Re: Volatility of I-131 NaI

[carol marcus <csmarcus@ucla.edu>]

At 11:13 AM 9/15/99 -0500, you wrote:
>Does anyone have any information on the volatility of I-131 NaI.  We are 
>updating our emergency response program and one scenario involves a spill 
>of an I-131 therapy dosage (100 - 200 mCi) in a patient room (either prior 
>to administration or by the patient vomiting
>shortly after receiving the dose.  Looking for an approximate % of the 
>original activity that would initially be airborne.
>
>Thanks for your help,
>
>Gordon Axt
>University of Iowa - Health Protection Office
>
>It's not about doughs, its about crust. (sorry Bill,  its the allergy 
>medication:) 
>
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Dear Gordon:

All commercially available preparations of NaI-131 are stabilized against
volatility.  If there was a spill and it was left untouched for 24 hours,
the volatility factor over that time would be about 1x10exp-6.  (They have
been measured in multiple laboratories for all manufacturers and for Syncor,
which stabilizes the CIS-US product, and they are roughly similar.)  As a
spill would be cleaned up within an hour, in all likelihood, the airborne
emission would be much less than that.

One of the ways in which the products are stabilized is by making the pH
very basic.  If the patient has swallowed the medicine and then vomits some
of it up, volatility will depend, in part, on how much acid was in the
stomach to neutralize the base.  My own, rather extensive experience of
patients vomiting is that they very, very rarely do this as soon as the dose
is administered.  They usually do it some hours later.  At this point, all
the I-131 has been absorbed and the I-131 concentrated by the stomach lining
from the blood-borne I-131 is definitely acidic.  However, how acidic
varies.  Hypothyroid patients (and thyroid cancer patients getting high
doses of I-131 should all be hypothyroid) put out less acid that euthyroid
ones, and so the short answer is that I don't know how much volatility there
will be.  Back in the years when NRC, for absurd reasons, forbid Syncor to
stabilize its NaI-131, I measured the airborne losses from two such doses at
10% and 16%.  I then went on the warpath and demanded that Syncor be
permitted to stabilize preparations, charging that NRC was a bigger danger
to public health and safety than all of nuclear medicine combined.  I
finally threatened Admiral Carr (then Chairman) that I would go to the
Washington Post and the wire services to expose him if he did not relent.
He did relent, and this was one of the issues that led to the "Radiopharmacy
Rule".  It was incredible to me at the time that the NRC, charged with
protecting public health and safety, could insist on continuing to forbid
Syncor from stabilizing its I-131 EVEN AFTER IT FOUND OUT HOW DANGEROUS THIS
WAS.  This was one of the issues that indelibly defined to me the
intellectual level at which the NRC performs.  The people at NRC responsible
for this are still very actively involved in the "Medical" Program.  By the
way, I-131 contamination at a very low level was measured in my
technologist's thyroid after administration of  an unstabilized dose of
NaI-131.  We never had a spill, and the patients, if they vomited at all,
vomited in the toilet so that there was no problem with airborne emissions.
My tech took perchlorate, to help decrease further I-131 uptake, and I did
not use Syncor's I-131 again until the pharmacists were stabilizing it.

When the EPA was working on the radionuclide NESHAPs, I got a call from its
subcontractor asking about the volatility factors of I-131 from belching and
farting!  I didn't know then, don't know now, and one of the best coups I
ever pulled was exempting I-131 after it had been administered to patients
from the radionuclide NESHAPS, on the basis that it was uncontrollable by
Authorized Users.

In summary, I don't think that airborne emissions from NaI-131 use in
patients is a problem.  In the event of a spill, it would be prudent for
those who clean it up to take some SSKI first, and I always keep some handy
for emergencies.  I also send over a fresh bottle of SSKI from time to time
to my RSO, in case I am not around during an accident.  NaI-131 used for
radiolabeling is NOT stabilized, and so it could be more of an issue in
research laboratories than on Nuclear Medicine services.  If there are
laboratories around that use significant quantities of NaI-131 or NaI-125,
it would probably be enough to keep some SSKI around those labs.  As it is
available only by prescription, get one of your docs to write as many
prescriptions as are necessary, and instruct that anyone using it after an
accident should report to Nuclear Medicine for a thyroid uptake.  As thyroid
uptake probes are not calibrated for I-131 or I-125 for any clinical
purpose, you might invest in some standards to do so in case of a worker
contamination situation.  At Harbor-UCLA, the RSO and Nuclear Medicine have
uptake probes, and whenever the RSO calibrates his probe, he sends the
sources over to Nuclear Medicine for a calibration as well.  

Ciao, Carol

<csmarcus@ucla.edu>

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