effect of dietary iodine in modifying the carcinogenic risk posed by radioiodine; the type, frequency, and clinical course of thyroid tumors in those exposed to radioiodine as children; the risk of thyroid carcinogenesis in adults exposed to radioiodine in fallout; the risk and mechanisms of autoimmune disease and hypothyroidism after radioiodine exposure; and the risk of tumor development at other sites after radioiodine exposure.

On the basis of information presented in this report, the committee concentrated on three main subjects for assessing the five issues posed in the statement of task: risks and benefits of potassium iodide distribution; implementation issues related to potassium iodide distribution and stockpile programs; and additional research needed. A summary of the background and rationale is provided for each recommendation, and the text is organized to present the link between the various elements of the committee’s charge and the findings and recommendations.

Benefits of and Risks Posed by Potassium Iodide Distribution

On the basis of its assessment, the committee reached the following conclusions and offers a number of recommendations.


Conclusion 1: Exposure of susceptible populations to radioiodine from a radiation incident increases the risk of thyroid cancer and other thyroid disorders.

Radioactive iodines (radioiodines, such as 131I) are produced during the operation of nuclear power plants (NPPs) and during the detonation of nuclear weapons. Radioiodine is one of the contaminants that could be released into the environment in the event of a radiation incident that involves a disruption of the integrity of the fuel assembly and containment structures of a nuclear power plant (NPP), because of an accident or terrorist activity. Because iodine concentrates in the thyroid gland (it is essential for the synthesis of

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