nuclear crisis

The important points to note on iodine tablets are:

(1) During a nuclear power plant accident, there are plenty of fission products released. Radioactive iodine is ony one of them.

(2) Taking of (stable) iodine tablets can only protect the thyroid from the hazard of inhaling radioactive iodine, but cannot protect the damge to other body organs from inhalation of other fission products, such as radioactive caesium, strontium, ruthenium... etc.

(3) Iodine tablets is not an antidote (解毒劑). It should be taken prior to exposure of radioactive iodine or within 6 hours after exposure. The protection to the thyroid would be drastically decreased if the tablet is taken long than 6 hours after exposure to radioactive iodine.

(4) There is intrinsic risk associated with the taking of stable iodine. Some people are allergic to iodine.

(5) In view of the intrinsic risk of taking stable iodine, the World Health Organization advises that it is not justifiable for perople of age 40 or above to take iodine tablets in a nuclear emergency situation, unless the prejected dose to the thyroid might exceed 5 Gy, which would cause acute deterministic effect.

You may refer to the Q&A in the following web-page. Q2 and Q15 are related to iodine tablets.

http://www.dh.gov.hk/faq_tc.html

Excessive iodine tablets taking can saturate the thyroid gland from further absorbing iodine. Therefore, if the thyroid is iodine saturated. It will not absorb all iodine, including radiative iodine (I-131). The radio active iodine is not easily absorbed by our body and causes absorbed dose through internal contamination.