Re: I-131 Thyroid Uptake

["Thatcher, Drew" <dht0303@doh.wa.gov>]

There are several references which can assist in answering your 
questions.

Kaul, A. and Roedler, H.  "Radioiodine:  Biokinetics, Mean Dose and Dose 
Distribution",  Radiation and Environmental Biophysics, Vol. 18, 1980, 
pp. 185-195.

Coughtrey, P.J., Janckson, D., and Thorne, M.C., "Rradionuclide 
Distribution and Transport in Terrestrial and Aquatic Ecosystems, vol 3.  
AA Balkema Pub, Rotterdam, Netherlands, 1983.
Included in Coughtrey's discussion is a graph of fractional thyroid 
uptake of iodine as a function of time based upon different daily intake 
rates.

Dunning and Schwarz (HP 40(5)) report an average value of 0.19.  Some of 
the data that the ICRP uses is from injections and may have a higher 
uptake than that of oral intake.  Based upon the graph and information 
from Dunning and Schwarz, an uptake of 0.3 appears to coincide with an 
upper 95% CI.

Bottom line, if you can determine the daily intake rate of iodine for 
your area, you should be able to estimate the fractional iodine uptake 
rate.  As a point of reference, between 1959 and 1967, the U.S. mean 
fractional uptake decreased from 286 to 154 ęg/d.  The fractional uptake 
for 150 ęg/d is about 0.27 and about 0.18 for close to 300 ęg/d (using 
graph from Coughtrey).

Sincerely,
Andrew H. Thatcher, MSHP, CHP
Washington Department of Health
360-236-3255 voice
360-236-2255 fax
dht0303@doh.wa.gov
-standard disclaimers apply-

What is the typical percent of a iodine intake (we happen to be concerned 
with I-131) that will be taken into the thyroid gland?  My 1972 copy of 
Shapiro, "Radiation Protection" says 30%, but there is some indication 
that it may be as low as 3% (at least for some individuals) according to 
other sources.

So, is the answer a range, say about 3 to 30%?  Does the pathway make a 
difference, e.g. nuclear medicine injection vs. reactor release and 
subsequent accidental inhalation?

Thanks,
Mike McCarty
Health Physicist/Emergency Planner
mccartmj@state.mi.us

Michigan Department of Environmental Quality
Drinking Water and Radiological Protection Division
Radiological Protection Section
Nuclear Facilities Unit
   phone:  517-335-9414
     fax:  517-335-8706

mailing address:
     Michigan Department of Environmental Quality
     Drinking Water and Radiological Protection Division
     3423 North Martin Luther King Jr. Blvd
     P.O. Box 30630
     Lansing, MI 48909-8130

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