Estimating thyroid masses for children, infants, and fetuses in Ukraine exposed to (131)I from the Chernobyl accident.

For the purpose of improving retrospective internal thyroid dose estimations for children and adolescents following the Chernobyl accident, age- and gender-dependent thyroid masses have been estimated for the children of Kiev and Zhytomyr oblasts, which are two of the most contaminated regions of Northern Ukraine. For children ages 6-16 y, the thyroid masses were based on the measurements by ultrasound of the thyroid volumes of about 60,000 children performed by the Sasakawa Memorial Health Foundation in the 1990s. For children aged 0 to 36 mo, because thyroid mass values for Ukrainian children were not found in the literature, autopsies were performed for the specific purpose of this paper. Thyroid mass values for children aged 3-5 and 17-18 y were either interpolated or extrapolated from the measured data sets. The results for children aged 6-16 y indicate that the thyroid masses of rural children are, on average, slightly higher (by about 8%) than the thyroid masses of urban children. The geometric means of the thyroid masses were estimated as 5.2 g, 9.0 g, and 15.8 g for boys and 5.2 g, 9.4 g, and 16.0 g for girls aged 5, 10, and 15 y, respectively. Those values are greater than the reference values that ICRP recommends for iodine-sufficient populations, thus reflecting the fact that the northern part of Ukraine is iodine-deficient.

Children of chernobyl cleanup workers do not show elevated rates of mutations in minisatellite alleles.

The disaster at the Chernobyl Nuclear Power Plant in April 1986 was accompanied by the release of large amounts of radioisotopes, resulting in the contamination of extensive regions of the Ukraine, Byelorus and the Russian Federation. Cleanup workers (liquidators) and people living on land contaminated with radioactive materials were most exposed. To assess the genetic effects of exposure to ionizing radiation after the Chernobyl accident, we have measured the frequency of inherited mutant alleles at seven hypermutable minisatellite loci in 183 children born to Chernobyl cleanup workers (liquidators) and 163 children born to control families living in nonirradiated areas of the Ukraine. There was no significant difference in the frequency of inherited mutant alleles between the exposed and control groups. The exposed group was then divided into two subgroups according to the time at which the children were conceived with respect to the fathers' work at the power plant. Eighty-eight children were conceived either while their fathers were working at the facility or up to 2 months later (Subgroup 1). The other 95 children were conceived at least 4 months after their fathers had stopped working at the Chernobyl site (Subgroup 2). The frequencies of mutant alleles were higher for the majority of loci (i.e. 1.44 times higher for CEB1) in Subgroup 1 than in Subgroup 2. This result, if confirmed, would reconcile the apparently conflicting results obtained in the chronically exposed Byelorus population and the Hiroshima-Nagasaki A-bomb survivors.

Analysis of blood lymphocyte subsets in children living around Chernobyl exposed long-term to low doses of cesium-137 and various doses of iodine-131.

Epidemiological studies have found that children living around Chernobyl have rates of respiratory tract illness that are higher than those seen in the area before the Chernobyl accident. The present study investigates the possible effects of radiation exposure on the composition of peripheral blood lymphocyte subsets in children living around Chernobyl. Two hundred nineteen healthy children and children suffering from recurrent respiratory diseases aged 6-14 years who received both low doses of radiation to the whole body from (137)Cs and various doses of radiation to the thyroid from (131)I as fallout from the accident were assessed 5 (1991) and 8-10 years (1994-1996) after the accident. A total of 148 healthy children and children suffering from recurrent respiratory diseases living in noncontaminated areas were also evaluated as controls. Children with recurrent respiratory diseases who lived around Chernobyl had a significantly lower percentage of T cells and a higher percentage of NK cells compared to control children with recurrent respiratory diseases during the study period. In contrast to the findings in 1991, a significant decrease in the percentage of helper-inducer cells was observed in children with recurrent respiratory diseases in 1994-1996. In contrast to 1991, there is a positive correlation between the percentage of helper-inducer cells, the helper-inducer/cytotoxic-suppressor cell ratio, and the dose of radiation to the thyroid of healthy children from (131)I in 1994-1996. There was a positive correlation between the dose of radiation to the thyroid from (131)I and the percentage of helper-inducer cells in children with recurrent respiratory diseases 5 years (1991) after the accident. Further, the dose of radiation to the thyroid from (131)I correlated negatively with the percentage of T and B cells and positively with the percentage of NK cells in children with recurrent respiratory diseases 8-10 years (1994-1996) after the accident. These results raise the possibility that long-term exposure to low doses of (137)Cs may have altered the composition of the T-cell subsets and NK cells in children with recurrent respiratory diseases. The differences in the composition of the peripheral blood lymphocyte subsets between healthy children and those with recurrent respiratory diseases may be attributed to long-term low-dose exposure of the whole body to radiation from (137)Cs and exposure of the thyroid to radiation from (131)I subsequent to the Chernobyl accident.

131I dose-dependent thyroid autoimmune disorders in children living around Chernobyl.

We assessed the major lymphocyte subsets in the peripheral blood, thyroid ultrasonography, levels of serum autoantibodies to thyroglobulin (AbTg), thyroid hormones, and thyroid-stimulating hormone (TSH) in 53 children without any chronic diseases living continuously around Chernobyl. The subjects ranged in age from 7 to 14 years and had different doses of 131I to their thyroid. Healthy children living on noncontaminated areas were assessed as controls. The majority of children with doses of 131I had normal levels of thyroid hormones. However, the percentages of positive sera for AbTg, TSH levels, ultrasonographic thyroid abnormalities, and abnormal echogenicity were significantly higher in children with doses of 131I than in controls. The dose of 131I to thyroid correlated positively with serum AbTg levels, percentage of CD3+CD4+ cells, and CD3+CD4+/CD3+CD8+ cell ratio and negatively with number of CD3+CD8+ and CD3-/CD16, CD56+ cells. Thus, our study demonstrates an association between dose of 131I and autoimmune thyroid disorders in this population of children.

Analysis of blood lymphocyte subsets in children living on territory that received high amounts of fallout from Chernobyl accident.

The major lymphocyte subsets in the peripheral blood were assessed in 120 children 6-13 years old living on areas that received high levels of radioactivity as fallout after the Chernobyl nuclear power plant accident. Seventy-one of the children were suffering from recurrent respiratory disease (RRDC) and 49 were not (non-RRDC). As controls, a total of 87 RRDC and non-RRDC living on noncontaminated areas were evaluated. We did not find significant differences in major lymphocyte subsets between the values in non-RRDC living on radionuclide-contaminated areas and noncontaminated areas. However, RRDC living on radionuclide-contaminated areas had a significantly lower percentage of CD3+ T and CD3+CD4+ T-helper/ inducer cells compared to control RRDC. Furthermore, the decrease in percentage of CD3+CD4+ cells was more profound in RRDC living in radiation-contaminated settlements with an average summary dose (ASD) Cs-137(134) and Sr-90 for the population > 1.0 mSv than in RRDC living in contaminated settlements with an ASD Cs-137(134) and Sr-90 < 1.0 mSv. These data indicated that long-time exposure to small doses of radiation could affect the immune system in children living around Chernobyl.