food and milk sources will be controlled, so ingestion of radioactive iodine will be very unlikely.

  • Is KI effective in preventing the risk of thyroid cancer after a nuclear incident?

Yes, taking stable iodine (in the form of KI) within a few hours before or after exposure to radioactive iodine through inhalation or ingestion of fallout will protect the thyroid from thyroid cancer caused by such exposure in vulnerable populations. See Chapter 2 for thyroid physiology and Chapter 4 on stable iodine prophylaxis.

  • Who should take KI when an accident occurs?

The most vulnerable people are the young. It is most important for KI to be taken by children, infants and pregnant and lactating women (to protect fetuses and breast-feeding infants). See Chapter 2.

  • What is the radiation exposure intervention level at which KI or other protective measures should be taken?

We recommend that KI prophylaxis be ordered if there is likely to be an avertable cumulative radioiodine dose of 50 mGy (5 rad) to children’s thyroids. See Chapters 2 and 5 for discussion of different agencies’ recommendations on radiation dose thresholds beyond which protective actions should be taken. We also recommend that this threshold for intervention be kept under review as further information on the consequences of exposure to radiation from fallout from Chornobyl and from other radiation incidents becomes available. See Chapter 6 for radiation dose levels used in other countries.

  • Is KI safe?

Yes, in general. Relatively small numbers of people should not take KI, including those with some pre-existing thyroid conditions, iodine allergies, and some other rare medical conditions. Thyroid conditions tend to occur after the age of 40 years. See Chapter 2. It is important to avoid overdosage of the fetus and the very young child, by following the 2001a FDA guidelines. When KI is given to infants



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