Document kD2rQDjXKXGg1moaONboq2G9V

FILE NAME DuPont DUP DATE 1969 Nov 25 DOC DUP009 DOCUMENT DESCRIPTION Letter to Charles D. Cook from James Morgan - Method of Reporting Asbestos Dust Levels ce D. D. WilminWig lmt ino gtn on ( | November 25 1969 CHARLES D. CROOK TEXTIL^ TEXTIL^ FIBERS , OLD HICKORY TENN EXHIBIT Morgan- Morgan- Morgan- 6 10-23-86 10-23-86 10-23-86 DATE 10-23-86 MASTROIANNI & FORMAROLI INC CERTIFIED SHORTHAND REPORTERS METHOD OF REPORTING ASBESTOS DUST LEVELS This is in reply to your letter of Octobe2r 1969 inviting comment on the proposition The best method to report asbestos dust level is fibers per milliliters longer than 5 microns in length I have reviewed your letter and the discussion which it contains and I have also reviewed a letter written by D. D. Drummond to P. J. Tracey August 21 1969 copies of which you and I received I have seen the references cited in Drummond's letter and in addition have seen the Threshold Limit Values of airborne contaminants adopted by ACGIH for 1969 and the intended changes The current Threshold Limit Value for asbestos dust remains at five million particles per cubic foot of air based on impinger samples counted by field techniques It is now generally recognized that this level and this method have outlived their useful- ness This is reflected in the notice of intended changes ACGIH 1969 in which an option is presented of using two million particles per cubic foot of air based on impinger samples counted by field techniques or limit of 12 fibers greater than five microns in length per milliliter of air as determined by the membrane filter method at 430 times phase contrast magnification The latter method of collecting and counting is meeting with increasing favor among those who are faced with the task of evaluating asbestos dust exposures because it gives a more direct measure of the agent which needs to be controlled in order to eliminate asbestosis C. D. Croak Page2 It can be argued that a sound rationale would exist for adopting 0.5 upper 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 ACGTE levels To go beyond this rationale as the Construction Division has done and utilizing a level of 0.5 mppef 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 microns phase contrast magnification on samples collected ORIGINAL SIGNED BY JAMES & MORGAN JAMES F. MORGAN JTM 14m G15 B283 B283 B283