Re: Potassium Iodide -Reply -Reply

[Charles Willis <CAW@nrc.gov>]

Victor, Emil, Joe, Franz and others with an interest,

The advisability of the use of KI by the general public as a protective measure in
the event of a severe nuclear accident is a complex issue.  This, of course, does not
excuse the production of a "poorly written report;" excuses are irrelevant so I can
only offer an apology and an invitation to let me know where and how we went awry.
It may be relevant to note that our charter was not to make a case for a particular
course of action; rather, we were to provide the technical information relevant to
making the decision.

Without question, the timely administration of stable iodine (preferably KI, 
because it seems to be less of an intestinal irritant than the iodate, KIO3) can
substantially reduce internal thyroid doses from radioactive iodine.   Thus, KI has
long been considered an appropriate protective measure, in certain circumstances;
the question is whether it is appropriate for the general public.

The limitations of stable iodine prophylaxis are important.  KI protects only one
organ and protects against only five of the hundreds of nuclides that may be
released.  Furthermore, KI offers no protection against external radiation from any
nuclide.  Because of these limitations, there is little question that there are
superior protective measures: evacuation for the plume phase and interdiction of
contaminated foodstuffs (especially milk) during the ingestion phase (in the April
draft of its recommendations, the WHO advises against the use of KI in the
ingestion phase).  Thus, the question is reduced to the advisability of the use of KI
as a supplement to these principal protective measures.

One concern is suggested by Victor's reference to the KI tablets as "magic pills." 
While Victor may be fully aware of the limitations of KI, most Americans would not
have such knowledge.  This lack of knowledge might lead people to feel safe and to
fail to take essential protective actions such as evacuation.

Another concern is the hazard from KI itself.  Properly administered, KI seems to
be a relatively safe drug.  According the recent draft WHO recommendations,
proper administration includes carefully adjusting the dose according to the age of
the individual and not giving KI to people with certain medical problems or to 
people who are taking certain other medications.  Some people (those who are
allergic to iodine) know about these limitations: at the Minneapolis meeting,
several people made remarks to the effect that "130 mg of KI would kill me in an
hour."  Other people do not know about their vulnerability.  In fact, one of the
authors (Congel) did not realize until a couple of weeks ago that his medication
makes KI quite dangerous to him, ("cardiac arrest" is a decidedly adverse
reaction). With a little discussion, we learned that several other people who work
nearby are taking similar medications.  We do not yet have the data, but it seems
that this problem may be more significant in the US than in less medicated societies
(perhaps Poland).  Then there is the possible long-term hazard: KI may be
carcinogenic; KI has been found carcinogenic is some laboratory studies and there
are no human data (so far as we know, anyway).

There are other complicating considerations (aside from the political) but I have
said too much already.  Please let me know how we can improve the report; it was
seriously offered as a "draft for comment."

Charlie Willis
caw@nrc.gov