Document pLBX2xgEwEzx7mojaYJgBEZd

FILE NAME Talc TALC DATE 1973 May 8 DOC TALC103 DOCUMENT DESCRIPTION Proceedings of the Symposium on Talc - US Dept of the Interior = IC 8639 Bureau of Mines Information Circular Proceedings of the Symposium on Talc Washington D.C. May 8 1973 UNITED STATES DEPARTMENT OF THE INTERIOR 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. UNITED STATES DEPARTMENT OF THE INTERIOR Rogers C. B. Morton Secretary BUREAU OF MINES Thomas V. Falkie Director This publication has been cataloged as follows Goodwin Aurel comp Proceedings of the Symposium on Talc Washington D.C. May 8 1973. Washington U.S. Bureau of Mines 1974 102 p illus tables U.S. Bureau of Mines Information circular 8639 Includes bibliography 1. 1973. Cong I. Symposium on Talc Washington II U.S. Bureau of Mines III Title Series D.C. TN23.U71 no 8639 622.06173 U.S. Dept. of the Int Library CONTENTS Abstract cc ec cee cece eee ete tee te eee eee tebe eee nett t ben eaneseeenes Introduction Introduction Introduction Introduction Introduction Introduction Introduction Introduction .. . Opening Statement by Donald P. Schlick ... e ns eees eee toes eee tees see seee . Opening Remarks by Arthur P. Nelson Mortality Experience of New York Talc .. cece sac cece cr crt eee Miners and Millers by Morris Kleinfeld . ccc ccc Characterization of Talc Dusts by R. cece eet e ete n ee seeereres sae cceees 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 The Biological by William E. Smith Action of Talc and Other Silicacteece ccc cece creer erect este teens Minerals by Gerrit W. H. Schepers eee ceeee 29 Applicability of Asbestos Standard to Fibrous Talc by William J. Nicholson bee enees ee Aspects of Mineralogy of Talc by Arthur M. Langer Y 220 220 Mineralogy Identification by T. D. Oulton by Richard Spiegel Medical Aspects of Talc and Quantification of Airborne Talc Dust enero eenas M. tevneeee . Cd eneeerne 2 97 PROCEEDINGS OF THE SYMPOSIUM ON TALC WASHINGTON D.C. MAY 8 1973 compiled by Aurel Goodwin 1 ABSTRACT A symposium on the health hazards of respirable dust in the mining and milling of talc was held on May 8 1973 in Washington D.C. The results of medical effects on both human and animal subjects were presented Methods for identification and classification of talc minerals were also presented Ana- lytical techniques discussed included ray diffraction scanning electron microscope observation electron probe and optical microscopy INTRODUCTION The Secretary of the Interior has the responsibility under the Nonmetallic Mine Safety Act to develop standards for the purpose of tection of life and the promotion of health and safety in metal and Metal and the prononmetal mines There are approximately 66 different mineral commodities produced by these mines The multitude of minerals in the ore and host rock present a varied hazard to the health of employees of the mineral industries It therefore becomes necessary to attempt to evaluate the unique health effects and levels of exposure individuals exposed to which these can be tolerated minerals without for the adverse working lifetime of effect on their health It also becomes necessary to be able to identify and quantitatively measure the concentration of these minerals in respirable dusts This symposium effects and mineral was held to receive data identification of talc relevant to both the health Talc is a term used for a product having certain physical properties The mineral composition of talc varies depending on its source and on the uses for which it is intended Presentations were given relating to the characterization of airborne dust from mining and milling of talc minerals and medical data from studies of talc workers asbestos workers and animal studies Chief Division of Health Metal Chief Health Division Mining MESA Washington D.C. and Nonmetal Mine Health and Safety now Enforcement and Safety Administration OPENING STATEMENT by Donald P. Schlick name Ladies and gentlemen I should is Donald P. Schlick and I am like to welcome you to this Deputy --Health and symposium - My Safety Until about 30 years ago occupational chest disease meant primarily diseases related to breathing dust containing free silica Now however we recognize that a number of other dusts also are involved in contributing to occupational diseases such as coal dust and the silicates and talc This symposium was called to obtain data relating to the characterization of talc dust and the adverse affects on persons occupationally exposed to talc dust during their working life This data is intended to provide at least a partial basis for developing a standard adequate to protect those persons employed in the mining and milling of talc minerals As used commercially the term talc refers primarily to physical properties rather than to a specific mineral Thus the American Conference of Governmental Industrial Hygienists in their Threshold Limit Values refers to tale and to talc fibrous In the documentation of TLV the TLV's they refer to talc nonasbestiform and talc tremolite fibrous talc is the talc with the associated amphibole Thus The only reference in the documentation for nonasbestiform talc is dated 1935 and the most recent reference to fibrous talc is dated 1963 Current standards for exposure in mining and milling Because of the difficulties in of talc are the Threshold Limit Values distinguishing fibrous and nonfibrous talc and because of much recent work on asbestos particularly on the toxic effects of the different types of asbestos we have called this meeting This meeting is called however to consider asbestos only as it relates to called fibrous talc ing Our goal is to establish in the mining and milling a standard which will assure that persons work- of talc will not suffer impaired health due to their employment We hope that this symposium will result in providing to- date information on which to base a standard As stated in the announcement of the before meeting we shall however include written June 1 1973 as part of this symposium I communications should like to received request that all speakers who do not have written statements provide a written copy of their presentation by that time I Arthur thank you all for P. Nelson Acting coming and I will now turn the meeting over to Assistant Director Metal and Nonmetal Mine Health and Safety Acting Deputy Washington Administrator D.C formerly Mining Deputy Enforcement and Safety Administration Director Health and Safety Bureau of Mines OPENING REMARKS by Arthur P. Nelson,, This the first meeting we have had of this type for Metal and Nonmetal Mines We are gathering data prior to developing new standards and presenting them to our Advisory Committee As you know our standards for air quality presently are the American Conference of Governmental Industrial Hygienists Threshold Limit Values We have found inadequacies in these standards and will probably deviate from them more in the future as better data become available The talc industry is composed of approximately 65 operations employing about 1,200 workers These operations are distributed throughout the United States U.S. production in 1972 was about 1.1 million tons with 86 percent produced in five States California Montana New York Texas and Vermont A small amount of talc about 30,000 tons is imported annually mainly from Canada Italy and France The proceedings of this meeting will be used in part to arrive at standards for exposure of persons working in mining and milling of talc minerals The Bureau of Mines and the U.S. Department of Health Education and Welfare are planning a joint survey of environmental conditions and health status of employees in the talc mining and milling industry Data that will be presented here will contribute much that in the past development of improved standards today should has not been be of immense value and available to support the I welcome you here today and I hope that you have a good and productive meeting Thank you Acting Assistant Administrator Metal and Nonmetal Mine Health and Safety Mining Enforcement and Safety Administration Washington D.C formerly Acting Assistant Director Metal and Nonmetal Mine Health and Safety Bureau of Mines MORTALITY EXPERIENCE OF NEW YORK TALC MINERS AND MILLERS by Morris Kleinfeld M.D.1 My former colleagues in the Division of Industrial Hygiene of New York State and I have had the opportunity to conduct numerous studies of talc workers in New York State including clinical physiological radiological and environmental observations 5 .3 In addition we have also studied the mortality experiences among workers in talc mining and milling In most instances we have had the invaluable opportunity to correlate the clinical with the environmental data In general we have found that sustained inhalation of significant amounts of commercial talc dust over an extended period of time or where there was a significant elapsed time from initial exposure can produce a symptomatic form of pneumoconiosis The commercial talc to which the talc workers were exposed contained not only the mineral talc but also other silicates such as serpentine tremolite anthophyllite and other ingredients predominantly carbonates Moreover free silica was often pres- ent in the dust in variable amounts usually not averaging more than 3 percent Specifically with regard to our mortality experiences among talc workers we found in an earlier study of talc workers miners and millers who had 15 or more years of carcinoma of the exposure lung and to talc dust pleura among that the proportional mortality from these workers was four times that of the general population However the significant increase in incidence of malignancy appears in the older talc workers namely those in the 60- to year age group rather than in the 40- to year age group 3 This observation in the talc workers was at variance with those found in a group of asbestos insulators who had the same duration of exposure covering a similar time period 2 The asbestos insulators showed an mortality from lung cancer in both age categories increased incidence of The incidence of carcinoma of the gastrointestinal tract and nificantly different from that of asbestos insulators the incidence peritoneum among talc workers was not sigthe general population whereas among the of gastrointestinal malignancy was signifi- cantly higher than earlier occurrence that of the general population We postulated that the of malignancies among the asbestos insulators was due to two factors The first was the relatively greater carcinogenicity of the chryso- tile asbestos as comparetdo commercial the insulators to greater quantities of talc workers who were exposed to lesser talc the second was the exposure of chrysotile asbestos as compared to the quantities of commercial talc dust which was admixed with appreciable amounts of tremolite and anthophyllite asbestos Our observations favored the first factor The earlier study 3 also showed an increased incidence of deaths due to talc pneumoconiosis and its complications Formerly Director Division of Industrial Hygiene New York State Underlined numbers in parentheses refer to items in the list of references at the end of each chapter A followup study was made to bring our mortality data among the talc workers up to date and to provide additional information not reported in the earlier study The pertinent data is presented in the material that follows All the talc workers employed in 1940 who had accumulated 15 or more years of exposure to commercial talc dust imum of 15 years of such exposure between as well as those who achieved a min1940 and 1969 were included in the followup study The group overall number constituted totaled 260 workers and the total work force in it is believed that the the worker population under study The data were obtained from a number of sources Plant records were examined and the work history of each individual was detailed to include job changes and specific years of employment all instances where they were available Death certificates were studied in The records of the physicians who had attended the workers privately were reviewed Substantial medical information on the majority of the workers was available in the files of the Division of Industrial Hygiene and was used as an additional source of data Hospital records including autopsy reports and histological specimens were examined wherever available Autopsy or biopsy records were obtained in 38 of the 108 deaths A comparison was made of the observed proportional mortality rates from the specific causes with the expected rates among similar population groups and was found satisfactory for a descriptive study of this nature The proportions of observed mortality attributed to cancer of the lung and pleura and of the gastrointestinal tract and peritoneum and cardiac diseases were compared to the expected mortalities due to the above causes in the various age groups The expected mortality for the total group represents the proportion of deaths among white men in the United States due to the specific causes in the year 1955. This particular year was chosen as standard because it was the median year of death among the 108 deaths For each of the year periods the median years namely 1942 1947 1952 1957 and 1962 were selected were In the group of 260 tale workers studied there were a total of 25 deaths from malignancies Of these 25 108 deaths There deaths 13 were due to lung and pleural malignancies 9 were due to gastrointestinal and peritoneal malignancies and 3 were due to other malignancies Thirty deaths resulted from cardiac disease other than cor pulmonale and 29 deaths were attributable to pneumoconiosis and its complications Accidents and suicides accounted for 8 deaths and there were 16 deaths due to other causes table 1 The average age at death of the 108 talc workers was 60.3 years with a range of from 38 to 84 years Environmental exposure data was available in 97 of the 108 death cases The mean duration of exposure for this group was 24.1 years with a range of 15 to 47 years The dust exposure was predominantly to talc tremolite anthophyllite carbonate dusts and a small amount of free silica Comparative dust counts at the talc mines and mills prior to 1945 and between 1946 and 1969 were obtained table 2 TABLE 1. - Causes of death in 108 talc workers from 1940 to 1969 Cause of death Malign0a ... n cecc e eei e cee ce ens ces Cee e we eeenes Lung and pleura cece se ecncccceeces bees eenee Gastrointestinal and peritoneal eee eeee cece eee All other malignan cccc cca i cecee ceces ces Cardiac deaths other than cor pulmonale Pneumoconiosis and complications Accidents or suicides cc ccc ec cece ccc e ese ceeeeces All other causes .. cece cece cence cre eececccaecees Total eet ceca ees cee ees eee ses No. {| Percent 25 23.1 13 12.0 9 8.3 3 2.8 30 27.8 29 26.9 8 7.4 16 14.8 | 108 100.0 TABLE 2 - Comparative dust and fiber counts at the various talc mining and milling operations Drilling Mucking Crushing Screening Milling Garnering and Dust count,, Dust count,, Fiber : . Average Average Median 1945 1946-65 818 413 5 3 120 30 5 5 1948 1948-65 1948-65 Average Median 1966-69 19 19 9 9 1966-69 Average 1972 7 7 3 3 counte 32 32 180 69 69 42 232 61 37 232 28 - 20 - 35 15 62 - - - 92 75 25 20 40 24 7 7 25 separating 278 70 222 2223 Pulverizing - - 222 2223 Bagging 151 129 222 2223 Railroad - 29 - 25 13 - 9 - 27 - 27 27 47 and truck loading - - 73 63 43 20 Blow room 1,227 | 1,196 - - - - Open chutes 125 83 = - - : count Dust in mppcf 1 counts in No. fibers 5...in Fiber ' Operation discontinued after 1948 length 36 - = 28 - = 24 1 = With regard to the deaths due to malignancies 12 of the 13 malignancies of the lung and pleura were carcinomas of the lung and 1 was a fibrosarcoma of the pleura Of the nine malignancies of the gastrointestinal tract and perito- neum three were cancers of the stomach two were cancers of the liver one of of which was a primary hepatoma of the liver and the other a metastasis from a gastrointestinal malignancy one was a cancer of the colon two were cancers of the pancreas and one was a pertoneal mesothelioma The three retroperitoneal involving other sites included one chronic lymphatic leukemia and one Hodgkins reticulum cell disease table 3 malignancies sarcoma one The overall proportional mortality or carcinoma of the lung and the pleura was four times that expected Consistent with our previous observation a significant increase appeared to occur in the 60- to 79 year age group rather thanthan in the 40- to age group table 4 As I have already mentioned this finding year was at variance with what we had observedobserved among asbestos finding among talc workers insulators where the observed values in both the 40- to 59 year and 60- to 79 nificantly different from the expected values year age groups were sigIn the absence of adequate smoking data one cannot assess the role played by smoking smoking in accounting for the differences in the occurrence of malignancies TABLE 3. - Causes of death in 108 talc workers,, from 1940 to 1969 Cause of death Malignancies 1940-44 1945-49 1945-49 1950-54 1955-59 1960-64 1965-69 1965-69 | Total Lung pleura Stomach and - 2 511 21 13 ..c.ccececsssccvees - - 511 - 21 3 Liver cece ceens cece esc c Colon cccesecrccce toes - 511 - + 2 - - Pancreas see ed teeee - - HIINI - - 1 cee - = 2 Peritoneum Other malignancies Cardiac diseases Pneumoconiosis and 1 1 - - HIINI - - HIINI 1 3 - 16 10 1 3 16 HIINI 6 00 7 30 complications Accidents and suicides Othe cece r cee rs eece Total see toes Includes workers having had at 21 1 - 7 least least 4 423 423 17 15 or more 21 21 1 8 years 82 925 82 925 1 925 25 28 of exposure to 1 29 1 8 6 16 23 108 talc dust TABLE 4 - Deaths and proportional mortality from carcinomas of the respiratory tract of the gastrointestinal tract and from cardiac diseases among workers by age group from 1940 to 1969 Age group 40 40-59 60-79 80-84 Total mortality Total deaths Deaths and proportional Deaths and proportional and proportional from respira- mortality from gastro- mortality from cardiac tory cancers intestinal cancers diseases No. ObservedObserved Expected Observed Expected Observed Expected percent | percent percent | percent percent percent 3 0 0 1.6 0 0 2.5 1 33.3 21.1 47 4 8.5 5.2 3 6.4 5.7 11 24.4 44.2 54 9 16.6 3.6 4 7.4 7.2 17 31.5 47.8 4 0 0 1.1 1 25.0 5.3 1 25.0 47.1 108 13 12.0 3.7 8 7.4 6.5 30 2.8 45.8 When carcinoma of the lung and pleura was related to each of the six year periods namely from 1940 to 1969 it is important to note that the observed proportional mortality from carcinoma of the lung was approximately four times as much as the expected mortality during the period 1945-49 and dropped to approach the expected mortality from 1960 to 1964 and from 1965 to 1969 table The differ- ences between the observed and expected mortality rates were significant in 1950-54 and insignificant in 1960-64 and in 1965-69 The improved mortality experience between 1960 and 1969 and to 1973 for lung and pleural cancers is particularly pertinent since environmental control have resulted in an appreciable reduction in the dust count in ent threshold the mines and mills although limit value for asbestos dust the fiber count still by approximately four exceeds to five the prestimes table 2 This finding indicates that the present threshold limit value of 5 fibers with a fiber length greater than 5 microns for fibrous including tremolite and anthophyllite is basically adequate talc TABLE 5. - Deaths and expected mortality from cancer of the lung and pleura and of the gastrointestinal tract and peritoneum among talc workers from 1940 to 1969 Lung and pleura Gastrointestinal tract and peritoneum Proportional mortality Proportional mortality Deaths percent P Deaths percent P 1940-44 0 1945-49 2 1950-54 1 1955-59 5 1960-64 3 1965-69 2 Total | 13 Observed 0 11.7 12.5 20.0 10.7 8.7 = | Expected 2.0 3.1 4.3 5.7 6.7 7.7 = 1 1 SSS 1 SSS 1 S 3 NS 1 NS 2 > 9 Observed | Expected 14.3 7.8 NS 5.8 7.8 NS 12.5 7.1 NS 12.0 6.7 NS 3.6 6.3 NS 9.5 6.1 NS - - - P = Probability S ====== Significant NS = Not significant With regard to cancer of the gastrointestinal tract and peritoneum among the talc workers we did not find any significant difference between the observed and expected values in the overall and specific age groups studied table 4 and these findings are consistent with those reported by Kiviluoto and Meurman 1 among anthophyllite workers These findings differ from those observed in asbestos insulators where a significant increase in the observed incidence of gastrointestinal malignancy was found in the overall and specific age groups studied 3 Our findings among asbestos insulators were similar to those reported by Selikoff Hammond and Churg 7 Of the 29 deaths due to pneumoconiosis and its complications 20 were due to cor pulmonale 5 to advanced tuberculosis and 4 to bronchopneumonia The lapsed time from the first commercial talc dust exposure to death in this group averaged 30.9 years with a range of 15 to 46 years All 29 had their initial exposures prior to 1945 at which time more effective engineering controls including wet drilling in the talc mines were introduced The percentage of deaths due to pneumoconiosis and its complications has decreased by more than 50 percent in the last year period studied namely 1965-69 as compared to the preceding year period 1960-64 table 3 The number of deaths probably reflects the greater exposures which occurred in the earlier years of employment A longer interval must elapse however before the effect of controls on the incidence of pneumoconiosis can be appraised more definitively in the plant studied It is noteworthy however that in another study of a different plant processing a similar mixture of talc tremolite and anthophyllite but wherein controls were installed at the inception of opera- tions in 1948 only 1 out of 39 workers had a chest roentgenogram consistent with pneumoconiosis The mean exposure of the 39 workers was 16.2 years with a range of from 11 to 22 years The worker whose chest roentgenogram was consistent with pneumoconiosis was a year old man who had cough a Grade 1 dyspnea and who worked a nonproductive incidence of as a janitor for 11 years The low fiber count pneumoconiosis was found despite and dust count in this plant 4 the presence of relatively The fiber count exceeded high to six times the present treshold limit value of 5 fibers with a lengbtyh two greater than 5 microns In terms of ciates 6 found no asbestosis among weighted averages Murphy workers exposed less than 60 and asso- ticles per cubic foot mppcf years to chrysotile and million par- struction ations 4 In the it was study found of the that plant having controls amosite in ship since the start con- of oper- an appreciable number of workers exceed the 60 years but did not show any evidence of by the criteria of Murphy and associates The pneumoconiosis as determined plant having controls from the findings from the study of the start of operations suggest that tremolite and daunstthophyllite are less fibrogenic than chrysotile or amosite at comparable exposures Of the 30 cardiac deaths excluding cor pulmonale 22 had Rdaitsheearse 5 had hypertensive heart disease and 3 had rheumatic hceoarrotnardyisaeratseery surprising was the observation that the observed from cardiac disease was lower than proportional mortality the expected mortality in all year periods except the first namely 1940-1944 table 6 It seems reasonable to state on the basis of the remaining data that the overall observed tional mortality from cardiac disease propor- propor- among talc workers was lower than the expected mortality The decreased mortality from cardiac disease workers cannot be attributed to a among talc predisposition to lung cancer which gener- gener- ally results in the death of these workers be expected to succumb to cardiac disease at earlier As ages before they might demonstrated the decreased proportional mortality from cardiac disease was present in both the 40- to year as well as the 60- to year age groups table 4 If the lung was a factor one would have expected a difference in imnacliidgennacency of between these two age groups cardiac disease is to The true explanation for the lower incidence of open conjecture The rural environment in which the talc workers lived as well as the possibility that they smoked account for the lower mortality due to cardiac disease less may national rate as compared to the TABLE 6 - Deaths and expected mortality from cardiac disease among talc workers from 1940 to 1969 1940-44 1945-49 1950-54 1955-59 1960-64 1965-69 Total Deaths | Proportional mortality percent Observed Expected 3 42.8 37.4 6 35.3 41.0 0 0 46.0 6 24.0 46.5 8 28.6 46.6 7 30.4 45.5 30 - - 10 I trust that the information I have submitted this morning will hparzoavriddse the Bureau of Mines with essential data relating to the occupational dust in order to evaluate the of exposure to talc fibrous talc and tremolite limit value for pure talc and talc mixed adequacy of the existing threshold with tremolite and anthophyllite 11 References Kiviluoto R. and L. Meurman Results of Asbestos Exposure in Finland Ch in Pneumoconiosis ed by H. A. Shapiro Proc of the Internat Conf Johannesburg South Africa 1969 pp 180-186 Oxford Press Cape Town 1970 University Kleinfeld M. J. Messite and O. Kooyman Mortality Experience in a Group of Asbestos Workers AMA Archives of Environmental 1967 pp 177-180 Health v 15 Kleinfeld M. J. Messite O. Kooyman and M. Zaki Mortality Among Talc Miners and Millers in New York State AMA Archives of Environmental Health v 14 1967 pp 663-667 Kleinfeld M. J. Messite and A. M. Langer to Asbestiform Minerals in Commercial Talc Res v 6 No. 2 June 1973 p 132 A Study of Workers Exposed Manufacture Environmental Kleinfeld M. J. Messite J. Shapiro and R. Swencicki Effect of Talc Dust Inhalation on Lung Function AMA Archives of Environmental Health v 10 1965 pp 431-437 Murphy R. L. M. Jr. B. G. Ferris of Low Concentrations of Asbestos 1971 pp 1271-1278 W. A. Burgess and New England J. of others Effects Medicine v 285 Selikoff I. J. E. C. Hammond and J. Churg Mortality Experiences of Asbestos Insulation Workers 1943-1968 Ch in H. A. Shapiro Pneumoconiosis ed by Proc of the Internat Conf Johannesburg South Africa 1969 pp 180-186 Oxford University Press Cape Town 1970 12 CHARACTERISTICS OF TALC DUSTS,, by R. S. Lamara The Nature of Commercial Talcs talc It is important to make a clear distinction between commercial talc and mineral Pure talc mineral is a hydrous magnesium silicate having the OH composition Mga 020 Limited isomorphous substitutions can occur within this structure Crystal form is generally monoclinic Individual particles of pure finely milled talc appear platy or micaceous under the microscope Commercial talcs may or may not be pure talc mineral These products commonly mixtures of talc mineral with other related minerals that were involved in the paragenesis of the talc mineral are These associated minerals are in many cases calcite dolomite quartz serpentine magnetite magnesite chlorite tremolite anthophyllite and in some cases chrysotile These may occur in various amounts and proportions in commercial talcs from different sources or mines Not all of these associated minerals occur in all commercial talcs Some products are entirely free from asbestiform minerals and this distinction is also important.e important.e The called fibrous talcs appear fibrous because of the presence of asbestiform minerals Pure talc mineral rarely appears fibrous in crystal habit and is much more commonly we disagree with the definition Documentation of the Threshold platy lamillar or micaceous Specifically of talc --tremolite as it appears in Limit Values for Substances in Workroom Air published by the American Conference of Governmental Industrial Hygienists 3d edition 1971 p 243. It is our opinion that this documentation for talc fibrous should be rewritten to eliminate any reference to fibrous talc but should refer to the fact that the talc ores can contain fibrous contaminants which are asbestiform minerals This is important in view of the fact that John Wiley & Sons Inc. Encyclopedia of Chemical Technology Talc V. 19 2d ed 1969 p 608 Research Manager Celite Division Manville Corporation Deer W. A. R. A. Howie and J. Zussman Forming Minerals Sheet Silicates Longmans Green and Co. Ltd. London 1962 V. 3 p 121 Page 124 of work cited in footnote 3 Pages 126-129 of work cited in footnote 3 Page Ben M. Talc Deposits of Steatite Grade Inyo County California Div of Mines State of California Special Rept 8 August 1951 Wright Lauren A. Geology of the Silver Lake Talc Deposits San Bernardino California Div of Mines State of California Special Rept 38 July 1954 13 the definition of the American Conference of Governmental Industrial Hygienists is part of the Federal Mandatory Standard under the Metal metallic Mine Safety and Health Act and Non- In addition to these mineralogical differences supplied in a wide range of particle sizes from 200 commercial talcs are also than micron maximum particle size mesh or finer to less The end use for the product generally determines the particle size required Characterization of Talc Dusts Talc dusts may be characterized cal composition particle shape and described separately according to mineral particle size Each composition chemi- of these will be Characterization of Mineral Composition methoTdhsis may be done according to a variety of commonly used and accepted Petrographic Examination A highly skilled petrographer working with a petrographic microscope can in many cases determine various mineral cal species by measuring such opti- properties as index of refraction extinction angle birefringence crystal habit.8 As the particle size of a mineral dust is reduced and below 5 microns these to much measurements become increasingly difficult and less reliable Most commercial talcs contain a high proportion of particles smaller than 5 microns and other methods are therefore more reliable Electron Probe The basic principle underlying the identification of materials or by electron diffraction is that each by ray crystalline substance has its own characteristic atomic structure which diffracts rays or electrons in ticular pattern The recognition of the a par- pattern establishes uniquely the dif- fracting substance Newly developed electron probes operating through an electron microscope make possible the identification of individual as small as 1 micron by this method particles The equipment is very costly and not readily adopted to routine measurements Ray Diffraction eral This is probably characterization the most powerful and useful tool available for of talc dusts. ,, Using equipment and techniques the min- commonly Industrial Minerals p9 Talc Micronized Grades Lead the Way January 1971 Brindley G. W. Experimental Methods Crystal Structures of Clay Minerals Page 1 of work cited in footnote 8 Ch 1 in ed by G. The Ray Identification Brown 1961 pp 35-36 and 14 employed in the talc cent of tremolite in industry otherwise it is possible to identify as little as 1 per- pure talc mineral There is evidence that dif- ferent tremolites respond differently and may show different lower limits of detectability depending on crystal size and perfection Differential Thermal Analysis DTA This procedure is useful but not as definitive as ray diffraction Talc chlorite serpentine and the D.T.A. curves but many of the peaks carbonate minerals show characteristic overlap and are not clearly defined in mineral mixtures Tremolite shows a relatively weak D.T.A. reaction because of its low content of chemically combined water.10 While D.T.A. is a useful tool for qualitative analysis it is of limited value for quantitative deter- minations Particle size sample composition and experimental and instru- mental variables are complicating factors Characterization by Chemical Composition Complete chemical analyses are useful in identifying talc dusts but are by no means definitive Quantitative analyses by conventional wet methods or by ray fluorescent methods only help but do not yield the type of positive mineral identification obtainable by ray diffraction Particle Shape Partial morphology shape and structure are powerful tools for identifi- cation of mineral dusts Measurements made with an ordinary microscope can be misleading For example a talc platelet observed on edge or on an angle may appear to be a fiber Scanning electron micrographs are far more reliable and revealing because of greater possible magnification and depth of field When observed in this manner some talc platelets appear to roll up into a tubular shape However in the case not unlike halloysite or of talc this tubular structure serpentine is far more rare and is seldom complete Particle Size Particle size may be determined by direct microscopic measurement using a filar micrometer eyepiece or by measurement of particles in an electron micro- Television scanning techniques and equipment are also available graph.11 Other procedures involve settling rate determinations in water or other purpose liquids The Andreasen pipette is commonly used for this Mackenzie Robert C. ed The Differential Thermal Investigation Mineral Soc Clay Minerals Group London 1957 Allen Terence Particle Size Measurement Chapman and Hall Ltd. 1968 pp Orr Clyde Macmillan 45-61 Jr. and Company J. M. DallaValle Fine Particle New York 1959 pp 43-78 Measurement of Clays London The 15 Conclusions Conclusions We have attempted to show in the above presentation that the characteri- zation of talc dusts is definitive We believe not simple that mineral No one procedure or composition can best method is completely be determined by ray diffraction Particle morphology is best defined by means of scanning electron micrographs and particle size determined by sedimentation involving the Andreasen pipette 16 CHARACTERIZATION AND OCCURRENCE OF TALC by H. T. Mulryan,, My name is H. T. Mulryan I am president of Cyprus Mines Corporation's United Sierra Division The division is the world's largest producer of talc in terms of product value It operates talc mines in the States of Montana Nevada California Texas and talc processing units in the States of Montana California and Nebraska Belgium and through an affiliate Mexico and The division employs about 180 persons at its talc production units Approximately half of them work in our Montana mines and mills the remainder are scatterd among the other eight talc locations The Montana product approaches the purity of pure talc mineral and its habit is platy or granular depending on the material source and fineness of grind Figures 1 and 2 illustrate the nature of the particles by transmission and scanning electron microscope respectively On the other hand mixtures of minerals from other sources may contain little or no talc mineral and still be correctly known commercially as talc Figures 3 and 4 show the particle shapes of talcs from the Gouverneur district of New York State The needles or fibers are mainly tremolite with anthophyllite also commonly present This type of commercial talc is not confined to New York State being extensively mined and processed in California Table 1 compares the mineral content of talc from New York California and Montana The Silver Lake Calif tremolitic talc is similar to a typical New York State talc except for the missing anthophyllite and quartz impurities TABLE 1 - Comparison of mineral content of talc from New York California and Montana in percent Talc type New York weet Silver Lake Calif Panamint Calif Yellowstone Mont Beaverhead Mont Talc 62 54 82 99 98 Carbonate | 132 132 12 1 1 Tremolite 30 43 - - Anthophyllite 5 3 - - Other - - Trace Mont 4 Mica - 0.5 - : - 1 Chlorite President Cyprus Mines Corporation's United Sierra Division = | 5 micrometers FIGURE 1. - Nature of particles by transmission and scanning electron microscope X 6,000 18 j CnC 5 micrometers FIGURE 2. - Nature of particles by transmission and scanning electron microscope X 4,400 i | 5 micrometers FIGURE 3. " Particle shapes of talcs from the Gouverneur District of New York State X 6,000 20 f ^' i i % 5 micrometers FIGURE 4. - Particle shapes of talcs from the Gouverneur District of New York State X 880 21 Another California talc the Panamint contains cipal impurities with no asbestos minerals present Yellowstone and Beaverhead are high purity and also calcite The two free of and mica as prinMontana talcs asbestos minerals It has been the policy of the Cyprus Mines Corporation to ray the production workers at all of our operations annually This policy has been in 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 tory disease of any kind respira- All Seven of the employees were first exposed to talc the long service group were California workers who tremolitic talcs as well as tremolite materials dust 25 to 44 years had been exposed to ago When the threshold limit values for tremolitic talcs were lic we became concerned about the possibility that our people vertently exposed to a health hazard and we took two steps first made pub- had been inad- First the division ceased production of amounts of tremolite and established an ray California mines to assure control all talcs containing diffraction facility detectable at our Second the seven service employees together with four retirees and employees were subjected to exhaustive physical examinations with emphasis on the respiratory system chest and abdomen This group's first exposure to talc dust ranged from 25 to 49 years ago There are no records to tell us nor what conditions were like in the talc mines and mills of the 1920's and 1930's but neither were milli min llig ng techniques designed with dust control as a major objective The oldtime worker was therefore amounts of dust than his modern counterpart exposed to vastly greater Nevertheless these exhaustive examinations cancer among any of the service group signs of possible pneumoconiosis One failed of the to detect any sign of retirees did reveal for Cyprus Mines Corporation's interest in this proceeding the welfare of its workers and for the truth Although is one of concern the medical data presented are admittedly limited they contain no indication that tales of either the pure Montana type or less pure California varieties are carcinogenic We should emphasize that Cyprus talc operations are in compliance with threshold limit values both as relates to dust from nonasbestiform talc and fiber count We realized that any dust tive health factor and are making every in excessive amounts cannot effort to minimize employee be a posi- exposure 22 DISCUSSION OF THE MINERALOGY OF INDUSTRIAL TALCS by C. S. Thompson Ph D.1 Discussion The purpose of this presentation lography and morphology of the major also to present information regarding materials with the hope of clarifying is to discuss the mineralogy crystal- constituents of industrial talcs It is the nomenclature used to describe these the terminology which is so important in the formulation and understanding of regulations Industrial talcs vary greatly in pure mineral talc Mge 020 OH to numerous other minerals principally mineralogic composition from relatively mixtures containing mineral talc and serpentine Si205 OH antigorite and chrysotile dolomite CaMg tremolite Ca Si 022 OH OH anthophyllite MgFe and chlorite 16. Mg 020 Due to the recent definition of the term asbestos in the Federal Register of June 7 1972 which incorrectly included all forms of anthophyllite tremolite and actinolite as asbestos minerals many domestic industrial talc producers have found themselves legislated into being asbestos producers as well It is the purpose of the following dis- cussion to correct this error The term asbestos see appendix is a nonscientific commercial term normally restricted in use to the long threadlike fibrous varieties of several hydrated silicate minerals whose fibers can be separated mechanically and pressed spun or woven into articles of all types that are resistant to heat and chemical action Although present usage is generally limited to the commercially available silicate minerals chrysotile crocidolite amosite anthophyllite asbestos tremolite asbestos and actinolite asbestos other minerals regardless of chemical composition which possess similar qualities of great elongation flexibility tensile strength heat and chemical resistance spinability etc. could properly be classified as asbestos The asbestos minerals mentioned above all have nonasbestos counterparts of the same chemical composition and crystal structure which are far more abundant and widespread than the asbestiform variety These see table ) occur as common forming mineral constituents of many igneous and metamorphic rocks The crystallization of these normally nonfibrous minerals in fibrous form is a rare occurrence in nature dependent upon unusual combinations of physical and chemical conditions during the metamorphism of preexisting non- asbestiform minerals As shown in table 1 the asbestiform varieties of the serpentine and amphibole minerals names which in themselves imply groups have in part their fibrous nature been given individual In the case of the Manager of Ceramics Paper R. T. Vanderbilt Company and Specialties Inc. Research and Development 23 three amphiboles anthophyllite tremolite and actinolite rarely as the asbestiform variety all three account for an cent of the total asbestos production no special name was which occur so estimated 1 per- given to the asbestiform variety and therefore a qualifying morphological term such as anthophyllite asbestos tremolite asbestos and actinolite asbestos must be used when referring to that particular crystal form I am convinced that it was this lack of a special name in the mineralogical and other literature which caused incorrectly the inclusion of all forms of anthophyllite trem- olite and actinolite in the Asbestos Dust Standard 29 CFR 1910.93a instead of only the asbestiform varieties as was undoubtedly intended by the formulators of the regulation It is obvious from the studious omission of the nonfibrous varieties of the other asbestos minerals that is antigorite riebeckite and cummingtonite from the asbestos standard that if special names had existed for the asbestiform varieties of the remaining amphiboles they would have been included as well and anthophyllite tremolite and actinolite would also have been omitted TABLE 1. " Asbestos minerals as listed in Federal Register Asbestiform variety Serpentine group Chrysotile Chemical composition Mg,Si OOH 4 seers Nonasbestiform variety Antigorite lizardite Amphibole group Crocidolite sseccecscccerseves ccc Amo cces nccci crcest ccecee ceee Anthophyllite asbestos Tremolite asbestos Actinolite asbestos | Na F-- SiO22 OH | Mg Fe SiO22 OH | Mg Si^-- 2O 2 H | Mg5 Si 22 OH 2 Ca Mg Fe S2O2 H | Riebeckite | Cummingtonite | Anthophyllite | Tremolite | Actinolite NOTE Underlined mineral designations are those listed in the Federal Register The term fiber connotes a greatly elongated particle with threadlike qualities such as tensile strength flexibility spinability etc. see appendix Asbestos fiber in particular refers to a particular crystallization of common nonfibrous forming minerals resulting in long fiber bundles which continue to break down during crushing or processing into fibrils of smaller and smaller diameter until near molecular diameters are reached while still maintaining relatively aspect ratio length to width of 3 to 1 as defined in the Federal Register NIOSH and great elongation The use of an the lower limit of a fiber as so forth most certainly refers to fragments or pieces of much longer previously recognizable asbestos fibers since it is obvious that any other nonasbestos nonfibrous minerals such as feldspars pyroxenes amphiboles calcite gypsum etc. could not be consid- ered to have become fibrous on the basis that during processing they are reduced to particles or fragments which exceed an aspect ratio of 3 to Many such minerals normally occur in elongated prismatic or acicular crystals which have a tendency to elongate as they are subjected to attritioning but have little tensile strength tend to be quite brittle and are therefore not fibrous 24 The accompanying sets of photographs and photomicrographs will illustrate the marked morphological difference between the asbestiform and nonasbestiform varieties of the asbestos minerals under discussion We must apologize for the lack of pictures Several specimens so identified A study of the asbestiform varieties of tremolite and actinolite labeled have been examined but all had been mistakenly of these pictures figs 1 through 11 will indicate the differences just mentioned as well as the great similarity of the physical forms and grinding characteristics of the nonasbestiform amphibole varieties riebeckite cummingtonite anthophyllite tremolite and actinolite A comparison of these photographs with those of the talc products figs 12 through 17 clearly shows that the amphibole minerals occurring in domestic indus- trial tales are present as the nonasbestiform variety It is hoped that this presentatihoans accomplished the following 1. Illustrated the differences varieties of the same mineral between asbestiform and nonasbestiform 2. Helped clarify the nomenclature used in reference to asbestos 3. Indicated the importance of correct terminology in the formulation of regulations 4. Presented evidence which with domestic industrial talc are are therefore not asbestos shows that present as the the amphibole minerals associated nonasbestiform variety and 25 25 FIGURE 1. - Chrysotile asbestiform asbestiform variety variety variety A Specimen B closeup C photomicrograph 2.75 ) m Div 26 FIGURE 2. - Antigorite nonasbestiform variety A Specimen B closeup C photomicrograph 2.75 Div 27 FIGURE 3. - Crocidolite asbestiform variety A Specimen B closeup C photomicrograph 2.75 Div 28 FIGURE 4. > Riebeckite nonasbestiform A Specimen B closeup C photomicrograph 2.75 Div 29 FIGURE 5. - Amosite asbestiform variety A Specimen B closeup C photomicrograph 2.75 Div 30 FIGURE 6. - Cummingtonite asbestiform variety A Specimen B closeup C photomicrograph 2.75 Div 31 git : * cyt pied Pe pk FIGURE 7. - Anthophyllite asbestos asbestiform variety A Specimen B closeup C photomicrograph 2.75 Div 32 - Anthophyllite nonasbestiform variety A Specimen B closeup C photomicrograph 2.75 Div 33 scaly . set eM ale os aa , y Peden s . C FIGURE 9. - Tremolite asbestos asbestiform variety A Speci- men B closeup C photomicrograph 2.75 Div 34 - Tremolite nonasbestiform variety A Specimen B closeup C photomicrograph 2.75 Div 35 FIGURE 11. - Actinolite nonasbestiform variety A Specimen B closeup C photomicrograph 2.75 Div 36 FIGURE 12. New York talcs Nytal 99 50 percent tremo- lite 5.5 ...m Div FIGURE 13. - New York talcs Nytal 200 -45 percent tremo- lite 5.5 ...m Div FIGURE 14. - New York talcs Nytal 400 -40 percent tremo- lite 5.5 ...m Div 37 FIGURE California Western hard ore -35 percent tremolite 5.50 Div FIGURE 16. - California talcs Westal 301 -30 percent tremo- lite 5.50 ...m Div FIGURE 17. - California talcs Westal 404 -20 percent tremo- lite 5.50 m Div 38 Appendix Bibliography of Asbestos Terms Source 1 Berger Hans translated by Ralph E. Osper Asbestos FundaOrigins Properties Mining Processing Utilization Chemical Publishing Company Inc. New York 1963 In the mineralogical sense the term asbestos is extended in part also to other fibrous minerals without reference to composition structural constitution properties and industrial significance Two main groups are differentiated with respect to origin mode of formation mineralogical relationships structure composition and properties of the asbestoses namely the serpentine asbestoses chrysotiles and the amphibole asbestoses The fibrous crystalline variants of the minerals have in part been given individual names to which in the interest of a precise terminology the word asbestos must not be appended For example the fibrous form of serpentine is called chrysotile serpentine or fibrous serpentine not chrysotile asbestos The accepted names of the five asbestoses used commercially are given as follows Group Designation of mineral Designation of asbestos Serpentine Serpentine ,.... Amphibole asbestos Riebeckite Chrysotile Crocidolite blue asbestos Do. Gruenerite Amosite Do Anthophyllite asbestos.1 asbestos Do. serecece sees Tremolite 1 These varieties have no special designation Source 2 HM Factory Inspectorate United Kingdom tions in Industry Department of Employment Health Asbestos Health Precau and Safety at Work No. 44 1971 Asbestos is the common name given to a number of inorganic fibrous silicate minerals that possess a crystalline structure Chrysotile the most abundant of the fibrous silicates and the one most extensively used in of forming minerals industry belongs to the serpentine group and is mined mainly in Canada Russia and Rhodesia The other forms of asbestos belong to the amphibole group They are crocidolite commonly known as blue asbestos which is found in South Africa Western Australia and Bolivia amosite which occurs only in which is found South Africa anthophyllite the fibrous form of in Finland and Africa and the fibrous forms of trem- olite available in Italy and actinolite which has been found in South Africa Asbestos means crocidolite amosite any of the following minerals that is to chrysotile fibrous anthophyllite and any ture containing any of the said minerals say mix- 39 Source 3 Ladoo Raymond Bardeen York 1st ed 1925 Metallic Minerals McGraw New Asbestos amphibole asbestos hornblende asbestos and Italian asbestos are various terms given to the monoclinic amphi- boles tremolite Car Mg O22 and actinolite Si FeO Si3 O3 when they occur in fine silky fibers Source 4 Dana Edward Salisbury A Textbook of Extended Treatise on Crystallography and Physical Sons Inc. New York 1947 Mineralogy Mineralogy With an John Wiley & Actinolite magnesium amphibole crystals either short or bladed as in tremolite columnar or fibrous granular massive fibrous and radiated kinds are often called asbestiform actinolite and radiated actinolite Asbestos Tremolite actinolite and other varieties of amphibole excepting those containing much alumina pass into fibrous varieties the fibers of which are sometimes very long fine flexible and easily separable by the fingers and look like flax These kinds are called asbestos from the Greek for incombustible CROCIDOLITE Blue Probably to be considered as a fibrous variety of riebeckite Fibrous cate and easily separable asbestos fibers long bur deli- Source 5 Hurbut Cornelious S. Jr. Dana's Manual of Mineralogy Wiley & Sons Inc. New York 18th ed 1971 John Serpentine occurs in two distinct forms 1 a platy variety antigorite which conforms in its properties to those of the phyllosilicates and 2 a fibrous variety chrysotile The variety chrysotile is the chief source of asbestos The uses of asbestos depend upon its fibrous flexible nature which allows it to be made into felt and woven into cloth and other fabrics and upon its incom- bustibility and slow conductivity of heat Asbestos products fore are used for fireproofing and as an insulation material there- against heat and electricity Massive serpentine which is translucent and of a light to dark green color is often used as an orna- mental stone and may be valuable as building material Source 6 Gary Margaret R. McAfee Jr. and C. L. Wolf Glossary of Geology American Geological Institute Washington D.C. 1972 Amosite A commercial term for an rich ety of amphibole occurring in long fibers It may orthorhombic amphibole anthophyllite and gedrite clinic amphibole commingtonite or grunerite asbestiform variconsist of an or of a mono- Asbestos A commercial term applied to a group fibrous silicate minerals that readily separate into of highly long thin strong fibers of sufficient flexibility to be certain fibrous varieties of amphibole 40 Crocidolite A lavender indigo or green asbestiform variety of riebeckite occurring in silky fibers and in massive and earthy forms Syn Blue asbestos Krokidolite Source 7 Deer W. A. R. A. Howie and J. V. 2 Longman Group Ltd. London 1963 Zussman Rock Forming Minerals Riebeckite also occurs as an extremely fibrous mineral when it is known as blue asbestos or crocidolite The best known occur rences of blue asbestos are in South Africa where it occurs in bedded ironstones the seams of crocidolite conforming to the bed- ding of the ironstones The composition of the crocidolite is remarkably similar to that of the ironstone and the crystallization of the amphibole initially in the form of massive riebeckite occurred with little or no addition of material under conditions of moderate temperature and pressure consequent on the burial of the ironstones to moderate depth Both Peacock 1928 and Hall 1930 favor the hypothesis that Na2O was originally uniformly distributed throughout the ironstone and subsequently concentrated in certain bands The later transformation of the massive riebeckite to the fibrous crocidolite may result from the instability of the riebeck- ite during a period when the ironstones were subjected to shearing stress ..... members of the cummingtonite series are typically found in both regionally and contact metamorphosed rocks The more magnesian members are found also in some igneous rocks including those of hybrid origin The asbestiform varieties amosite and montasite are of economic importance The characteristic habit of the members lar or fibrous The of the cummingtonite series is asbestiform variety amosite when fresh acicuis grey in color the mineral however is frequently coated with iron oxides when the color is brown to yellow The fibers of the montasite variety are less harsh than amosite and are often soft and silky in texture .... habits of the anthophyllite minerals vary from fibrous and asbestiform to bladed and prismatic The fibers of anthophyllite asbestos generally do not have any great tensile strength and are of less economic importance than the amosite and crocidolite fibers fiber anthophyllite asbestos occurs as a replacement mineral in ultrabasic rocks at Kamiah Idaho Anderson 1931 ..... Laudermilk and Woodford 1930 have described an asbestiform anthophyllite in veins in serpentinite at Coffe Creek Carvill California Source 8 Deer W. A. R. A. Howie and V. 3 Longmans Green and Company Ltd. J. Zussman Rock Forming London 1962 Minerals The principal minerals of the serpentine group all have the , approximate composition Si209 and comparatively little substi- tution of other irons is found to occur in natural specimens The most well known serpentine mineral chrysotile often occurs in veins of silky fibers and is the most important source of commercial asbestos 41 Source 9 Read H. H. Rutley's Elements of Mineralogy pany London 25th ed 1953 Thomas Murby & Com- Mineralogically asbestos includes the fibrous forms of amphibole the fibers are generally very long fine flexible and easily separated by the fingers the color term asbestos in the but strictest sense the asbestos of is confined to the fibrous forms of commerce includes fibrous varieties actinolite of a number of silicates Source 10 Huggins Charles W. BuMines RI 5551 1959 14 pp Electron Micrographs of Asbestiform Minerals fragments Tremolite does not break down into fibers that approach a uni- form rectangular cross section as crocidolite does Two samples figures 9 and 10 indicate that the fibers break into Some of the fragments are quite thin while others are rather thick The fragments are composed of thin sheets Some of the small sheets figure ) are so thin that they are almost translucent to the elec- tron beam Dark streaks are again noticeable in the thin sheets of tremolite as they are slightly wrinkled for Bragg reflections thin sheets are probably less than 100 A. in thickness The Actinolite is generally considered the member The fibers of actinolite are quite basic poor amphibole asbestos and because it rarely has commercial value it is not very well known The sample examined was splintery and very brittle It was not expected that the mineral would break down into fibers for electron microscopic study but we felt it worth the effort to try since it is the basic member of the amphibole group Figure 11 reveals that it did not break into single fibers Low magnification was used as the mate- rial broke into large opaque pieces Source 11 Gaze Richard The Physical and Molecular Structure of Asbestos Ann New York Academy of Science article 1 v 132 1965 pp 23-30 The name asbestos is used to describe any mineral that breaks down into fibers when it is crushed or processed Source 12 Kingery W. D. Inc. New York 1963 Introduction to Ceramics John Wiley & Sons Asbestos Asbestos is the name given to a group of hydrous magnesium silicate minerals which have a fibrous tal structure of these minerals is characterized texture The crys- by the presence of long chains of silicate tetrahedra which can be readily cleaved in directions parallel to the silicate chains but not in directions that cut the chains with the result that these minerals can be shredded into fibers 42 Source 13 McGraw Book Company Inc. Mineral Raw Materials by the Foreign Minerals Division U.S. Bureau of Mines 1937 p 16 Asbestos is not a distinct material but a commercial term used to express the fibrous nature of several minerals Source 14 Colliers Publishing Co. Colliers Encyclopedia 1972 Asbestos any of several varieties of fibrous minerals whose fibers may be spun or felted to make fabrics panels or coatings that are resistant to heat and chemical action Asbestos is also valued for its electrical insulating properties Source 15 Encyclopedia International Edition 1969 Asbestos general name for a group of silicate minerals that occur as fibers or fibrous masses and that can be woven into heat resistant materials The fibers are separated mechanically and pressed spun or woven often with cotton wire rubber or cement to produce fireproof articles of all types clothing curtains electric cable insulation brake linings and clutch facings insulating boards sheets shingles and talcs Asbestos is a fibrous mineral substance its natural state asbestos is found encased in rocks Its fibrous quality makes it a remarkable mineral Asbestos is as dense as the rock in which it is encased but it is a mass of tiny fibers that become as fluffy and light as thistledown when separated mechanically from rock Source 16 Encyclopedia Britannica 1971 Fibre fibre may be defined as a unit of matter of hair dimensions whose length is at least 200 times greater than its width 43 EXPERIMENTAL STUDIES ON BIOLOGICAL EFFECTS OF TREMOLITE TALC ON HAMSTERS by William E. Smith M.D.1 My name is William E. Smith I am director of Health Research Institute at Fairleigh Dickinson University Madison N.J. I am a doctor of medicine Over the past 25 years I have studied more than 200 chemical materials for carcinogenicity tific journals various mineral in animals and have reported results of these tests in scienIn the past 8 years my associates and I exposed animals to dusts maintained them over their natural life spans and studied them for pathologic changes by gross and microscopic examination of their tissues and organs The principal purpose of these latter studies has been to develop information on possible fibrogenic and carcinogenic properties of various preparations of mineral dusts The principal support for this work was provided by Research Grant EC 00226 from the Bureau of Occupational Safety and Health U.S. Public Health Service Thus far we have published five papers listed in the bibliography section of this paper describing some of our findings in animals exposed to various preparations of asbestos Today I would like to offer a brief summary of our experiments with asbestos and describe as yet unpublished data from studies we have made with a sample of talc containing a large amount of tremolite From our work we identified the Golden Syrian hamster as a species that was capable of developing pulmonary fibrosis resembling asbestosis seen in man Those experiments were done by repeated intratracheal injections of chrysotile or amosite asbestos The method used for those experiments weekly intratracheal injections is technically tedious and time consuming We found that we could compare the relative fibrogenicity and carcinogencity of mineral dusts more conveniently by depositing the dusts by a single injection into the pleural space of hamsters After single intrapleural injection of preparations of the chrysotile amosite anthophyllite or crocidolite types of asbestos we found that hamsters developed extensive pleural adhesions These adhesions were composed mainly of round cells and multinucleated giant cells in the first few months after injection Within 5 months these adhesions became densely fibrotic Adhesions induced by the chrysotile amosite anthophyllite or crocidolite types of asbestos tended to extend over large areas of the surfaces of the lungs Director Health Research Institute Fairleigh Dickinson University Madison N.J. 44 In contrast we saw very little reaction when we gave hamsters intra- pleural injections of a sample of tremolite talc which I shall identify by our sample number FD After intrapleural injection of this tremolite talc the particles were gathered into small depots on the lung surface These depots contained round cells and multinucleated giant cells but there was very little formation of fibrous tissue The experiments thus show that fibrogenic activity of tremolite talc is very much less than the fibrogenic action of the four principal types of asbestos Also in hamsters that had principal types of asbestos we as mesotheliomas table 1 been given intrapleural injections found intrathoracic tumors that we of the four designate TABLE 1. - Number of mesotheliomas of 50 hamsters in groups Dose mg 25 10 1 Chrysotile | Amosite | Anthophyllite 9 - - 4 3 3 0 0 - Crocidolite - 10 2 From the data in table 1 it can be seen that the yield of mesotheliomas in groups of 50 hamsters per sample was related to dose In response to a large dose 25 mg of chrysotile nine hamsters developed mesotheliomas In response to a smaller dose 10 mg of chrysotile four hamsters developed mesotheliomas In response to a still smaller dose 1 mg there were no mesotheliomas This experiment provides evidence to show that the carcinogenic action of chrysotile is related to dose hence should be controllable by appropriate industrial hygiene measures to control dose At the 10 mg dose level amosite and yield of mesotheliomas as did chrysotile double the number of mesotheliomas gotten anthophyllite gave about the same but crocidolite induced more than with the other types of asbestos Also crocidolite induced mesotheliomas in two hamsters treated with the lowest dose level 1 mg whereas no mesotheliomas occurred in animals treated with that dose of chrysotile or amosite Table 2 shows results of tests for carcinogencity of six preparations of chrysotile in groups of 50 hamsters each Each of these preparations was tested at our highest dose level 25 mg per injection The table gives data on the mean fiber length and mean fiber diameter of these samples It can be seen that 8 to 10 mesotheliomas were induced by three of these samples harsh chrysotile soft chrysotile and the same treated to achieve some of the properties samples that proved carcinogenic had mean sample of soft chrysotile heatof harsh chrysotile These three fiber length of 5.3 to 6.9 microm- eters and mean fiber diameter of 0.2 to 0.8 micrometer These milling to three active preparations of chrysotile were subjected to further reduce the majority of particles to submicroscopic dimensions The 45 table shows that this reduction in particle size eliminated the carcinogenic .effect of these samples It also greatly reduced their fibrogenic action TABLE 2 - Tests for carcinogenicity of six preparations of chrysotile in groups of 50 hamsters each Chrysotile preparation Soft Soft heated Harsh Mean fiber length OM EM micrometers micrometers 32.5 6.9 - - Mean fiber diameter OM EM micrometers micrometers 2.2 0.18 - - 38.9 5.3 2.9 2 No. of mesotheliomas 8 10 9 Soft - .9 - .03 0 Soft heated - - - - 0 Harsh - .4 - .07 0 OM Optical microscope EM Electron microscope Now we have tested a sample of tremolite talc for carcinogenicity in hamsters Electron diffraction studies of this sample showed it to contain 50 percent fibrous tremolite and 35 percent talc table 3 A majority of the talc particles were platy but some were rolled or fibrous TABLE 3 - FD tremolite talc Composition Selected area electron diffraction Fibrous tremo cccl cei ce oct ssee uas Antigorite ccc cece cece eee cecceees Talc ... ccc ccc cece ee eeee eect ecnene Chlorite rece c anes Of this about 75 percent is platy and 25 percent is rolled or fibrous Percent GUHU GUHU GUHU GUHU In this sample the fibrous particles had an average length of 5.7 micrometers and an average diameter of 1.6 micrometers table 4 They are therefore in a size range that might be carcinogenic in our experiments with chrysotile However this sample of tremolite talc induced no mesotheliomas after intrapleural injection into hamsters TABLE 4 - FD tremolite talc Size measurement,, Phase microscopy 10x ocular 100x objective | Length micrometers | Diameter Range Average Range Fibrous particles 2.5-16.5 5.7 1-5 Platy particles - 1-10 Ratio fibrous to platy particles 3 to 1 micrometers Average 1.6 2.0 46 Table 5 gives detailed data on these tests which were conducted at our highest dose level 25 mg In view of the long latent period before developrelative carcinogenicity of different ment of tumors if we wish to compare samples validity of the comparisons depends on the number of animals surviv- ing into the later periods of the tests In table 5 the number of survivors the denominator The cumulative in each group at each time period is shown as number of animals bearing mesotheliomas is shown as the numerator TABLE 5 - Yields of mesotheliomas in hamsters after intrapleural injection at mg dose level1 a Sample Soft chrysotile Harsh chrysotile 151 days | 0/40/3 | | | 0/440/33 0/40/3 | | 4/9 | | | 1/41 340 | days | 0/440/33 4/26 372 | 450 | 500 days | days | days | 1/30 1/20 4/11 4/21 7/16 7/13 550 | days 4/9 7/9 | 600 days | 7/3 8/5 | 650 days | 8/1 9/2 700 days 3 ') treated soft 0/37 | 1/35 | 1/32 | 1/27 | 4/17 0/270/23 5/15 8/4 0/201/15 10/1 3 chrysotile talc 0/52 | 0/35 | 0/34 with 0/29 mesotheliomas 0/270/23 0/270/23 0/270/23 mesotheliomas 0/20 0/210/5 0/15 0/7 Tremolite Numerator Cumulative number of hamsters with mesotheliomas Denominator Survivors at Number of hamsters surviving 650 days in chrysotile groups on stated day were killed on that day Pleural adhesions but no tumors were found in them We started with found at 151 days in about 50 hamsters in each group The first tumor was an animal that had been treated with harsh chrysotile Now let us look at the situation as it was 500 days after start At that time 4 mesotheliomas had occurred in the group treated with chrysotile and only 11 animals survived of tests soft and In the group treated with harsh chrysotile 13 hamsters were still living 7 mesotheliomas had occurred In the group given treated liomas and 17 survivors soft chrysotile there were 4 mesothe- By comparison no mesotheliomas had occurred in the group treated with tremolite talc and there were 27 survivors The group on tremolite talc thus had many more animals at risk in the no mesotheliomas developed in them late stages of the tests yet In the three groups on preparations of chrysotile all of died or were killed to close out those groups by 650 days At final yield of mesotheliomas in those groups was 8 9 and 10 the animals had that time the respectively tremolite talc had developed no mesotheliomas By comparison the group on and at risk in that group by 650 days and there were still 15 animals living at that time 47 Eight of these survivors died of various causes between 650 and 700 days No mesotheliomas were found in them tion The remaining at 700 days seven survivors on tremolite talc were No mesotheliomas were found in them killed for examina- Throughout the tests animals treated with the preparations of chrysotile in table 5 were found to have thick fibrous pleural adhesions extending over large areas of the lung surfaces whereas animals treated with tremolite talc never showed more than small depots of the mineral particles with relatively little tissue reaction In summary our experiments show profound differences between the biologic effects of tremolite talc in respect to both fibrogenicity and carcinogenicity as compared with the biologic effects of the four principal types of asbestos chrysotile amosite anthophyllite and crocidolite 48 Bibliography Miller L. W. E. Smith and S. W. on pyrene Carcinogenesis the New York Academy of Sci v Berliner Tests for Effect of Asbestos in the Respiratory Tract Annals of 132 article 1 1965 pp 489-500 Smith W. in Lung E. Asbestos in Relation to Tumors of Tumors in Animals ed by L. Severi 1966 pp 565-570 the Respiratory Tract Ch University Perugia Italy Smith W. E. D. D. Hubert and M. Badollet Response to Long and Short Asbestos Fibers Assoc J. v 33 February 1972 p A162 Biologic Differences in Am Industrial Hygiene Smith W. E. L. Miller and J. Churg An Experimental Model for Study of Cocarcinogenesis in the Respiratory Tract AEC Symp ser 21 1970 pp 299-316 Smith W. E. L. Miller R. E. Carcinogenicity of Asbestos v 132 article 1 1965 pp Elsasser and D. D. Hubert Tests Annals of the New York Academy of 456-488 for Sci 49 THE BIOLOGICAL ACTION OF TALC AND OTHER SILICATE MINERALS by Gerrit W. H. Schepers M.D. D.Sc.- Introduction The recent revelation that prolonged human inhalation of certain fibrous minerals for example of malignant neoplasia crocidolite of the lung may and be associated with excess even of other organs such prevalence as the stomach or colon has the fibrous minerals focussed attention on the biological For reasons not quite clear to this potentials of all author talc has somehow and probably quite unjustifiably become embroiled in the issue of the carcinogenicity of asbestiform minerals means a fibrous mineral Talc though a silicate is by no It is quite important however to thoroughly review biological reactiv- ity to talcs because their industrial uses are so diversified Direct human exposure is considerable involving all elements of humanity practically from cradle to grave There also is a contradiction between the stringent rules for dust suppression in mining or milling of talc and the almost total lack of controls over talc when released for private use The crucial issue is whether all silicate minerals are equally pathogenic To resolve this question it is necessary to review what is on record concerning the biological action of talc and compare this with what is known about the adverse properties of other silicates and especially the asbestiform minerals The biological potentials of a variety of natural and synthetic silicates have been personally researched over the past 3 decades These studies have included investigation of human subjects experimental animals and a review of the literature Human studies include observations on crocidolite and amosite miners and millers in Africa chrysotile tremolite and talc miners millers and industrial workers in the United States and Canada and textile workers in fiberglass and synthetic fiber industries The number of human subjects studied exceeds 10,000 These studies are evaluated against a background of familiarity through personal clinical experience and research of the pathogenic action of a variety of other natural and synthetic siliceous nonsiliceous and chemical and synthetic substances The clinical subjects exceed 100,000 and necropsies have been performed on over 10,000 deceased industrial workers Animal studies have recently been reviewed in a Primates and Rodents 7 These included researches ties of 407 industrially important materials through 7,906 animals publication on Tumors of on the biological properexperimental exposures of Chief Medical Service of Veterals Administration Lebanon Pa 50 The published literature is vast and ever increasing In excess of 4,000 papers have been reviewed If these do not include all that has been written on this subject of pneumoconiosis any omissions would be unintentional For practical purposes all references cannot be cited nor will it be reasonable in a paper of the intended scope of this presentation to recapitulate all that is known about the biological actions of talc and fibrous environmental agents It will be feasible only to summarize pertinent highlights Fibrous and Nonfibrous Dusts There appears to be considerable difficulty in differentiating between respiratory inhalants which may be called fibrous as compared with nonfi- brous substances There is no problem when we consider substances such as crocidolite amosite chrysotile anthophyllite fiberglass rockwool or natural or synthetic textiles wool cotton nylon rayon dacron orlon etc. These materials are predominantly composed of elongated delicate component elements which are indisputably fibers There appears to be no absolute definition of what constitutes a fiber neither with mineralogists nor with textile experts Review of discordant terminologies almost it is obviously so would be a substance leads one to the conclusion that a fiber is a fiber when Physicochemically speaking however a fibrous mineral with a propensity for cleavage in two planes of space Some mineral fibers can however also form when aluminosiloxane sheets are rolled to form tubules als Sporadic and possible spurious attempts have been made to classify miner such as talc or tremolite as fibrous dusts This is apparently on the basis of three properties 1. There is the fact that talc and fiable as silicates as are most fibrous tremolite are minerals such mineralogically as the asbestos classiseries 2. Some samples of talc and tremolite contain a minority of oblong particles which are considerably longer than they are thick These elongated particles are only very rarely true fibers in the conventional sense and are more properly designated spicules rods or needles 3. It is a fact that some talc or tremolite deposits occur geologically in close juxtaposition to chrysotile or other ore bodies so that some contami- contami- nation of talc with serpentine dolomite magnetite pyrophyllites and clays may occur The logic in designating any nonfibrous silicataes fibrous for the latter two reasons somehow evades this author If this principle were applied to other substances there would be no sensible way to classify minerals or environmental contaminants For example hematitite or magnesite ores are often contaminated with siliceous materials both fibrous and crystalline Coal often contains mica clays asbestos silica etc. Do these admixtures justify classifying hematite as anything other than hematite 51 + 16+ 10- awe ee { \ 4x Si | lx K 14 \1 ' Tr 1} . 90 Oo5 a { OF, TL \ SILOXANE SERAANE 4x0-- \ OH- \.. SILOXANE ft % een 16+ + % > ee | ++++ 11 ) i i + we o .9 8 magnetite as anything but magnetite coal as anything except coal and so forth Perhaps the solu- tion lies in subclassi- fying the silicate materials table 1 as those which belong to an asbestiform group and those that are not primarily asbestiform in nature This may make mineralogical sense and may agree with some of the bio- logical propensities of these materials Such a classification may also be extended to embrace minerals and textiles whether natural or synthetic 1xK 6x0- FIGURE 1. - Diagram of the siloxane templates of silicates To resolve these issues it is necessary to take a closer look at the physicochemical relationships of the various silicate minerals These substances were all formed in nature because of certain highly characteristic characteristic coordinative ties of silicon oxygen and aluminum atoms proper- proper- When the earth's crust was formed these of silicates atoms This sought one another to form form the substrate is the alumina substrate for varieties siloxane moiety formed in all silicates fig 1 Individual silicates differ from one another whether and how certain other elements such according to as iron magnesium manganese sodium and calcium become interposed in the micropores of the siloxane frame work and the degree to which and the mannermanner in which these siloxanes hydrated are This is a highly complicated althoughalthough virtually fully decoded sci- ence Indeed because of the advanced state of the science of silicate chem- istry it already is industrially possible to synthesize a number of these multibillion natural silicate minerals not yet yet at suffi- ciently low cost to be competitive with mineral silicates For our present purposes it is pertinent to summarize summarize that based on the siloxane tem- plate concept there is a precise physicochemicalphysicochemical explanation why silicate minerals are present in nature as microporous microporous microporous crystalline substances or sheetlike tubular ribbon or lathlike , oblongate acicular or fibrous miner- als A classification of the silicates silicates on the basis of this principle is presented in table 2 52 TABLE 1 - Fibrous respirable aerosols Natural Silicate Asbestiform Crocidolite Amosite Anthophyllite Chrysotile Nonasbestiform Talc Tremolite ! MINERAL Synthetic Silicate Fiberglass Rockwool Nonsilicate Potassium titanite Nonsilicate Brucite Cotton Wool Hair Silk TEXTILE Nylon Dacron Orlon Rayon TABLE 2. - Silicate minerals Microporous Laminar Analcite Chabazite crystalline | Tubular or Hydrated Chrysotile Endellite hollow Heulandite Fibrous Natrolite Sheetlike Sheetlike Aluminous Montmorillonites Montmorillonite Nontronite Hectorite Saponite Micaceous Biotite Illite Muscovite Phlogopite Vermiculite Pyrophyllite Kaolinites Anhydrous Halloysite Ribbonlike Attapulgite Sepiolite Paligorskite Oblong particulate Tremolite Acicular SericiteAntigorite Antigorite Sillimanite Fibrous Actinolite Anthophyllite Amosite Crocidolite Kaolin Actinolite Nonaluminous Talc It is to be noted that talc is here classified as a sheetlike silicate which is in a group quite separate from other laminar silicates or from tremo- lite which is often also called talc Because talc Mg Si400 10 OH aluminum atoms which have such a strongly bonding effect between the lacks the siloxane 53 polymeric layers the talc silicate readily splits primarily and predominantly along one plane of space to form fine lamina However cleavage along the two other planes of space occurs secondarily This provides for the fine divisibility of talc The nonadherence of the flat particle surfaces to one another furnished the greasy or slippery property of talc Scanning electron microscopy has well demonstrated this flaky character of the talc particle fig 2 Tremolite also is often classified as talc perhaps because it also lacks the aluminum atom Since two calcium atoms substitute for aluminum tremolite belongs mineralogically with the amphiboles which all have achieved comparable substitutions It has the empirical formula 022 From the point of view of its siloxane structure tremolite differs from talc in that it cleaves almost equally readily in two planes of space whereas cleavage in the third plane is a secondary feature For this reason the classical tremolite particle is cuboidal to oblongate instead of platelike fig 3 A minority of tremolite crystals cleave less well in the third dimension than they do in the other two These particles then manifest as stiff rods or needles For this reason the appropriate location of tremolite in table 3 lies between the sheetlike silicates and the acicular silicates sericite antigorite and sillimanite The latter habitually cleave in such a manner that their natural format is a short needle or rod The amphibole minerals as mentioned above have substituted other elements for aluminum Thus in actinolyte and anthophyllite both magnesium and FIGURE 2. - Electron microphotogram of tale showing its laminar characteXr 7,500 FIGURE 3. - Microphotograph of typical oblong tremolite crystals Magnification unknown 54 iron are OH OH bivalent present MgFe SiO22 - In crocidolite there are both sodium and trivalent iron Na2 F32 F33 SiO22 . Amosite is a mixture and of actinolite and anthophyllite Aluminum is absent from all of these Their cleavage in relation to the siloxane substrate is predominantly and equally in two parallel planes For this fibers which will bend rather reason they occur in nature as than break in the third spatial elongated plane Conse- quently these fibers have high tensile strength and flexibility which is why they are so industrially important TABLE 3 - Pathogenicity of silicates Rating 0 1 2 3 4 5 6 7 8 9 Minerals Montmorillonite kaolinite talc tremolite Talc + antigorite magnesite dolomite and spinell Tremolite with many rods or needles Sericite antigorite sellimanite mica Chrysotile.. Actinolite Anthophyllite Amosite Crocidolite Asbestos + silica or other minerals Chrysotile is unique among the nonaluminum silicates Its empirical formula is S4010 It is classifiable as a tubular or hol- low silicate Its siloxane template however is basically a sheet which becomes rolled upon itself to form a tube For this reason chrysotile is classifiable with endellite which is rolled in the opposite direction When dehydrated to form halloysite the prior endellite tube splits lengthwise to assume a ribbonlike or lathlike form It then resembles the silicates attapulgite sapiolite and paligorskite What does all this have to do with the biological properties of talc Probably a great deal silicates are the bases These physicochemical for their particulate characteristics of the various size their ease of entry into the respiratory system their penetration into cellular and intercellular tissue elements their retention in or elimination from tissues their solubilization their chelation or interaction with other elements within the bio- logical system and their acceptance or rejection by living matter These biological counterparts may now be examined Differential Biological Properties of Silicate Minerals There are marked differences between the capacities of the individual classes of silicate minerals to provoke responses in human and animal tissues There also are major misconceptions as to what these substances can do when inhaled by man or other mammals Two of the most extreme of these are 1 that all siliceous minerals are equally pathogenic and 2 that there is even the least semblance between the effects of the asbestiform and the non- asbestiform silicates 55 To express these differences in a practical manner one may accord a percentile value of pathogenicity to each substance Since it is not really possible to discriminate biological responses with complete precision a scale of zero to 10 may suffice My appraisal of the differential pathogenicity of the silicate minerals is recorded in table 3 Since there are in the medical literature disease categories such as talc lung or talc pneumonconiosis many explanations are needed to clarify why talc and tremolite as pure substances have been given a zero rating and why chrysotile asbestos is classified at the lower end of the pathogenic spectrum whereas crocidolite and amosite asbestos are at the opposite end Since it is extremely difficult to disprove a Jack and the Bean Stalk myth multiple facets of the problem need be explored It is necessary to examine more closely the origins and the erroneous premise that all silicate mineralarse equally injurious The loose use of the terms asbestos or asbestosis and the facile identification of other amphiboles with asbestomasy be a factor How did this come about Part of the problem originates in the manner in which physicians make diagnoses of conditions such as asbestosis or the techniques used in dramatizing a description of newly identified disease entity Often the diagnosis is not based on precise and painstaking verification of the pertinent issues Not uncommly loose association and coincidence are the guiding criteria Careful work histories are not always taken so that a lung lesion found in an employee of a certain industry may become identified with the final occupation whereas it might have had its origin in nocuous dust exposures encountered in a prior unrelated decade Far too often the isolated rare exotic example is the sole basis for the generic concept of a new pneumoconiosis The exception becomes the rule Even unrelated disease such as tuberculosis or mycosis or sarcoidosis have been misidentified as new pneumoconioses merely because they occurred in an employee of the suspected occupation This problem has been discussed more fully elsewhere 2-3 8 Pneumoconiosis usually is identified during life through radiography The radiologist who expertly examines shadows of lesions must rely on the pathologist who has studied necropsy specimens The latter often is quite uncritical of the source of his material and not uncommonly quite poorly informed in the field of pneumoconiology In the entire United States with its thousands of excellent pathologists there are probably not more than a half a dozen true connoisseurs of this eclectic branch of forensic medicine This may be true also in other countries To make a reliable identification the pathologist must not only have had years of experience in decoding this type of made disease but must also have access to appropriate microscopy chemistry and petrographic equipment and skills It also is quite unusual to encounter pure cases of a particular disease Industrial workers especially in America tend to be quite mobile They shift from one trade to another and potentially receive multiple exposures so that the pneumoconiosis which ultimately emerges often is a manifestation of a prior dust or chemical exposure or a composite of many 56 successive exposures to diverse agents some of which may not even be sepa- rately pathogenic but which may produce disease through the principle of potentiation The phenomenon of individual susceptibility often also is overlooked and disease which develops in an unusual isolated case among many unaffected employees is seized upon as a typical example of how dangerous the suspected silicate may be Sometimes insufficient heed is paid to the question of dosage Almost any substance is harmful in overwhelming amounts Even substances which are biological necessities can be harmful in excessive concentration We all need oxygen but cannot survive perpetually in an all oxygen environment without adverse results Our bodies need water but our tissues can drown therein So it is with inert minerals If a worker is grossly recklessly and long exposed to almost any dust the pulmonary defenses will be overcome and harm will result This point is well illus- trated in experiments for instance with fiberglass utilizing the intratracheal versus the inhalation techniques If a quantity of glass fibers is injected into the lungs of animals gross pulmonary lesions swiftly follow fig 4 When however the same glass particles are inhaled in smaller daily dosage for periods of up to 2 years no disease is induced even though the total amount of glass inhaled may greatly exceed the amount introduced as a single slug fig 5 FIGURE 4. - Pulmonary lesion induced within 4 months in a guinea pig by intratracheal injestion of 1 mg of glass fibers in successive doseXs 40 FIGURE 5. " Lack of pulmonary response to glass fibers inhaled daily by guipn ig feora18 monthisn an gerosol concentration of 1 mg per cubic foot of air X 40 57 Careful analysis of the mineralogic composition of the lungs and the work histories of deceased industrial workers with various grades of silicateinduced disease has shown that pure examples of specific silicatoses are extremely rare It is almost axiomatic that if any advanced grades of disease are found among workers in silicate industries the causative agents are multiple and likely to have potentiated each other's adverse propensities For this reason the worst examples of severe pulmonary fibrosis or other lesions generally fall in category 9 as shown in table 3. A typical example of such a severe mixed silicatosis is illustrated in figure 6 are found among workers in silicate industries the causative agents are multiple and likely to have potentiated each other's adverse propensities For this reason the worst examples of severe pulmonary fibrosis or other lesions generally fall in category 9 as shown in table 3. A typical example of such a severe mixed silicatosis is illustrated in figure 6 Pure crocidolite or amosite pneumoconioses are rarely found in America today They used to be common in England 30 or more years ago and of course are specifically associated with South Africa The severe disease category 8 or ) which these intensely and relentlessly fibrogenic silicates cause figs 7 and 8 has strongly influenced the image of asbestosis For decades crocidolite pneumoconiosis was the word asbestosis is today used in asbestosis relation to The problem is that when other fibrous silicates such as chrysotile the horrible image of crocidolite pneumoconiosis is con- jured up Indeed asbestosis it is extremely difficult to find examples of pure chrysotile Most workers with advanced pulmonary disease who are said to have chrysotile asbestosis usually have had prior or secondary exposure to other silicates silica and other minerals or chemicals The few rare cases of pure chrysotile asbestosis are not characterized by gross pathology such as is found with amosite or crocidolite asbestosis fig 9 Chrysotile pathogenicity is therefore given a value of 4 on the scale of 0 through 9 The only human examples of tremolite or talc pneumoconiosis which have been tion placed on record were of needles or rods or caused by tremolite which contained a high proportalc which was significantly adulterated with other minerals such as tremolite Ca Mg 022 dolomite CaMg spinell MgA1204 magnesite MgCO3 magnetite Fe2O3 antigorite Mg OH Si40 chromite FeCr2 etc. The amount of disease seen in these cases even after prolonged exposure is minimal fig 10 Pathogenicity ratings of 2 and 1 have been accorded these aberrant variants of tremolite and talc Pure talc 4010 appears to be biologically inert It is true that the mineral can be found in sure but it is simply here as a the lungs after significant prolonged stored material Histologically this expois a thesaurosis only without any thesaurismosis for example cytogenic cytotoxic or fibrogenic reaction to the talc particles For this the clays and crystals with reason talc is accorded a zero pathogenicity kaolin Tremolite also belongs here when it a minority of rods or needles rating occurs along with as oblong - 58 FIGURE 6. - Dense pulmonary carnification in human subject occupationally exposed to successive aerosols containing quartz flux diatomite crocidolite amosite and chrysotile X ) FIGURE 7. " Dense interstitial fibrosis caused in human lung by exposure to dust X ) crocidolite FIGURE 8. - Subpleural and interstitial pul- monary fibrosis caused in man through exposure to crocidolite and amosite X ) 59 ae FIGURE 9. - Limited reaction the human lung to the inhalation of chrys- otile dust for 22 years as a miner and mill worker X ) Histological FIGURE Gradation 10. - Limited human path- ology characterizing exposure to impure tremolite dust for 18 years X ) The differential biological potentialities of the silicates are also recognizable histological review of pure examples of human exposure Starting with talc the examples of tissue reaction shown in figures 11 to 13 clearly demonstrate the inert nature of this mineral The close of the myriads of talc particles which are brilliantly revealed by cporloawrdiiznegd light microscopy is typical The individual represented in the ray had worked in an automobile tire manufacturing factory for 2 decades and during all of this time he was regularly and heavily exposed to talc dust He then left this industry to take employment for 11 years in a nondusty trade He never developed symptoms during life He died following an automobile acci- dent The talc lesions were discovered on routine review of the tissues and the work history as described was reconstructed retrospectively The lack of tissue reaction particularly the lack of fibrogenesis correlates well with the symptomless state during life There is no damage to the bronchial or vascular elements and alveolar space pleura and regional lymph nodes remained unaffected despite the abundant presence of talc particles around or in these lung components The number of talc particles per unit square area of lung tissue at standard magnification is inversely proportional to the tissue lar or reactivity to silicates The excessive dysratio interstitial tissue is about as great as one may of particles ever observe to celluand serves as an index of biological inertnesosf talc By subsequent petro- graphic and ray diffraction techniques the talc retained in the lung tissue 60 | FIGURE 11. - Microphotograph of talc par- ticles in the alveolar wall of the human lung rendered visible by polarization of transmitted light grade 0 thesaurosis X 1,000 . oe oa . i, st ey FIGURE 12. - Microphotograph of talc particles in the human bronchial lymph node visualized by polarization microscopy grade 0 thesaurosis X 1,000 FIGURE 13 - Transmitted light microphotograph of the alveolar wall in a man who had been occupationally exposed to talc dust for 20 years grade 2 thesaurosis X 100 61 of this case was shown to be an approximately 70 percent talc and 30 percent tremolite mixture This case therefore further demonstrated the inertness of tremolite and proves that genicity which talc may have tremolite does or vice versa not potentiate any latent patho- The next example shows that tissue reaction in a talc worker who had been exposed for a protracted period to talc which contained a variety of impuri- ties including tremolite rods clays and silica The worker remained essen- tially sympton free during approximately 24 years of exposure to this dust His death was due to a myocardial infarction about 7 years after retirement Three features are evident by contrast with the first case fig 14 First there is patchy or minimal interstitial fibrosis of alveolar walls Second collars of filled cells may be observed in the lymph channels around small blood vessels and bronchiles Third occasional ferruginous bodies can be seen in the areas of fibrosis fig 15 There is minimal distortion of the air spaces and some focal pleural sclerosis This grade of tissue pathology is therefore no longer a thesaurosis or mere storage response such as was seen in the case of pure talc exposure We are now dealing with an example of early thesaurismosis or true tissue reaction to stored dust but without physiologically discernable adverse effect This class of response typifies mineral or grade 1 reaction to the silicate dust The stage 2 pneumoconiotic reaction is characterized by a quantitatively greater prevalence of the abnormalities seen with stage 1. There are about twice as many fibrotic plaques in the alveolar walls fig 16 There is weU.Y & ont fy 8 f. FIGURE 14. - Focal lesions in human lung of an employee who had been exposed to dust containing talc tremolite clay and silica Grade 1 silicatosis X 100 ; FIGURE 15. > Ferruginous bodies revealed by Perl's stain in case 15 X 1,000 62 lung after prolonged occupational exposure to tremolite containing a high proportion of rods or nee- dles X 100 FIGURE 17. - Typical focal lesion caused by prolonged inhalation of chrysotile fibers sili4 csialticoastos X 100 FIGURE FIGURE 18. > Chrysotile body as visualized by transmitted light Note the splintered clublike ends of the body X 400 FIGURE 19. - Chrysotile body showing the ferroproteinaceous matter in the capsule around the chrysotile fiber Perl's stain X 400 63 minimal alveoloar space and bronchilar distortion displayed no symptoms during life despite his known tremolite which contained about 20 percent rods and The patient had however prolonged exposure to needles Chrysotile dust inhalation when unaccompanied by slightly more reaction than that just described This reactivity There now is more involvement of alveolar other exposures causes is grade 4 biological walls and characteris- tic spiderlike or octopus lesions are found fig 17 The chrysotile fibers are quite characteristic and may be found as chrysotile bodies fig which also stain vividly blue and in typical dumbbell fashion with Perl's 18 stain fig 19 Under oil immersion X 1,000 magnification bare chrysotile fibers of great delicacy may also be visualized fig 20 There is fairly diffuse pleural thickening and slight perivascular and peribronchiolar fibrosis is discernable throughout Slight airspace distortion is evident even though there was no macroscopically or physiologically detectable emphy- sema This man had worked as a chrysotile miller for approximately 23 years and had never been exposed to any other dust having formerly been a farmer in Quebec Province Detailed physiological analyses were inconclusive for func- tional deficits No diffusion defect was revealed The reason for this is readily evident when the relationship of the alveolar fibrosis to the alveolar fibrosis to the alveolar capillaries is analyzed fig 21 Since the capillaries remain intact on the alveolar surfaces no physiological impairment has resulted except for minimal stiffening of the lungs with sequential minimally increased breathing effort Gas exchange has remained unaffected Such cases of pure chrysotile exposure are extremely rare More usually the disease is the culmination of dust exposures which occurred during a mixed career of mining and participation on other dusty occupations Depending on the variety in the mixture of dusts and the intensity and duration of exposure FIGURE 20. - Bare chrysotile fibrils imbed- ded in fibrous tissue within an alveolar wall of a chrysotile miller Masson tri- chrome stain X 1,200 64 FIGURE 21. - Alveolar wall of chrysotile mil- ler showing integrity of capillaries despite underlying fibrosis Masson stain X 1,200 FIGURE 22. - Interstitial lesion representa- tive of grade 6 silicatosis Prolonged occupational exposure to anthophyllite dust X 10 FIGURE 23. - Interstitial pulmonary lesion produced by prolonged expo- sure to crocidolite Grade 8 silicatosis X 10 FIGURE 24. - Interstitial reaction to mixed silica chrysotile dust ex- posure Grade 9 silicatosis X 10 65 all gradations of tissue reaction from 5 through 9 may be found figs 22-24 Strongest potentiation is between silica quartz and chrysotile as happens in the transit pipe industry The lung tissue becomes diffusely and densely carnified leaving very little viable and functional lung This happens relatively swiftly and the tragedy is that the fibrogenic process goes on relentlessly long after exposure to dust has ceased This silica destroys what chrysotile avoids and vice versa The lesions severe grades 7 produced and 8 by amosite or crocidolite acting alone Characteristically the fibrous amosite are very or crocido- lite fibers seek out perivenous perilobular and pleural lymph and tissues fig 25 Dense sclerosis results in a weblike manner thus producing severe pulmonary restrictive damage There is so much fibrous tissue that the causa- tive crocidolite fibers are relatively scarce and difficult to detect especially since these fibers are less ferrophilic than the less harmful chrysotile fibers fig 26 Proliferation of pleural mesothelium is a classical sequel to crocidolite exposure which leads to neoplasis mesothelioma in a high proportion of cases fig 27 Experimental Evidence The differential pathogenicity of silicates has been experimentally probed by this author and several others Some results of personal researches have been published 9 but much additional data remain to be reported One of the principle experiments was to explore the comparative effects of fibrous and nonfibrous types of silicates and to evaluate the pathogenicity of long versus short fibers and milled fiberless silicates The intra- tracheal intravenous intracardiac intracerebral intraocular subcutaneous and inhalation routes were utilized by this author Others have experimented additionally with the intrapleural and intraperitoneal routes Rats guinea pigs rabbits and monkeys were the principal experimental subjects of this author Others have also conducted experiments on mice cats dogs and hamsters Talc has consistently stood out in all experiments as an inert material It could be injected into diverse tissues in relatively large quantities without evoking the least reaction When introduced into the bloodstream talc was still found cirulating freely after 18 months In this respect talc differs radically from silica as quartz which vanished from the bloodstream within hours after intravenous or intracardiac introduction The experiment with talc was limited to a study the silicate No fibrous talc was obtainable and by chemical definition probably does not exist of the nonfibrous the aformentioned form of physico- Tremolite could be studied in both its particulate and rod or needle form As a particulate variant even when there were up to 5 percent rods tremolite proved wholly inert As the proport ofiroon ds was increased about 20 percent of focal lesions were demonstrable in the experimental aminals Intratracheal 66 FIGURE 25. - Proliferation of perivenous tissues in person occupa- tionally exposed to amosite dust X 100 ue FIGURE 26. M Typical crocidolite fiberfiber in pulmonary lesion X 400 FIGURE 27. - Pleural mesothelioma which developed exposure after prolonged to crocidolite X 100 67 injection induced significant pulmonary pathology By inhalation however the tremolite proved relatively innocuous even though some fibers were trapped in alveolar phagocytes and converted to tremolite bodies fig 28 Although these bodies resemble those of asbestos the tremolite bodies do not have the ominous significance of the asbestos bodies When the effects of short tremolite rods less than 5 microns were compared with long rods 20 to 50 micrometers an interesting result was obtained The short needles proved inert The long tremolite rods induced tissue reaction This emphasized the fact that it is not the chemical composition which is the basis for biological reactivity to the silicate but only the elongated shape of particles which furnishes a pathogenic stimulus Comparable results were obtained with anthophyllite and chrysotile Long fibers 20 to 50 micrometers consistently induced pulmonary lesions in all experiments These varied in severity according to dose or duration When fibers were milled to less than 5 micron length neither of these silicates produced significant pathological responses in experimental animals This reaffirmed the principle that it is the length of the anthophyllite or chryso- tile fiber particles and not their chemical composition which serves as the pathogenic stimulus This author has not had comprehensive personal experience with the effects of amosite or crocidolite on experimental animals The few experi- ments personally performed and review of the sparse literature on this subject confirms however that these two silicates are significantly more pathogenic to diverse animal species than is either anthophyllite or chrysotile This reaffirms the high pathogenicity classification offered in table 3 FIGURE 28. Tremolite body located with- in alveolar space of guinea pig fol- lowing prolonged daily inhalation exposure at concentration of 1 mg per cubic foot of air X 400 68 A further principle was brought out in parallel experiments with fiberglass Inhalation by guinea pigs of long and short fibers did not result in interstitial fibrosis These glass fibers were 5 microns or more in caliber An experiment performed with fibers less than twentieth of this diameter average 0.2 micron resulted in significant pulmonary fibrogenesis This result suggests that the biological activity of glass in particular and per- haps other fibrous particle diameter truly apply to all silicates may be a product of either the particle length or It is not known at this stage if this principle would fibrous silicates Nor is it known whether length and fine- ness of fiber caliber can potentiate each other in producing tissue responses The latter experiment still needs to be performed There is however human evidence that this may be the case The electron microscope has some in recent years been applied to the study of pneumoconiotic lesions Through this instrumental modality it has been possible to demonstrate large numbers of extremely fine asbestos fibers within pulmonary fibrotic lesions which appeared almost devoid of asbestos bodies as visualized by conventional optical microscopy Electron microscopy has also revealed that there are delicate fibers among conventional fibers normally discernable in many asbestos dusts as viewed by maximum magnification optical microscopy Similar fine submicron fibrils have not been observed in specimens of talc or tremo- lite The presence of therefore constitutes the biological actions these ultramicroscopic components in asbestos minerals a further explanation for the great differences between of the talcs and asbestiform silicates ra Carcinogenicity the The controversy over applicability of this the carcinogenicity of some asbestos minerals to the tales now requires closer examination and The propensity of crocidolite and amosite to evoke neoplastic responses in man has been a documented phenomenon for more than half a century requiring almost no further elaboration except the following comments 1 There is today less lung cancer in crocidolite workers than formerly because of improved dust control 2 pleural mesotheliomatosis has recently recently emerged as an important neoplastic sequel to crocidolite exposure 3 there is an enhanced prevalence of cancer of nonpulmonary tissues in employees of crocidolite industries 4 cigarette smoking and urban air pollution have in surfaced as a complicating issue so that there may now be some rdeocuebnttwhyeeatrhser all crocidolite neoplasia is exclusively due to the crocidolite 5 inhalation experiments with crocidolite have not been con- vincing in demonstrating neoplasiogenesis 6 implantation studies espe- space deposition of large quantities of crocidolite have shown cially pleural and crocidolite dosage 7 the a positive correlation between oncogenesis demonstration that ordi- latter observation is mitigated by the experimental narily noncarcinogenic substances such as quartz dust can also produce pleural mesotheliomatosis so that the pleural response is in a sense nonspecific Amosite probably also is carcinogenic though perhaps not as decisively as There also is some question whether the crocidolite or amo- is crocidolite whether other chemicals with which site are in themselves carcinogenic or 69 these fibers are impregnated or mineralogically associated are the oncogenic agents Benzpyrenes and producing metal salts arsenic nickel beryllium have been demonstrated in crocidolite and amosite ores Nothing comparable has been demonstrated for talc or tremolite Because the latter has been classified as an amphibole mineral it has naturally come under suspicion as a theoretical carcinogen Theory and fact however have never matched up in either human experience or animal experimentation For decades workmen have been engaged in talc and tremolite mining or milling or have been exposed to tale products in secondary industries employing talc and tremolite as slippage agents or fillers or for insulating purposes etc. Excess prevalence of lung cancer which could not equally reasonably have been accounted for in terms of exposure to cigarette smoke urban pollution or to prior concurrent or sequential exposure to true asbestos has been convincingly recorded One of the earlier epidemiological surveys of tremolite miners in New York State did hint at an enhanced incidence of lung cancer among relatively young 45 to year employees of selected mines This was a disturbing observation However subsequent surveys of the same miners have shown a distinctly lower incidence of neoplasia even though the miners now were an average of 1 decade older with commensurately longer tremolite exposure and of course with longer periods of cigarette smoking Two explanations may clarify this change The first is that the average level of dustiness in the tremolite miners had been appreciably reduced during the past 2 decades Prior to the institution of vigorous dust control it was not uncommon to find mine and mill workers smothered in clouds of tremolite particle counts probably having been 100 to 1,000 times greater than has recently been permitted The second feature uncovered by detailed analyses of the work histories of the tremolite industry employees of the prior era that is before 1955 showed that with rare exceptions all these employees had spent a large part of their working lives in industries other than talc mining Many had been exposed to asbestos or to rock and metal ore dusts Analysis of the lung tissue of a representative number of these employees confirmed the presence of quartz asbestos metals and other substances This clearly created doubt whether the earlier epidemiological findings have true validity with respect to tremolite The alleged carcinogenicity of chrysotile which is mined in the vicinity of one of the major tremolite deposits in North America has been an additional confusing factor Persons who are not thoroughly familiar with the rather major mineralogical and biological differences between tremolite and chrysotile may have been confused by the geological close association of these ore bodies and the erroneous assumption that both tremolite and chrysotile are asbestos minerals The latter issue has already been discussed and it has been established that although tremolite may be an amphibolelike substance such as anthophyllite amosite or crocidolite there are no premises for assuming that tremolite is likely to behave biologically as do the other three amphiboles 70 Is chrysotile a carcinogen crescendo of popular opinion has author remains unconvinced The This is a very perplexing question A sought to incriminate chrysotile This main premise for carcinogenicity stems from epidemiological observation of employees of the insulation and shipbuilding industries In both these industries there has been in the past considerable exposure of pipe laggers to asbestos dust Only in recent decades however have these insulation bats been composed predominantly of chrysotile In former years crocidolite and amosite were important components Studies of lung well tissues of deceased laggers have verified the presence of amphibole as of serpentine asbestos Which then was the carcinogen It is a known fact also that in recent years fiberglass has to an increasing extent begun to substitute for asbestos in this industry The increasing demonstration of lung cancer in insulation workers coincides with the latter event Which agent then is the carcinogen It is further known that insulation workers have during decades become heavily exposed to methylethyl ketone solvents in the synthetic glues presently used to bond the bats of asbestos or fiberglass to the pipes or ducts which are being insulated Formerly the glues did not contain such highly volatile solvents Indeed one of the occupational diseases of significance in this industry now is polyneuropathy due to the inhaled solvent vapors These solvents come in direct contact with respira- tory epithelial surfaces whose lipid surface membranes and organelles are highly vulnerable since they are readily solubilized into methylethyl ketones or similar solvents Which then is the true carcinogenic substance Finally it should be pointed out that the role of cigarette smoking has not been satisfactorily discounted in the referenced epidemiological studies of lung cancer among insulation workers In some groups reported an excess prevalence of lung cancer was not demonstrable when cigarette smoking was taken into consideration Epidemiological surveys of chrysotile workers in Quebec showed no excess of lung cancer in Canada also failed to focus attention A review of pleural mesothiliomatosis on Quebec or any other center where chrysotile industries are concentrated There also is conflicting experimental evidence about chrysotile In one personally conducted study the theoretical carcinogenicity of chrysotile asbestos was probed by an inhalation study in which tumor induction in rats exposed to beryllium sulfate a potent carcinogen was compared with tumor rates in rats similarly exposed to chrysotile dust and to chrysotile following sulfate and also to chrysotile dust exposure preceding exposure to beryllium the mean BeSO4 The results were striking 2 7 In the beryllium group incidence of lung cancers was 15.4 percent In rats exposed to both chryso- tile and B-- SO4 the malignant tumors totaled only 8.5 percent No tumors in rats which were exposed only to chrysotile and there were none in developed shows that so far from undosed controls observed for 24 months This clearly chrysotile acting as a carcinogen or as a cocarcinogen with a known potent the carcinogen the chrysotile behaved like an anticarcinogen with respect to beryllium Mention may also be made of an synthetic chrysotile deposited into ciated with some tumor production experiment conducted with natural versus the pleural space The latter was assoThe synthetic chrysotile had the contrary 71 effect 1 The difference between the two is that natural chrysotile some times is contaminated with metallic salts absorbed by the serpentine fiber surfaces or perhaps trapped within the chrysotile tubules Some of these metals include known carcinogens such as nickel chromium and arsenic Since these metals are not universally present in equal degree in all samples of chrysotile caution must be used in stigmatizing this mineral unnecessarily as a carcinogen It should also be stressed that the intrapleural experiment is highly artificial so that cancer production by this technique may be expected with true carcinogens as well as with substances which are not ordinarily carcinogenic for man for example silica The demonstration therefore that synthetic chrysotile natural tremolite and talc are incapable of evoking pleural mesotheliosis may be highly significant testimony that these sub- stances may not possess latent carcinogenic properties for man Sequelae and Complications Carcinogenesis has been separately discussed since it is not established whether it is an independent property of carcinogenic minerals or a sequel or complication of the pneumoconiotic pathology induced by these silicates It is necessary to review several principle sequelae and complications of exposure to dusts The first is tuberculosis The close association between pulmonary tuberculosis and silica inhalation has been convincingly established through epidemiological studies and experimental inquiry and the pathogenic principles for tuberculogenesis by siliceous minerals has probably been fully clarified 5 Do the silicates also promote the development of pulmonary tuberculosis There is no real epidemiological evidence for this and no laboratory proof The relatively closed communities in South Africa where crocidolite and amosite are mined and processed and the comparably closed community in Quebec where chrysotile is produced constitute excellent epidemiological models No significant excess of tuberculosis has been demonstrated for these occupational groups whose life careers could be followed to a satisfactory degree A large number of these miners and mill workers were personally studied by this author and a number of necropsy specimens were likewise examined By contrast with silica workers tuberculosis was consistently conspicuous by its absence or infrequency Since the pathogenic asbestiform silicates proved nontuberculogenic it is no surprise that tuberculosis has not been associated with talc and tremolite mining Of 300 mine and mill workers who have been followed over the past 25 years not a single individual developed tuberculosis This is an amazing record which speaks for itself since tuberculosis is by no means a conquered disease especially among industrial workers Heart Disease There are no indications that arteriosclerotic heart disease is any more prevalent in asbestos workers than in the general population The incidence indeed appears to be lower This may be due to the excess prevalence of cor 72 FIGURE 29. : Partly destroyed blood ves- selin lung of asbestos work- er X 10 FIGURE 30. - Perivascular fibrosis show- ing stenosis of pulmonary blood vessels Silica and asbestos exposure X 10 FIGURE 31. - Asbestos bodies in wall of blood vessel as demonstrated by Perl's stain Mixed amosite and chrysotile exposure X 10 73 pulmonale The latter constitutes a significant problem and has a explanation in the perivenous pulmonary fibrosis and elastosis and quent destruction of the vascular system figs 29 to 31 direct the conse- conse- In tremolite workers some cor pulmonale does occur This is traceable to prior concurrent or subsequent exposure to asbestos usduuasltly Review of the life histories of 300 tremolite employees shows an incidence of 8.3 percent of the fatal cardiac disease This is not significantly different from the occurrence of arteriosclerotic heart disease among matched con- trol groups that never were exposed to tremolite Less is know about talc industrial groups pure The lack of epidemiological data at least established that thus far no problem has surfaced Emphysema Bronchitis and Bronchiectasis So many industrial agents cause emphysema and bronchitis 4 that an inquiry about this matter seems pertinent There are no indications that either emphysema or bronchitis are selec- tively more prevalent among asbestos workers The underlying pathology induced by asbestos than with is not of the general public such a nature as to foster either of these conditions There is no primary bronchopathy and consequently no alveolar distension induced by obstruction Nor is there alveolar mural destruction The very nature of asbestosis protects the lungs against this since the fibrous and elastic tissue in the alveolar walls strengthens rather than weakens these structures fig 23 At a later there may be some compensatory emphysema as areas of the lung collapse is however limited and regional only stage This Bronchiectasia is another matter It is quite a common sequel of pro- gressive interstitial pulmonary fibrosis in asbestosis The bronchi and bronchioles are distended by the contraction of fibrous tissue nary parenchyma between them This form of lung pathology may late sequel of crocidolite amosite or chrysotile asbestosis in the pulmo- be seen as a Unlike bron- chiectasis in nonoccupational groups the asbestotic form of the disease is initially nonsymptomatic because there is little or no associated infection However the latter may occur later None of this is seen with pure talc workers There has been no excess prevalence of either emphysema bronchitis or bronchiectasis unless there has been prior or concurrent or subsequent asbestos exposure Precise epidemiological data are available for tremolite workers Thus of 264 employees followed since 1948 only four developed emphysema This reflects an incidence of approximately 1.51 percent This is far below the incidence of emphysema in the general population Bronchitis without emphysema was observed in seven individuals No bronchiectasis was found among these workers This clearly shows that talc and tremolite not only behave differently from chrysotile amosite or crocidolite but may even be associated with a lower incidence of these disorders which now are among the most in North America Whether talc or tremolite prevalent and disabling illnesses protect the lungs against 74 emphysema and perhaps bronchitis seems answered affirmatively on the basis of a fair question to pose the above evidence and can be Conclusion of talc and tremolite currently exceeds 3 million tons World prTohdeusceticolnearly are useful mineral products which play an imporotfant per annum rubber and roofing materials as components part as fillers of asphalt textiles wall tiles cement stucco ceramics paints insecticides paper foundry parting compounds A small proportion wire and cable coverings or as industries Through of talc enters into the toiletry and food processing contact with thousands of human subjects come into these multitudinous uses contributing to their production Amer- talc and tremolite for every employee of the world production It is dif- ica produces and uses more than third be sustained without these use- ficult to imagine how modern civilization can ful and relatively inexpensive minerals therefore that talc and tremolite are so biologi- It seems fortunate the United States today to eliminate all cally inert There is a mood in with the humanitarian ideology environmental hazards No one can quarrel have been haphaz- haphaz- inspiring such enthusiasms Too many hazardous materials environment and it would be better to control ardly released into the human maximum security Not only does substances equally to achieve restraints which all industrial but it seems reasonable to counsel against this seem logical the cost of living for everyone or which may gum will unnecessarily increase After all the human body and partic- the works somewhere along the line itself as up have some defenses The lung constantly replaces be ularly the lungs It would seem that although these defenses can part of normal existence asbestos minerals this is not estab- overwhelmed through long exposure to This fact should be lished for talc or tremolite in modest corengcuelnattriaotnisonfor dust control in the taken into consideration in formulating talc industry Summary relationships of silicates are reviewed 1. The physicochemical between the empirical formulas of Although there are superficial resemblances there are significant tremolite chrysotile amosite and crocidolite molecules talc structural differences between their respective physicochemical be best classified in terms of their capacity 2. Mineral silicates may ribbons oblong crystals needles or fibers to be formed as sheets tubules classifications of serpentines instead of using the conventional mineralogical or amphiboles or of asbestiform minerals relatively inert substances and 3 Talc and tremolite are biolgocally of amosite and crocido- this contrasts sharply with the marked pathogenicity but its biological pro- lite Chrysotile occupies an intermediate position pensities are closer to those of talc and tremolite 75 4. Experimental and epidemiological studies provide closely confirmatory data with respect to the points just mentioned It is extremely difficult to identify large numbers of employees who have been exposed exclusively to one or another mineral Many pulmonary lesions in industry employees are composites of multiple and chemical exposures and many of the nocuous agents derive from sources other than the silicate industry in question 5. Lung cancer has been definitely associated epidemiologically with exposure to crocidolite the biological propensity There is no evidence to induce neoplastic that talc lesions or tremolite possess There also is some doubt as to ies suggest the role of chrysotile in carcinogenesis that chrysotile may foster the development Even though some studof lung cancer under certain circumstances other studies flatly contradict this evidence so that the issue still seems unresolved 6. The sequelae and complications of exposure to asbestos include bronchiectasis and cor pulmonale Obstructive bronchopathy and emphysema do not normally occur as a consequence of exposure to asbestos Talc and tremolite exposure are devoid of any of these pathological responses 76 References ... Gross P. Fibrous Dust Seminar Industrial Hygiene Foundation of America Medical Bull No. 16 1970 Effects of Asbestos Annals of the New 2 ScYhoerpkerAscadG.emWy. oHf. Sc Biiolo1g9i6c5al pp 121 132 246 385 437 504 596 599 601 Archiv f^...r Gewerbepath und Gewerbehyg v 19 3 . Chronic Berylliosis 1962 4 5 6 7 8 9 Industrial Bronchitis and Asthma v 24 1955 p 52 Ind Medicine and Surgery . 1964 Silicosis p 381 and Tuberculosis Ind Medicine and Surgery v 33 Thesaurosis Versus Sarcoidosis JAMA v 181 1962 p 635 . Tumors of Primates and Rodents Ind Medicine and Surgery v 40 . 1971 p 48 Schepers G. W. H. and T. Dust on the Human Lung M. Durkan The Effects AMA Archives Industrial of Inhaled Health v Talc Mining 12 1955 p 182 An Experimental Study of the Effects of Talc Dust on Animal Tissue . AMA Archives Industrial Health v 12 1955 p 317 77 APPLICABILITY OF ASBESTOS STANDARD TO FIBROUS TALC by William J. Nicholson Ph.D.1 I would like to speak about the application of the current asbestos stan- dard to fibrous tales to tremolite and to the variety of fibrous minerals that are found in several of the talc deposits especially those talc deposits that have widespread industrial use in the United Statesespecialy Specifically I would like to demonstrate here that health data indicate that all fibrous min- min- eral material should be considered equally for the purpose of standard setting that the current asbestos standard is limited in its provisions and represents a bare minimum standard for all fibrous minerals and finally that control measures exist that would reduce dust concentrations in mines and mills below those required by the current asbestos standard and Let me briefly go into some of the background of the asbestos standard the data that led to the specification of a current standard of five fibers per milliliter of air and a later standard in 1976 of two fibers The standard specifically includes the six asbestiform minerals crocido- lite chrysotile tremolite anthophyllite and actinolite it is applicable to all industries covered by the Department of Labor in the United States The equality of consideration of the various minerals has a back- ground in several studies For example crocidolite and its severe problems have been documented in work that has come out of South Africa and Great Britain in studies by Dr. Wagner and Dr. Newhouse In have been developed by Dr. Selikoff of the Mount Sinai the United States School of Medicine data on the mortality experience of factory workers exposed only to amosite Here one finds that roughly half of those individuals who died died either of cancer or asbestosis More extensive data have developed among the insulation workers These workers have been exposed predominantly to chrysotile also to a little amosite during World War II and since World War II especially in shipyards Of that group of workers one in five who died died of lung cancer nearly one in 10 of mesothelioma one in 10 of gastrointestinal cancer three times the expected amount and almost 10 percent died of other forms of cancer Another 7 percent of the deaths are from asbestosis of the lungs All told 53 percent of the deaths of a group of New York and New Jersey insulation workers are from one of these two asbestosis or cancer Nearly 40 percent of their total deaths can be related to their occupational exposure to asbestos We can also consider a major asbestos manufacturing facility one which uses extensive amounts of chrysotile In fact 95 percent of the manufactured products asbestos used in manufacturing in the United States utilize Mount Sinai School of Medicine of the City University of New York 78 chrysotile asbestos Again the same statistics are obtained with one excep- and that is in the textile department Here the percentage of deaths tion due to cancer were relatively low about 20 percent This came about because the deaths due to pneumoconiosis in the textile department resulting from the extremely high dust concentrations exceeded 40 percent So we have the grim data that pneumoconiosis can in one sense protect against cancer These of the die before they reach the time of onset of lung cancer or any persons other cancers In fact the period of time from onset of exposure to death due to either mesothelioma or lung cancer among asbestos insulation workers is about 35 years Very few deaths occur prior to 30 years virtually none prior 20 since onset of exposure The cancers we are speaking about those to years to asbestos are a long time in coming associated with occupational exposure If any cause gives rise to death prior to that then the cancers will not be seen If we look now at the very limited data available on the mortality of talc miners and millers we see that asbestos exposure results in similar of death In the early data of Kleinfeld for example we have infor- causes mation on 91 workers and the causes of their death which were as follows 20.9 percent malignancies 27.5 percent cardiac deaths other than cor pulmonale 30.7 percent pneumocotnhieosdiesathasnd atthterirbeutmeadinitnogma2l0i.g9napnecrycewnetre due other causes Approximately half to cancers of the lung and pleura While we have only limited data on what happens to humans exposed to talc mine dust containing the wide variety of minerals Dr. Langer haansd u ds ee scroifbesduchfor you the mortality data we do have indicates that the mining caution In fact as an aside if one minerals should be treated with extreme the mining and milling of talc with the mining and milling of Cana- compares dian chrysotile as reported by McDonald one would postulate that talc is a However I do not think material that is far more dangerous than chrysotile that this is necessarily an appropriate assumption to make From the data we for saying have I do think it can be said at this time that there is no reason of the asbestos varieties or a fibrous talc is more carcinogenic that any one fibrogenic than another or less carcinogenic or more fibrogenic or less Some animal data have been referred to previously in this symposium all such data must be considered with caution They can be used to Virtually indicate potential problems and indeed problems have been suggested by ani- the National Cancer Institute mal experiments For instance recent data from of their NCI indicate that all durable fibrous material irrespectively chemical composition when implanted on the pleura of animals act as a car- cinogen with equal intensity For example fibrous glass fibrous aluminim in these NCI experiments induced oxide and the various forms of asbestos in mesothelioma at approximately the same frequency Similar experiments in which fibrous glass several varieties of asbestos and fibrous Germany injected into the peritoneum of animals also produced mesothe- the most nemolite were lioma roughly of equal intensity I think in this case nemolite was carcinogenic Thus two separate experiments with animals indicate that a wide variety of fibrous materials are equally potentially dangerous 79 A technical reason also indicates that all fibrous mineral material should be treated equally in a standard It is impossible for an individual technician counting fibers in an industrial air sample to distinguish whether it is a fibrous talc an asbestos mineral or any other mineral fiber All one can determine using a phase contrast microscope is the presence of a fiber determined by its length and width Without the very sophisticated instrumentation that you have already heard about it is inappropriate to require that a dust counter either in the Bureau of Mines or in industry dis- tinguish between fibrous minerals Currently in a mixed exposure with asbestos no such discrimination is made by the U.S. Department of Labor in assessing exposure The data we have just discussed the evidence Dr. Langer has presented of asbestos in talc deposits the finding of severe health problems in one group of talc mines and mills the similarity in toxicity of all fibrous minerals in animals and the inability of a technician to distinguish one fiber from another using a phase contrast microscope all these indicators show that the standard for asbestos should be applied to all fibrous minerals in talc mines and mills When one suggests that the asbestos standard be equally applicable to the fibrous minerals that led to that associated with standard to get talc let us briefly consider the background an appreciation of its adequacy here Infor- mation on dust levels associated with disease is limited Six studies have documented asbestos dust levels exposures ranging from 10 to 15 in insulation work All fibers per milliliter of of them give average air but none were done been 20 to 30 years ago directly on documented In a recent group the groups of workers of workers whose mortality that were examined by has Dr. Selikoff much lower exposure levels were associated with radiographic evi- dence of asbestosis These were workmen who sand the taping compound the spackly that is applied to the joints of wallboard In the past they did this no more than 20 percent of their time and now even less Dust counts here showed average exposures on the order of five fibers per milliliter or less when sanding These data give no comfort with a standard of five fibers per milliliter When one speaks of dust count in terms of fibers per milliliter of air it should be recognized that one is looking only at the tip of an iceberg The standard specifies that only fibers longer than five microns be counted because these fibers are readily seen in an optical microscope In the elec- tron microscope myriads of shorter fibers can be seen This would not be a problem if it is not the In fraction counted were the same in chrysotile exposures we have seen all the exposures Unfortunately fraction counted to be 1 in 250 or 1 in 50 or even 1 in 20. When other asbestos minerals were counted such as amosite the fraction could be as great as 1 in 3. So what we have is a standard that specifies determining an asbestos exposure with what is really a rubber yardstick We are looking at tips of icebergs but the icebergs unfortunately have variable densities What we have really is only a very qualitative estimate of exposure in any occupational circumstances where fibers are determined by this standard One should exercise extreme caution in certifying that a work place is safe to a workman who may 7 80 have to spend 8 hours per day 5 days per week 50 weeks per year in such an environment in considering this standard little weight was given to a Moreover for cancer No data exist on the safety factor that would be appropriate and there is no indi- possibility for a threshold for asbestos cancer cation that the five fibers per milliliter currently specified as badly defined as it is provides adequate protection against cancer for U.S. workmen using asbestos and other fibers Finally the data on the incidence of asbestosis which went in doubt into the curThe data were rent standard and which received great weight are now concerned with the prevalence of asbestosis in men who worked only after the of dust control measures from 1931 to 1933 in a British asbestos application factory The men were examined in 1966 All were still at work of and only That 13 individuals in the study group had more than 30 years exposure has been reexamined 5 years later and the data have been pub- s laimsehegdroupThn eo rew is considerably more evidence of asbestosis among the workers than was first published perhaps 10 times as much that the asbestos standard that I suggest be applied here as itThhauss bw ee enseien the past to the fibrous forms of talc and tremolite is a standard that is really a very inadequate one It represents an absolute min- inum standard We do not have the luxury of relaxing it whatsoever Moreover of that standard should be applied to the fibrous minerals con- the full scope the application of engi- sidered here Mandatory monitoring and surveillance controls the use of personnel protection equipment the availability neering medical examinations are important of change rooms for workmen and periodic parts of that standard Along with such protection for the workmen it is necessary that labeling to the fibrous talc similar to those in the asbestos standard apply provisions and the fibrous minerals that may be present in talc Much of these materials extensive user that are later used in industry The rubber industry is one has already been mentioned Similarly concern for the Board exposure extends into the of Education of New York consumer area For instance last summer had in their stockrooms modeling material that contained City found that they 50 percent asbestos This was used by children who mixed the dry powder with models and art water to form a paste that could be used for shaping various works The Board of Education went to the supplier and told him that this said We'll change material was unsafe and they did not want to use it He our formulation The formulation that came back substituted fibrous talc The material dis- from the Gouverneur deposit in New York for the asbestos the material that was substituted for played on the slides by Dr. Langer was allow its use this modeling material Again the City of New York did not because of the concern for health Caution labels as applied in the current asbestos standard are certainly applicable to all such fibrous mineral mate- rial that can be disseminated into the air for surveillance and maintaining a safe environment in the The concern and here the currently proposed standard of mines extends into the community 81 the Environmental Protection concerned with the Agency EPA places a special burden sions does not monitoring consider mines of mines and mills The with EPA the standard for on those asbestos emis- from such sources will be controlled assumption that emissions measures in the work place by the maintenance of I only hope this confidence of atphperopriate control justified EPA is Control is feasible I where average fiber levels was recently in an asbestos mill determined by the Bureau of Mines in California Department of Health ranged from two to five fibers and the State pure asbestos ore levels were achieved that per milliliter With dard I am suggesting be applied to were in compliance with the stan- of fibrous material ore bodies containing only a small fraction In summary I would in the past be strongly urge that the procedure which continued The existing standard for was followed applied to fibrous talc and the asbestos should be various asbestos minerals present in the Equal application of the standard health and to all fibrous minerals is tale technical reasons The dictated by tively weak one and standard to be applied is no relaxation of it should be considered in fact a rela- application of such a standard is Finally the exist that will allow it to be metappropriate because engineering controls 82 ASPECTS OF MINERALOGY OF TALC by Arthur M. Langer,, My name is Arthur M. Langer I am an Associate Professor of Mineralogy at the Mount Sinai School of Medicine For the last 8 years I have been pro- fessionally associated with the Environmental institution I serve as Head of the Physical Sciences Sciences has concentrated in the environmental and occupational Laboratory in that Section My research health areas My field of specialization is mineralogy and I concern myself with the identification of biologically important mineral particles in the environment identification and characterization of mineral particles in human tissues and in various types of consumer products I have written many papers in these areas and they are available upon request I am going to apologize because I was not present at the symposium this morning I think that some of my statement might be a review of what has previously been covered However some of these points are important and worth stressing again Talc I would like is a mineral to emphasize first the complex nature of species However the word talc as often the term talc used in industry refers to a property rather than a true mineral entity Finely ground material with a resultant high surface area is often called talc The simi- ends here between the mineral talc and talc as used in the industrial larity experience The same word therefore means different things to different people One must define mineralogically the talc in question Talc geologi- is a cally forms generally from an altered ultramafic rock one which is composed mainly of magnesium silicates Anthophyllite and serpentine asbestos chrysotile may form during this process as well Talc may also originate through the metamorphism of a carbonate rock with the introduction of silica In this latter rock type the introduction of silica would produce calcium mag- nesium silicates which may include the asbestos mineral tremolite There are 10 States in the continental United States that are major producers of talc In thoe f s thee se States genegrenaerlall lyy different geologic material respon- sible for the talc production The nature of these deposits may be extremely at the Gouverneur New York talc deposit several of complex For example the asbestos fiber types occur with the talc The senior author of a paper on that deposit is here in the audience Dr. Malcolm Ross of the U.S. Geological He and his colleagues published their findings in the American Survey would recommend this paper to anyone wishing to learn about Mineralogist I and almost the complexities of the talc deposits Talc deposits are complex always include asbestos as a natural contaminant Associate Mineralogy Mount Sinai School of Medicine of the City University of New York 83 of some about the health experiences rock. this morning Kleinfeld Kleinfeld from this about health experiences some Dr - and millers spoke this morning health experiences experiences aerosols aerosols some miners miners exposed exposed were from from rock They significant disease much which generated asbestos asbestos They rock The significant disease State which peculiar related might be in the the tales from minerals peculiar they representative of representative deposits deposits Talc talc themselves that may themselves example example New York example tremolite there minerals are fine These plates that associated with intergrown with asbestos asbestos tremolite These microscopic intergrown intergrown other other particles present sublight microscopic range These These talc incTihdeeynttaenld linycidentally are specifically specifically selected they mill well intergrain they amphibole asbestos minerals do not enter are representative minerals asbestos The anthophyllite There crocidolite amosite and minerals tremolite crocidolite they amosite Crocidolite Crocidolite amosite not enter anthophyllite because because commonly occur in consideration In aforementioned State talc The into types . two tremolite aforementioned York deposit there tremolite other silicate varieties alonwehich common common calcium species magnesium magnesium are silicate phase hexagonite site manganese rich tremolite as manganese manganese substitutes in octahedral magnesium magnesium iron substitutes amphibole , calcium manganese manganese as fiber well Another tirodite amphibole occurs in manganese with deposit anthophyllite anthophyllite occurs as in this deposittrue also have two structuralvarieties of mineral talc in Platy talc the mineral occurs here with monoclinic triclinic sym- so there different physical chemical responses responses metries metries two biological environment biological thing physical New chemical deposit deposit in biological amphibole - One more York State in in addition asbestos serpentine minerals occur Within serpentine serpentine phase chrysotile fibers occur asbestos amounts amounts in asbestos fiber chrysotile trace to major amounts trace naturally Three from deposits These may tremolite in deposits are anthophyllite These to in talc does talc samples We prefer electron instrumentation characterize differentiate from prefer prefer micro- example electron to object asbestos transmission ~ elongated scope scope example characterized observed a transmision micro- morphological istics istics may characterized electron diffraction identified morphological which you structural character- information selected area information diffraction pattern analysis structural structural concerning particle able microchemical characterize instrument electron informt atioy n pe instrument routinely in this manner characterize characterize min- identify mineral . We can talc routinely separate asbestos True fibers fibers tend with more curvilinear curvilinear Tale erals edges with asbestos truncations termination termination occur platy minerals minerals truncations common plates yield characteristiccharacteristic hexagonal electron diffraction patterns Talc quantified in talc characterized identified and quantified characterized in some cases identified, Let yield describe describe fibrous fibrous talc Let met is what the looks like as viewed with a transmission electron microscope fig Some fibers are anthophyllite anthophylite are are microscope These mineral fibers anthophyllite all available of tremolite tremolite techniques techniques including mineral mineral ray phases diffraction identified diffraction light just about all Gouverneur deposit microscopy available analyzed talcs from York Gouverneur constituted found found that that the samples talc true mineral talc 16 talcs samples talc the true mineral constituted constituted only have analyzed talc, the 16 samples, that in 16 of the FIGURE 1. - Transmission electron micrograph of a typical fibrous talc sample from the Gouverneur deposit New York State Fibers constitute a significant proportion of the sample The fiber population is made up of talc fibers tremolite and anthophyllite Arrow in center of photograph indicates a 2- by microm- eter fiber of tremolite Magnification unknown one of the major mineral phases within the samptlreemtolaibtlee 1 AgaiMnajoorthceornsatniat-u- ents in all cases were also anthophyllite and lytical techniques supported this observation as well With resolution contain many transmission electron microscopy one sees that talc plates may mineral entities with a single grain Intergrowths of talc with different asbestos minerals are common fig 2 What the biological consequences are of such minerals which may incumbent upon the inhalation of large quantities a cellular level for a very long time period is presently be retained on microchemical analysis of unknown We do know from our experience with 85 asbestos fibers that particles are chemically degraded while residing in vivo They also have an extremely long period of residence in the biological systems talc particles themselves may be intergrowths of many mineral phases some of which may be asbestos TABLE 1. - Minerals identified in the New York State fibrous talc deposit by ray diffraction,, 2 3 Sample | TALC MAJ MAJ MIN MIN TREM MAJ MAJ ANTH MAJ MAJ SERP CHLOR MAJ | TR MIN | TR Sample | TALC MAJ MAJ MAJ TREM MAJ MAJ ANTH MAJ MAJ SERP CHLOR MAJ | TR MAJ | TR MAJ MAJ MAJ 5 eee eens MAJ MA eeJ e MAJ 7 MAJ MAJ MAJ MAJ MAJ MAJ MAJ .. MAJ MAJ MAJ MAJ Major phase MAJ MAJ MAJ MAJ MAJ | TR | NIL | TR | NIL | TR MAJ MAJ MAJ MIN | TR 13 MAJ MAJ MAJ MAJ | TR 14 MAJ MAJ MAJ MAJ | NIL 15 MIN MAJ MIN MAJ | NIL 16 MA MAJ MIJ N MAJ | TR MIN Minor phase only most intense reflections are visible TR Trace major peaks discernible but just above background NIL No peaks observed Prominent mineral phases TALC = the mineral talc TREM = tremolite ANTH == anthophyllite SERP = serpentine minerals CHLOR = chlorite Other phases observed rich calcite phlogopite ? pyrophyllite pyroxene various diopside The number of peaks observed in the scans 3 to 70 2 0 theta averaged about 60 with intensities 5 times greater than background All visible reflections numbered about 90. Many of the overlapping peaks were counted as single reflections The above phases account for more than 85 percent of each sample analyzed I will now discuss some of our experience in human case material This illustration is an electron micrograph of a tissue obtained from a workman who worked in a rubber factory for 30 years fig 3 He worked with talc the talcs used in this factory were fibrous talc Those particles that you see are both amphibole and chrysotile asbestos fibers It is possible to examine tissues of workmen exposed to talc dust and determine with a high degree of certainty what the mineral particles are which were retained in the lung tissues Examination of lung tissues of individuals who have worked with talc shows invariably that inhalation of talc dust means inhalation of asbestos as well I think that the major points stressed indicate that there are talcs and there are talcs Some mineral deposits are extremely complex and the mineral- ogy reflects this The methods recommended for proper characterization of talc would be polarized light microscopy ray diffraction using step scanning mode transmission electron microscopy with selected area electron diffraction and microchemical analysis Asbestos minerals may be distinguished from talc in this manner 86 FIGURE 2. - Transmission electron micrograph of a talc composite grain from the Gouverneur deposit arrow The amphibole asbestos fiber to the right of the grain is about 0.2 micrometer thick The amphibole fibers intergrown in the talc host are only several hundred angstroms in thickness Magni- fication unknown from FIGURE 3. " Transmission electron micrograph of a carbon extracted lung tissue specimen workman exposed to talc dust in a rubber factory This individual died of talcosis and lung cancer as primary causes Autopsy revealed the presence of a primary cancer of the sigmoid colon Most fibers shown in this photograph are chrysotile Talc plates are also visible Magnification unknown 87 We would feel and I think I am speaking for the rest of my group that it would be prudent at this time for the Bureau of Mines not to change the present restrictions on fibrous talc We feel that talc is a mixture of many different components including asbestos and that talc deposits themselves are extremely complex and zoned so that any one mine cannot be counted upon to yield the same kind of dust by the month or even by the day add Thank you This is the some pertinent remarks end of my formal presentation I do not know whether this was I would like to discussed this morning but I would like to comment on a group of men studied by Kleinfeld and colleagues 3 who were exposed to talc dust at the mines and mills of Gouverneur New York None of the cohort of 39 men had ray evidence of pneumoconiosis However 25 percent showed clinical signs of shortness of breath dyspnea and cough which could be correlated with early stages of pneumoconiosis We have reported these observations in that paper These men exposed only some 16 years on the average were apparently exposed to extremely high concentrations of talc dust so that on a comparative scale we would consider that talc contaminated with asbestos would be somewhat less fibrogenic than comparable dust exposures to pure asbestos But there are several nuances here of which everyone should be aware It takes an extremely long time for the clinical symptoms of disease related to asbestos exposure to manifest themselves Generally it takes 20 to 30 years from onset of exposure to asbestos dust to bring about either lung scarring asbestosis or the various malignancies associated with the exposure Therefore in our report we were very cautious We indicated that the time period of observation of this small group of men was too short to really make any dramatic statement that tremolite talc anthophyllite talc or talc itself is a biologically less harmful material than pure asbestos We feel that this group of men has to be followed for a much longer time period and that malignancies if they do occur certainly would not appear for another 10 years at least 88 Bibliography Hobbs A. A. P. 488 A Type of Pneumoconiosis Am J. Roentgenology v 58 1950 Kleinfeld M. J. Messite O. Kooyman and M. Talc Miners and Millers in New York State mental Health v 14 1967 p 663 H. Zaki Mortality Among AMA Archives of Environ- Kleinfeld M. J. Messite and A. A. Langer A Study of Workers Exposed to Asbestiform Minerals in Commercial Talc Manufacture Environmental Res v 6 June 1973 Porro F. W. J. R. Patton and A. A. Hobbs Pneumoconiosis in the Talc Industry Am J. Roentgenology v 58 1942 p 488 Ross M. W. L. Smith and W. Ashton Triclinic Talc and Associated Amphiboles From Gouverneur Mining District New York Am Mineral v 53 1968 p 751 89 MINERALOGY , IDENTIFICATION AND QUANTIFICATION OF AIRBORNE TALC DUST by T. D. Oulton,, Introduction As representatives of the Engelhard Minerals & organization which mines and Chemicals Corporation Johnston Vt I together witphroMcre.sseE.s mJ.ineTrrailglitaaleandofMrt.heD.plAa.ty variety at attended the symposium We to the meeting but certain had not intended to make any formal Jacobs presentation unsaid things that were said and much that was left persuade Engelhard Minerals & Chemicals tional remarks which we feel will be Corporation to present addi- which we intend to make and which relevant and appropriate will be expanded in part in a The points supplemen- tary discussion section may be summarized briefly as follows supplemen- 1. The discussed by went was in mineralogy of talc as compared to that of the asbestos minerals Dr. C. S. Thompson while interesting and correct so far as it our opinion quite insufficient A more complete exposition of example physiological toxicity carcinogenicity industrial as so ably reviewed in the discussions by Drs Kleinfeld SchheapzearrsdouasnndesSsmi,th " 2. The crystallographic structural control of talc been determined as a mineral which has symmetrical layer phyllosilicate provides a argument against even the possibility of talc existing in a fibrous strong Therefore we object to terminology in any official form any way the existence of fibrous tale document which implies in instead an or talc fibrous and support expression such as talc in association with fibrous and elongate and asbestiform mineralogical particulates 3. We urge the use of a more precise descriptive mineralogical terminol- iodgyentiinfiacnaytioofnfsicial document and deplore the mixed descriptive mineralogical istration such as are used in the Occupational Safety and Health Admin- OSHA 29 CFR 1910.93a wherein a trivial amosite is given equal weight with the or trade name such as for some of the other amphiboles systematically correct nomenclature We also object to the strained tion of the term fiber as used in the interpreta- little doubt about what is same document Although there can be actually meant in the context the term fiber in Engelhard Minerals & Chemicals Corporation Johnston Vt 90 general English usage certainly implies a whole quite distinct and different from the called to at least some of the amphiboles set of functional properties fibrous character assigned the blanket identification arbitrarily as asbestos or as 4. We regard matter with a projected area length to diam- asbestiform or any particulate ratio of 3 to 1 when observed at X 450 magnification by phase contrast eter oversimplification and we microscopy as a completely unacceptable technical indeed be hold that the burden of proof that such an observed particulate can demonstrated or proven to be asbestos or an asbestos particulate lies wholly with the observer furtherance of the preceding remarks we fully support the conten- 5. In tions advanced by Dr. Stanley and others as well as by Dr. Thompson that it and observational tech- is necessary to bring the most sophisticated anaalnydticclaalssification of these niques available to the correct identification of Pfizer Inc. that trans- materials However we must take issue with Stanley for such final mission electron microscopy is the only acceptable technique decision In our experience the scanning electron microscope SEM electronanalysis is every bit as techniques combined with dispersive electron even less ambiguous than is transmission powerful and in some cases combined with selected area electron diffraction The fact is of and supple- microscopy that all of these available techniques serve to complement course and that no single simple test or limited group of tests can ment one another and complete identification of provide the necessary information for reliable these complexly interrelated minerals to the very transparent attempt of the Mt. Sinai group 6. We object and Rohl to arbitrarily include tale into the Drs Langer Nicholson diminish the importance of the broad group of asbestos minerals One cannot full awareness of the pathology of work of the Mt. Sinai group in developing asbestos minerals the related physiological activity of certain asbestos and that there is necessarily an identifiable But it does not follow from this be labeled talcosis or even follow- pathological response to talc that can Drs Kleinfeld Shepers and discussion and evidence presented by ing the records of talc miners and workers Smith as well as the vital personnel there is necessarily an identifi- reviewed by Lamar Mylryan toandtrBemaoclointe thtahtat can be labeled as tremolitosis able pathological reshpaodnsneo new evidence to offer and merely restated the old fibrous The Mt. Sidnaatia gerxotuepnded only by implication and hypothesis to talc asbestos rational discussion and hard new evidence while the other speakers presented quite contradictory to the position taken by the Mt. Sinai group the moderate position taken by Dr. Sykes representing 7. We endorse that much research still needs to be done and Ralph Nader Associates namelbye answered before fully rational decisions many questions still need to be resolved No one for example can regarding the talc questifoineldcaninspection to have ready access to all the expect a paraprofessional that has been mentioned above On highly complex diagnostic instrumentation and incredibility the other hand there is evident widespread dissatisfaction OSHA phase contrast microscopic method associated with the present standard 91 for fiber identification and field method that is both counting There is a clear requirement for a new to be more reliable and accurate but no such method seems presently at hand This would seem to be an reference to a appropriate problem for definitions concensus and organization for the development of consensus Committee 34 consensus standard We therefore test methods such as the newly formed ASTM urge that this problem be presented to the Executive Subcommittee of 34 with a and referred to the request that the assignment be accepted appropriate working subcommittee for resolution 8. Nothing in the foregoing remarks should be the standard limitations in taken as an objection to concentrations of airborne nuisance dusts tainly every employer should be sensitive to his Cer- and safety of his employees in the workplace responsibility for the health But an oversimplistic and considered we wish to emphasize that and milling industry could regulatory document for the talc mining easily result in such severe economic dislocations that an important American industrial mineral to a point from which material supply could be reduced recovery would be extremely difficult Structural Crystallographic and Compositional Which Distinguish the Amphibole and Characteristics Serpentine Miner Froam l Tas lc The technical mainly on standard discussion which makes up the following sections is mineralogical and crystallographic reference sourcebsas3ed Classification of the Silicate Minerals Based on Grouping of Si04 Tetrahedra Class I. Nesosilicates II Sorosilicates III Cyclosilicates IV Inosilicates , Phyllosilicates VI Tectosilicates Grouping of Sio_ tetrahedra Singles Groups sisters Rings tweens Chains caee Sheets scenes oe Frameworks Linkages of S104 tetrahedra 0 1 2 2 3 4 Oxygen atoms per 4 Si 16 14 12 12 10 8 Of these classes we are concerned which the amphiboles are only with the inosilcates IV of hedra a subgroup based on a double chain of silica tetra- extending infinitely linearly in one direction and with the phyllosilicates V sheets in which the linkages of silica tetrahedra extend ainntfiignoirtietley ainnd twtohe directions for example planar and of which the kaolinite- pyrophyllite structures are subgroups Winchell erals 3 A. N. Elements of John Wiley & Sons Optical Mineralogy New York 1951 Pt 2 Description of Min- Pavarennykh A. S. Press New York Crystal Chemical Classifications of Minerals 1972 Plenum 92 Inosilicates IV The amphiboles in the subgroup of inosilicates IV are common rockforming minerals which make up a substantial fraction of the earth's crust any of the amphiboles may be but are not necessarily fibrous in morphology and in fact the commercially useful fibrous amphiboles are relatively rare Following the notation suggested by Pavarennykh be represented by the formula 1 R2 S140 OH the amphibole group can where and RR combined are basic cations supplying a total of 14 plus charges ' indicates that the silica double chain structure is linear and can extend infinitely in only one direction Another common system of nomenclature groups all of the amphiboles except anthophyllite cummingtonite under the generic name hornblende which is further divided into the common hornblendes the oxyhornblends which may be partially or totally dehydroxylated and the hornblendes in which sodium plays a prominent role in the basic cation R5 +14 charge complement In some of these varieties there may also be some ionic proxying for Si in the Si40 ] double chain silica tetrahedral amphibole characteristic portion of the structures According to Pavarennykh's systematic classification Anthophyllite subgroup orthorhombic monoclinic Z = 1 2 not all members included Name Chemical formula 1 Anthophyllite | Mg7 Si420O 1H 1 : Cummingtonite Mg Si4011 2 OH 1 Amosite magnesian S1402 S1402 S1402 OH grunerite Space group D16 - Pnma Cah - C2 C h - C2 a b c 18.56 | 18.08 | 5.28 9.56 18.45 | 5.34 9.56 | 18.45 | 5.34 Tremolite subgroup monoclinic Z = 2 not all members included Name Chemical formula Space group a b B Tremolite Actinolite Ferroactinolite Ca S1401 2 OH 200 h Ca MG Si40 21 OH 200 2h Si40 1 2 OH - C2 - C2 - C 2 18.05 104 18.14 105 18.34 104 --Actinole is partially dehydroxylated approaching oxyhornblende composition with Na furnishing the 15th + charge required for negative lattice charge compensation 93 The structural analogy between tremolite and actinolite can be recognized by rewriting the formulation in the preceding tabulation stitution of Na for H in the hydroxyl grouping thus perhaps to show better the sub- Ca ,MgSi 011Si 011 ] ONa OH Glaucophane subgroup monoclinic Z = 2 Name | Na2 Glaucophane a soda_hornblende Chemical formula Mg Fe S1402 2 OH 2 Space Ch - group C2 a b c B 18.02 104 18.14 NOTE --Glaucophane has perfect Fe3 isomorphism and somewhat less Fe isomorphism so that under this complete acquires a more classification the name glaucophane glaucophane generalized meaning while the old species glaucophane and riebeckite become the subspecies alumoglaucophane and ferri- glaucophane The fibrous form of the latter is commonly called crocidolite which thus has the ideal crystallographic formula 401J 1 OH It may also be noted at this point that the mineral name amosite found in any standard mineralogical reference or classification and thactannto het n bo emen- clature is not recognized by mineralogists Amosite is in fact a trade name based on the acronym for Asbestos Mines of South Africa and is applied to the of these mines in which the major mineral constituent production of magnesian grunerite that is of the approaches the ideal structure MgFe which in turn is the ferrous member cummingtonite subspecies of anthophyllite all At the this point prescribed structure that is belong to the same differ only in the it is now fibrous possible to amphiboles 1 compare the crystallographic structure of representing the amphibole part of the S14011 2 OH % as R it is evident that all of these species space group have substantially identical lattice parameters and composition of the balancing 14+ divalent cations thus Anthophyllite Amosite Tremolite Actinolite Ferroactinolite Crocidolite Mg R MgFe R Ca R. Mg5 R Ca R. N where R is R S14S10 40 12ON OH12 There seems to be at hand substantial evidence that the biological activity of these structures may vary over a relatively wide range of intensity if so the cause for this may most reasonably be sought in the cation complex compositions with already some suggestions that those species highest in iron are relatively more carcinogenic than those from which iron is absent Phyllosilicates The phyllosilicates are the sheet or layer structures in which the silica tetrahedra are arrayed extended infinitely in two directions that is planar The group relevant to this discussion is the antigorite group These are 94 1 to 1 layer lattice silicates consisting of parallel sheets of silica tetrahedra and basic cations in octahedral coordination Quoting Pavarennykh The minerals assigned here are structurally identical but represent polytypes and products of isomorphism The kaolinite subgroup minerals have 2/3 of the positions in the octahedral layer filled the octahedral subgroup whereas all positions are filled in the antigorite subgroup the trioctahedral subgroup Both may have a tubular chrysotile structure which is more common in the antigorite subgroup Again following the Pavarennykh classification hedral and the magnesian trioctahedral structural represented the aluminian dioctaanalogues can be 1. Kaolinite subgroup triclinic monoclinic not all members included Name Chemical formula Space group | a b B Kaolinite S14010 OH C - P1 5.14 7.37 | 104 Metahalloysite OH | C - Cm 5.15 | 7.9-7.5 105 2. Antigorite subgroup monoclinic serpentines Name Chemical formula | Space group Antigorite Lizardite Chrysotile Mg6 S14010 S14010 OH N8 Mge Si4010 Si4010 OH Mge S14010 OH Cm C2 C2 a b C B 5.30 | 9.20 | 7.46 | 24 5.31 | 9.20 | 7.31 | 90 5.34 9.25 | 14.65 | 16 Of these minerals both metahalloysite and chrysotile are tubular while kaolinite antigorite and lizardite are planar or platy A possible explanation acceptable to many mineralogists was suggested by Bates by which the tubulation was due to the slight dimensional misfit between the tetrahedral and octahedral layers due to the different ionic sizes and bond lengths of the dioctahedral +++ and the trioctahedral Mg layers Such misfits set a strained lattice structure which can be relieved by a rolling of the usptructure into a tubule with the Si04 lattice layer on the outside as in metahalloysite but as in chrysotile with Many the magnesian octahedral lattice layer on the outside of the special properties of these minerals can be accounted for on such a basis No such strain relief is permitted to the planar or platy varieties kaolinite antigorite or lizardite so that structure fit must be adjusted by distortions the tetrahedral SiO4 sheet in bond angles and bond length The point to be emphasized here is that chrysotile is a tubular fibrous ) Bates T. F. Morphology of Layer Labs v 42 1951 pp 83-92 Lattice Silicates Dennison Univ J. Sci 95 1 to 1 layer lattice phyllosilicate structure any of the amphiboles totally unrelated to that of The possibility of lattice strain relief by tubulation available to the 1 to 1 layer lattice structure is also layer lattice structures considered in the not available to the next section 3 Pyrophyllite subgroup monoclinic Name Pyrophyllite Talc ccc eeee Chemical formula 2 A S140 ] OH Mg3 S14010 OH | Space group C9 - C2 C - Cc 4 a b 5.15 | 8.92 | 5.27 9.12 c 18.95 | 18.85 B | 55 | 100 The pyrophyllite group structure is that of two nets of lel to 001 with the free SiO4 tetrahedra paral- net of Al Mg vertices facing each other octahedra Talc is therefore the and between these nets analogue of pyrophyllite and because trioctahedral structural rical with the magnesia layer is spatially symmet- is respect to the silica layers on each side no curling or tubulation in any way possible The physical form of talc is therefore ated with highly perfect cleavage on 001 platy foli- In all of our electron micrographic studies we have dence of curled rolled tubulated or elongated talc never seen any evi- suggested that those who have structures and it is reported observations of such particulate forms were actually looking at some other mineral demonstrated by structural or chemical species and that such could be area electron diffraction analysis as by for example selected or by selected area energy dispersive electron analysis The preceding structural elucidation and the comparison of the amphiboles serpentines and talc is the technical basis for our remarks in 2 3 4 and 5. Based on the same paragraphs 1 analytical procedure based considerations it also becomes clear why no on ray diffraction alone can yield any reliable estimate of the concentration of any of these form minerals when they are admixed with prescribed asbestos or asbesti- the any other material Any and all of amphiboles as well as the serpentine antigorite subgroup minerals and do occur intimately admixed with both the platy and fibrous varietiecsanand ray diffraction alone simply cannot discriminate between the two morphologies Finally we would like to make an additional comment relative to the definition of fiber We have searched the encyclopedic and lexiconographic sources and can find nothing that bears any etymological relation to the word as used by OSHA One essential characteristic of a fiber is that it can be spun into a thread and woven into a cloth a characteristic of the varieties of asbestos included in the only a few of OSHA list ASTM does have a con- sensus definition see ASTM D 2946-71 wherein a fiber is defined as follows Fiber material in a average maximum traverse verse dimension of 0.255 form such dimension mm that it has of 10 to 1 a minimum length to and a maximum trans- 96 We wish to thank thethe and we also wish to thank supplementary remarks for Bureau of Mines for organizing the the organizers forfor the opportunity the record Talc Symposium to make these 97 MEDICAL ASPECTS OF TALC by Richard M. Spiegel M.D.- Pneumoconiosis The literature contains several studies over the past 3 or 4 decades cerned with the incidence of talc pneumoconiosis con- 3-4 6 9 11-12 16 21-22 or talcosis and with its pathogenesis 19-20 in addition to numerous case reports and autopsy evaluations 1 5 8 14 17-18 The bulk of the workers investigated have been involved in mining and milling although various areas have also been examined usage One short summary statement that nearly all of author findings would port is that talc exposure can produce a clinical picture virtually supindistin- guishable from asbestosis but at a lower rate than with comparable asbestos exposure The pulmonary function alterations decreased vital capacity and diffusion capacity the often thin and chronically ill appearance of the subjects the ferruginous bodies found on lung sections the pleural plaques and calcifications and the roentgenographic picture of interstitial fibrosis predominantly in the lower lung fields with diffuse reticular irregular small opacities are all findings in common with talcosis and asbestosis Importantly they are special in each person quite different from those usu- ally seen silicosis Many cases with silicosislike signs are reported but these are invariably in workers exposed to talc with high silica content and undoubtedly represent silicotalcosis This brings up the major problem in establishing the toxic potential of defining what we mean by talc The term is used in industry to refer to certain physical properties rather than chemical composition Commercial talc with which all of the studies are concerned can contain a great variety of related and unrelated constituents in an even greater variety of proportions mixed with pure talc a hydrous magnesium silicate often to the point where pure talc is a minor component 2 20 24 The still unresolved question is how much damage if any is caused in the lungs by true talc and how much by the contaminants The major suspects because of their established pathogenicity are free silica and the asbestiform materials such as tremolite anthophyllite and serpentine The role of the former however can easily be separated as previously mentioned by different clinical manifestations and simple environmental assaying The role of the latter substances on the other hand including also hydrous magnesium silicates is very hard to determine True talc is to a great extent formed in nature by hydrothermal alteration of asbestiform Medical Investigations Branch Division of Field tigations National Institute for Occupational nati Ohio Studies and Clinical Inves- Safety and Health Cincin- 98 the mined material is not only usually a mixture of deposits and therefore even in samples taken in the two but can also vary in percentage markedly relative close proximity This compounds the problem because differentiation even in the laboratory is extremely difficult and entails generally electron microscopy Because asbestos fibers generally form a part of tale eaxuptohsoursre coanndcluthdee resultant talcosis is fairly identical with asbestosis some that talc pneumoconiosis is actually being caused by the tremolite or other asbestos contaminants and that true talc plays no role Supporting this is one study 19 which suggests that talc and tremolite produce different in animal tissue the former cytotoxic and the latter fibrogenic and responses cytotoxic However intuitively it would seem likely that talc particles as seen in fibrous talc with similar structure and chemistry to asbestos particles similar diseases Also as differentiation of these particles sishouolfdtepnroudnufceeasible and fibrous talc is invariably contaminated with asbestos there is no practical reason at this time to prove their relative toxicities American Conference of Governmental Industrial Hygienists stan- The present talc at 5 fibers in dard reflecting this view is set for fibrous length the same as asbestos without reference to type of fiber and is in a combined standard for talc fibrous - tremolite The differentiation implied just described between fibrous or tremolitic talc and nonfibrous granular or nonasbestiform talc creates another source of disagreement The distinction is based on the geologic com- of the mined deposit rather than on any filtering process with the position ends of a continuum rather than being separate two types lying at opposite both fibrous talc and granular entities In any occupational tale exposure talc standards must be met that is if the fiber content is lower than the fibrous TLV the exposure can be considered strictly granular and must then meet the present American Conference of Governmental Industrial Hygienists granular talc limit of 20 mppcf This standard is apparently based for some talc miners and millers which reason on Dreessen's study 3 of Georgia included a group of workers exposed to levels of approximately 17 mppcf none of whom had evidence of pneumoconiosis However not only was the talc involved 10 percent tremolite certainly not granular but no attempt was made to establish duration of exposure Hogue and Mallette's study 4 sponsored the Firestone Tire and Rubber Company might be better suited for this pur- by pose They examined 20 company employees with exposures of 10 to 36 years levels at the time of the study only 4 employees less than 20 years and levels in the past and ranging from 15 to 35 mppcf with allegedly higher The talc used was reportedly pure they found no evidence of pneumoconiosis tale containing no free silica tremolite chrysolite chrysotile or actinolite although no evidence was presented to support this statement this would be some studies of Kleinfeld and Messite 9 16 which Opposing both tales can pro- concluded that while the fibrous type was more pathogenic fibrosis Their identification of the granular talc is not duce pulmonary substantial however One study involved workers in two milling plants one allegedly using fibrous the other granular talc but no evidence is offered 99 of the to confirm this classification In the other areas in New York State one fibrous and the study they compared two mining other granular examining only a single sample to establish the nature latter Weiss 24 mentions this area In a different study same region as producing on the contrary very fine tremolite fibrous talc Essentially then the toxicity of true granular talc has not been well documented probably in some measure because rare use of its Carcinogenesis There has been only one mortality study in the literature talc but fortunately it was a good study has followed a group of fibrous talc on workers , The New York State Department of Labor miners and millers since 1940 and has published over 10 articles concerning their health Kleinfeld's status among which was mortality study 12 of workers who had at least 15 years of talc exposure prior to 1965. Of the 220 1940 or who subjects in achieved 15 the cohort years there of exposure were 91 between 1940 and to the high rate of deaths due to deaths In addition overall death pneumoconiosis and its complications the rate from lung and pleural malignancies 10 deaths was three to four times that predicted on the basis of age and sex Much attention is given to analyzing this rate and that seen in asbestos workers contrasting it with 2 12 The only generalization that can be drawn from such a comparison however is that for has probably a greater a given exposure asbestos carcinogenic potential It is quite possible that this nevertheless high risk of lung and pleural malignancy seen in fibrous talc is a result of the asbestiform exposure to inite evidence either components but there is no def- way Summary The potential pathologic sequela of talc exposure depends on the constit- uents of the talc in question If free silica is present the worker risks developing silicotic lesions With the fibrous variety of talc variable amount of asbestiform including a almost identical with contaminants talcosis may develop clinically asbestosis disease has not been established The role of the pure talc fibers in this It also has not been established granular talc without asbestiform clearly if contaminants can produce talcosis Fibrous talc exposure has shown to yield a significantly high lung and pleural malignancies though probably not as high as with exposure Whether pure talc is carcinogenic has not been studied risk of asbestos 100 Annotated Bibliography Chronologically references 21 and 22 report the initial morbidity study in 1940 of 221 fibrous talc workers Thirty percent of those with over 10 years of exposure demonstrated advanced fibrous References 6 and 16 present results of a followup study in the 50's New cases appeared less severe attributed to improved mining techniques In reference 16 a comparison was made between the original and miners in another area where talc was less fibrous and comgroup parably less disease was seen 1 Alivisatos G. P. and others Talcosis of Unusual Rapid Development British J. of Industrial Medicine v 12 1955 pp 43-49 Eight heavy case reports from Greece of talcosis exposure From description silicosis after very short probably played a but very role 2. Blejer A. P. and R. Arlon Talc A Possible Occupational and Environmental Carcinogen J. of Occupational Medicine v 15 February 1973 pp 92-97 Good recent summary of talc toxicity compared to asbestos Only new information concerns consumer exposure in food experience 3 Dreesen W. and J. M. Dalla Valle The Effects of Exposure to Dust in Two Georgia Talc Mills and Mines Public Health Repts v 50 February 1935 pp 131-141 One of the first documented incidence of pneumoconiosis half surveys of talc workers showing high of the heavily exposed subjects 4 Hogue W. L. and F. S. Mallette A Study of Workers Exposed to Talc and Other Dusting Compounds in the Rubber Industry J. of Industrial Hygiene and Toxicology v 31 November 1949 p 359 Industry study of 20 workers with long exposure to allegedly pure talc yielded no pneumoconiosis 5 Hunt A. C. Massive Pulmonary Fibrosis From the Inhalation of Talc Thorax v 11 1956 pp 287-294 Case report and discussion Attributes massive pulmonary fibrosis to talc alone disregarding silica because of lung ash findings 6. Kleinfeld M. J. Messite and others Talc Pneumoconiosis AMA Archives of Ind Health v 12 July 1955 pp 66-72 References 6-13 16 and 21-22 are all from the New York State Department of Labor and are concerned with longitudinal study of talc miners and millers 7 . Problem Areas in Pneumoconiosis AMA Archives of Environmental Health v 5 November 1960 p 498 A general discussion of the state of the art See also reference 6 101 8 - Talc Pneumoconiosis AMA Archives of Environmental Health v 7 July 1963 pp 101-115 mortem reports on six subjects with talcosis to asbestosis and silicosis See also reference 6 Findings compared 9 - Lung Function in Talc Workers AMA Archives of Environmental Health v 9 November 1964 pp 559-566 A comparative morbidity study of workers exposed to fibrous and granu- lar talc dusts using a different from that above population all millers in two separate facilities Those allegedly exposed to only granular talc had significantly less signs and symptoms of disease See also reference 6 10 - Pulmonary Ventilation Diseases of the Chest AMA November 1964 p 592 Function Archives and Talcosis of the Lung of Environmental Health v 42 Intensive pulmonary function evaluation of 20 men with clinical radiologic diagnosis of talcosis See also reference 6 and 11 . Effect of Talc Dust Inhalation on Lung Function AMA Archives of Environmental Health v 10 March 1965 pp 431-437 Study population from controls in morbidity reference 6 9 as a whole compared with a group of matched study showing significant differences See 12 - Mortality Among Talc Miners and Millers in New York State AMA Archives of Environmental Health v 14 May 1967 pp 663-667 Mortality study of original population See reference 6 13 - Mortality Experience in a Group of Asbestos Workers AMA Archives of Environmental Health v 15 August 1967 pp 177-180 Similarly designed mortality study of asbestos workers apparently set up primarily to compare with study 12. See reference 6 14. 15 McLaughlin A. I Ind Medicine Discussion and G. and others Talc Pneumoconiosis v 6 1949 pp 184-194 literature review of case report British J. of - Dust Diseases v 12 1955 p 83 General discussion in Great Britain AMA Archives of Ind Health 16. Messite J. M. Kleinfeld and others Pulmonary Talcosis Clinical and Environmental Study pp 408-413 AMA Archives of Ind Health v 20 1959 See reference 6 17 Moskowitz R. Talc Pneumoconiosis 1970 pp 37-41 A Treated Case Chest v 58 July Recent case report of talcosis from chronic aerosol inhalation changes on open biopsy shown to be granulomatous responded well Early to steroid treatment leaving small amount of more typical fibrosis 102 18 Schepers G. W. H. and M. E. Durkan on the Human Lung AMA Archives of pp 182-197 Histologic and mineralogic analysis men with talcosis The Effects of Inhaled Talc Mining Ind Health v 12 May 1955 of lung tissue from autopsies on 19 . An Experimental Tissue AMA Archives Study of the Effects of Talc of Ind Health v 12 1955 Dust on Animal pp 317-328 Animal experiment with intravenous and intratracheal injection of and its contaminants in a variety of species talc 20 Schulz R. Studies D. J. and C. R. Williams of Ind Hygiene and Commercial Toxicology Talc Animal v 24 April and Mineral 1942 pp 75-79 Animal studies using mixed talcs injected intraperitonally 21 Siegal W. and others Talc Mining Including Roentgenological Findings in Talc Workers Am J. of Roentgenological Radiation Therapy v 49 January 1943 pp See reference 6 11-29 22 . Study of Talc Miners State Dept. of Labor Div 1943 See reference 6 and Millers Industrial Bull of Ind Hygiene v 22 No. 11 New York November 23 24. Van Ordstrant H. D. July 1970 p 2 Good recent review Talc Pneumoconiosis An Editorial Chest v of the state of the art except for omission of 58 evi- dence of carcinogenicity Weiss B. Archives and E. A. Boettner Commercial of Environmental Health v 14 Talc and February Analysis of various talc deposits in this country review on talcosis Talcosis AMA 1967 pp 304-308 and a literature U.S GOVERNMENT PRINTING OFFICE 1974-705-925 BU.OF MINES 19313