Environmental Health Perspectives 105, Supplement 6, December 1997

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Chernobyl-related Thyroid Cancer: What Evidence for Role of Short-lived Iodines?

Juerg Peter Bleuer,1 Yury Ivanovich Averkin,2 and Theodor Abelin1

1WHO Collaborating Centre for Epidemiology of Radiation and Thyroid Disease, University of Bern, Bern, Switzerland; 2State Research Institute of Oncology and Medical Radiology, Lesnoy/Minsk, Republic of Belarus

Abstract
Over 500 cases of thyroid cancer were diagnosed in Belarus between 1986 and 1995 among persons exposed as children (under 15 years of age) to radioactive contamination from the Chernobyl nuclear accident. There is little doubt that radioactive iodine isotopes emitted during the nuclear explosion and subsequent fire were instrumental in causing malignancy in this particular organ. Comparison of the observed geographic distribution of Chernobyl-associated thyroid cancer incidence rates by districts with contamination maps of radioactive fallout shows a better fit for estimated 131I contamination than for 137Cs. Because 131I used for medical purposes had not been considered carcinogenic in humans in the past, and in view of the unusually short latency period between exposure and clinical manifestation of cancer, it is suspected that not only 131I but also energy-rich shorter-lived radioiodines may have played a role in post-Chernobyl thyroid carcinogenesis. Measurements of iodine isotopes are not available, but reconstruction of geographic distributions and estimations of radioactive fallout based on meteorological observations immediately following the accident could provide a basis for comparison with the distribution of thyroid cancer cases. In this paper, data from the Epidemiological Cancer Register for Belarus will be used to show geographic and time trends of thyroid cancer incidence rates in the period from 1986 to 1995 among persons who were exposed as children, and these will be compared with the estimated contamination by radioiodines. Tentative conclusions are drawn from the available evidence and further research requirements discussed. -- Environ Health Perspect 105(Suppl 6):1483-1486 (1997)

Key words: Chernobyl, thyroid, cancer, incidence, iodine, geography, distribution, children

This paper is based on a presentation at the International Conference on Radiation and Health held 3-7 November 1996 in Beer Sheva, Israel. Abstracts of these papers were previously published in Public Health Reviews 24(3-4):205-431 (1996). Manuscript received at EHP 7 April 1997; accepted 3 July 1997.

We thank the Swiss Federal Office of Public Health for financial support.

Address correspondence to Dr. J.P. Bleuer, Department of Social and Preventive Medicine, University of Bern, Finkenhubelweg 11, CH-3012 Bern, Switzerland. Telephone: 41 31 631 38 67. Fax: 41 31 631 48 61. E-mail: bleuer@ispm.unibe.ch

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