A total of 13,127 of the 32,385 individuals living in the most contaminated area of the Ukraine during the nuclear plant meltdown and who were under 18 at the time were screened between 1998 and 2000, Dr. Geoffrey R. Howe of Columbia University in New York and colleagues report. They found that 45 cases of thyroid cancer occurred compared with 11.2 cases that would have been expected in the absence of radiation exposure. Plus, the higher the dosage of radioactive iodine, the greater the thyroid cancer risk.
     The study is the first to measure the risk of thyroid cancer associated with specific radiation dosage, Howe and his team note in the Journal of the National Cancer Institute. Radioactive iodine and cesium were the main components of the Chernobyl fallout. Because radioactive iodine is used frequently in medicine -- and is also likely to be a chief contaminant released in any future nuclear emergency -- understanding the risk associated with exposure is a public health concern, as well as of scientific interest, the researchers point out.