Document e54xdzdkoqrdvrZVB5pr2Ke0M

FILE NAME DuPont DUP DATE 1969 Nov 25 DOC DUP119 DOCUMENT DESCRIPTION Letter to Charles Crook from James P. Morgan RE Method of Reporting Asbestos Dust Q-c6aa7 November 25, 1969 CHARLES CHARLES CROOK TEXTILE FIBERS OLD HICKORY TENN METHOD OF REPORTING ASBESTOS DUST LEVELS proposition This This in reply to your letter The best level is the level level fibers per milliliters longer of October , 1969 inviting method October 1969 inviting inviting than method report asbestos asbestos and the discussion which it eontains reviewed your letter discussion discussion which contains : have havaelso reviewed a letter written by Drummond Drummond to I P. J. Tracey August 21 1969 copies of which you I received received hhavae vheave ss eeen etn he references LciimtitedVianluDersumomfonadi'rsbolrentetecrontaminants addition ACGIH for Threshold by for 1969 and the intended changes by ACGIH remains remains million million Threshold LicmuibticVaflouoet faiorraaisrbebsatsoesd impinger remains is now generally generally samples samples counted particles per is now generally recognized that this lightfield techniques techniques this method have outlived useful- useful- ) is reflected level and intended changesACGIH useful- notice of ) T In hia sn option reflected presented using using million million particles cubic field air based impinger presented counted light techniques foot of limit of fibers fibers greater samples microns length length milliliter milliliter or the membrane five method 430 times phase milliliter of air determminead gdentermiinedfidcetaetrimionned . the membrane filter contrast contrast contrast method The counting counting meeting with with evaluating increasing favor among those collecting faced the task of evaluating it gives the the exposures exposures because more direct measure measure asbestos needs be controlled in order order eliminate eliminate asbestosis agent be controlled order agent which needs to C. D. Crook Page2 It can be argued that a sound rationale would exist for adopting 0.5 mppof based on impinger samples counted by light techniques because this would represent the application of a safety factor of four to one of the optional ACGIH levels To go beyond this rationale as the Construction Division has done and utilizing a level of 0.5 mppof as determined by the membrane filter method at 430 times phase contrast magnification is to introduce an innovation which is in- consistent with the efforts at standardization I concur in the time would be to count in length at 430 times by membrane filter proposition that our best bet at the present asbestos particles greater than five erons phase contrast magnification on samples collected MIGINAL Signed BY JAMES E. MORGAN JAMES F. MORGAN 615