JFFICIAL USI ONL - 4 - Committee aware that they may be approached at some future date for an evaluation (and perhaps recommendations) on permissible radiological conditions for this special population, Pions in Cancer Therapy. Dr. N. F. Barr, DBM, discussed the potential advantages of negative pi mesons in cancer therapy. He outlined the status of experimental work with mesons from the 184" cyclotron at Berkeley. He compared physical dose distributions which might be obtainable with protons and other heavy ions, and with distributions obtainable with multiport applications of neutrons and X-rays. On the basis of physical dose alone, pigns appear to be superior to protons and comparable to multiple port X-rays and to neutrons. When some weighting for biological effectiveness is applied, the pion distributions seem to be superior to both. The enhancement ratio (OER) for neutrons has been experimentally determined and is low. It has not been obtained for negative pions. Indications are that the OER for pions should not be as low as for neutrons. This fact may very well overcome the advantage of dose distribution so the choice between pions and neutrons is difficult. Clarification on the basis of experimental work is unlikely with presently available pion beams. Status of Film Dosimetry Evaluation, BNW. Dr. Lough gave a brief report on the status of the study in progress and almost completed at Pacific Northwest Laboratory which has as its objective the development of a report in which the study group will present recommendations for "The Establishment and Utilization of Film Dosimeter Performance Criteria." A brief outline of the method pursued by the study group was given, and an indication of the number of film dosimeter processors who participated in the study was presented in order to demonstrate that a large fraction of the total industry was involved. It is anticipated that the report will show that the principal cause of difference between film processors probably lies in the reliability of calibration films rather than variations arising during the process of development and interpretation of individual dosimeters. Indeed, if calibration is reliable, considerable variation in processing seems to be acceptable. The Battelle group has concluded tentatively that if one is prepared to allow an exposure of 5 rem/yr over 47 years, which would amount to an accumulated dose of 235 rem, it would be possible to estimate such total dose within + 69%. Preview of the draft report:suggests that the recommendation of the Battelle group will be one which would lead to very useful practical application. Utilization of the recommendation will be dependent upon the readiness of the regulatory group or groups concerned to establish a laboratory to carry out the function along the lines recommended. The ACBM agreed that any statement from the Committee concerning this study should be withheld pending a review of the report upon its completion, Follow-up on Harbor Study. Mr. L. Joe Deal, DBM, reported on the Project Harbor Review, a study conducted by National Academy of Sciences-National OFFTCIAL USE ONLY