Document jmGy4RgEwk7JYypxxXQgZODJR

MEMORANDUM oe . _^<- DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE PUBLIC HEALTH SERVICE FOOD AND DRUG ADMINISTRATION T O 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 'ta u 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, unger separate cover, tne ronowing samples: DCST-77-1371 DCST-77-1372 DCST-77-1373 DCST-77-1374 DCST-77-1375 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. b I 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 knew 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 airphibole and serpentine minerals, ' Thank you for your cooperation, assistance and interest. Ronald L. Yates 1 TO: M e m b e rs of the C T F A T ask F o r c e on M ethodology for the D etection of A sbestos in Talc A t t h e S e p t e m b e r 11, 1974, m e e t i n g o f t h e C T F A T a s k F o r c e on ' m ethodology for the d etection of a s b e s to s in talc for c o s m e tic use, the re s u lts of our round robin an aly sis w e re d iscu ssed . The two "cookbook" p ro ced u res for the d etectio n of ch ry so tile and a s b e s tifo rm am p h ib o le in c o s m e tic g ra d e talc h av e now been m od ified as a re s u lt of this evaluation. The two m ethods would a s s u re that a ta lc is 9 9 .0 to 99.5% f r e e of a s b e s tifo r m m i n e r a l s . A sh o rtco m in g of the round robin a n a ly sis for chrysotile in talc is that no one p erfo rm ed the n e c e s s a ry optical m ic ro sc o p y -d isp e rsio n staining back up m ethod to the DTA p r o c e d u r e . This m ethod is of g re a t im p o rta n c e since the p r im a r y m eth o d (DTA) is specific only to the s e rp e n tin e class of m i n e r a ls ; that is, a n tig o tite, c h ry s o tile , etc. which have different morphology's. E n clo sed you will find th r e e coded talc s a m p le s p ossibly containing c h ry s o tile . Would you p le a s e ex am in e th ese sa m p le s s tric tly in & c c o r d t * n . v vr LLh y i - u y u s e u u D i i c a i r m r . r o s r o n v - c i i s p e r m r > cfo r? ing te st m ethod, a copy of w hich is attach ed , I w i l l c o n t a c t y o u b y 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 com m ents. Thank you, F . R obert Rolle, Ph.D . C h a irm a n , T ask F o rc e on M ethodology for the D etection of A sb e sto s in Talc A -* - Optical M icroscopy and D ispersion Staining H aving failed the DTA te st for serp en tin e m in e ra ls, the sa m p le m u st next be tested by optical m ic ro s c o p y /d is p e r s io n stain in g o r by t r a n s m ission electron m icroscopy. The following optical m ethod uses the B ecke line p ro ced u re for d e te r m ining 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 b y 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 rg ille r e f r a c tiv e index liquid 1.550, und er a 22 x 22 m m . co v er g la s s . 2. On exam ination with the polarizing m icroscope any chrysotile fibers or fiber bundles in the p rep ared slide w ill exhibit: a. in the c ro s s e d p olars m ode, low o rd e r (firs t o rd e r, grey-white) retardation colors and straight extinction characteristics. b. distinctive fibrous m orphology - in m ost cases a length: d i n m e t c " * r a t i o o f s e v e r a l h u n d r e d tr o n e . c . i n t h e p l a n e - p o l a r i z e d l i g h t m o d e a. r e f r a c t i v e i n d e x m a tc h w hen the long d ire c tio n of the fib er is p a r a lle l to the plane of p o la riz a tio n . In the plane p e rp e n d ic u la r to this the fib ers w ill exhibit a re fia c tiv e index less than that of the liquid. 1 3. R epeat 1 and 2 using C arg ille re fra c tiv e index liquid 1.544. U nder these conditions for 2 .c . (above) the re fra c tiv e index m a tc h w ill o ccu r w hen the sh o rt (d iam ete r) d ire c tio n of the fiber is p a r a lle l to the plane of p o la riz a tio n . The o th er index e x hibited will be g re a te r than that of the liquid. 4 . U s i n g t h e s l i d e p r e p a r e d i n 1, e x a m i n e t h e s a m p l e in t h e d i s p e r s i o n staining mode with central stop (dark-field). Any chrysotile fibers p resen t will exhibit blue colors, distinctly separating them from the non-chrysotile p articles. If this test is c a rrie d out with plane polarized light as the illu m i nating source the color exhibited will vary with fiber orientation, so that as the stage is rotated the chrysotile fibers will change color: blue --y blue -p u rp le . . -5- Again, for positive confirm ation, both co lo r and m orphology ( f ib e r s , la rg e l:d) c r i t e r i a m u s t be s a ti s f i e d . 5. If optical m ic r o s c o p y /d is p e r s io n stain in g gives n egative r e s u lts , ch ry so tile m ay be p r e s e n t w ith a d ia m e te r too s m a ll to be d etecte d by optical m icroscopy, thus, tra n sm issio n electron m icrosco p y w ith SA ED m u s t be e m p l o y e d . Follow ing is the tr a n s m is s io n m ic r o s c o p e p ro c e d u r e . If c h ry s o tile serp en tin e is detected at the s a m e level found by DTA by e ith e r m icro sco p ical m ethod, then the talc fails. / rwj f First Draft: February 1, 1973 / Microscopic Detection of Asbestos in Talc 1 by Arnold E. Schulze and William V. Eisenberg U.S. Food and Drug Administration, Washington, D.C. The six.kinds of asbestos can be 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 a JL .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 in 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 tlie 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 the 1.574 liquid look for asbestiform fibers with indices less than 1.574 in both extinction positions, and in the 1.590 liquid look for fibers with indices exceeding 1.390. 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 asbestiform 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 asbestiform fibers, make mounts in appropriate refractive index liquids, and refer to the optical crystallographic cata in the accompanying table. Substance Actinolite (variety of tremolite) Anosite Anthophyllite * Chrysotile OPTICAL CRYSTALLOGRAPHIC CHARACTERISTICS OF ASBESTOS MINERALS AND TALC Reference for n (2) p. 172 (8) p. 285 (4) p. 261 (4) p. 261 (2) p. 170 (2) p. 222 (5) p. 298 (2) p. 222 (2) p. 172 (6) p. 236 (2) p. 173 (2) p. 116 (2) p. 99 (2) p. 100 (3) p. 154 (8) p. 260 (6) p. 290 (8) p. 260 (2) p. 104 (1) p. 40 (1) P. 40 no: 1.614 1.615-1.655 s 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 n(3 1.630 1.625-1.665 ny 1.641 1.64-1.68 ~- -- mm mm -- 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 1.557 1.560 - 1.517 1.522 1.537-1.567 1.54-1.55 1.555 1.555 1.557 1.557 1.560 Extinction Inclined Parallel . Parallel Elongation Positive Positive Positive * T n0 Page 2 - OPTICAL CRYSTALLOGRAPHIC Substance Reference for n_________ na Crocidolite (Riebeckite) Talc Tremolate (2) P- 125 (2) P- 187 (6) P* 241 (2) P- 226 (2) P- 226 (2) P* 127 (8) P* 25 9 (2) Po 164 (3) p- 167 (6) p- 281 (8) p* 259 (1) p- 41 (1) p- 41 (1) p- 41 (7) p* 758 (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 1.693 1.695 1.695 1.697 1.538-1.545 1.539 1.539 1.539 1.540 1.541 1.544 1.545 1.599 1.599 1.599-1.612 1.600 1.602 1.602 1.602-1.623 1.6u4 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 __ 1.697 1.703 -- 1.703 1.589 1.539 1.589 nearly = ny 1.585 1.592 1.594 1.584 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 Page 3 - OPTICAL CRYSTALLOGRAPHIC CHARACTERISTICS OF ASBESTOS MINERALS AND TALC Rex ERENCES 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 Mlneralogist 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. The Microscopical Characters of Artificial Inorganic Solid Substances. New York. 1964.