Exposure to radioactive iodine increases the risk of thyroid cancer

Jul 4 2006

Exposure to radioactive iodine increases the risk of thyroid cancer in children and adolescents, a study of thyroid cancer prevalence after the Chornobyl accident shows.

The study is published in the July 5 issue of the Journal of the National Cancer Institute.

In 1986, an accident at the Chornobyl nuclear power plant exposed large numbers of people in Belarus, Ukraine, and the Russian Federation to radioactive material high in isotopes of iodine and cesium. Numerous studies have shown that exposure to certain types of radiation increases the incidence of thyroid cancer in children and teens. However, few studies have examined the effects of exposure to radioactive iodines, and only three studies have examined cancer risk from the Chornobyl-related exposures.

Geoffrey R. Howe, Ph.D., of Columbia University in New York, and colleagues screened 13,127 people for thyroid cancer who at the time of the Chornobyl accident were under 18 and lived in highly contaminated areas of Ukraine. The researchers estimated each participant's individual radiation dose using thyroid radioactivity measurements made shortly after the accident and interview data obtained during screening.

The researchers found 45 cases of thyroid cancer in the screened group in comparison with the 11.2 cases expected without the accident. Subjects had a tendency toward lower risk of thyroid cancer with increasing age at the time of the exposure. The authors suggest that exposure to radioactive fallout from the Chornobyl accident increased thyroid cancer in those exposed as children and adolescents.

The authors write, "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 Chornobyl accident."