Document 0qBmx3ojq6z4Ja338dRxYrvzR

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 r o b i n #3) their own proposed optical microscopy procedure to be used only^ and after one obtains a positive for serpe n t i n e 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 w h i c h one (sample A) was reported by T E M 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 M c C r o n e Assoc i a t e s for T E M / CAr> v y 11**i . Mofrririo Accnf.isfpfi rp'norts no chrvsGtri.e .i l l > CXlliJ- J . C - 1 x ilC - V n v -- -- .. -- 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: - ,lIn _sample A we f o u n d an e xtremely h igh content of fibrous materials, mos t of w h ich were rolled talc, talc charts and ribbons, plus some blocky talc. This talc was of extremely poor quality because of the l<h i g h 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 d i f f r a c t i o n and one par t i c l e w h i c h we found to te - -antigorite. Most of this talc looks very similar p. to a n t i g o r i t e in its structure and general ap pearance w i t h extr e m e m o t t l i n g of the" talc, w h i c h leads me to b e l i e v e that there are h igh concentrations of~~ impurities in the talc. We also found large numbers of talc fiber ribbons and blocky talc which--anpeaxed- ^ s imilar to tremoldte inJjphysixaJ_a p p e a r a n c e s but w h i c h ele c t r o n d i f f r a c t i o n confirmed as t a l c . :l The corrected results from Round Robin #3 appears below, but regrettably the inconsistence of results among three competent groups of micrcscopists still does not support the v a l i d i t y of the ba c k u p optical m i c r o s c o p e procedure to the DTA procedure. i.v.v.i.v,*: ja r.v .v .v .V A r.v.v.v.-.v.v; 1 V .V .V /.V .V . ::::::::::: :: :::::i'-v.v.v.v.v. Investigator and Results Coded Sample &Luc y Walter M c C r o n e 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 * chrysotile found fail rpiC - 1.27= n hrnnc none found in platy talc. none found none found For the past year I have played the role of Sherlock Holmes trying to ob t a i n a sample of n a t u r a l l y occurring chrysotile in talc to c b u s e d in m e t h o d d e v e l o p m e n t from members of the CTFA and t a l p r o d u c e r s and importers. All leads end (so' far) saying that chrysotile is not commonly or uncommonly (or ever?) a s s o c i a t e d w i t h talc - can chrysotile in ta]c be a red herring? f- hi (b) (5) F. Ro b e r t Rolle, Ph.D. Chairman, Methodology Committee