The Chernobyl nuclear power plant accident happened on April 26, 1986. We investigated the cause of the striking increase in frequency of thyroid cancer in children who lived within a 150 km radius of Chernobyl and who were born before and after the accident. No thyroid cancer was seen in 9472 children born in 1987-89, whereas one and 31 thyroid cancers were recorded in 2409 children born April 27, 1986, to Dec 31, 1986, and 9720 born Jan 1, 1983, to April 26, 1986, respectively. Short-lived radioactive fallout caused by the Chernobyl accident probably induced thyroid cancer in children living near Chernobyl.
The method of processing and the results of measurements of 131I content in the thyroids of Russian people performed in May-June 1986 are presented. The contribution of radiation from Cs radionuclides in the human body was taken into account in the processing of measurement data with an SRP-68-01 device. The greatest individual 131I content was found in the thyroids of inhabitants of the Bryansk region, up to 250-350 kBq, and in the Tula and Orel regions, up to 100 kBq. The average 131I thyroid activity in the middle of May 1986 reached 80 kBq for inhabitants of some settlements in the Bryansk region, 5-8 kBq in the Tula region and 5 kBq in the Orel region.
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.
The 131I activity was measured in 30 human fetal thyroids in Zagreb district after the Chernobyl accident. A model of radioiodine metabolism in the mother and human fetus which takes into account the age dependence of the uptake and retention of radioiodine in the fetal thyroid was developed. Having assessed that the total intake by the average mother was about 1330 Bq, a good correlation between calculated and measured fetal thyroid activities was found (r = 0.77, P less than 0.001). The fetal thyroid dose reached the maximum of 0.43 micro Gy/Bq intake at about the fifth month of gestation. It was concluded that the risk of having a child with a harmful trait due to 131I absorbed by the mother was negligible.
137Cs activities were measured in a variety of epigeic and epiphytic lichens in Austria before and after contamination by the Chernobyl fallout. For comparison, the activity of the naturally occurring 40K was also determined in each lichen sample. The high 137Cs activities found after Chernobyl suggest that lichens are suitable and inexpensive biological detectors of the fallout pattern.