Persons exposed to radioactive fallout from the Chernobyl accident as children and adolescents have an increased risk of follicular adenoma or benign tumor of the thyroid gland, according to researchers at Columbia University Mailman School of Public Health.
Results of the study further suggest that age at exposure, history of thyroid diseases, and location of residence do not modify its risk. This is the first epidemiologic study of the association between radiation exposure from radioactive iodine fallout from the Chernobyl accident and subsequent risk of follicular adenoma in those exposed at 18 years old or younger. The paper is published in the February 2008 issue of the American Journal of Epidemiology.
The Chernobyl accident in 1986 was the largest nuclear accident ever and exposed many individuals to radioactive iodines. Thyroid cancer is one of the most radiosensitive tumors when exposure occurs at young ages. Previous studies showed that the risk of thyroid cancer increased with radiation dose from radioactive iodines, but the effects of radiation on benign thyroid diseases has been largely unknown.
Researchers selected a random sample of 32,385 persons from a database of more than 75,000 records of thyroid radioactivity measurements taken within two months after the incident in those under the age of 18 who resided in three heavily contaminated areas in Ukraine. Various methods were used to trace these subjects and invite them for screening which consisted of an examination of the thyroid gland and sonogram, blood and urine tests, a detailed questionnaire, and an independent clinical examination by an endocrinologist. Those with suspicious findings were further referred for fine-needle biopsy and surgery as needed. The scientists reported a significant three-fold increase in risk for those exposed to the standard measure of 1 gray of radiation compared to those with zero dose. The study further indicates that women had a notably higher risk of follicular adenoma compared with men.
“The Chernobyl accident presented an unparalleled opportunity to study the association between radioactive iodines and a spectrum of thyroid diseases,” said Lydia B. Zablotska, MD, PhD, principal investigator of the project and assistant professor of Epidemiology at the Mailman School of Public Health. “While there have been several analytical epidemiologic studies of thyroid cancer following the Chernobyl accident, none had evaluated follicular adenoma in particular. This paper presents risk estimates of follicular adenoma in relation to individual thyroid doses as well as the effects of gender, age at exposure, iodine deficiency, and other possible effect-modifying factors.”