Estimating individual thyroid doses for a case-control study of childhood thyroid cancer in Bryansk Oblast, Russia

Following the Chernobyl accident, radioactive fission products, including (131)I and (137)Cs, were deposited in Bryansk Oblast in Russia. Intakes of radioiodines, mainly (131)I in milk, were the principal sources of radiation doses to thyroids of residents of the contaminated areas, but those radionuclides decayed before detailed contamination surveys could be performed. As a result, (137)Cs deposition density is the primary measure of the contamination due to the accident and there are relatively few measurements of the ratio of (131)I to (137)Cs in vegetation or soil samples from this area. Although many measurements of radiation emitted from the necks of residents were performed and used to estimate thyroidal (131)I activities and thyroid doses, such data are not available for all subjects. The semi-empirical model was selected to provide a dose calculation method to be applied uniformly to cases and controls in the study. The model was developed using dose estimates from direct measurements of (131)I in adult thyroids, and relates settlement average thyroid doses to (137)Cs contamination levels and ratios of (131)I to (137)Cs. This model is useful for areas where thyroid monitoring was not performed and can be used to estimate doses to exposed individuals. For application to children in this study, adjustment factors are used to address differences in age-dependent intake rates and thyroid dosimetry. Other individual dietary factors and sources (private/public) of milk consumed are reflected in the dose estimates. Countermeasures that reduced thyroid dose, such as cessation of milk consumption and intake of stable iodine, are also considered for each subject. The necessary personal information of subjects was obtained by interview, most frequently of their mothers, using a questionnaire developed for the study. Uncertainties in thyroid dose, estimated using Monte Carlo techniques, are presented for reference conditions. Thyroid dose estimates for individual children made using the semi-empirical model and questionnaire data compare reasonably well with dose estimates made for 19 children whose thyroid burdens of (131)I were measured from May to June 1986.     

Contribution of different foodstuffs to the internal exposure of rural inhabitants in Russia after the Chernobyl accident

In a large village, Veprin of the Bryansk region of Russia contaminated with radionuclides as a result of the Chernobyl accident, 137Cs concentration in food products of agricultural produce and natural origin was regularly measured, local inhabitants were polled on the composition of their diet, and the 137Cs content in their bodies was measured at the same time. These results were used as the basis for calculation of annual effective doses of internal exposure to inhabitants and for reconstruction of the dose during the entire period after the accident (1986-1996). The efficiency of countermeasures performed for reduction of the internal dose was assessed. The internal dose in inhabitants during the 10 years after the accident was shown to be reduced by countermeasures by a factor of 2, namely down to 35 mSv instead of the expected 70 mSv. The dose of external gamma radiation during the same time period is close to the obtained dose of internal exposure. The presence of peat and water-meadow soils in the vicinity of this village that are characterised by high transfer factors for radionuclides from soil to vegetation causes a high contribution of internal exposure to the total dose of population exposure. The contribution of natural products to the internal dose increased from 6% in 1987 increased to 25% in 1996. The individual content of 137Cs in the body of inhabitants reliably correlates with consumption of milk in the initial period after the accident and with consumption of forest mushrooms in the subsequent period.     

Influence of radionuclides distributed in the whole body on the thyroid dose estimates obtained from direct thyroid measurements made in Belarus after the Chernobyl accident

Thyroid dose reconstruction is most accurate when using the results of direct thyroid measurements, in which gamma radiation emitted by radionuclides present in the thyroid and in the remainder of the body is recorded by means of a radiation detector positioned against the neck. A large number of such measurements were performed in Belarus in May-June 1986. Owing to the short half-life of 131I and to the intake and accumulation of caesium radioisotopes (mainly 134Cs and 137Cs) in the body, the thyroid doses derived from thyroid measurements made after the beginning of June 1986 have so far been often considered to be unreliable. To evaluate the influence of the caesium radioisotopes to the signal recorded by an instrument performing measurement of 131I activity in the thyroid, a Monte Carlo method was used to calculate the calibration factors of that instrument. These calculations were made for males of six reference ages: newborn, 1, 5, 10 and 15 years old, and adult. The calibration factors were combined with estimated time-dependent intake functions for 131I and caesium radioisotopes. The fractions of the instrument indications that were due to 131I in thyroid were thus estimated as a function of the age of the subject that was measured and of the time elapsed since the accident. Using this information when processing the thyroid measurements made in May 1986 would improve the accuracy of the thyroid dose estimates, and may make it possible to use a larger proportion of the thyroid measurements made in June 1986.     

Contributions of short-lived radioiodines to thyroid doses received by evacuees from the Chernobyl area estimated using early in vivo activity measurements

A series of in vivo gamma spectrometric measurements of 65 people evacuated from Pripyat 1.5 days after the Chernobyl Nuclear Power Plant Unit 4 explosion was performed in St Petersburg, Russia, as early as 30 April 1986. The historical spectra and interviews were recently processed and the results used for thyroid dose estimation. Activities of 131I in thyroid and 132Te in lungs were determined easily; for estimation of 132I and 133I activities in thyroid, sophisticated methods of spectral processing were developed. According to thyroid measurement data, the mean ratio of 133I/131I activities (at the time of the accident) inhaled by residents of Pripyat was 2.0. The mean ratio of thyroid dose from 133I inhalation to that caused by 131I amounts to 0.3, which confirms the accuracy of dose estimates based on the evolution of the Chernobyl accident. The mean ratio of 132I activity in thyroid to that of 132Te in lungs was assessed from the human measurement data to be 0.2, which is in reasonable agreement with the metabolic properties of these radionuclides. The mean ratio of thyroid dose from 132I originating from 132Te deposited in lungs to the dose caused by 131I was 0.13 +/- 0.02 for Pripyat residents who did not take KI pills and 0.9 +/- 0.1 for persons who took KI pills. Thus, the contribution of short-lived radioiodines to total thyroid dose of Pripyat residents, which was on average 30% for persons who did not use stable iodine prophylaxis, and about 50% for persons who took KI pills on 26-27 April, should be accounted for in the assessment of thyroid health effects.     

Internal exposure monitoring of 131I-radiopharmaceutical production workers in Iran

The programme and results of internal exposure monitoring of four individuals who have worked for 7 to 10 years in a 131I radiopharmaceutical production laboratory are described. The monitoring has been carried out using an in vivo thyroid measurement technique. The maximum and minimum average annual intakes of 131I received by the laboratory workers was 536 and 79 kBq, respectively. The highest estimated annual intake of 131I, incurred by one of the workers in a single year, was nearly 3.8 MBq. The mean values of the annual intakes by all the workers in their working periods in the laboratory was below the intake limits recommended by the ICRP.     

Radiation-epidemiological studies of thyroid cancer incidence in Russia after the Chernobyl accident (estimation of radiation risks, 1991-2008 follow-up period)

This study presents an analysis of the thyroid cancer incidence in the population of the most contaminated territories of Bryansk, Kaluga, Oryol and Tula oblasts affected by the Chernobyl accident. The follow-up period is 1991-2008, and the cohort size is 309 130 people. For that period 978 thyroid cancer cases were detected. The excess relative risk per 1 Gy (ERR/Gy) is found to be statistically significant for children and adolescents (0-17 y of age) at the time of the Chernobyl accident (ERR/Gy=3.22; 95 % confidence interval (1.56; 5.81). In boys, the ERR/Gy was higher than in girls -6.54 and 2.24, respectively. A statistically significant decrease in ERR/Gy with time since exposure, by a factor of 0.37 per 10 y, was observed for the whole cohort and for boys separately, but not for girls. No radiation risks of a thyroid cancer among people of 18 y of age at exposure and older were found.     

Study of a Greek area with enhanced indoor radon concentrations

In this paper the focus is on Arnea Chalkidikis, an area in Greece with granitic geological background and indications of possible elevated radon concentration indoors. Data are reported of indoor radon measurements with etched track detectors and those are used for dosimetric estimations. Moreover, data are reported on soil gas and soil radon concentrations in Arnea, as well as radon and uranium concentrations in water samples. From the measured radon concentrations in water samples the contribution to the overall dose has been calculated. For a period of 1 month, indoor radon and progeny activity has also been monitored in the dwelling that has the maximum indoor radon concentration in Greece. This dwelling is in Arnea and the dose delivered to the inhabitants has been calculated. The mean annual effective dose due to indoor radon was 4.5 mSv and about 11% of this was due to the use of water. Mean soil gas concentration and soil radon concentration were (90 +/- 30) kBq m(-3) (p<0.05) and (30 +/- 5) kBq m(-3) (p<0.05) respectively. Mean uranium concentration of the water samples was (98 +/- 13) mBq l(-1) (p<0.05).     

Uncertainties in thyroid dose reconstruction after Chernobyl

The most significant impact of the Chernobyl accident of 26 April 1986 is the increased incidence of thyroid cancer among Belarusians, Russians and Ukrainians who were exposed as children to radioiodines in fallout resulting from atmospheric releases. The US National Cancer Institute (NCI), in cooperation with the ministries of health of Belarus and Ukraine, is involved in epidemiological studies of thyroid diseases related to the accident. Individual thyroid doses, as well as uncertainties, have been estimated for the members of the cohort studies (approximately 13,000 Ukrainians and 12,000 Belarusians). The cohort subjects, who were selected from the large group of children whose thyroids were monitored for gamma radiation within a few weeks of the accident, provided personal information on their residence history and dietary habits during interviews. Thyroid dose estimates range from 1 mGy to more than 20 Gy. The uncertainties are found to be approximately log-normally distributed, with geometric standard deviations ranging from 1.6 to 5.0. The medians of the geometric standard deviations are 1.7 for the Ukrainian subjects and 2.1 for the Belarusian subjects. The major sources of uncertainty in the thyroid dose estimates are found to be those related to the thyroid mass of the subject and to the estimation of the thyroidal content of 131I at the time of thyroid monitoring.     

Excretion of volatile ¹³¹I from rats following administration of Na¹³¹I or MIBG-¹³¹I

Current practice for radiation protection associated with (131)I therapy mainly focuses on external and internal exposure caused by physical contamination of the hospital staff, other patients and family members. However, if volatile (131)I is excreted by the treated patients, these individuals could also be exposed through inhalation of (131)I. This study quantifies the amount of volatile (131)I excreted by rats after intravenous administration of metaiodobenzylguanidine (MIBG)-(131)I or Na(131)I, the two most common forms of (131)I therapy. The results indicate that in 4 d following administration, the total excretion of volatile (131)I was 0.036 and 0.17 % of the administered activities of MIBG-(131)I and Na(131)I, respectively. As administered activities for (131)I therapy are typically of the order of 1-10 GBq, the overall excretion of volatile (131)I from a patient can be as high as 20 MBq. As a result, a family member can receive up to 0.07 mSv committed effective dose from inhaling the volatile (131)I excreted by the patient.     

Estimated potassium content in Hanford workers

Potassium content in male and female workers at the US Department of Energy Hanford Site was estimated based on measurements made in 2002 of 40K activity in the body. The 40K activity in females ranged from 2.1 to 4.1 kBq with an average of 3.1 +/- 0.02 kBq. The total body potassium (TBK) content in females averaged 98 +/- 0.6 g. The 40K activity in males ranged from 2.8 to 6.6 kBq with an average of 4.2 +/- 0.01 kBq and the average TBK was 136 +/- 0.3 g. The average TBK value for males aged 20-49 y was 140 g. The average TBK values for both genders decreased with age. The average potassium concentrations calculated for the different age ranges for males were 15-25% less than the value (1.9 gK per kg) obtained using the reported ICRP reference potassium and reference weight values. Potassium concentrations were inversely correlated with body-build index, body-mass index and body weight. These correlations could possibly be utilised to help assess the risk for disease. Future work is planned to evaluate whether monitoring of potassium concentrations could be used as a tool for the detection of diabetes and hypertension.     

The problems and state of measurements

  On April 21–25, 2008, the Bauman Moscow State Technical University hosted the 10th All-Russia Conference on “Problems and State of Measurements,” which was dedicated to the 140th anniversary of the Faculty of Machine Industry Technologies. It was attended by representatives of colleges: Lomonosov Moscow State University, Zhukovskii VVIA, MAI and Stankin Moscow State Technical Universities, Goryachkin MGAU, Ural (Ekaterinburg), Orel, Perm, Tula, and Penza State Universities, the Russian Academy for the State Service under the Russian Federation President, the Maimond Classical Academy, the Novomoskowsk Institute of the Mendeleev Russian Chemical Engineering University, Kharkov Electronics National University; and also research institutes in the RAS system: the Keldysh Institute of Applied Mechanics, the Lebedev Physics Institute of the Academy of Sciences, the Trapeznikov Institute of Control Problems, the Institute of Psychology, IMASh and the Blagonravov Nizhnii Novgorod branch of IMASh, and IPMASh (St. Petersburg); the Malaya Therapy Institute (Ukraine) and sectoral institutes: the Astrofizika Scientific and Production Association, Snegirev NITI, VNIIMS, NIIizmereniya, Moscow Institute of Expert Evaluation and Testing, LITMAShDETAL’, and the Omskenergoremont OAO PRP. In this number of the journal and the next one, we present a selection of articles from the conference. We also publish a survey article by the chairman of the organizing committee of the conference, Professor M. I. Kiselev. Translated from Izmeritel’naya Tekhnika, No. 10, pp. 3–5, October, 2008.     

Environmental radioactivity measurements in Greece following the Fukushima Daichi nuclear accident

Since the double disaster of the 9.0 magnitude earthquake and tsunami that affected hundreds of thousands of people and seriously damaged the Fukushima Daichi power plant in Japan on 11 March 2011, traces of radioactive emissions from Fukushima have spread across the entire northern hemisphere. The radioactive isotope of iodine (131)I that was generated by the nuclear accident in Fukushima arrived in Greece on 24 March 2011. Radioactive iodine is present in the air either as gas or bound to particles (aerosols). The maximum (131)I concentrations were measured between 3 and 5 April 2011. In aerosols the maximum (131)I values measured in Southern Greece (Athens) and Northern Greece (Thessaloniki) were 585±70 and 408±61 μΒq m(-3), respectively. (131)I concentrations in gas were about 3.5 times higher than in aerosols. Since 29 April 2011, the (131)I concentration has been below detection limits. Traces of (137)Cs and (134)Cs were also measured in the air filters with an activity ratio of (137)Cs/(134)Cs equal to 1 and (131)I/(137)Cs activity ratio of about 3. Since 16 May 2011, the (137)Cs concentration in air has been determined to be about the same as before the Fukushima accident. Traces of (131)I were also measured in grass and milk. The maximum measured activity of (131)I in sheep milk was about 2 Bq l(-1) which is 5000 times less than that measured in Greece immediately after the Chernobyl accident. The measured activity concentrations of artificial radionuclides in Greece due to the Fukushima release, have been very low, with no impact on human health.     

226Ra, 228Ra and 228Th in scale and sludge samples from the Campos Basin oilfield E&P activities

More than 40 scale and sludge samples from the Campos Basin oilfield were analysed in terms of 226Ra, 228Ra and 228Th. Although the exact origin of the samples was not known, scale samples derived from production pipes and sludge samples from water-oil separation units. Reported values ranged from 0.13 to 331 kBq.kg(-1) for 226Ra, from 0.10 to 245 kBq.kg(-1) for 228Ra and <0.10 to 272 kBq.kg(-1) for 228Th in sludge samples. The concentrations in scales were much more regular than in sludges and ranged from 16.2 to 93.2 kBq.kg(-1) for 226Ra, from 4.0 to 36.9 kBq.kg(-1) for 228Ra and from 4.5 to 18.5 kBq.kg(-1) for 228Th. Based on the Basic Safety Standards recommendations and on the derived results, these activities cannot be regarded as exempted and specific procedures should be designed for their radiological control.     

Uncertainties on the committed equivalent dose to the thyroid as a function of age for different iodine isotopes

This study compares uncertainties of equivalent doses after internal contamination by 125I, 129I or 131I. Uncertainties were calculated using reported distributions of physiological parameters and Monte Carlo simulation. In adults, uncertainties increase from 131I to 125I and 129I with 1% of the population receiving 3.9, 4.0 and 7.2 times the median dose for the respective isotopes. In newborns, these values were 7.5, 12.3 and 19.0 for 131I, 125I and 129I respectively. The ratio of the beta dose delivered to the epithelium versus a homogeneous distributed dose was estimated for different iodine concentrations in colloid, epithelium and interstitium. In adults, for 131I, about 40% of the beta dose was delivered to the epithelial cells, whereas this fraction varied depending on the concentration for 125I and 129I, i.e. 20-30% at a relative epithelial concentration of 20% and 7-14% at a concentration of 3%. Small variations were observed depending on age.     

The Effect of Hydrophobization of Ag-Containing Zeolites on Absorption of CH3131I from the Water Vapor-Air Phase

The effect of hydrophobization of Ag-containing nonmodified and acetylene-modified zeolites with poly(vinyl chloride) (PVC) on sorption characteristics of sorbents with respect to CH₃ ¹³¹I was studied. The PVC coating on the sorbent results in increased absorbtion of CH₃ ¹³¹I from a water vapor-air flow at a humidity of up to approximately 70 vol %; the decontamination factor of approximately 10⁵ is reached. The sorbent modified with PVC retains radioiodine at heating to 300°C and can be proposed for practical purposes.     

Radiation exposure to the population of Europe following the Chernobyl accident

On the occasion of the 20th anniversary of the Chernobyl accident an attempt has been made to evaluate the impact of the Chernobyl accident on the global burden of human cancer in Europe. This required the estimation of radiation doses in each of the 40 European countries. Dose estimation was based on the analysis and compilation of data either published in the scientific literature or provided by local experts. Considerable variability has been observed in exposure levels among the European populations. The average individual doses to the thyroid from the intake of (131)I for children aged 1 y were found to vary from approximately 0.01 mGy in Portugal up to 750 mGy in Gomel Oblast (Belarus). Thyroid doses to adults were consistently lower than the doses received by young children. The average individual effective doses from external exposure and ingestion of long-lived radiocaesium accrued in the period 1986-2005 varied from approximately 0 in Portugal to approximately 10 mSv in Gomel Oblast (Belarus) and Bryansk Oblast (Russia). The uncertainties in the dose estimates were subjectively estimated on the basis of the availability and reliability of the radiation data that were used for dose reconstruction in each country.     

Sorption of CH3131I from Steam-Gas Phase on Modified Ag-Containing Zeolites

Sorption of CH₃ ¹³¹I from the steam-gas phase on Ag-containing zeolites modified with acetylene was studied. The radioiodine adsorption in a column depends on the silver concentration in the sorbent, humidity of the steam-gas flow, and the temperature. The modified sorbents AgX-m containing 30-57% silver efficiently localize CH3I at the humidity up to 80% and sorption temperature from 120 to 195°C. Under these conditions the decontamination factor of a gas flow with respect to CH₃ ¹³¹I at 7.5-cm height of the sorbent bed and a 0.2 s gas-sorbent contact time exceeds 99.99%. The sorption properties of the modified Ag-containing sorbents are better that those of the nonmodified sorbents and known Ag-substituted zeolites.     

Analysis of radon concentration in drinking water in Baoji (China) and the associated health effects

This paper presents the results of radon concentration measurements in drinking water from the municipal water supply system and private wells located in Baoji, China. The measurements were carried out on 69 samples. The mean values of tap water and well water were found to be 12 kBq m(-3) with a maximum of 18 kBq m(-3) and 41 kBq m(-3) with a maximum of 127 kBq m(-3), respectively. The well water samples obtained from different depth-well (water-bearing levels), i.e. shallow well (well depth under 10 m) water, middle well (well depth 10-30 m) water and deep well water, have respective mean values of 24, 34 and 56 kBq m(-3). The contributions of the observed radon concentration in drinking water to indoor radon account for 2.8-13.2% of the mean value of Shaanxi indoor radon concentration and the effective dose to the dweller owing to inhalation of radon emanating from household water is 0.03-0.14 mSv y(-1).     

Effect of Site-Specific Parameters on the Transfer of 137Cs and 90Sr into Freshwater Fishes1,2

The content of ¹³⁷Cs in fallout, fish, and water was measured with the aim to study the role of site-specific parameters on the transfer of ¹³⁷Cs into fishes. The temporal changes of 137Cs and 90Sr in various types of fishes were studied at two sites of Lake Saimaa. The ¹³⁷Cs content in fishes in the Ukonvesi area, which is the north-western part of the lake, was clearly lower than that in the southern parts of the lake, in Ala-Saimaa, although the fallout of ¹³⁷Cs to the Ukonvesi area was somewhat higher than that to Ala-Saimaa. The fallout in 1986 was about 6 kBq m^{- 2} to the Ukonvesi area and about 3 kBq m^{- 2} to the southern parts of the lake. The ¹³⁷Cs content in fishes was the highest in 1988-1989 in Ala-Saimaa, approximately 700 Bq kg^{- 1}, while that in the Ukonvesi area was only about 300 Bq kg^{- 1}, where the values were the highest in 1987. In Ukonvesi the ¹³⁷Cs content in fishes decreased rapidly, being already in 1990 almost at the same level as in 2000. In the southern parts of the lake the decrease in the ¹³⁷Cs content in fishes was much slower. Also the ⁹⁰Sr content in fishes in Ukonvesi was lower than that in Ala-Saimaa. The ¹³⁷Cs content of the water in the Ukonvesi area decreased rapidly, being about 7 Bq m^{- 3} in 1998, while that in the lower areas of the lake was still 15 Bq m^{- 3} in 2000. The ⁹⁰Sr content in water was approximately the same at the both sampling sites (7-8 Bq m^{- 3}). The water chemical parameters, such as potassium, total phosphorus, total nitrogen, chlorophyll a, and electrical conductivity were significantly higher in Ukonvesi than in Ala-Saimaa.     

131I exhalation by patients undergoing therapy of thyroid diseases

In the departments of nuclear medicine, patients are treated with relatively large activities of (131)I for therapeutic purposes. The applied activities are in the range of 200-10 000 MBq. Consequently, individuals situated in the dwellings of the patients dismissed from the hospital are subjected to an external as well as an internal radioiodine exposition. Internal exposition is due to the inhalation of (131)I exhaled by the patients. In this article, the measurements of radioactivity exhaled by patients with various thyroid diseases, treated with (131)I in the department of Nuclear Medicine of the Radiological Centre in Goettingen and in the Hospital of Nuclear Medicine in Wuerzburg are presented. The measurements of activities exhaled by patients were repeated daily, up to 25 d after the treatment. In addition, the residual activities were monitored by measuring the external dose rates, and by measuring the (131)I activity in the urine of these patients. In some cases, the exhaled radioiodine was separated into three fractions: the elemental, the organically bound and the aerosol-bound iodine fraction. On the basis of the proposed measurements, the doses received by the family members of a discharged patient treated with (131)I were estimated by a model calculation.