Researchers at Columbia University Mailman School of Public Health have found that people exposed to radioactive fallout from the Chernobyl accident as kids and adolescents have an increased risk of follicular adenoma or benign tumour of the thyroid gland.
The findings of the study further suggest that age at exposure, history of thyroid diseases, and location of residence do not modify its risk.
This study is the first one to provide a link 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.
For the study, the 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 1986 Chernobyl accident in those under the age of 18 who resided in three heavily contaminated areas in Ukraine.
They conducted a 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.
The researchers 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 indicated that women had a notably higher risk of follicular adenoma as compared to 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.
"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," Zablotska added.
The researchers noted that the radioactive iodines accumulated in the human thyroid gland via the consumption of contaminated milk and other food items.
Ukraine is known to have a mild to moderate iodine deficiency previously shown to affect radiation-related risks of thyroid cancer.
In this study, several indicators of iodine deficiency such as place of residence, history of thyroid diseases, and current urinary iodine excretion did not modify the risk of follicular adenoma.
"Our findings confirm that follicular adenoma is strongly related to exposure from radioactive iodines, and while we found that the risk is modified by gender, age at exposure, place of residence, and personal history of thyroid diseases do not affect its subsequent development," Zablotska said.
The study is published in the February 2008 issue of the American Journal of Epidemiology.