Document rxa5qgnRGjaLVYZJ69rZL3RN0

}V EMORANDUM U C '^ ' S --Z'-- DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE PUBLIC HEALTH SERVICE FOOD AND DRUG ADMINISTRATION TO George H. Boone Director of Science, HFR-2160 New York District d a t e : October 5, 1976 FROM SUBJECT: Product Composition Branch, HFF-446 Division of Cosmetics Technology Asbestos in Talc 'Xtau L5L. vrMZjZ^\rr\ "">} / / / ,X W:/' tv"/ /AA( A/ //// /, / / IA-UL-' This memorandum is in reply to your telephoned offer to provide us with assistance in the development of analytical methods for the detection and determination of asbestos in cosmetic talds. It is my understanding that you expressed interest in the development of methods for the detection of chrysotile arid tremolite by optical microscopy and that you would like to receive some samples for analysis. Per your request we are sending you, anger separate cover, tne roilowing samples: DCST-77-1371 DOST-77-1372 DCST-77-1373 DCST-77-1374 DCSTW7-1375 DCST--77-1383 DCST-77-1384 DCST-77-1385 These samples consist of talc with known amounts of added chrysotile or tremolite. The talc used to prepare these samples is a commercial product which was analyzed by x-ray diffractometry-and differential thermal analysis. The analysis indicated the absence of tremolite, chrysotile and chlorite at the limit of detection. To make the samples as uniform in composition as possible, the talc and asbestiform mineral were mixed in a blender using alcohol as a mixing aid. The alcohol was then removed by evaporation and the sample remixed. <b7 George H. Boone 2 We would appreciate receiving the results of your analyses when you have completed the examination of these samples, We would .like to know the identity^ of the asbestos in each sample and, to the extent possible, the amount present. We would also appreciate receiving a copy of your methodology or a reference. Enclosed are seme reprints of material dealing with the microscopic identification of amphibole and serpentine minerals. Thank you for your cooperation, assistance and interest. cc: HFF-440 HFF-446 HFF-446 Ronald L. Yates 1 TO: M em bers of the CTFA Task F o rce on Methodology for the Detection of Asbestos in Talc A t th e S e p t e m b e r 11, 1974, m e e t i n g of t h e C T F A T a s k F o r c e on methodology for the detection of asbestos in talc for cosmetic use, the results of our round robin analysis w ere discussed. The two "cookbook" procedures for the detection of chrysotile and asbestiform amphibole in cosmetic grade talc have now been modified as a result of this evaluation. The two methods would assure that a talc is 99.0 to 99.5% free of asbestifo rm m in erals. A shortcoming of the round robin analysis for chrysotile in talc is that no one performed the necessary optical microscopy-dispersion staining back up method to the DTA procedure. This method is of gre?-t importance since the p rim ary method (DTA) is specific only to the serpentine class of m inerals; that is, antigohite, chrysotile, etc. which have different morphology's. Enclosed you will find three coded talc samples possibly containing chrysotile. Would you please examine these samples strictly in accordauv... with uui Miupuseu uDucai mi r.rosr onv-disp^r cmn ^ ing test method, a copy of which is attached. I wil l c o n t a c t you by t e l e p h o n e o n ' o r a r o u n d O c t o b e r 31, f o r y o u r results and comments. Thank you FRR/gm Attachment F. Robert Rolle, Ph.D. Chairman, Task Force on Methodology for the Detection of Asbestos in Talc .\ -** - Optical Microscopy and Dispersion Staining Having failed the DTA test for serpentine minerals, the sample must next be tested by optical m icroscopy/dispersion staining or by tra n s mission electron microscopy. The following optical method uses the Becke line procedure for deter mining relative refractive index. . 1. P r e p a r e a m i c r o s c o p e s l i d e by d i s p e r s i n g a p p r o x i m a t e l y 0 . 3 m g . of talc in C a r g i l l e r e f r a c t i v e in d e x liquid 1. 550, u n d e r a 22 x 22 m m . cover glass. 2. On examination with the polarizing microscope any chrysotile fibers or fiber bundles in the prepared slide will exhibit: a. in the crossed polars mode, low order (first order, grey-white) retardation colors and straight extinction characteristics. b. distinctive fibrous morphology - in most cases a length: ofc" ratio of several hunBr^d to one. c . in th e p l a n e - p o l a r i z e d light m o d e a. r e f r a c t i v e in d e x m atch when the long direction of the fiber is parallel to the plane of polarization. In the plane perpendicular to this the fibers will exhibit a refiactive index less than that of the liquid. 1 .3. R e p e a t 1 and 2 u s i n g C a r g i l l e r e f r a c t i v e i n d e x liquid 1. 544. Under these conditions for 2.c. (above) the refractive index m atch will occur when the short (diameter) direction of the fiber is parallel to the plane of polarization. The other index ex hibited will be greater than that of the liquid. 4. U s i n g the s l i d e p r e p a r e d in 1, e x a m i n e the s a m p l e in the d i s p e r s i o n staining mode with central stop (dark-field). Any chrysotile fibers present will exhibit blue colors, distinctly separating them from the non-chrysotile particles. If this test is carried out with plane polarized light as the illumi nating source the color exhibited will vary with fiber orientation, so that as the stage is rotated the chrysotile fibers will change color: blue -- blue -purple . . -5- Again, for positive confirmation, both color and morphology (fibers, large l:d) c rite ria m ust be satisfied. 5. If optical m icroscopy/dispersion staining gives negative results, chrysotile may be present with a diam eter too sm all to be detected by optical microscopy, thus, transm ission electron microscopy with SAED must be employed. Following is the transm ission m icroscope procedure. If chrysotile serpentine is detected at the sam e level found by DTA by either microscopical method, then the talc fails. V, r rwj First Draft: February 1, 1973 I Microscopic Detection of Asbestos in Talc ' by Arnold E. Schulze and William V. Eisenberg U.S. Food and Drug Administration, Washington, D.C. The six,kinds of asbestos can he distinguished from talc and from each other by their refractive indices, other optical crystallographic properties, and morphology. Talc occurs mainly in the form of thin plates, which may appear to be fibrous when seen edgewise in microscopic view. Beta and gamma indices of talc vary from about 1.575 to 1.590, beta being very close to gamma. All of the principal, refractive indices of chrysotile are less than 1.574, and those of the amphibole types of asbestos are greater than 1.590. One can, therefore, distinguish chrysotile asbestos from fibrous looking talc particles in aJL.574 refractive index liquid, and the amphibole types from talc in a 1.590 liquid. The accompanying table of optical crystallographic properties for talc and the asbestos minerals shows refractive irdices which are usually encountered bn these minerals, but occasional samples may have indices which are somewhat higher or lower. * Method Weigh out 1 mg. of a representative portion of talc on each of two microscope slides. Mix the talc on one slide with a drop of 1.574 refractive index liquid, and the other with 1.590 liquid, and place on each a cover glass sufficiently large so that the liquid will not run out from the edge (IS mm. in diameter or larger). Observe the material with a polarizing microscope at a magnification of about 400 X, using the optical crystallographic technique to detect the presence of asbestos. In -he 1.574 liquid look for asbest'iforrn fibers with indices less than 1.574 in both extinction positions, and in the 1.590 liquid look for fibers with indices exceeding 1.590. If any such particles are found, check type of extinction and sign of elongation to confirm tentative identification as asbestos. Count and record the number of asbestifom fibers found in 1 mg. as determined from a.scan of either or both slides at a magnification of about 400 X. To determine specific identity of asbestifonn fibers, make mounts in appropriate refractive index liquids, and refer to the optical crystallographic cata in the accompanying table. OPTICAL CRYSTALLOGRAPHIC CHARACTERISTICS OF ASBESTOS MINERALS AND TALC Substance Reference for n Actinolite (variety of tremolite) (2) p . 172 (8) p. 285 Anosite (4) p . 261 (4) p. 261 Anthophyllite * (2) p. 170 (2) p. 222 (5) p. 298 (2) p . 222 (2) p. 172 (6) p . 236 (2) p. 173 (2) p. 116 Chrysotile (2) p. 99 (2) p . 100 (3) p . 154 (8) p . 260 ' (6) p. 290 (8) p . 260 (2) p. 104 (1) p . 40 C D p . 40 na 1.614 1.615-1.655 1.663* 1.675*' 1.598 1.598 1.59^-1.674 1.608 1.619 1.619-1.633 1.629 1.633 1.493 1.508 1.529-1.559 1.53-1.54 1.542 1.542 1.546. 1.546 1.548 1.630 1.625-1.665 ny____________Extinction 1.641 1.64-1.68 Inclined -- -- 1.623 -- 1.605-1.685 1.630 1.630-1.642 1.635 1.638 1.623 1.615-1.697 1.631 1.640 1.640-1.657 1.640 1.652 1.504 1.512 1.530-1.564 -__ 1,543 (calc.) 1.550 1.55-7 1.560 ' 1.517 1.522 1.537-1.567 1.54-1.55 1.555 1.555 . 1.557 1.557 1.560 P arallel . P arallel Elongation P o sitiv e P o sitiv e P o sitiv e * r T n|3 Page 2 - OPTICAL CRYSTALLOGRAPHIC Substance Reference for n_________ na Crocidolite (Riebeckite) (2) p. 125 (2) p. 187 (6) p. 241 (2) p . 226 (2) p. 226 (2) p. 127 1.693 1.695 1.695 1.697 Talc (8) p. 259 (2) p o 164 (3) p. 167 (6) p. 281 (8) p. 259 (1) p . 41 (I) p . 41 (1) p . 41 (7) p. 758 1.538-1.545 1.539 1.539 1.539 1.540 1.541 1.544 1.545 Tremolite (2) p. 222 (8) p. 285 (3) p. 169 (2) p. 169 (2) p. 222 (2) p. 222 (6) p. 237 (7) p. 766 (2) p. 222 (2) p. 222 (2) p. 222 (2) p. 222 1.599 1.599 1.599-1.612 1.600 1.602 1.602 1.602-1.623 1.64 1.604 1.609 1.609 1.613 CHARACTERISTICS OF ASBESTOS MINERALS AND TALC nf3____________ ny 1.687 1.695 1.695 -1.698 1.700 -- 1.589 1.539 1.589 nearly = ny 1.585 1.592 1.594 1.584 -- . 1.697 1.7- 0- 3 1.703 1.575- 1.590 1.589 1.589 1.589 1.575 1.585 1.592 1.594 1.584 1.613 1,613 1.613-1.626 1.616 1.614 1.618 1.613-1.638 1.612 1.617 1.622 1.623 1.621 1.625 1.625 1.625- 1.637 1.627 1.635 1.631 1.624- 1.650 1.628 1.630 1.636 1.636 1.634 Extinction______ Elongation Parallel Negative Parallel or 2 or 3 Positive Inclined Positive Rci* ERENCES Page 3 - OPTICAL CRYSTALLOGRAPHIC CHARACTERISTICS OF ASBESTOS MINERALS AND TALC I. Chides ter, A. H. Petrology and Geochemistry of Selected Talc-bearing Ultramafic Rocks and Adjacent Country Rocks in North-Central Vermont, Geological Survey Professional Paper 345. U. S. Department of the Interior. 1962. 2.. Larsen, E. S. and H. Berman. The Microscopic Determination of the Nonopaque Minerals. Geological Survey Bulletin 848. U. S. Department of the Interior. 1934. 3. McCrone. W. C., et al. The Particle Atlas. Ann Arbor, Michigan. 1967 4. Peacock, M. A. The Nature and Origin of Amphibole-Asbestos in South Africa. The American Mineralogist 13 : 241-286. 1928 5. Rabbitt, J. C. A New Study of the AnthophyHite Series. The American Mineralogist 33 : 263-323. 1948. 6. Rogers, A. F. and P. F. Kerr. Thin-Section Mineralogy^ New York. 1933. 7. Ross, M . , W. L. Smith, and W. H. Ashton. Triclinic Talc and Associated Amphiboles from Gouverneur Mining District, New York. The American Mineralogist 53 : 751-769. 1968 S. Winchell, A. N .; and H. Winchell. Substances. New York. 1964. The Microscopical Characters of Artificial Inorganic Solid