CHAPTER 4 - THE RADIOIODINE PROBLEM--INHALATION 1. There is an insufficient basis for ruling out the threat of thyroid damage attributable to inhaled radioiodine vapor released in local fallout, even though it is the consensus of the ACCD/NAS Fallout Subcommittee and many others that the radioiodine inhalation threat is relatively minor compared to the ingestion threat. 2. However, there is little question that the danger of thyroid damage due to ingestion of radioiodine is significant and requires protective measures. The principal and probably only important ways by which radioiodine could be ingested are through drinking contaminated water or contaminated fresh milk. Thus, protection against ingestion could be achieved by avoiding water from open reservoirs, cisterns, and the like, where fallout has been deposited, and by keeping milk cattle from grazing on contaminated pasture or not using their milk if they do. 3, A third means of protecting the thyroid against ingested (and/or inhaled) radioiodine is through prophylaxis, i.e., using pre-administered stable compounds of iodine such as potassium iodide tablets to block the uptake by the thyroid of the radioactive iodine #, 4. There could be radioiodine hazards to the U.S. population associated with a nuclear war even though the war did not directly involve the U.S., i.e., the so-called world-wide fallout that would result from an overseas nuclear exchange between, say, China and Russia. Also, there could be a radioiodine hazard due to an accidental release of radioactivity from a nuclear reactor accident, 5. It seems obvious that any national system designed to provide radioiodine protection should take into account the various possible threats, and it is equally obvious that the nature of the system may change depending on which threats are to be covered. Therefore, a final recommendation about the nature of the national protective system should await the conclusion of current studies of the problem. II-10