July 6 (HealthDay News) -- Childhood exposure to radiation from the 1986 Chernobyl nuclear power plant disaster may raise risks for thyroid cancer, a new report finds.

The Chernobyl incident exposed large numbers of people in the Ukraine, Belarus and the Russian Federation to radioactive material high in isotopes of iodine and cesium.

For this study, researchers at Columbia University in New York City provided thyroid cancer screening for more than 13,000 people who were younger than 18 years of age at the time of the Chernobyl disaster and lived in highly contaminated areas of the Ukraine.

Each person's individual radiation dose was estimated by using thyroid radioactivity measurements made shortly after the disaster and through interview data collected during screening for the study.

The study identified 45 cases of thyroid cancer among the participants, compared to an expected 11.2 cases in the same number of people not exposed to this kind of radiation. The older the study participants were at the time of the incident, the lower their risk of thyroid cancer as adults.

"We estimate that 75 percent of the thyroid cancer cases would have been avoided in the absence of radiation," the team wrote. "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."

The findings were published in the July 4 Journal of the National Cancer Institute.

SOURCE: Journal of the National Cancer Institute, news release, July 4, 2006