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Mr. G. Sandland, Chairman CTFA Committee on Asbestos in Talc SUBJECT: Corrected Results of Round Robin (#3) Using the CTFA Proposed Optical Microscope Procedure For Detection of Chrysotile in Talc. As you may remember the Task Force on Methodology for the detection of asbestos in talc evaluated (round robin #3) their own proposed optical microscopy procedure to be used only, and after one obtains a positive for serpentine by DTA. It was hoped that this microscope procedure would distinguish between fibrous serpentine (chrysotile) and non-fibrous serpentine (antigorite). To test this proposed optical method three coded samples were prepared by me, of which one (sample A) was reported by TEM to contain several percent of naturally occurring chrysotile in talc. Sample A along with another sample not related was sent at a later date to McCrone Associates for TEM fc Ah >"!n + A c c n n ' s f p c i T P rifirtS TlO c h t V S G t l i . 6 JL11 c) CXi.ii j l C n i J - i i U p r o * , u v t i v&tv -- -- w w w-- --------------------- - - - - reports now that the TEM analysis was done by a technician not using selected area diffraction and he would support the detailed McCrone finding. The McCrone report states: "In sample A we found an extremely high content of fibrous materials, most of which were rolled talc, talc charts and ribbons, plus some blocky talc. This talc was of extremely poor quality because of the high loading of fibers. W e did not find any /< chrysotile in this sample,but we did find one fiber which we believe to be attapulgate from electron diffraction and one particle which we found to te - -antigorite. Most of this talc looks very similar to antigorite in its structure and general appearance P with extreme mottling of the talc, which leads" me to believe that there are high concentrations ofimpurities in the talc. We also found large numbers of talc fiber ribbons and blocky t ? similar to tremoiite in^phy-s-jcaJ_appjbarance^ but which electron diffraction confirmed as talch1 The corrected results from Round Robin #3 appears below, but regrettably the inconsistence of results among three competent groups of micrcscopisto still does not support the validity of the backup optical microscope procedure to the DTA nrocedure. r.v.v.v. r.v .'.v .v .v .v . ' f.- .v.v.v.v.v ::::::::::: Investigator and Results Coded Sample Lucy & Halter McCrone H. Stanley D . Hamer McCrone Associates Pfizer Johnson & Johnson A - Fibrous and platy talc. Antigorite none detected pass chrysotile chrysotile found found - fail fail B - 1% chrysotile in talc prepared by a simulated indus trial milling process. chrysotile found fail none found pass . c - chrysotile found fail C - 1.2% none found n hrmi c r p i,r' r.SRg in platy talc. none found >000 none found --- For the past year I have played the role of Sherlock Holmes trying to obtain a sample of naturally occurring chrysotile in talc to b^ used in method development from members of the CTFA and tal : producers and importers. All leads end (so far) saying that chrysotile is not commonly or uncommonly (or ever?) associated with talc - can chrysotile in ta]c be a red herring? r-v.v.".v.v-v. p .V .'.V .V .V v .v .v .::* ." : L.-.'.v.'.v/.v 1 Jv.v.v.v.'/,; ' (... tv.v.v.v. i.v.v.v.v.".: tv.:;:*.:::: f(jA_ *. F. Robert Rolle, Ph.D. ' - Chairman, Methodology Committee FRR/gm cc: Task Force Members Mrs. L. McCrone Dr. W. McCrone ' - .V .V .V - V .', .'.V .V .V .V .V v .v .'.* .:::: v.:: -.v.;v.v.: j: t::::