A study of thyroid cancer prevalence after the Chernobyl disaster has shown that exposure to radioactive iodine increases the risk of thyroid cancer in children and adolescents.
Published in the Journal of the National Cancer Institute, the study was conducted by Geoffrey Howe, from Columbia University in New York, USA, and co-workers.
The researchers screened 13,127 people for thyroid cancer who at the time of the Chernobyl accident were under 18 years of age and lived in areas of Ukraine that were highly contaminated by the fallout from the disaster.
Forty-five cases of thyroid cancer were detected in the screened group compared with the 11.2 cases expected without exposure to Chernobyl radiation.
Howe et al observed a trend for a lower risk of thyroid cancer associated with increased age at the time of exposure to radioactive iodine.
Interestingly, there was also a strong and approximately linear relationship between individual thyroid dose estimates – based on radioactivity measurements made shortly after the accident and on interview data – and the incidence of thyroid cancer.
The investigators calculated that exposure to Chernobyl radiation had increased the estimated relative risk of thyroid cancer by 5.25 per gray.
"The results of the present study show a strong positive and approximately linear relationship between thyroid dose and subsequent risk of thyroid cancer," the investigators comment.
"We estimate that 75% of the thyroid cancer cases would have been avoided in the absence of radiation. With appropriate adjustment for dose, this estimate demonstrates a substantial contribution of radioactive iodines to the excess of thyroid cancer that followed the Chernobyl accident."