Tobacco Documents Online

w A b Z6TSOT£90Z - CHLORITE d(oo.) ® KAOLI NITE dM) I SERfENTINE dVy,(oo4),taa2) HALLOYSITE d(00z) ° DICKITE dW4) Figure 4. Peak positions and relative intensities. The data of Tables 2 and 3 are presented combined, illustrating the problems of XRD identification when chlorite and serpentine, and possibly kaolinite, halloysite, or dickite are also present.

Three essential features are demonstrated in Tables 2 and 3, and Figures 2, 3, and 4: 1. The diagnostic peaks show considerable variation in the position in which thV occur (a2e=0.79° for chlorites and 1.05° for serpentines). 2. The chlorites and serpentines overlap and interfere with each other. 3. Basal peaks of the clay minerals kaolinite, halloysite, and dickite overlap the positions of the chlorite and serpentine peaks, and will interfere when present. The significance of the chlorite-serpentine interference is increased by the fact that chlorite is a very common accessory mineral associated with talcs, whereas serpentine is much less commonly associated. In spite of the chlorite-serpentine problem, numerous investigators have performed XRD identification and/or quantification of serpentine in chloritic talcs. It is obvious to us that they have misidentified asbestos as being present by overlooking the chlorite/serpentine interference and by misconcluding that a chlorite peak was serpentine. Other Methods Infrared Spectroscopy (IR) The infrared absorption spectrum of a material results from vibrational and bending frequencies of various atomic bonds within the structure. For example, Si-0 stretching frequencies produce similar IR peaks for all silicate minerals. As a result, IR spectra are not particularly useful for identifying the minerals present in a mixture, and the method certainly is not capable of determining whether or not a detected mineral is the asbestiform variety. Differential Thermal Analysis (DTA) The rearrangement or decomposition of mineral crystal structures due to thermal heating is a characteristic and reproducible reaction. It follows that DTA can identify specific minerals in a mixture but the method is not capable of determining morphology. Therefore, any DTA data which might point to the presence of a serpentine mineral could lead to misidenfying chrysotile asbestos in a talc when the mineral could well be a normally occurring platy antigorite having the same DTA pattern. Electron Microscopy Electron microscopic techniques of identification of asbestos have been amply covered in other presentations during this workshop. We do not intend to cover that subject again, but rather to point out some areas where asbestos can be misidentified. The high magnification attainable with electron microscopy is, in itself, inadequate as the sole index of mineral identity. For example, chrysotile is often identified by the presence of a hollow central core and streaked electron diffraction spots. But the clay mineral halloysite also crystallizes in that form and will produce a similar electron diffraction pattern. Therefore, In the absence of exact chemical composition, halloysite can be misidentified as asbestos. Similar care must be exercised to avoid misidentifying other fibrous clay inerals as asbestos, e.g., attapulgite and alpha sepiolite. In addition, talc ribbons can be mistaken to be asbestos, especially when some talcs have particles which roll up into spiral tubes giving the appearance of a chrysotile particle. Selected area electron diffraction is routinely used to identify a mineral particle as amphibole. Many investigators simply observe the electron diffraction pattern in the microscope and decide on the basis of general pattern geometry whether or not the particle is an amphibole. This can lead to misidentification, since numerous other minerals can give electron diffraction patterns with amphibole pattern geometry [10,11]. Careful measurement of an electron diffraction pattern is required in order to identify the type 350

of mineral which produced the pattern. Chemical composition is further required in order to have a chance at identifying the particular species when the mineral is a member of a complex group such as the amphiboles. Otherwise, misidentification will result. Cosmetic Talc Free from Asbestos ~ In the United States, we have a self-regulating association known as the Cosmetic Toiletry and Fragrance Association. In certifying the purity of the talcs which they use, they are aware that no single method can identify asbestos and their most recent spec- ification for cosmetic talc [12] combines two methods (XRD and optical microscopy) for monitoring their types of talc. The rationale is that a talc is first examined by XRD, and if even the smallest amount of amphibole is indicated, then the test proceeds into optical microscopy using a dispersion staining technique to determine whether or not the material contains asbestiform particles in the amphibole group. Summary This paper has categorized the main methods which have been used for detection of asbestos in talcs. The basic principles of the various methods were categorized to explain how asbestos has been and can be misidentified in talc. Generally, misidentifications arise by jumping to a conclusion from a single mineral characteristic, when, in fact, many characteristics are required to fully identify a mineral species and/or its variety. Both optical microscopy and XRD required a more detailed review than other methods since they have received the most attention from a monitoring point of view. This review is presented with the hope that our guidelines will enable analysts to avoid the misidentification of asbestos in talcs. References [1] Ampian, S. C., Asbestos minerals and their nonasbestos analogs. Mineral Fibers Session, Electron Microscopy of Microfibers Symposium, Penn State Univ., August, 1976. [2] Thompson, C. S., Discussion of the mineralogy of industrial talcs. U.S. Bureau of Mines Information Circular 8639, Proceedings of the Symposium on Talc, Washington, D.C., May 8, 1973. [3] National Bureau of Standards Staff, A report on the fiber content of eighty industrial talc samples obtained from, and using the procedures of, the Occupational Safety and Health Administration, 51 pp. (1977). [4] Bowndy, M. G., Gold, K., Burgers, W. A., and Dement, J. M., Exposure to industrial talc in Vermont talc mines and mills: AIHA Conference presentation, May 1977. [5] Rohl, A. N., Langer, A. M., Selikoff, I. J., Tordini, A., Klimentidis, R., Bowes, D. R., and Skinner, D. L. , Consumer talcums and powders: mineral and chemical characteriza- tion, Jour. of Toxicology and Environmental Health, 2, 255-284 (1976). [6] Rohl, A. N. and Langer, A. M., Identification and quantification of asbestos in talc, Environmental Health Perspectives, 9, 95-109 (1974). [7] Snider, D. W., Pfeiffer, D. E., and Mancuso, J. J., Asbestos form impurities in commercial talcum powders, Compass of Sigma Gamma Epsilon, 49, 65-67 (1972). [8] Scholl, R. and Drafts, R., 1977, XRD characterization of asbestiform reference minerals. Symposium on Electron Microscopy and X-Ray Applications to Environmental and Occupational Health Analyses, April 1977. 351 2063105144

0-9 [9] Jenkins, R., A review of x-ray diffraction procedures as related to the quantitative analysis of air particulates. Symposium on Electron Microscopy and X-Ray Applications to Environmental and Occupational Health Analyses, April 1977. [10] Zoltai, T. and Stout; J. H., Comments on asbestiform and fibrous mineral fragments, relative to Reserve Mining Company taconite deposits: Report to Minnesota Pollution Control Agency, 89 pp. (1976). [11] Lee, R., Electron optical identification of particulates: Symposium on Electron Microscopy and X-Ray Applications to Environmental and Occupational Health Analyses, April 1977. [12] CTFA Specification - COSMETIC TALC Issued 10/7/76, The Cosmetic, Toiletry and Fragrance Association, Inc. Discussion A. WILEY: You said that instantaneous recognition of SAD patterns is difficult. Could you give some examples as to what kind of confusions could exist in this? Can you confuse amphibole with serpentine or amphibole with talc, or is that kind of a gross mistake possible? J. KRAUSE: Those kinds of mistakes probably would not generally happen if you are looking at pyroxenes or olivine. Electron diffraction is not one of my areas of real expertise, but I think that you could possibly get feldspars that would give confusing patterns, depending upon their orientation in the microscope. L. MADSEN: We are using all the methods that have been talked about today for identi- fication for asbestos materials and do not in any way limit ourselves to fiber length and aspect ratios. J. WAGMAN: I would like to comment that it is possible by x-ray diffraction and through a special technique to identify and measure the presence of asbestos fibers even when they are in the presence of their non-fibrous counterparts. About two years ago this was demonstrated in a study which we supported at the Naval Research Laboratory in which samples were pre-treated so that fibers were first aligned and then the x-ray diffraction intensities measured at two different orientations with respect to the x-ray beam and in this way the intensity due to the non-fibrous counterparts could be subtracted from the total diffraction intensities. KRAUSE: You were putting the fibers in some specific preferred orientation in the sample and then looking for those orientations by XRD. WAGMAN: That is correct, and this had the advantage of not only making possible corrections, that is correcting for the non-fibrous material present, but also it greatly enhances the detectability for the fibers themselves. KRAUSE: Is this method being currently used? WAGMAN: This is a method whose feasibility was demonstrated and there are two publica- tions on this in the literature. Actually our objective was to apply this method to airborne samples, which is a much more difficult application incidently, I should think than in the case of talc. The problem here is a preparative problem in that an air sample usually has a lot of organic material, sticky material present which interferes with the ability to orient the fibers. This is a preparative problem which will have to be overcome. But I should think that in the case of talc samples you probably would not have that problem. 352

K. HEINRICH: Would the talc plates interfere just as well with the orientation of the fibers? WAGMAN: The orientation of the fibers is accooplished in an electric field, and the platy material does not preferentially orient itself. 'HEINRICH: I mean, just in the sense of a passive restraint to the movement of the fibers. WAGMAN: This of course would have to be tested experimentally. A. LANGER: We heard today from a representative of one of the member organizations of the Cosmetic, Fragrance, and Toiletry Associations, that of 3800 consumer talcs examined none contained chrysotile. Today you presented some interesting information on the identification of crocidolite in talc. Have you seen crocidolite in many talcs you have examined? . KRAUSE: No I have not seen it, nor did I say that I have. LANGER: It does not occur in consumer talcs, or is it industrial talc. I just do not see why the crocidolite issue was raised; have you seen it? KRAUSE: Just because I have not seen it certainly does not mean that it could not conceivably exist. All I was trying to do was point out that choosing a specific amphibole peak as being representative and definitive for giving a good identification of a particular amphibole species has great potential for error. There are many, many other minerals that could fall within that same two theta region. LANGER: I would agree with you that even though talcs occur in nature and they have great mineralogical variability they are still bound by the physical and chemical laws involving calcium-silicate rock systems. A mineral phase such as you described would not occur normally. N O 353 W ~ 0 ~ t