Dataset Information

Uncertainties in Radiation Doses for a Case-control Study of Thyroid Cancer among Persons Exposed in Childhood to 131 I from Chernobyl Fallout.

ABSTRACT: Uncertainties in thyroid doses due to I intake were evaluated for 2,239 subjects in a case-control study of thyroid cancer following exposure to Chernobyl fallout during childhood and adolescence carried out in contaminated regions of Belarus and Russia. Using new methodological developments that became available recently, a Monte Carlo simulation procedure was applied to calculate 1,000 alternative vectors of thyroid doses due to I intake for the study population of 2,239 subjects accounting for sources of shared and unshared errors. An overall arithmetic mean of the stochastic thyroid doses in the study was estimated to be 0.43 Gy and median dose of 0.16 Gy. The arithmetic mean and median of deterministic doses estimated previously for 1,615 of 2,239 study subjects were 0.48 Gy and 0.20 Gy, respectively. The geometric standard deviation of individual stochastic doses varied from 1.59 to 3.61 with an arithmetic mean of 1.94 and a geometric mean of 1.89 over all subjects of the study. These multiple sets of thyroid doses were used to update radiation-related thyroid cancer risks in the study population exposed to I after the Chernobyl accident.

SUBMITTER: Drozdovitch V

PROVIDER: S-EPMC7728628 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

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Uncertainties in Radiation Doses for a Case-control Study of Thyroid Cancer among Persons Exposed in Childhood to 131 I from Chernobyl Fallout.

Drozdovitch Vladimir V Kesminiene Ausrele A Moissonnier Monika M Veyalkin Ilya I Ostroumova Evgenia E

Health physics 20200801 2

Uncertainties in thyroid doses due to I intake were evaluated for 2,239 subjects in a case-control study of thyroid cancer following exposure to Chernobyl fallout during childhood and adolescence carried out in contaminated regions of Belarus and Russia. Using new methodological developments that became available recently, a Monte Carlo simulation procedure was applied to calculate 1,000 alternative vectors of thyroid doses due to I intake for the study population of 2,239 subjects accounting fo ...[more]

PMID: 33290004

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Project description:Prenatal exposure to external radiation has been linked to growth retardation among atomic bomb survivors in adolescence. It is unclear from previous studies whether in utero exposure to internal radiation such as iodine-131 (I-131), which concentrates in the thyroid gland, has an effect on physical growth. We examined the associations between estimated thyroid gland dose from prenatal exposure to I-131 and self-reported height and weight in a cohort of 2,460 individuals exposed to radioactive fallout from the 1986 Chernobyl nuclear accident [mean I-131 dose = 72 (mGy)] and screened for thyroid diseases in adolescence. Using multivariable linear regression models, we estimated the mean differences in height, weight and body mass index (BMI) per unit increase in dose (100 mGy) in models adjusted for gender, age at examination, type of residence (rural/urban) and presence of thyroid disease diagnosed at screening. All of the adjustment factors as well as the trimester of exposure were evaluated as potential modifiers of the dose response. Overall, no significant dose response was found for height (P = 0.29), weight (P = 0.14) or BMI (P = 0.16). We found significant modification of the dose response for weight and BMI by presence/absence of thyroid disease (P = 0.02 and P = 0.03, respectively), but not for other factors. In individuals without thyroid disease (n = 1,856), there was a weak, significant association between I-131 thyroid dose and higher weight (210 g per 100 mGy, P = 0.02) or BMI (70 g/m² per 100 mGy, P = 0.02) that depended on individuals (n = 52) exposed to ≥500 mGy. In individuals with thyroid disease (n = 579, 67.4% with simple diffuse goiter) no significant association with I-131 for weight (P = 0.14) or BMI (P = 0.14) was found. These results do not support the hypothesis that in utero exposure to I-131 at levels experienced by a majority of study subjects may be associated with meaningful differences in adolescent anthropometry. However, additional studies are needed to clarify whether in utero exposure to I-131 at levels > = 500 mGy may be associated with increases in weight/BMI and to evaluate the confounding or modifying role of thyroid disease, past iodine deficiency, maternal and prenatal/postnatal factors.

Project description:In the last three decades, an increase in thyroid cancer incidence has been observed worldwide, as well as in Lithuania. Although the rise was linked to overdiagnosis, the role of lifestyle and environmental factors, including exposure to ionizing radiation, cannot be excluded. In our retrospective study, we aimed to assess the association between the average age-specific thyroid dose due to the radioactive iodine uptake during childhood and adolescence from the Chernobyl fallout in Lithuania, and the trends of incidence of thyroid cancer from 1991 to 2015 in different regions. Averaged age-dependent thyroid doses were estimated for every municipality based on radioiodine activity in milk, reconstructed from available 131I activity measurements in the grass. Thyroid cancer incidence rates were calculated for the entire population and for two age at the time of exposure groups: 0-19 years and 0-9 years. Thyroid cancer relative risk (RR) was estimated for three municipality-specific thyroid dose (for 0-year-old babies) categories: less than 100 mGy (reference group), 100-199 mGy, and ≥200 mGy. Over the study period (1991-2015), a total of 5664 cases of thyroid cancer were registered in the entire Lithuanian population; 817 cases in the age group from 0 to 19 years at the time of the Chernobyl accident, and 266 cases in the age group from 0 to 9 years. Age-standardized thyroid cancer incidence rates have notably increased since 2000, peaked in 2009 (especially in females), and then slightly decreased and stabilized. The estimated average municipality-specific age-dependent thyroid doses ranged from 270 mGy in western Lithuania to 1.5 mGy in central and northern Lithuania. For the age group of 0-19 years at the time of the accident, in the period 1991-1995, the thyroid cancer relative risk was significantly increased (RR 3.91; 95 % CI: 1.27-10.29, p=0.01) in the highest dose category, compared to the lowest (although based on a small number of cases). For the age group 0-9 years at the time of the accident, a tendency of increased RR in the highest dose category appeared in the most recent period, 2011-2015. Our observations need to be confirmed by further following trends of thyroid cancer incidence in the cohort of 0-19-year-old Lithuanians at the time of the Chernobyl accident.

Project description:The 1986 accident at the Chernobyl nuclear power plant remains the most serious nuclear accident in history, and excess thyroid cancers, particularly among those exposed to releases of iodine-131 remain the best-documented sequelae. Failure to take dose-measurement error into account can lead to bias in assessments of dose-response slope. Although risks in the Ukrainian-US thyroid screening study have been previously evaluated, errors in dose assessments have not been addressed hitherto. Dose-response patterns were examined in a thyroid screening prevalence cohort of 13,127 persons aged <18 at the time of the accident who were resident in the most radioactively contaminated regions of Ukraine. We extended earlier analyses in this cohort by adjusting for dose error in the recently developed TD-10 dosimetry. Three methods of statistical correction, via two types of regression calibration, and Monte Carlo maximum-likelihood, were applied to the doses that can be derived from the ratio of thyroid activity to thyroid mass. The two components that make up this ratio have different types of error, Berkson error for thyroid mass and classical error for thyroid activity. The first regression-calibration method yielded estimates of excess odds ratio of 5.78 Gy(-1) (95% CI 1.92, 27.04), about 7% higher than estimates unadjusted for dose error. The second regression-calibration method gave an excess odds ratio of 4.78 Gy(-1) (95% CI 1.64, 19.69), about 11% lower than unadjusted analysis. The Monte Carlo maximum-likelihood method produced an excess odds ratio of 4.93 Gy(-1) (95% CI 1.67, 19.90), about 8% lower than unadjusted analysis. There are borderline-significant (p = 0.101-0.112) indications of downward curvature in the dose response, allowing for which nearly doubled the low-dose linear coefficient. In conclusion, dose-error adjustment has comparatively modest effects on regression parameters, a consequence of the relatively small errors, of a mixture of Berkson and classical form, associated with thyroid dose assessment.

Project description:ObjectiveTo investigate childhood cardiac arrhythmia and chronic exposure to caesium-137 (137Cs) resulting from the Chernobyl accident.DesignProspective cross-sectional study using exposed/unexposed design conducted in the Bryansk region from May 2009 to May 2013 on children selected on the basis of 137Cs soil deposition: control territories ([137Cs]<37 kBq per square metre, where children were considered as unexposed) and contaminated territories ([137Cs]>555 kBq per square metre, where children were considered as exposed).SettingRussian territories affected by the Chernobyl fallout (Bryansk region).ParticipantsThis cross-sectional study included 18 152 children aged 2-18 years and living in the Bryansk region (Russia).Main outcome measuresAll children received three medical examinations (ECG, echocardiography and 137Cs whole-body activity measurement) and some of them were given with a 24-hour Holter monitoring and blood tests.ResultsCardiac arrhythmia was diagnosed in 1172 children living in contaminated territories and 1354 children living in control territories. The crude prevalence estimated to 13.3% in contaminated territories was significantly lower than in control territories with 15.2% over the period 2009-2013 (P<0.001). Considering 137Cs whole-body burden as exposure, cardiac arrhythmia was found in 449 contaminated children and 2077 uncontaminated children, corresponding to an estimated crude prevalence of 14.5% and 14.2%, respectively, which does not differ significantly (P=0.74). Also, we investigated the association between territory, exposure to 137Cs and cardiac arrhythmia: the adjusted OR was not significant (0.90 with 95% CI 0.81 to 1.00; P=0.06) for the territory. For 137Cs whole-body burden, the ORs close to 1 did not reach statistical significance (P for trend=0.97).ConclusionThis study does not observe an association between cardiac arrhythmia and 137Cs deposition levels in the Bryansk region exposed to Chernobyl fallout. The suspected increase of cardiac arrhythmia in children exposed to Chernobyl fallout is not confirmed.

Dataset Information

Uncertainties in Radiation Doses for a Case-control Study of Thyroid Cancer among Persons Exposed in Childhood to 131 I from Chernobyl Fallout.

Publications

Uncertainties in Radiation Doses for a Case-control Study of Thyroid Cancer among Persons Exposed in Childhood to 131 I from Chernobyl Fallout.

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