Nuclear Power Plant  Accidents

 and Stable Iodine prophylaxis

What Iranian Physicians Need to Know

Iraj Nabipour, Endocrinologist, The Persian Gulf Health Research Center,

Bushehr University of Medical Sciences

Iran is rapidly going to obtain nuclear technology. Despite rigorous safety systems, there remains a finite probability that an accident can occur in a reactor that can lead to the fuel in the core overheating or melting. It sets out various protective actions including "stable iodine prophylaxis" which refers to the blocking of the uptake of radioiodine after nuclear accidents. It is a protective action for which preparedness arrangements can be made as part of the overall emergency response plan, and that can protect specifically against internal exposure from inhalation and ingestion of radioiodines.

Isotopes of iodine are likely to be important components of the release from a sever accident. Radioactive iodines can give rise to both external exposure and internal exposure. The most likely treatment of internal contamination would be the use of potassium iodide to prevent radioiodine from accumulating in the thyroid, deterministic effects (hypothyroidism, for example) and stochastic effects (for example, thyroid cancer, and benign nodules). Evidence of a marked excess of thyroid cancer in children exposed to the fallout from the Chernobyl accident has been established. The most affected area in Belarus, the yearly incidence has risen more than 100-fold compared to the situation before the accident. However, over ten million children, sixteen years of age and under, and approximately seven millions adults received at least one dose of potassium iodide prophylaxis in Poland. Two children had thyroid nodules, but no thyroid cancers developed in children in a preliminary Polish four-year follow-up study. The information suggest that stable iodine prophylaxis for children up to the age of 18 years should be considered at 10 mGy. For adults over 40, the scientific evidence suggests that stable iodine prophylaxis not be recommended until doses to the thyroid from inhalation are expected to exceed levels that would threaten thyroid function.  The recommended daily dose of potassium iodide is 130 mg for adults, 65 mg for children 3 to 18 years old, and 16 mg for children 1 month to up 3 years old, and 16 mg for infants less than 1 month old. To be effective, it must be taken within three to four hours after the radiation exposure.

In summary, potassium iodide is a relatively safe and effective salt that protects only the thyroid from exposure to radioactive iodine that might be released during a nuclear reactor emergency. Therefore, in the vicinity of nuclear reactors, redistribution of potassium iodide to households should be seriously considered. However, within the framework of the overall nuclear emergency plan, the responsibility for distribution of stable iodine and instructing the public on how to use it should still be clearly assigned to the appropriate authorities.