption of a short one- 50, 300 and 500% [6]. As a result of time contamination of the environment verification of available data and re- was based on data on daily depositions lated work, the Class 1 data bank on of 131I registered by Goskomhydromet net- residents of Belarus contains about 130 work which, regrettably, is not as dense thousand individual doses, whose cer- as one would need for dose reconstruc- tainty groups, in terms of 131I measure- tion. The general scheme of applying ad- ment in thyroid, can be characterized by justments for the long-term character of relative errors: to 60%, within 60 to fallout is described in detail in Guide- 200% and 200 to 400% respectively. As- lines [14] and will be used in future as suming that the indicated intervals cor- much in detail as kinetics of local respond to 95% confidence probability depositions of 131I is refined, which was with lognormal distribution, the intro- promised, in particular, by the authors duced certainty groups can be character- of work [16]. ized by the values of standard geometri- A model of 131I intake that differs in cal deviation of 1.3; 1.7 and 2.2 (1-st, principle has been used for calculation 2-nd and 3-d certainty groups, respec- of individual internal thyroid dose for tively). population of Bryansk, Tula and Orel re- The main body of Class 1 measurement gions [8] (a “ stepwise” model). It was data for residents of Kaluga region assumed that during the first 15 days (about 28 thousand [3, 13]), Bryansk, after the first fallout the radioiodine Tula and Orel regions of Russia (about intake by people had the same rate and 3.3 thousand [8]) can be referred to the later on the rate was decreasing in ac- 2-nd certainty group (standard geometric cordance with effective half-period of deviation of 1.3 - 1.7). It should be cleaning of pasture grass equal to 5 emphasised that given a fairly large days. In calculations account was taken amount of Class 1 data for residents of of protection measures resulting in bans a populated point, the random component on consumption of contaminated milk. of the error in determination of mean With no protection measures taken, the values goes down to quite acceptable deviation of results of calculation with values. the “ stepwise” model from those with The above characteristics account for the Guidelines model [14] do not exceed only part of uncertainty in determina- 20%, given the measurements of 131I were tion of individual internal thyroid dose made later than 15-20 days after ra- form 131I. The second component of this dioiodine started to enter the body. It uncertainty is related to models trans- should be said that in all the populated lating measured 131I into absorbed dose. points of Bryansk region discussed in At present, most Class 1 data on resi- work [8] protection measures banning dents of contaminated areas, i.e. Be- consumption of contaminated milk were larus [6], Russia (Kaluga region) [3, introduced. In such cases the results of 13] and Ukraine [7] have been brought to calculation with the “ stepwise” model practically the same methodological base for younger age groups and postponed outlined in Guidelines [14] and in work dates of measurement can exceed by a [15]. factor of 1.4-1.5 the values calculated At the first stage all estimates of by Guidelines [14] using the model of absorbed doses have been derived from one-time contamination of pasture. the assumption of a short-time passage As was pointed out earlier, the Class of a radioactive cloud using a model of 2 data are estimated based on results of
64 "Radiation & Risk", 1996, issue 7 Scientific Articles calculation of individual internal thy- in inhalation regime (from sleeping to roid doses included in Class 1 for popu- active physical work) and local changes lated points in which part of residents in 131I concentration in the air. underwent dosimetric survey in May - 4. It is assumed that the “ per os” early June 1986. component of dose is wholly determined At the first stage mean absorbed thy- by 131I intake with milk, and for a spe- roid doses are determined for different cific person (k) from age group (i) the age groups and then with account taken “ per os” component of individual dose of mean daily consumption of milk in Pik is related to the component Pic which these groups and individual mean daily is a mean for an age group (i) in a consumption for a person of known age given populated point with a simple re- (as of April 1986) an individualised ab- lation: sorbed dose is found. Implementation of this scheme became possible because rec- ords (“ passports” ) were drawn up for P P ik ic , (1) more than 1000 populated points located V V on the contaminated areas of Belarus ik ic [17] and Russia [13]. Using these pass- where V and V is daily milk con- ports one can estimate not only the ik ic value of the personalised dose but also sumption by an individual (k) and by in- its confidence interval. Also, devia- dividuals from the i-th age group on the tions from typical life style in a spe- average in the populated point, respec- cific populated point can be taken into tively, L/day. account. The results of polling regarding When the passports were designed some daily milk consumption among rural popu- assumptions were made, the principal of lation in Belarus and Russia were simi- which are: lar to these, which leads us to assume 1. It is assumed that the distribu- that within an age group individual tion of individual doses within an age daily milk consumption is adequately de- group is described by a lognormal dis- scribed by a lognormal distribution with medians V and with practically the same tribution function with parameters found im for each populated point documented in standard geometric deviation of 1.6 0.1 [17, 18]. The values V accepted for the passport. im 2. It is assumed that the components rural population during passportization related to 131I intake with milk and in- of the populated points of Belarus and halable air are also characterised by Kaluga region of Russia are presented in lognormal distribution. Table 1. 3. It is assumed that in the absence In order to make the passports on in- of protection measures the mean arithme- ternal thyroid exposure easier to use in tic value of the inhalation dose of in- practice, all initial data were divided ternal thyroid exposure in adults of any into 19 age groups without regard for populated point is 20 times lower the sex. Of them, the first 18 (children and mean arithmetic dose due to 131I intake adolescents) were formed with the step with milk (and leaf vegetables), and the of 1 year (the first group - birth dates standard geometric deviation of inhala- from 25.04.86 to 26.04.85) and the last tion component of individual dose in all 19-th group included all persons at the cases is 2.9. Such a large standard geo- age of 18 years and older (as of metric deviation was taken with “ a mar- 26.04.86). gin” to allow for possible variations
Table 1
Median values Vim (L/day) of mean daily milk consumption by rural population of Gomel and Mogilev regions of Belarus and Kaluga region of Russia, accepted for pass- portization of populated points with respect to internal thyroid exposure
Region Age on 1 May 1986, years
< 3 3 - 13 13 - 16 16
Gomel and Mogilev re- 0.4 0.4 0.5 0.7 65 "Radiation & Risk", 1996, issue 7 Scientific Articles
gions of Belarus Kaluga region of Russia 0.5 0.4 0.4 0.7
The passport of a populated point on rival-departure dates, consumption of internal exposure of thyroid is a table goat milk etc.). A scheme is described of 19 lines (age) and 13 main columns for calculating internal thyroid doses (daily milk consumption from 0 to 4 in infants due to intake of radioiodine L/day and a column for the case when with mother’s milk and calculating doses personal information on daily milk con- received in the intrauterine period. sumption is not available). Each box of All aspects of drawing up the pass- the table gives an absolute median esti- ports of populated points on internal mate of internal thyroid dose from 131I thyroid exposure have been described in for which a standard geometrical devia- detail in [17-19, 21, 23]. tion is given, which permits calculating Table 2 contains general information bounds of confidence probability for an on Class 1 data banks and shows to what individualised dose value. The instruc- degree the populated points were covered tion on the passport use describes the by passports permitting an individual- procedure of determination of individu- ised estimate of internal thyroid dose alised dose including methods to correct (Class 2 data) to be derived for the the tabulated value, if personal condi- population of the contaminated areas of tions of thyroid dose formation differ Belarus and Russia from the typical ones (for example, ar- Table 2 Information on Class 1 data banks and number of populated points with passports in the contaminated areas of Belarus and Russia (Class 2 data) characterizing internal thyroid doses
Class 1 data: number of persons with individual doses calculated from Class 2 data: num- measurements of 131I content in thyroid, ber of rural popu- Territories thousand lated points with passports Younger 18 Adults Total years (on 26.04.86) 8 areas of Gomel region 25.4 63.1 88.5 678 of Belarus [6] 5 areas of Mogilev re- 4.5 8.9 13.4 253 gion of Belarus [6] Minsk [6] 7.3 12.9 20.2 - Gomel, Mogilev, Mozyr 3.3 5.2 8.5 - and other contaminated areas [6] 7 areas of Kaluga region 24.2 3.7 27.9 140 of Russia [3, 13] Bryansk, Orel, Tula re- 1.0 2.2 3.2 22* gions of Russia [8]
* - Mostly populated points of town type.
2. Relation between internal thyroid The performed surveys of the areas dose in residents of a populated point contaminated after the Chernobyl acci- and fallout density dent have resulted in accumulation of a large volume of information enabling an in-depth analysis of relations between 66 "Radiation & Risk", 1996, issue 7 Scientific Articles internal thyroid doses and characteris- The distribution of individual thy- tics of radioactive contamination in roid doses within relatively small ter- certain populated points. In order to ritories, which the administrative areas avoid any major distortions in expected are, is fairly well approximated by the trends, the requirements were set for lognormal function [18]. This can not be the data to be used for analysis. applied, however, to density of radioac- Of more than 1000 populated points tive fallout and therefore, it would be having passports on internal thyroid ex- unwise to include in the analysis proce- posure, consideration was given only to dure the properties which are specific those for which at least 25 individual for the lognormal function. Ultimately, dose estimates were available. It is it was decided that at the first stage clear that relations like “ dose - area of iteration a more objective quantita- contamination level” can be analysed if tive characteristic of contamination of data are comparable in terms of protec- area X is a mean arithmetic value (here- tion measures. Adjustments for such inafter unless otherwise defined, we use measures for specific populated points the term “ mean” ) of contamination den- are strongly dependent on adopted calcu- sity: lation models. For example, in the case when the consumption of contaminated 1 N xjx ,, (3) milk was banned 8 days after one-time 137N 137 contamination of pastures, the adjust- j1 ment for multiplicity of reduction in jx, internal thyroid dose calculated by the where 137 is mean density of contami- “ stepwise” model [8] is by a factor of nation of the j-th populated point lo- 1.9 higher that calculated by the Guide- cated on area X. lines [14]. Then, of course, other values in- To avoid possible distortions related volved in the correlation analysis to such adjustments, we have excluded should be estimated by mean values. To from the analysis all populated points avoid additional difficulties related to from which residents had been evacuated age features we used in the analysis prior to 5 May 1986 (Gomel region in Be- mean values Dj,x of internal thyroid larus). doses for adults of the j-th populated Cities and district centres have also point located on the area X. As separate been excluded from the analysis as they areas X we took administrative dis- were supplied with food stuffs in a dif- tricts, which is, of course, not an op- ferent way as compared to rural popu- timum solution in terms of physics of lated points. The number of populated transport of radioactive materials, but points meeting the above requirements can be justified, as the first approxi- was 250 in Gomel and Mogilev regions in mation, by lack of adequate description Belarus and about 60 in Kaluga region, of these processes for all areas of in- i.e. 1/3 of the total number of passpor- terest. tized points. Fulfilment of the above requirements, As basic data characterizing the con- as applied to specific populated points, tamination of populated points we used has also a negative side, as the group official data on surface density of 137Cs of populated points left for the analy- depositions [24, 25]. We also relied on sis may appear not to be a representa- data of Institute of Nuclear Power, tive sample for a corresponding area. Minsk [26] and data obtained by special- Table 3 includes mean absorbed thyroid ists of Institute of Biophysics, Moscow doses for three districts of Gomel re- (F.Levochkin, A.Titov, S.Panchenko et gion of Belarus located beyond the 30 km al) in determination of mean ratios Rj zone, for which the greatest amount of 131 137 of I content to Cs ( 137) in soil cal- individual doses (Class 1) are available culated by the time moment of main ra- and a lot of populated points left after dioactive contamination of the j-th “ sorting out” based on the above re- populated point. The 131I deposition den- quirements. It should be emphasised that j in these three areas the proportion of sity 131 used in the correlation analy- sis was found from the relation: persons supported with Class 1 data is particularly high (more than half of all jj rural population). 131 137 Rj. (2)
67 "Radiation & Risk", 1996, issue 7 Scientific Articles
As can be seen from data of Table 3 x 137 found from the totality of official for the three areas of interest the sam- data with the mean values of nx, found ples of the populated points can be con- 137 with the sample from n of populated sidered quite representative, at least x with respect to the main indicator - points left for analysis. These parame- mean dose. ters for 11 administrative districts of The representativeness of samples of Belarus and 3 areas of Kaluga region of populated points for other areas of Be- Russia are given in Table 4. This table also includes mean values of ratios Rx larus and Russia is rather difficult to 131 137 be assessed in a similar way, since of I activity to Cs activity referred there is no guarantee that the body of to the date of principal contamination of area X, and a number m of populated Class 1 data for adults of these areas x points for which the values of R have are representative. x The representativeness of samples of been found based on direct measurements nx, populated points left for correlation of samples. The columns of Rx and 137 analysis D jx, , by the second char- also indicate mean square deviations of j,x 137 jx, 137 R and for separate populated acteristic - Cs contamination density j,x 137 can be assessed by comparing the set points.
Table 3 Mean internal thyroid doses for adults of administrative districts of Gomel region of Belarus (territory beyond the 30-km zone) calculated from the whole array of data and from samples of populated points selected for correlation analysis
Parameter Administrative district Bragin Narovlya Khoiniki Number of adults with individual doses 15084 2499 10560 Mean dose based on the whole data array, mGy 400 360 480 Number of populated points in a sample 70 21 47 for a correlation analysis Mean dose for a sample of populated points, 320 390 450 mGy
Table 4 Main indicators of the radioactive contamination of areas and populated points jx, jx, selected for analysis of correlations such as Dj,x 137 ; Dj,x 131
131 137 Rx is the relation of I and Cs deposition densities referred to the date of main radioactive contamination of area X;
mx is the number of populated points for which Rx is estimated.
x , nx,, Area 137 R m 137 n kBq/m2 x x kBq/m2 x Districts of Gomel region, Belarus Bragin (outside 30-km zone) 330 29 21 76 190 170 70 Vetkov 440 13.7 7.4 35 580 330 11 Loev 92 23 14 9 78 92 19 Narovlya (outside 30-km zone) 470 16.9 8.6 56 470 230 21 Rechitsy 100 36 35 11 85 37 17 Khoiniki (outside 30-km zone) 480 24 15 56 350 240 47 Districts of Mogilev region, Belarus
68 "Radiation & Risk", 1996, issue 7 Scientific Articles
Klimovichi 52 22 33 12 450 300 7 Kostyukovichi 250 10 15 26 1000 440 19 Krasnopol 260 8.8 2.9 69 1000 920 18 Slavgorod 390 11.3 7.2 34 580 360 9 Cherikov 240 10 12 16 670 520 11 Districts of Kaluga region, Russia Zhizdra 110 96 52 17 Ulyanovo 170 170 70 20 Khvastovichi 89 150 100 24
It can be seen from Table 4 that un- like Gomel and Kaluga regions, the sam- statistical test there is a positive ples for the areas of Mogilev region D and jx, for all correlation between j,x 137 contain primarily the most contaminated three areas of Kaluga region of Russia, (as compared to the mean) populated populated points of Kostyukovichi and points located in the “ patches” of ra- Krasnopol areas of Mogilev region and dioactive depositions. Bragin and Rechitsy areas of Gomel re- Table 5 for all considered adminis- gion of Belarus. As to populated points trative districts of Belarus and Russia of other areas of Belarus indicated in contains empirical values of correlation Table 5, it is either lack of correla- coefficients r and the absolute values tion or at best, a weak positive corre- of correlation coefficients r and r . 0.1 0.01 lation (Vetkovsky and Klimovichesky ar- If the latter are exceeded, with the eas). The positive correlation between given size of the sample, it means that dose D and contamination density jx, there is a correlation between the con- j,x 137 sidered values at a relatively low level suggests that it is possible, in es- of significance 0.1 and high level of sence, to use the useful information in- jx, significance 0.01, respectively, under corporated in a specific value 137 to the assumption of the normal distribu- propose a way to determine values Dj,x tion law of these random values. for a specific populated point. Based on the data presented in Table 5 it can be stated that by a rather hard
Table 5 Empirical values r of correlation coefficients of mean arithmetic dose of internal 137 thyroid exposure in adults Dj,x and Cs contamination density qj,x(Cs) of populated point (j) on area X and bound values r(0.1) and r(0.01) which, if exceeded by abso-
lute values rx, indicate correlation of the values at significance levels 0.1 and 0.01, respectively.
Area rr0.1 r0.01 Districts of Gomel region, Belarus Bragin + 0.48 0.20 0.30 Vetkov + 0.66 0.52 0.73 Loev + 0.33 0.39 0.58 Narovlya + 0.26 0.37 0.54 Rechitsy + 0.63 0.41 0.61 Khoiniki + 0.25 0.24 0.37 Districts of Mogilev region, Belarus Klimovichi + 0.84 0.67 0.87 69 "Radiation & Risk", 1996, issue 7 Scientific Articles
Kostyukovichi + 0.68 0.39 0.58 Krasnopol + 0.68 0.40 0.59 Slavgorod 0.28 0.58 0.80 Cherikov 0.43 0.52 0.73 Districts of Kaluga region, Russia Zhizdra + 0.62 0.41 0.61 Ulyanovo + 0.64 0.38 0.56 Khvastovichi + 0.57 0.34 0.52
* - marked are the lines showing the areas for which r > r0.01.
The methodological guidelines [27] in force recommend that the mean internal mGy, thyroid dose D be estimated with: x x 131 137 j,x where 131, 137 are mean I and Cs contamination densities for populated jx, 2 DKjx, x 137 , (4) points on areas X, respectively, kBq/m ; jx, jx, 131 , 137 are mean contamination den-
where Kx is “ dose“ proportionality sities of the j-th populated point with coefficient whose value should be speci- 131I and 137Cs located on area X respec- fied for each specific area. tively, kBq/m2; Work [28] proposes a linear formula Rx, Rj,x are coefficients of correla- for any regions. In our designations it tion between 131I and 137Cs contamination can be written as densities. Formula (6) can be rewritten as jx, D jx, 051.. 014 137 , mSv, (5)
jx, jx, 2 x 131 where 137 is measured in kBq/m . D jx, 0036.(.)131 1 04 The data on populated points of the x 131 . (7) considered contaminated areas of Belarus R jx, and Russia show inadequacy of models (4) 0036.(.R x 1 04 jx, 137 ) x 137 x and (5). This is particularly well seen Rx 137 in consideration of values of the ratio jx, jx, Dj,x/ 137 as a function of 137 : at small values this ratio is much higher than at It is clear that the second summand large ones [12]. Such a dependence is in the brackets will strongly influence universal and is rather far from that the calculated value of dose Dj,x only described by relation (4). The calcula- for those populated points for which 131 jx, tion with model (5) does not give a good mean contamination density of I - 131 agreement with empirically found values considerably exceeds the mean x for either. 131 the area. Meanwhile, on a whole, it can Table 6 includes characteristics of be said that in the zero approximation correlation relations between internal the internal thyroid dose in the popula- thyroid doses and measurements of 131I tion of specific populated points is soil contamination density available for primarily determined by the mean charac- some areas. The performed analysis has teristic of radioactive contamination of permitted presenting all data in the the considered areas, and this can be following equivalent forms: explained by fundamental properties of the processes responsible for formation xjx, D 0036.. 0013 of internal doses. jx, 131 131 (6) x jx, 0036..,RRx131 0013 jx, 131 Table 6
70 "Radiation & Risk", 1996, issue 7 Scientific Articles
Statistical characteristics of the relation of mean internal thyroid dose Dj,x and mean contamination density in populated points and areas 31 jx, 137 jx, I - 131 and Cs - 137
n is number of populated points (sample size); jx, 137 is a mean over the sample contamination density of the area; 131 137 jx, jx, r( I- Cs) is the correlation coefficient between 131 and 137 ; r(D -131I) is the correlation coefficient between D and jx, ; j,x j,x 131 r(D -137Cs) is the correlation coefficient between D and jx, ; j,x j,x 137 A is a free term of the equation of linear regression between D and jx, ; j,x j,x 131
Bj,x is the linear regression coefficient.
Administrative districts Estimated parameter Bragin Khoiniki Narovlya Kostyukovi- Krasnopol K+K chi n 42 26 13 11 8 19
jx, 2 9.6 11 8.1 2.5 2.3 2.4 Rx 131 , MBq/m jx, 2 6.5 0.78 9.1 1.7 11 2.3 7.4 1.0 8.9 2.5 8.0 1.2 137 , MBq/m r(131I-137Cs) 0.74 0.73 0.59 0.80 0.98 0.94 131 0.30 0.46 0.17 0.75 0.82 0.80 r(Dj,x- I) 137 0.38 0.44 0.006 0.60 0.79 0.72 r(Dj,x- Cs) 340 400 390 130 120 130 Aj,x, mGy 12 59 10 4.3 0.2 4.9 12 4 10 3.2 10 2.2 Bj,x, mGy/(MBq /m2)
- K+K is combined data on Krasnopol and Kostyukovichi districts.
3. Justification of empirical relations thyroid exposure in rural populated with features of phenomena and processes points is due to radioiodine intake with responsible for formation of internal milk, i.e. is directly related to con- irradiation tamination of pasture grass and to some extent, of soil which gets into the The fact that fundamental natural grazing cows. The proportion of radioio- processes are underlying the empirical dine deposited on the grass surface de- relations (6), (7) can be illustrated by pends on properties of grass itself and the characteristics of “ dry” and on chemical properties of compounds in “ wet” depositions of radionuclides. which iodine was incorporated in the ra- For this purpose one can consider a hy- dioactive cloud. This may lead to a cer- pothetical territory with the number of tain spread in the mean intake of ra- populated points sufficient for consid- dioiodine in different populated points eration of statistical regularities. On of the considered area. It should be the other hand, let us suppose that this pointed out that the Chernobyl accident area is relatively small in size, and occurred at the beginning of grazing hence it can be realistically assumed season when the density of grass mass that the integral of surface 131I concen- per unit pasture area was far from equi- tration in each populated point resulted librium values and the total density of from the passing radioactive cloud is “ dry” radioactive depositions did not practically the same. differ significantly from soil contami- It is obvious that the inhalation in- nation density. The value of deposition take of radioiodine averaged for each density grew sharply in case of local age group should be almost identical in rainfall and other local processes re- all populated points of the considered ferred to as “ wet” depositions (fogs, area. The main component of the internal hew). As a result, the contamination 71 "Radiation & Risk", 1996, issue 7 Scientific Articles level could increase by dozens of times, The considerations presented in the while the amount of radioiodine on the previous section make us even more to grass could remain virtually the same as believe that we have chosen the right with dry depositions [29]. It is clear approach to creating a simple workable that the absorbed dose D of internal model for reconstruction of internal thyroid exposure in the same populated thyroid doses in rural population of point could be almost the same as in an- those contaminated areas for which re- other one, in which there was no rain sults of direct measurements of radioio- and the ratio D/ 131 (where 131 is density dine content in thyroid are not avail- of soil contamination with iodine) dif- able. There is good reason to refer the fered for such a point by dozens of model presented by formula (6) and its times too. equivalent (7) to semiempirical, believ- ing that it can be applied to all con- Figure 1 shows the ratio D/ 131 as a taminated areas in Russia and Belarus. function of deposition density 131 cal- culated in accordance with the model In essence, the question needs to be an- ECOSIS-87 [30] (curve 1) under the as- swered: does the semiempirical model sumption of “ dry” and “ wet” deposi- provide more accurate estimates of thy- tions, with the same 131I concentrations roid doses in the populated points of integral in the surface air layer. In the contaminated areas, on the average, addition to this model, a term was in- as compared with (4) and (5)? troduced related to cow’s intake of the The performance of the above three radionuclide with soil [20] (it is as- models is convenient to be compared with sumed that the cow eats 30 kg/day of dimensionless quantities - ratios of em- fresh pasture grass, taking in 1 kg/day pirical values of dose Dj,x found based of soil). Also, a variant of the coeffi- on thyroid radiometry and values of Dj,x cient of radioiodine intake with grass, calculated with formulae (4), (5) and corresponding to the conditions of CIS (7), (8). countries [31] (curve 2) has been intro- For practical calculations by formu- lae (7, 8) an important simplifying as- duced. With the increase in 131 the ra- sumption has to be made: with the re- tio D/ 131 is decreasing and tends to limiting values which (in a wide spec- quired data missing it is assumed that trum of adopted characteristics of pas- for each j-th populated point considered ture grass) lie in the range as part of the area X, the ratio Rj,x is
equal and equals a mean Rx assigned to (1.1 1.8)10-8 Gym2/Bq = area X. Then formula (7) is reduced to = 0.011 0.018 mGym2/kBk. jx, DR0036.(. x 1 04 137 ). (8) As can be seen this range includes jx, x 137 x the value 0.0135 mGym2/kBq accepted in 137 formula (6) after generalising empirical data. The values of the proportionality co-
efficient Kx (formula (4)) for each area X, given sufficient amount of data (D , 4. About applicability of developed j,x jx, semiempirical model to the conditions of 137 ) can be determined by the least the areas contaminated after the Cherno- square method by the formula: byl accident
72 "Radiation & Risk", 1996, issue 7 Scientific Articles
2 131 Fig. 1. Dependence of D/ 131 (ordinate axis), Gy m /Bq on I deposition density - 131 (abscissa axis, relative units) built based on calculation by ECOSIS-87 model [30] for “ dry” and “ wet” depositions. 1 - calculation by ECOSIS-87 model without modifications; 2 - calculation by ECOSIS-87 model with allowance for the coefficient of radioiodine grass intake corresponding to CIS conditions.
jx, The results of comparison of calcula- D jx, 137 tions by different models with empirical K j . (9) x ()jx, 2 values, i.e. doses estimated from thy- 137 roid radiometry data are shown in Table j 7. The data of this table account for the spread in ratios of empirical values Yet, this approach does not work for to doses calculated by different model those areas X for which values of D j,x s- formulae (4), (5), (7) or (8). are not available and for which the It should be noted that in calcula- model is actually designed. In this tion by formulae (7) or (8) for the case, there is the only solution: to above mentioned areas of Russia it was take a certain area X as a reference 0 taken that: R = 67 for Zhizdra district, one and after determination of the pro- x R = 60 for Ulyanovo district and R = 26 portionality coefficient K for it from x x x0 for Khvostovici district. For Bragin formula (9) it derive the value of the district of Gomel region, Kostyukovichi coefficient K from the relation: x and Krasnopol districts of Mogilev re- gion the values of R were taken to be R x x. (10) 29, 10 and 8.9, respectively. KKxx0 x Rx0 If, preserving values of 137 given in Table 4, the adopted values of ratios R As a reference area we took are determined more precisely with ac- Kostyukovichi district of Mogilev region tual data (for example, results of 129I in Belarus, for which the proportional- measurements in soil samples), most ity coefficient K calculated by formula x0 probably, a conclusion will have to be 2 (9) appeared to be 0.21 mGym /kBq. made concerning correction of initial values of individual doses of Class 1. 73 "Radiation & Risk", 1996, issue 7 Scientific Articles
Anyway, even today two important factors later time of starting the grazing sea- become obvious which should be taken son and significant depositions of 131I into account during the second iteration at later dates, for example, as was reg- of thyroid dose reconstruction: possible istered in Obninsk, Kaluga region [32].
74 "Radiation & Risk", 1996, issue 7 Scientific Articles
Table 7 Characteristics of spreads of ratio of empirical values of mean internal thyroid
doses Di and doses Dð calculated using different models considered for some adminis- trative districts on the contaminated territories of Belarus and Russia
Characteristics Districts of Belarus1 Districts of Russia2
x 2 330 250 260 120 170 89 137 , kBq/m 2 0.59 0.21 0.19 1.4 1.3 0.54 Kx, mGy m /kBq Mean geometric value of ratio
Di/Dð: Equation (5) 1.9 2.7 2.5 2.0 3.2 1.1 Equation (4) 1.5 26 22 7.7 13 1.6 Model developed in this work - (7, 8) 1.2 0.91 0.98 0.99 0.84 0.87 Standard geometric deviation
of ratio Di/Dð from 1: Equation (5) 3.6 1.6 2.9 3.0 2.8 2.6 Equation (4) 15 2.0 3.6 27 23 8.4 Model developed in this work - (7, 8) 1.7 1.4 1.6 1.5 1.4 1.5
1 - Gomel region, outside the 30-km zone: 1 - Bragin, Mogilev region, 2 Kostyukovi- chi, 3 - Krasnopol; 2 - Kaluga region of Russia: 1 - Zhizdra, 2 - Ulyanovo, 3 - Khvastovichi.
Figures 2 and 3 illustrate variations justment - a correction factor which is in the ratio of empirical values of not necessarily related to abnormally doses and values calculated by different high values of ratio 131/ 137. The neces- models. As is seen from these figures sity of using such an adjustment is also and Table 7 the proposed semiempirical dictated by some systematic factors model (7, 8) certainly gives a better which influenced Class 1 data for these agreement of calculation results and em- areas. pirical values as compared with both First, for these areas the kinetics models (4) and (5). Th pooled body of of 131I may be essentially different from ratios of empirical to calculated values that assumed in the first calculations. for more than 300 populated points of Second, as can be seen from the for- the contaminated areas in Belarus and mal analysis of formula (7) the value Russia, with calculations by the semiem- x , a mean 137Cs deposition density on pirical model is satisfactorily de- 137 area X, may not have been determined scribed by the lognormal function with correctly and the boundaries of this median of 0.73 and standard geometrical area may be at variance with boundaries deviation of 1.8. So, even today it can of administrative districts. The values be acknowledged that the developed of jx, themselves are not completely model, on a whole, have a good applica- 137 bility. Of course, both the model itself identical and the physical meaning of and methods for implementing it in prac- these values should be understood when tice should be improved in future. using them in the developed model. It would be appropriate to discuss As to obtaining additional results the above mentioned issue of large val- required for refining the model and based on measurements there are only two ues of parameter Rx for the contaminated areas of Kaluga region which appear to options: a more detailed information on 131 137 be accepted for matching our semiempiri- deposition of I and Cs. The task of a 137 cal model (7, 8) with empirical values more precise determination of Cs depo- sition density is relatively simple. It of doses Dj,x. A similar situation is ob- served for Rechitsky and Loevsky dis- is more difficult methodologically and tricts of Belarus. In fact we had to in- more costly to solve the other problem 131 troduce for these areas a systematic ad- of I depositions using the only method 75 "Radiation & Risk", 1996, issue 7 Scientific Articles suitable for this - measurement of the byl origin. content of long-lived 129I of the Cherno-
Fig. 2. Ratio of K (ordinate axis) of empirical values of internal thyroid doses
(De) and estimates of doses (Dð) by semiempirical model (7, 8). 137 x 2 Abscissa axis - Cs soil contamination density - 137 , kBq/m . Circles - data for Bragin district of Gomel region; rectangulars - for Krasnopol district of Mogilev region of Belarus.
76 "Radiation & Risk", 1996, issue 7 Scientific Articles
Fig. 3. Ratio of K (ordinate axis) of empirical values of internal thyroid doses
(De) and estimates of doses (Dð) by the proportional model (formula 4). 137 x 2 Abscissa axis - Cs soil contamination density - 137 , kBq/m . Circles - data for Bragin district of Gomel region; rectangular - for Krasnopol district of Mogilev region of Belarus.
A draft methodology has been prepared cancers due to internal exposure to io- describing the procedure of calculation dine radionuclides for different age of internal thyroid doses based on de- groups. terminations of 129I in the area of in- It should be pointed out that the terest. The formula to relate dose Dj,x values of collective doses in Table 8 of internal thyroid exposure of adults are somewhat different from estimates in the j-th populated point in area X published earlier for Kaluga and Bryansk 129 jx, regions based on results of direct meas- using data on I depositions 129 can be easily derived from formula (9) based on urements [3, 8, 13]. This is because the the initial ratio of activities of 131I model discussed in this paper uses, as and 129I in the reactor prior to the ac- was mentions, a large volume of initial cident, which according to recommenda- data for different regions (about 160 tions [32] are taken to be (5.0 thousand measurements) and naturally 1.5)10 7: smoothes possible systematic differences associated with calculation of doses in specific regions. Possible sources of such discrepancies are discussed in sec- De (.18 xjx 06 . ,. ) 0 086 t, Gy, jx,129 129 tion 4. (11 Calculations of expected number of ) thyroid cancers during the whole life since the exposure time are made based on the following age and sex dependen- where the mean deposition densities cies of the radiation risk coefficient 129 jx, of I in the j-th populated point 129 [33]: and area X x are expressed in Bq/m2; - the annual risk of thyroid cancer 129 at the age to 18 years is 2.5 cases per the exponential factor provides for 131 129 10000 persons-Gy, given external acute change in ratio I/ I in time t (day) X-ray or -, -irradiation, the radio- after the reactor explosion prior to the sensitivity of adults being lower by a effective ” moment” of radioiodine factor of two than in children and ado- depositions on area X. lescents and efficiency of internal 131I Therefore, by formula (11) two major exposure is lower by a factor of three problems should be solved: 1 - the val- than in the indicated cases of acute ex- ues x and jx, need to be determined 129 129 ternal exposure; with a required accuracy and 2 - effec- - rediosensitivity of female popula- tive value of time t should be deter- tion is twice as high as that of male; mined. The first problem, in fact, is - the probability of annual manifes- the base for optimum design of direct tation of radiation-induced thyroid can- 129 measurements of I in the environment cers is approximately the same for the in conjunction with methods of extrapo- whole remaining life period after a 137 lation-interpolation of data on Cs minimum five years latent period of the deposition density. disease development. It should be borne in mind that addi- 5. Estimation of mean and collective tional number of radiogenic thyroid can- doses cers can result from exposure of a spe- cific organ to external -irradiation Table 8 contains mean and collective (and due to internal irradiation with thyroid doses calculated with the de- cesium radionuclides). We have estimated scribed semiempirical model for popula- the value of additional collective dose tion of different regions of Russia liv- of thyroid exposure due to external - ing in the areas with 137Cs soil contami- irradiation. This estimate is for the nation density more than 3.7 kBq/m2. It dose accumulated for 9 years after the also includes data on expected thyroid accident, i.e. April 1995. For the con- 77 "Radiation & Risk", 1996, issue 7 Scientific Articles taminated areas of eight regions of Rus- in 442 adults living in 23 populated sia indicated in Table 2 this value is points of five districts of Belarus with 25.9103 man-Sv, among them for Bryansk 137Cs soil contamination density from 220 region 11103 man-Sv, respectively. This to 766 kBq/km2 [35, 36] and in uncon- can lead to additional 77 cases of ra- taminated areas of two districts of diogenic thyroid cancers (of them 65 - Kaluga region. The results of measure- for persons younger than 18 at the expo- ments were adjusted for each individual sure time). In Bryansk region one can for contribution of natural background expect 33 additional cancer cases, of exposure during life time to the time of them 28 in persons before 18 years at tooth extraction. This contribution (by the exposure time. It should be remem- EPR-measurements of tooth enamel in bered that the exposure dose accumulated population of uncontaminated areas) is in the whole time period after the acci- (0.12 0.02)10-2 Sv/year. Besides, ac- dent can exceed the dose accumulated in count was taken of the adjustment for 9 years after the accident. Correspond- background signal due to the method used ingly, the additional number of cancers for EPR-dosimetry. This adjustment es- expected due to this can exceed the tablished based on results of interna- above estimates. tional intercalibration is (7.5 0.5) The estimate of additional external 10-2 Sv [37]. As a result, a correlation thyroid dose accumulated over 9 years has been derived between dose accumu- ext has been derived using the data obtained lated for 9 years since the accident D9 by EPR-dosimetry with tooth enamel [34]. and 137Cs soil contamination density (the In doing this use was made of results of correlation coefficient is 0.82): EPR-dosimetry of samples of tooth enamel
Table 8 Thyroid doses in different regions of RF and estimated expected number of thyroid cancers due to internal exposure of thyroid to iodine radionuclides following the Chernobyl accident
Contamination Expected radiogenic density x thyroid cancers by 137 , range Population,
all cont. areas 15 2 17 Ryazan’ 9.22 3.7 - 37 110.0***) 26.6 27.1 7 1 8 37- 185 182.0 64.4 34.3 16 3 19 all cont. areas 23 4 27 Leningrad 0.544 3.7 - 37 10.0***) 29.2 24.0 1 0 1 37- 185 19.5 49.9 27.9 1 0 1 all cont. areas 2 2 Total 233.734 592 103 695
*)-rounded off to integral numbers; **)-approximate estimate of the population taking into account regional centres; ***)-approximate estimate of the population.
tion of mean 137Cs contamination of dif- ext 5 D (.676 08 .) 10 , 3 ,(12) ferent areas of the region and the value 9 137 B of mean thyroid dose for the same areas. 137 where 137 is Cs soil contamination The thyroid doses calculated with the density in a populated point, kBq/m2. described semiempirical model are given It should be said that the above ex- for the adult population, doses for ternal radiation dose may be an overes- other age categories can be estimated timation by a factor of 1.5, considering using the relations from work [27]. the factor of “ hardness of tooth detec- Data of Table 9 demonstrate an in- tor” due to the input from scattered crease in frequency of detected thyroid radiation (estimation of this factor can cancers per 100 thousand children and be found in [38]). adolescents of this age at exposure time Table 9 demonstrates results of and living in the areas with mean 137Cs analysis of frequency of thyroid cancers soil contamination level in the ranges in children and adolescents detected (3.7-37), (37-185) and above 185 kBq/m2 since 1990 in the Bryansk region (under respectively as a function of thyroid 18 years in April-May 1986) as a func- exposure level.
79 "Radiation & Risk", 1996, issue 7 Scientific Articles
Table 9 Frequency of detected thyroid cancers in children and adolescents from the contaminated areas of Bryansk region depending on exposure level
137 c ( min - max) is mean (minimum - maximum) Cs contamination density of the populated point in which residents were diagnosed thyroid cancers;
Dc (Dmin - Dmax) is mean, minimal and maximum thyroid doses in adults of the popu- lated points in which thyroid cancers were detected;
N<18 is population at the age younger 18 in 1986;
C<18 is number of detected thyroid cancers for persons younger 18;
C<18/N<18 is frequency of detected thyroid cancers for persons younger 18 per 100000 people younger 18.
Measured c D N , C /N , on the c <18 C <18 <18 137 ( min - max), <18 2 (D - D ), thousand case/100000 area, kBq/m kBq/m2 min max mGy *) persons 3.7 - 37 14.4 5.7 (12.6 - 33.7) (3.1 - 13.3) 218.6 26 11.9 37 - 185 83.6 33.3 (50.7 - 137) (20 - 69) 48.9 8 16.3 more than 466 135 185 (295 - 640) (118 - 253) 44.2 13 29.4
* - coefficients for recalculation of absorbed doses in children and adolescents from absorbed doses in adults are presented in [10, 12, 14].
6. Estimation of individual doses the statistical analysis described in works [17, 18]. In order to pass from mean doses to Results of estimation of individual- individualised estimates results of spe- ised absorbed thyroid doses are pre- cial polling were used. The results of sented in Table 10. polling conducted in 1990-1994 include Retrospective estimates of individual data on age, sex of the examined, arri- thyroid doses have been derived for val and departure time, movement after thirty children and adolescents (age at the accidental contamination with indi- exposure time) from forty eight persons cation of addresses (particular details diagnosed thyroid cancer and living on for April-May 1986), information about the contaminated areas of Bryansk region iodine prophilaxis and protection meas- in May-June 1986 [39]. These estimates ures, if any. Also, questions were asked are needed for more accurate determina- concerning milk diet prior to the acci- tion of radiation risk using the “ case- dent, in April-May 1986 and afterwards. control” method of epidemiological Detailed information was obtained on analysis. consumption of both centrally supplied In 14 of 30 cases (47%) the most and home made food, including unskimmed probable values of individual doses were milk, sour milk, milk soups, porridge. in the range from 200 to 2700 mGy and in In case of pregnancy and breast feeding the rest 53% cases - 50mGy and less. 6 features of feeding infants were speci- children were administered stable iodine fied. The result of individual recon- after 10 May, and 12 - underwent multi- struction of doses of thyroid exposure ple additional X-ray examinations. to iodine radionuclides is the value of Within 85% confidence interval the mini- most probable individual dose with indi- mum values of reconstructed individual cation of probabilities of upper and doses were about 0.33 of the most prob- lower bounds of individual dose. The able value and the maximum values - statistical characteristics of individ- about 1.6 of the most probable value. ual dose distributions are obtained from 80 "Radiation & Risk", 1996, issue 7 Scientific Articles
It is pertinent to note that the not diagnosed thyroid cancer is differ- typical distribution of individual doses ent - for most children absorbed thyroid for the total population of children doses are below 200 mGy and a smaller living in the contaminated areas, but part of it - more than 200 mGy.
81 "Radiation & Risk", 1996, issue 7 Scientific Articles
Table 10 Results of reconstruction of individual thyroid doses from iodine radionuclides for children and adolescents of Bryansk region diagnosed thyroid cancer
S is patient sex; Y is year when thyroid cancer was diagnosed; 137 137 is mean Cs contamination density for a point of residence of a patient in May - June 1986;
Dpr is most probable value of thyroid absorbed dose;
Ai is attribute of iodine prophylaxis: “ +” - yes; “ -” - no; M is additional exposure due to medical procedures.
Birth Area of residence 137, Dpr, N Patient S 2 A ÌY date in May - June 1986 kBq/m mGy i 1 B.I.A. f 10.03.79. Novozybkov 573 1400 + - 1994 2 Zh.A.P. m 26.06.83. Novozybkov 573 900 ? - 1994 3 S.A.P. f 03.12.85. Novozybkov 573 2400 + - 1994 4 B.E.A. f 12.09.84. Novozybkov 340 900 ? - 1993 5 Zh.A.P. m 26.04.83. Novozybkov 718 800 + - 1994 6 P.E.V. f 29.04.78. Novozybkov 729 400 + - 1994 7 K.I.V. f 01.11.84. Novozybkov 340 1600 + - 1993 8 Zh.A.V. m 04.07.72. Klintsy 148 200 - - 1991 9 N.N.N. f 28.06.84. Klintsy 104 1000 - + 1990 10 Ch.O.Yu. f 12.09.85. Klintsy 85.1 700 - - 1992 11 M.A.V. m 09.05.84. Klintsy 104 1000 - - 1993 12 B.M.A. f 18.02.86. Klimovo 141 200 - - 1992 13 L.Yu.B. f 08.07.86. Starodub 70.3 <20 - + 1992 14 G.E.M. f 03.05.68. Dyat’kovo 26.6 20 - + 1993 15 K.V.I. m 13.09.71. Surazh 10.7 <10 - + 1990 16 K.S.V. f 07.05.68. Trubchevsk 55.5 20 - + 1992 17 L.O.V. m 25.10.76. Vygonichi 24.8 20 - + 1994 18 V.E.V. f 08.10.70. Karachev 20.7 <10 - + 1992 19 A.E.Yu. f 26.11.73. Karachev 20.7 <10 + + 1993 20 B.S.A. m 28.01.77. Suzem 18.5 <10 - + 1990 21 N.A.V. m 02.09.77. Komarichi 32.6 <10 - + 1993 22 Z.O.N. f 15.08.77. Seltso 9.25 50 - - 1994 23 P.O.G. f 07.09.78. Navlino 40.7 35 - - 1994 24 B.A.A. m 14.08.71. Bryansk 12.6 <10 - - 1992 25 K.A.A. m 29.11.73. Bryansk 12.6 <10 - + 1992 26 E.(Shch)T. f 28.07.78. Bryansk 12.6 20 - - 1993 P. 27 Ts.N.Yu. f 29.09.73. Bryansk 12.6 10 - + 1991 28 Yu.A.L. m 12.05.78. Bryansk 12.6 <10 - - 1994 29 Ch.I.K. f 15.02.86. Novozybkov 529 2700 - - 1994 30 K.S.A. f 03.06.73. Trubchevsk 17.4 10 - + 1994
Conclusion given missing data of dosimetric survey of thyroid. These estimates are consid- 1. The developed semi-empirical model ered as results of the first iteration of extrapolation-interpolation type has in development of practical methods of some important advantages compared to thyroid dose reconstruction. other models of such type and allows es- 3. Using the proposed model, collec- timation of internal thyroid dose with tive and mean doses have been calculated the accuracy characterized by standard for different regions of Russia and pre- geometric deviation of about 1.8. dictions were made for radiogenic thy- 2. The available data on individual roid cancers. In conjunction with data internal thyroid dose estimated based on of individual questionnaires the model direct measurements, which still need to allows estimation of individualized be refined have made it possible to com- doses for persons diagnosed thyroid can- pare average thyroid exposure levels cer. Such estimates have been derived with average contamination levels and for 30 diagnosed thyroid cases. make generalizatons to derive retrospec- 4. Work is now under way to continue tive estimates of thyroid doses for the retrospective estimates of individual population of the contaminated areas, thyroid doses for persons with diagnosed
82 "Radiation & Risk", 1996, issue 7 Scientific Articles thyroid pathology. Special attention is contaminated areas of Republic of Be- given to factors which can result in ad- larus. Bulletin of USSR AMS. - 1992. ditional adjustment of exposure dose - N 2. - P. 35-43 (in Russian). values: rainfall or its absence in popu- 7. Romanenko A.E., Likhtarev I.A., Shan- lated points in late April-early May dala N.K. et al. Hygenic estimation 1986, the beginning of grazing season in of thyroid doses in the population of this area in 1986, individual protection UkrSSR after the Chernobyl accident. measures or their absence in the acute Bulletin of USSR AMS. - 1991. - N 8. period after the accident, pathology of - P. 44-47 (in Russian). thyroid influencing its weight and io- 8. Zvonova I.A., Balonov M.I. Radioio- dine metabolism intensity etc. Soil sam- dine dosimetry and prediction of con- ples are being collected and saved to be sequences of thyroid exposure of the analysed for long-lived 129I of the Cher- russian population following the nobyl origin as an indicator of 131I de- Chernobyl accident. The Chernobyl pa- posited on these areas in 1986. Consid- pers, vol. 1. - Richland, Washington, eration of these factors can diminish 1993. - P. 71-126. the range of uncertainties for retro- 9. Likhtarev I.A., Shandala N.K., Gulko spective estimates of mean and individ- G.M. et al. Ukrainian thyroid doses ual doses. after the Chernobyl accident. Health Phys. - 1993. - N. 64 (6). - P. 594- 599. References 10.Gavrilin Yu.I. Khrushch V.T., Shinkarev S.M. Reconstruction of in- 1. Okeanov A.E., Dimidchik E.P., Ankudo- ternal thyroid dose for the popula- vich M.A. et al. Thyroid cancer in tion of the areas of Republic of Be- Republic of Belarus before and after larus contaminated after the Cherno- the Chernobyl accident. - Document of byl accident. (State of work and im- WHO/EOS/94.26. - Geneva, 1994 (in portant future tasks). Abstracts of Russian). presentations at the 3-d republic. 2. Tsyb A.F., Parshkov E.M., Shakhtarin conference, Gomel, 15-17 April 1992. V.V. et al. Characterization of thy- - Part 1. - P. 75-78 (in Russian). roid pathology in children and ado- 11.Gavrilin Yu.I., Khrushch V.T., lescents of the most contaminated ar- Shinkarev S.M. et al. Exposure of eas of Bryansk region of Russia after thyroid with radioiodine in the popu- the Chernobyl accident. - Document of lation of Belarus as a result of the WHO/EOS/94.15. -Geneva, 1994 (in Rus- Chernobyl accident. Papers of confer- sian). ence “ Nuclear energy and human 3. Stepanenko V.F., Tsyb A.F., Matveenko safety” . - Nizhny Novgorod, part 1, E.G. et al. Thyroid exposure doses p. 222-224 (in Russian). among the population of contaminated 12.Tsyb A.F., StepanenkoV.F., Gavrilin territories: methodology and results Yu.I. et al. Problems of retrospec- of measurements. Deutsch - russische tive estimation of exposure doses of Konferenz fur Messprogramm in population as a result of the Cherno- Russland. - Moskau, 1992. - S. 53 - byl accident: features of formation, 59. structure and exposure levels from 4. Khrushch V.T., Gavrilin Yu.I., Kon- direct measurements. Part 1: Doses of stantinov Yu.O. et al. Characteriza- internal exposure of thyroid. - Docu- tion of inhalation intake of radionu- ment of WHO/EOS/94.14. - Geneva, 1994 clides. Medical aspects of the Cher- (in Russian). nobyl accident. Proceedings of scien- 13.Tsyb A.F., Stepanenko V.F., Matveenko tific conference on 11-13 May 1988, E.G. et al. Structure and thyroid ex- Kiev. - Kiev: Zdorov’ya, 1988. - P. posure levels in the population of 76-87 (in Russian). the contaminated areas of the Kaluga 5. Exposure resulting from the Chernobyl region. Radiation and Risk. - 1994. - accident. Proceedings of the 37th Issue 4. - P. 129-135 (in Russian). session of UN SC. -Vienna, 6-17 June 14.Aref’eva Z.S., Bad’in V.I., Gavrilin 1988 (in Russian). Yu.I. et al. Guidelines on thyroid 6. Gavrilin Yu.I., Gordeev K.I., Ivanov dose estimation with human intake of V.K. et al. Specific features and re- radioactive isotopes of iodine. Ed. sults of determinations of internal thyroid doses for the population of 83 "Radiation & Risk", 1996, issue 7 Scientific Articles
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contaminated after the Chernobyl ac- enamel EPR-spectroscopy. Proc. of 4- cident. - Report of IEM SPA “ Ty- th International Symposium on ESR Do- phoon” of USSR Roshydromet, N 7028, simetry and Applications. GSF, Obninsk, 1990, 267 p. (in Russian). Munchen/Neuherberg, May 15-19, 1995. 33.National Council on Radiation Protec- - P. 214. tion and Measurements, Induction of 37.Chumak V., Baran N., Bugai A. et. al. thyroid cancer by ionizing radiation, The first international intercompari- Bethesda, MD: NCRP; NCRP Report N 80, son of EPR-Dosimetry with teeth: 1985. first results. Ibid p.197. 34.Ivannikov A.I., Skvortsov V.G., Ste- 38.StepanenkoV.F., Skvortzov V.G., Kon- panenko V.F. et al. Potential of EPR- drashov A.E. et al. ESR and TL do- dosimetry by tooth enamel for recon- simetry Systems: comparative measure- struction of external doses in liqui- ments for human phantom. Ibid. p. dators of the Chernobyl accident. 250. Physical Medicine. - 1992. - V. 1, 39.Parshkov E.M., Tsyb A.F., Stepanenko Issue 3-4 (in Russian). V.F. Analysis of thyroid pathology 35.Skvortsov V.G., Ivannikov A.I., Tsyb and thyroid cancers in children and A.F. et al. Results of surveys by adolescents affected by a iodine im- EPR-dosimetry for the population of pact as a result of the Chernobyl contaminated South-Western areas of disaster. Radiological, medical and Bryansk region. - Document of WHO/EOS socio-economic consequences of the /94.12. - Geneva, 1994 (in Russian). Chernobyl accident. Rehabilitation of 36.Skvortzov V., Ivannikov A., Ste- territories and population. Abstracts panenko V. et al. Regularities in of presentations at conference on 21- distribution of individual doses for 25 May 1995, Golitsino, 1995. - Mos- population of radioactive contami- cow, 1995. - P. 57 (in Russian). nated territories measured by tooth
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