Document 222d23moezEbba2K8K9Zw3Lr

Information Circular 8639 Proceedings of the Symposium on Talc, Washington, D.C., May 8,1973 Compiled by Aurel Goodwin Metal and Nonmetal Mine Health and Safety, Washington, D.C. PLAINTIFFS EXHIBIT C A M -1 6 UNITED STATES DEPARTMENT OF THE INTERIOR Rogers C. B. Morton, Secretary BUREAU OF MINES Thom as V. Falkie. Director AbstractIntroduction. Opening Statement, by Donald P. Schlick. Opening Remarks, by Arthur P. Nelson. Mortality Experience of Nev York Talc Miners and Millers, by Morris Kicinfeld......... Characterization of Talc Dusts, by R. S- Lamar.......................... Characterization and Occurrence of Talc, by H. T. Mulryan............... Discussion of the Mineralogy of Industrial Talcs, by C. S. Thompson..... Experimental Studies on Biological Effects of Tremolite Talc on Hamsters, by William E. Smith...................................... The Biological Action of Talc and Other Silicate Minerals, by Cerrit V. H. Schepers............................................... Applicability of Asbestos Standard to Fibrous Talc, by William J. Nicholson................................................ Aspects of Mineralogy of Talc, by Arthur M. Langer...................... Mineralogy, Identification, and Quantification of Airborne Talc Dust, by T- D. Oulton........................................................ Medical Aspects of Talc, by Richard M. Spiegel.......................... g t] Jg 21 4) 4f JJ H N ft Ics are *bs r, co lesa generally by R. S. Lamer3 The Nature of Conmerclal Talea Clon, ehead e will be accepted It is important to make a clear distinction between commercial talc and ,U mineral. Pure talc mineral is a hydrous magnesium silicate having the -p.'sition Mg* (SiaOao )(0H)4 .* Limited isomorphous substitutions can occur in this structure.4 Crystal form Is generally raonoclinic. Individual r'icles of pure, finely milled talc appear platy or micaceous under the ..r.sc op e . Commercial talcs may or may not be pure talc mineral. These products are '-rvnly mixtures of talc mineral with other related minerals that were .Wed in the paragenesis of the talc mineral. 1erose ope, ) g such opti* I gence, and d to much and less tic les These associated minerals are in many cases caldte, dolomite, quartz, r-vticine, magnetite, magnesite, chlorite, tremollte, anthophyllite, and in -t cases chrysotile.* These may occur in various amounts and proportions in -ircial talcs from different sources or mines. Not all of these associated :-<rals occur in all commercial talcs. Some products are entirely free from >tiform minerals, and this distinction is also important.6 ble. The so-called "fibrous talcs'* appear fibrous because of the presence of stiform minerals. Pure tale mineral rarely appears fibrous in crystal - it. and is much more conmonly platy, lamillar, or micaceous. Specifically, Is by X-ray its own ns in a pat* uely the dll* hrough an al partici* , y and not :"agree with the definition of talc (fibrous)--tremollte as it appears in '''r.icntatlon of tha Threshold Limit Values for Substances in Workroom Air," - i-.lied by the American Conference of Governmental Industrial Hygienists, iitlon, 1971, p. 243. It is our opinion that this docianentation for talc :-rous" should be rewritten to eliminate any reference to "fibrous talc" but -Id refer the fact that the talc ores can contain fibrous contaminants are asbestiform minerals. This is important in view of the fact that 1 I n Wiley & Sons, Inc. Encyclopedia of Chemical Technology. Talc. V. 19, I 2d ed., 1969, p. 608. I r*--search Manager, Celite Division. Johns-Manville Corporation. for tha quaa coiaimaly `r, W. A., R. A. Howie, and J- Zussman. Rock-Forming Minerals. V. 3, -heet Silicates. Longmans, Green and Co., Ltd., London, 1962, p. 121. *:- 124 of work cited in footnote 3. a m 1971 f 126-129 of work cited in footnote 3. Ben M. Talc Deposits of Steatite Grade, Inyo County, California. Div. nation * * > Mines, State of California, Special Rapt. 8, August 1951. p. 35-36. "r`~ght, Lauren A. Geology of the Silver Lake Talc Deposits, San Bernardino, California. Div. of Mines, State of California, Special Rept. 38, July 1' _______________________________________________________________________ 3 the definition of the American Conference of Governmental Industrial Hygienists is part of the Federal Mandatory Standard under the Metal and metallic Mine Safety and Health Act. In addition to theae mlnevaloglcal differences, commercial talcs are supplied in a vide range of particle sizes, from 200 mesh, or finer, to lei _ than 5-micron maximum particle size. The end use for the product generally determines the particle size required.7 Characterization of Talc Dusts Talc dusts may be characterized according to mineral composition, chm 1 cal composition, particle shape, and particle size. Each of these will be described separately. Characterization of Mineral Composition This may be done according to a variety of commonly used and accepted methods. Petrographic Examination < A highly skilled petrographer, working with a petrographic microscope, can, in many cases, determine various mineral species by measuring such o p d * cal properties as index of refraction, extinction angle, birefringence, and crystal habit.8 As the particle size of a mineral dust is reduced to much below 5 microns these measurements become Increasingly difficult and lesa reliable. Most conmercial talcs contain a high proportion of particles smaller than 5 microns and other methods are therefore more reliable. Electron Probe - -f The basic principle underlying the identification of materials by or by electron diffraction is that each crystalline substance has its own . characteristic atomic structure which diffracts X-rays or electrons in a per* ticular pattern. The recognition of the pattern establishes uniquely the dll' frac ting substance. Newly developed electron probes, operating through an electron microscope, make possible the identification of individual particle* as small as l micron by this method. The equipment is very costly and not readily adopted to routine measurements. X-Ray Diffraction This is probably the most powerful and useful tool available for the eral characterization of talc dusts.8 Using equipment and techniques ccesnoelT 7 Industrial Minerals. Talc: Mlcronlzed Grades Lead the Way. January 1971 p. 9. Brindley, G. W. Experimental Methods. Ch. 1 in The X-Ray Identification ( Crystal Structures of Clay Minerals, ed. by G. Brown. L961, pr . j5-3* page 1 of work cited in footnote 8. haracteri comp letelyv ned by -C scanning involving .loved in the talc industry, it is possible to Identify as little as 1 per,-t of tremolite in otherwise purs talc mineral. There is evidence that dif,ri-nt tremolites respond differently and may show different lower limits of ..testability depending on crystal size and perfection. docential Thermal Analysis (DTA) . This procedure is useful but not as definitive as X-ray diffraction. ,:c. chlorite, serpentine, and the carbonate minerals show characteristic ..A curves but many of the peaks overlap and are not clearly defined in .ral mixtures. Tremolite shows a relatively weak D.T.A. reaction because : its low content of chemically combined water.10 While D.T.A. is a useful 1 for qualitative analysis, it is of limited value for quantitative deteritions. Particle size, sample composition, and experimental and instru ct .U variables are complicating factors. rasterization bv Chemical Composition j Complete chemical analyses are useful in identifying talc dusts but are ' . :t.> means definitive. Quantitative analyses by conventional wet methods or V n y fluorescent methods only help but do not yield the type of positive .ral identification obtainable by X-ray diffraction. * :~tu`le Shape , Partial morphology, shape, and structure are powerful tools for identlfli.'u of mineral dusts. Measurements made with an ordinary light-microscope " He misleading. For example, a talc platelet observed on edge, or on an .-'.v. may appear to be a fiber. Scanning electron micrographs are far more iHie and revealing because of greater possible magnification and depth of -'d. When observed in this manner, some talc platelets appear to roll up - a tubular shape not unlike kaolln-halloysite or serpentine -chrysotile. - -'cr, in the case of talc, this tubular structure is far more rare and is -n complete. Icicle Size Particle size may be determined by direct microscopic meesurement using s . - --ir micrometer eyepiece or by nu srement of perticles in en electron micro * Television scanning techniques and equipment are also available. "ir procedures Involve settling rate determinations in water or other '-ids. The Andreasen pipette is commonly used for this purpose. 3 fi "ackenzie, Robert C. (ed.). The Differential Thermal Investigation of Clays. A Mineral. Soc., Clay Minerala Croup, London, 1957. A`len, Terence. Particle Size Measurement. Chapman end Hall Ltd., London, 1968, pp. 45-61. rr> Clyde, Jr., end J. M. DallaVslle. Fine Particle Me .surement. The Macmillan Company, New York, 1959, pp. 43-78. 5 We heve attempted to show In the above presentation that the charactai ration of talc dusts is not simple. Mo one procedure or method is complete) definitive. We believe that mineral composition can best be determined by X-ray diffraction. Particle morphology is best defined by means of acanalo electron micrographs and particle size determined by sedimentation involvir the Andreasen pipette. irav.t f. U1 Jck. rr. CHARACTERIZATION AND OCCURRENCE OF TALC by H. T. Mulryan1 Hy none 1 H. T. Mulryan. I am president of Cyprus Hines Corporation'a '.'sited Sierra Division. The division is the world's largest producer of talc tn terms of product value. It operates talc mines in the States of Montana, Nevada, California, and Texas and tale processing units in the States of Montana, California, and iehraska, Belgium, and through an affiliate, Mexico. The division employs about 180 persons at its talc production units. Approximately half of them work in our Montana mines and mills, the remainder *rv acatterd among the other eight talc locations. The Montana product approaches the purity of pure talc mineral and its habit is platy or granular, Spending on the material source and fineness of grind. Figures 1 and 2 Illustrate the nature of the particles by transmission and scanning electron ricroscope, respectively. Bw*:. On the other hand, mixtures of minerals from other sources may contain M:tU> or no talc mineral and still be correctly known commercially as "talc." ?Uures 3 end 4 show the particle shapes of "talcs" from the Gouverneur iixtrict of New York State. The needles or fibers are mainly tremolite with ncUophyllite also commonly present. This type of commercial talc is not confined to New York State, being txti-nsively mined and processed in California. Table 1 compares the mineral intent of talc from New York, California, and Montana. The Silver Lake, CUf., tremolitic talc is similar to a typical New York State talc except for -issing anthophylllte and quartz impurities. TABLE l.` - Comparison of mineral content of talc from New York. w California, and Montana, in percent *ju 0" 6,001k -- Talc type Talc Carbonate Tremolite Anthophylllte Quartz Other 5v York............ 62 - 30 53 - Stiver Lake, Calif... 54 3 43 -- - ?sanint, Calif..... 82 12 Trace 2 Mont. 4 Mica. Hows tone", Mpnt.... 99 Siyerhead Mont.... 98 l 1 - - <0.5 - - - 1 Chlorite rrfcstdent, Cyprus Mines Corporation's United Sierra Division. I 7 Is I_________ I 5 micrometer* FIGURE 2. - Nature ol particles by transmission and scanning electron microscope (X 4,400), FIGURE 4. * Particle shapes of " talcs" from the Gouverneor District of New York Stole (X 880). Another California calc, the Panamint, contains calcite and mica as pr cipal impurities with no asbestos minerals present. The two Montana talcs, Yellowstone and Beaverhead, are high purity and also free of asbestos miner It has been the policy of the Cyprus Mines Corporation to X-ray the production workers at all of our operations annually. This policy has been effect for 5 years and these examinations have not turned up any lung or pleural cancer among our talc workers, nor have they revealed chronic respir tory disease of any kind- Seven of the employees were first exposed to talc dust 25 to UU years All the long service group were California workers who had been exposed to tremolitlc talcs as well as tremollte-free materials. When the threshold limit values for tremolitlc talcs were first made pu` lie, we became concerned about the possibility that our people had been inad-, vertently exposed to a health hazard and we took two steps. First, the division ceased production of all talcs containing detectable, amounts of tremolite and established an X-ray diffraction facility at our California mines to assure control. Second, the seven long-service employees together with four retirees and ex-employees were subjected to exhaustive physical examinations with emphasis' on the respiratory system, chest, and abdomen. This group's first exposurs td| talc dust ranged from 25 to 49 years ago. There are no records to tell us what conditions were like in the talc mines and mills of the 1920's and 1930'l but neither were mining nor milling techniques designed with dust control ss a major objective. The oldtime worker was, therefore, exposed to vastly greats* amounts of dust than his modern counterpart. Nevertheless, these exhaustive examinations failed to detect any sign of cancer among any of the long-service group. One of the retirees did reveal signs of possible pneionoconiosis. Cyprus Mines Corporation's Interest in this proceeding is one of concern for the welfare of its workers and for the truth. Although the medical data presented are admittedly limited, they contain no indication that talcs of either the pure Montana type or leas pure California varieties are carcinogenic. We should emphasize that Cyprus ' talc operations ara in compliance with threshold limit values both as relates to dust from nonasbestiform talc and fiber count. We realized that any dust in excessive amounts cannot be a posl" tive health factor and are making every effort to minimize employee exposure.