f^SS^l          UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                                 WASHINGTON. D.C, 20460


                                                             SAB-RftC~88-QQl
      October 9, 1987
      The Honorable Lee M.  Thomas
      Administrator
      U.S. Environmental Protection Agency
      401 M  Street S.W,
      Washington,  DC 20460

      Dear Mr.  Thomass

           The  Science  Advisory Board's Radiation Advisory Cotanlttee lias reviewed
      the revised  plan  for  the Idaho Radlonucllde Exposure Study at the request
      of the Office of  Radiation Programs  (OEP).

           The  request  for  review  was received September 5,  1986 and the work
      plan was  first presented at  the Radiation Advisory Comftittee meeting
      October 1-2, 1986. A revised plan for the study was presented at the
      December  17, 1986 meeting and the final document describing the  study,
      sent to the  Committee March  30, 1987,  was reviewed at  the  June 12, 1987
      meeting*

           The  objective of the Idaho Radionuclide  Expogttre_Study Is "to
      determine the magnitude and  relative importance  of the various Industrial
      sources of radiation  and to  estimate the dose to the populations of Soda
      Springs and  Pocatello, Idaho from these sources."   This  objective is
      more limited than that found in the  September 5, 1986  work plan, and the
      Committee believes that it is achievable.

           The  Committee finds that the current version  of the study plan is
      of sufficient quality and detail to  achieve the  study's  objective.  This
      conclusion is due primarily  to changes iti approaches to  sampling and
      neasurement  of radlonuclides, enhanced use of existing data, and Improved
      use of meteorological Information.

           There are two additional Comlttee comments,  neither  of which will
      affect the overall plan, that will be  relatively easy  to address in the
      final report.

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     These comments include:

     1.  The March 30, 1987 OKP transmittal memorandum states  (on page  2,
item 7) that, in the absence of information on indoor/outdoor  polonium-
210 ratios, it will be assumed that the indoor polonium-210 concentration
is the same as the outdoor concentration; the memorandum points out that
this assumption will result in a conservative estimate of dose.  However,
this estimate may also be incorrect because it is generally accepted that
indoor concentrations of any aerosols originating outdoors are lower than
the outdoor concentrations.  A better approach would be to take a
conservative value for the indoor/outdoor ratio based on literature
values, rather than to assume the ratio is unity.

     2.  The Committee hopes that in the final report of the Idaho
Radionuclide Exposure Study lung doses due to inhalation will  be converted
into effective dose equivalents to permit these doses to be added to the
external dose from gamma rays originating in slag*  Since these two
pathways are expected to be the principal modes of exposure, it is important
that they be expressed in comparable units.

     Thank you for the opportunity to present our evaluation of this
study plan.  Vfe request and look forward to the Agency's response to our
report.

                                 Sincerely,
                                 Norton Nelson
                                 Chairman
                                 *Executiv
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