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sample under investigation. Great care must be exercised in the sample preparation, or the results become totally meaningless. Figure 8 shows a commercial talc in which approximately one percent of naturally occurring chrysotile was obscured from detection by the method of x-ray diffraction because of the presence of chlorite. w Figure 8. Commercial talc with naturally occurring co-deposits of chlorite and chrysotile asbestos. The asbestos is present at approximately the 1% concentration level. Bar is one micron. 335

1 Selected area electron diffraction was used in conjunction with the examination of morphology. Using this combined method, a single crystal or particle can be selected and analyzed. Single particles usually yielded spot patterns, but if a group or bundle of fibers was found and would transmit electrons, a polycrystalline ring type pattern would result. The use of selected area electron diffraction is mandatory to prove that the pseudo fibers of talc caused by plate-edge curling and talc plates on edge were actually talc, and not tremolite or an asbestiform mineral. A comparison of selected area electron diffraction patterns of these pseudo-fibers to that of the talc platelets showed that the identical compound, talc, was the only species present. Table 3 lists the principle electron diffraction maximum for talc, tremolite, and the asbestiform minerals [10]. In almost all cases, many more spots or rings were observed than are reported here. In Table 3, only the strongest lines which are the ones most likely to be observed have been tabulated. Table 3. Selected area electron diffraction maxima for talc and related mineralsa (in angstroms). Talc Tremolite Chrysatile Amosite Anthophyllite 4.60 4.51 4.58 3.88 4.58 2.62 2.59 3.67 3.45 2.65 2.32 2.53 2.61 3.00 2.27 1.74 2.32 2.14 2.64 1.75 1.59 2.27 1.70 1.74 1.55 1.53 2.04 1.55 1.61 1.33 1.33 1.86 1.34 1.55 1.28 1.28 1.69 1.29 1.32 1.23 1.65 a The data for chrysotile, amosite, and anthophyllite were taken from reference [11]. Conclusions The present work has shown that properly prepared samples of talc can be examined by x-ray diffraction to detect tremolite at levels down to 0.2 percent and chrysotile at the 0.5 percent level in the absence of chlorite. In the presence of chlorite, and at concen- tration levels lower than those stated above, the transmission electron microscope was found to provide reliable detection and identification of fibrous tremolite and the asbestifors minerals. The transmission electron microscope is the most sensitive we have found, and appears to be a more or less referee technique since, when morphology observations are coupled with selected area electron diffraction studies, there are no known interferences. light microscopy was helpful only in screening samples with large particles and high concentrations of objectionable fibers. Using the above techniques, we have been able to screen large numbers of talc speci- mens. We have been able to detect chrysotile and/or tremolite and the asbestiform minerals at levels down to 0.1 weight percent of fiber. We have been able to detect the asbestiform minerals in low concentration specifically by transmission electron microscopy with selected area electron diffraction, when the presence of the asbestos was masked by the presence of chlorite (which was also present at less than 5% concentration). We, there- fore, feel that we have a technique that allows us to detect and identify chrysotile fibrous tremolite, and asbestiform minerals at concentrations down to 0.1 percent by weight. 336

c, S References [1] Cralley, L. J., Key, M. M., Groth, D. H., Lainhart, W. S., and Ligo, R. M., Fibrous and mineral content of cosmetic talcum products, J. Amer. Indus. Hyq. Assoc., 29, 350 (1968). [2] Hogue, W. L. Jr. and Mallette, L. S., A study of workers exposed to talc and other dusting compounds in the rubber industry, J. Indus. Ea. Toxical. , 31, 359 (1949). [3] Smith, K. W., Plumonary disability in asbestos workers, Arch. Ind. Health, 12, 198 (1955). [4] Schepers, G. W. H. and Durkan, T. M., The effects of inhaled talc-mining dust on the human lung, AMA Arch. Indus. Health, 12, 182 (1955). [5] Brodeur, P., The magic mineral, New Yorker Ma aZine, p. 12, October 1968. [6] Merliss, R. R., Talc-treated rice and Japanese stomach cancer, Science, 173, 1141- 1142 (1971). [7] Sax, N. Irving, Ed., "Talc", dangerous properties of industrial materials, Reinhold Publishing Corp., New York, 1963, p. 1217. [8] Sax, N. Irving, Ed., "Talc", dangerous properties of industrial materials, Reinhold Publishing Corp., New York, 1963, p. 469. [9] Stanley, H. D., The detection and identification of asbestos and asbestiform minerals in talc, 34th Annual Proceedings of the Electron Microscopy Society of America, p. 618-619, August, 1976. [10] Timbrell, V., Characteristics of the International Union Against Cancer Standard Reference Samples of Asbestos, Proc. Int. Pneumoconiosis Conf., Johannesburg, 1969. 337 w 0

Discussion ,1. SCHELTZ: As the spokesman for the Cosmetic, Toiletry, and Fragrance Association, I would like to make several comments. First: In a survey conducted recently by that organization among its member companies, some thirty-four hundred samples of cosmetic talc from both domestic and international sources were analyzed and not a single sample was found to contain chrysotile asbestos. We are aware that the spiking of chrysotile asbestos into talc can be analyzed effectively by x-ray diffractometry. These samples of talc are cosmetic which, by definition, means that they contain at least 90 percent of the actual talc mineral species. I would also like to comment on quantitative analysis of amphibole minerals, by x-ray diffractometry. While x-ray diffractometry is a good technique to detect amphibole minerals, one needs to be very cautious in attempting to perform a quanti- tative analysis. I think Dr. Haartz from NIOSH just pointed out that there are major differences based not only on compositional variations, but also morphological character- istics that make not only peak heights but also integrated peak intensity variable. So, while x-ray diffractometry is a good method for detection, it is not necessarily good for quantitative analysis. I would also like to point out that the Cosmetic, Toiletry, and Fragrance Association is currently undertaking an extensive analysis of consumer talcum products for the traces of amphibole minerals. H. STANLEY: As I understand it, your first point is that x-ray diffraction is not particularly quantitative for determination of amphiboles in talc. We haven't found that to be the case in our laboratory, and I think there are a number of people here that I have been talking to the last several days that have had the same experience. The x-ray diffraction is good if you want to know, for example, the total amount of tremolite present, but if you want to know if some of that tremolite is fibrous, then as I attempted to point out, you have to go to transmitted electron microscopy with selected area diffraction. SCHELTZ: That's exactly my point. ..... (rest inaudible) ..... As to the second point, we were talking about cosmetic grade talc of at least 90 per- cent purity, the purity of the Montana talc is in excess of 96 percent, so I understand your point. 338