Document zb5vg6RwjZdVz4LQnYMg84Kna

FILE NAME: Talc (TALC) DATE: 1973 Aug 31 DOC#: TALC456 DOCUMENT DESCRIPTION: Memo RE FDA Proposed Talc Regulation P. A.. Martinson, 2 West R. S. Lamar, R&D Center D-j; August 31, 1973 <V FDA PROPOSED TALC'REGULATION? MORE'NUMBER EXERCIZES; HOPE FOR REEVES? . ' The FDA regulation calls for talc purities of 99.99 percent and 99.9 percent in- term's of chrysotile and tremolite, respectively. Their proposed test method, which is com pletely incompatible with these percent purity data, call for maximum counts of,100. for chrysotile,and 1,000 for tremolite in 1 mg of talc. The FDA. test method calls, for an optical method of counting at 40OX. The'FDA requirement states further than only fibers 5 microns or greater in length and having an aspect ratio of 3/1 or greater will be counted. At a magnification of 400X the lower limit of resolution with an optical microscope using heterochromatic light is 1 x 2 microns. In other words, no particles below this, size would be seen or counted by this method. Even at 5 microns petrographic identification ,is very difficult. Positive petrographic identification becomes more possible at 10 microns and above. The FDA test requires that a petrographic identification be made. A most significant point here is that the numbers of particles per unit of weight increases enormously as the size of the particles is reduced. In his report of August 27, 1973, to R. S. Lamar, V. E. Wolkodoff states that J-M Reeves talc, jet-milled Hazen Concentrate RD-73201-1 contains 6,720,000 particles per milligram by direct microscopic count. At- 500X with the optical microscope it is most likely that the greatest numbers ,of particles (b.elow 1 x 2 microns) are not seen and not counted. . ' This same sample was counted .using the Coulter Counter. This is a well recognized procedure now used in most, if not all hospitals and clinical laboratories for bloodcounts (in place of the older direct microscopic count), CRMC-HT-TALC-000086 Page 2 . p, ,\. Martinson ,August 31, 1973 Using the Coulter Counter to count Reeves RD-73201-1 down to 1.19 microns wo have determined that 1 mg of this sample has 92,000,000 particles. Even at 1.19 microns XoV/er limit or detectability the Coulter Counter is ignoring the greater numbers of particles actually present. Another way of calculating the total number of particles or all sites down to the very smallest is to v/ork _oac,< ma^n- omatically from the surface mean.diameter. This was^ determined by air permeability to be 0,50 microns ror Reeves RD-73201-1. By this method we estimate that i m g of this talc contains. 554,000,000 -particles. (See memo_ R.- S. Lamar to S. Spoil August 29, 1973.) Th is numaer is proba.bly closer to the truth than the other two values reported above . . Xh V. E. Wolkodoffs memo of August 27, 1973, he reports 504 particles of chrysotile and 336 particles of ..remoli-Q in Reeves. It is difficult hut very important to put' these data_in correct perspective. " On the basis of all. three counting methods, these calculate as follows: -U Counting Method Total Particles Percent Percen ' per mg . Treraolite Chrysot Optical; FDA 6,720,000 0.005 0.0075 Coulter Counter 92,000,000 0.00037 0.0005 Surface Mean Diameter (by air permeability) 554,000,000 . 0.00006 0.00009 Talc purity by the -three methods would be as follows: ' Counting Method Optical; FDA Coulter 'Counter Surface Mean Diameter Percent Talc Purity For Tremlate For Chrysotile 99.995 99.99-25 99.99963 99.9995 99.99994 99.99991 CRMC-HT-TALC-000087 Page 3 . P. A. Martinson . August 31, 1973 . ; Even under the most difficult counting procedure (optical; p d a ), we are talking about purities of 99.995 percent and v9.9.925 percent for tremoliti and chx/sotile in Reeves. This is pretty pure material by any rational standard : These numbers put this matter in a more rational, sane perspective. Does c y sanity yet remain in Washington, D.C? R . S . Lamar rr cc : L. VanDerbeek ~ 2 West' M. Sharratt - 2 West R. Keefe - 2 West L. Pundsack Speil - RSD Center - R&D Center C. Streib - R&D Center P. Carter - 5 West . E. Parker - 5 West J. Solon - 1 West , CRMC-HT-TALC-000088