Document KJG3DMBveXBpZoV4Q2483GwZx

Environmental Health Perspectives Voi 9. pp. 95-109. 1975 Identification and Quantitation of Asbestos in Talc by Arthur N. Rohl* and Arthur M. Langer* The currently u*ed analytical methods for identification, characterization and quantitation of asbestos liber in consumer talcum products include polarized light microscopy, x-ray diffrac tion analysis, transmission electron microscopy with selected area electron diffraction and elec tron microprobe techniques. Light microscope methods have severe limitations imposed by the ultimate size resolution of the light-bpticai system. Small particles go unresolved; those marginally resolved may possess optical properties different from those properties cited in the Uterature; most optical properties, e.g., indices of refraction, are difficult to measure on small particles. In addition to these dif ficulties, talc fibers often possess optical properties different from those of talc plates, which further confound analysis. Light microscopy is recommended for use only as a preliminary tool on Umited, large-sized, samples. Transmission electron microscopy is a good standard techni que for visualization of contaminant asbestos fibers. Together with selected area electron dif fraction, talc fibers may be easily differentiated from amphibole asbestos fibers on the basis of both morphological and structural characterization. Chrysotile fibers are easily distinguished on this basis as well. The amphibole asbestos minerals require chemical characterization to differentiate among the different fiber types. Probe analysis is mandatory for such fibers. The major drawbacks to electron beam instrumentation for the mineralogical characterization of talcum products are the time and effort required for data acquisition. These techniques do not lend themselves to routine study. X-ray diffraction analysis, utilizing the step-scan method, offers a relatively rapid, quan titative technique for gross fiber analysis. Baaed on comparison with standard specimens the fiber content of talcs may be quantitatively determined. It is essential to employ a specimen preparation technique which yields homogeneously dispersed particles. Tremolite may be determined at levels as low as 0.10% by weight, chrysotile 0.25%, and anthophyllite at 2.0% by weight occurrence in talc. The variance of these values depends upon many factors, including the mass absorption coefficient of the fiber types as compared to talc and selected diagnostic reflections and their relative intensities. Each of the above techniques is described in detail. A method for routine analysis of consumer talcum products is suggested. Introduction The mineral talc is a monoclinic, occasionally triclinic, hydrated magnesium sheet silicate with the ideal formula: MgtSitOufOHk Although a magnesium silicate, it frequently contains small amounts of iron and other trace metals in the structure. It can occur in several crystal habits from plates to fibers. (1, 2). In most talc deposits, plates tend to be far more 'Environmental Sciences Laboratory, Mount Sinai School of Medicine of the City University of New York, New York. 10029. common than fibers. The term "fibrous talc" im plies, mineraiogically, talc occurring with a fiber habit (form). As used in the medical literature, fibrous talc is synonymous for talcs containing any fiber, including asbestos. Geologically, talc occurs in rock masses often coexisting with a large number of other hydrated magnesium silicate mineral species U. + ). This latter observation is based on mineralogical analysis of naturally occurring talc deposits and laboratory studies of talc crystallization. Frequently, these coexisting mineral phases are asbestos (Table 1). December 1974 PLAINTIFFS EXHIBIT 95 Table 1. Talc and its associated asbestos minerals. Empirical formula Common chemical substitutions Talc MgcSinOaot OHu Fe for Mg A1for Si Tremolite CasMgsSinOzzf OH Fe fqr Mg Mn for Mg NaforCa Anthophyllite (MgFelSiiOij(OHtj Fe for Mg Al for Si Chrvsotile MgiSi<Oio(OHj> Fe for Mg Ni for Mg Structure and habit Sheet silicate: plates Chain silicate: fibers Chain silicate; fibers Sheet silicate; curved common; fibers com common: often as mas common: columnar or sheets form fibers; mon; forms massive sive aggregates; forms fibrous aggregates; often as compacted foliated aggregates; intergrowths in some forms intergrowths in fibers in pseudo-plates intergrowths on sub talcs on submicron some talcs; fibers tend (foliated masses), es micron scale; many talc scale; fibers tend to to be long and thin; size pecially in serpentine fibers observed in platy short and stubby; size ranges from visible by rock; forms interplanar talcs on submicron ranges from visible by eye to sublight micro (interlaminar) con? scale eye to sublight micro scopic. taminsint in talc plates; scopic fibers in talc tend to be sublight microscopic in size Crystal system Monoclinic: triclinic Monoclinic Orthorhombic Monoclinic orthorhombic Cleavage Parallel to plate: (001) Parallel and across Parallel and across Parallel to fiber axis; perfect: prism termi fiber axis: (110) per fiber axis; (110) perfect (001) for clino variety Optical properties nations fect "x 1.539-1.550 1.581-1.615 1.596-1.654 1.532-1.549 )lz ' 1.589-1.600 1.601-1.641 1.625-1.666 1.545-1.556 Indices higher for Indices lower for low- fibers iron chrysotiles Mass absorption co- -1032 -1335 -1072 -717 efficients (CuKq = 1.5421-* Occurrence Generally present as Common contaminant Often a contaminant Occasional contaminant the major mineral in in many talcs (in in talcs (in carbonate in talcs (especially in commercial talc carbonate rocks) and serpentine rocks) serpentine rocks) Other minerals comiponlv in talc: Carbonates (e.g., calcite); micas (e.g., phlogopite); days (e.g., montmorillomte); chlorite: feldspars (e.g., andesine); quartz; serpentine (e.g., antigorite): spinels (e.g., magnetite) a All coefficients calculated on the basis of the empirical formula for each. Talc rocks, those commercially worked for ore material, may form as the result of two major geological processes: hydrothermal alteration of preexisting mafic (Mg-Si--rich) rocks and lowgrade hydrothermal metamorphism of siliceous dolomite (silica-bearing, Mg-Ca-rich) rocks. These processes are geologically referred to as steatitization and serpentinization. They involve slightly different original bulk chemical com positions and end mineral products. Both mayproduce significant amounts of asbestos minerals, chrvsotile in serpentinization and amphibole asbestos minerals in steatitization. The metamorphism of siliceous dolomites almost invariably results in the formation of the asbestos mineral tremolite (2). During geological alteration of rocks, new mineral phases are frequently created from pre existing ones. Most commercial talc deposits are formed as the result of such processes. These deposits may consist of fine-grained, intimate mixtures of minerals, especially talc and asbestos. In addition to the mineral complexities of talc deposits, these ore bodies are often zoned. That is, the mineral composition and assemblage (reflecting changes in bulk 96 Environmental Health Perspectives chemistry) varies over short distances, several feet to several inches. This invariably means that the mined talc ore consists of mineral mix tures, since mineral phase separation is difficult if not impossible to achieve during mining. The complexity of mineral deposits may be il lustrated by a recent paper on the mineralogy and mineral paragenesis of the New York State talc deposits in the Gouverneur district (5). Because commercial talc deposits consist of natural admixtures of minerals, a number of mineralogically different materials have been used as commercial talc. The mineral talc is naturally soft and may be physically reduced in size with little mechanical effort because of the weak bonding forces between adjacent unit sheets. The material possesses a number of properties making it useful in hundreds of applications (6). Many of these applications, however, require small particle sizes, high sur face areas, and good surface sorption characteristics. Therefore, many of the talc products must be fine-grained, but need not be pure. The result is a requirement for a talclike rock rather than pure talc. Therefore, talc as used in industry does not refer to the mineral species talc, but rather to a property (7). A number of materials have been used as syn onyms for talc: asbestine talc, steatite, soapstone, tremolite talc, French talc, fibrous talc. All of these materials may contain quan tities of asbestos fiber. In 1973, there were 38 major talc producers in the United States; talc was mined in 10 states. The geological rock types from which these materials were mined covered the entire spec trum of geological possibilities. For example, in St. Lawrence County, New York State, 30% or less of the materials recovered as "talc" is the true mineral talc (5,6). In this deposit the amphibole asbestos minerals, tremolite and anthophyllite, as well as serpentine (including the mineral chrysotile) occur throughout (5). Therefore, the purity of any commercially available talc in the United States is related to both the nature of the original talc deposit and the extent to which the rock is upgraded to eliminate contaminant minerals. This latter process is often referred to as beneficiation. Some mineralogical analyses have been made of commercial talcs. One such study showed of the 51 talcs studied, none was 100% talc (7). The asbestos content of these materials ranged from 0 to 87%. Studies of New York State talc deposits and their asbestos contents have been carried out. Mineralogical analyses of these materials indicated all samples were predominantly asbestos (8). In another study, in which 22 available consumer talcum products were examined, it was found that fibrous con stituents were present in all of the samples (9). Biological Consequences of Talc Dust Exposure Exposure to talc dust, in intensity equivalent to an occupational exposure, has been shown to be associated with a diffuse interstitial lung scarring which has been termed talcosis (10-16). However, even in these studies, some questions were raised as to the specific pathogenic agent in the talc itself. For example, asbestos bodies were frequently observed in the lung tissues of individuals who died of talcosis (11, 13, 17); clinical and radiological similarities existed between the disease asbestosis and talcosis (12. 13, 18): and "fibrous" talc appeared to be more pathogenic than "platy" talc (19). Several investigators using the individual mineral components of Fibrous talc (made up of mixtures of tremolite asbestos and platy talc) observed different biological responses to the components in animals. They observed that the asbestos component induced a greater fibrogenic response in the animals (20). One in vestigator has also reported an increased in cidence of neoplasia amongst talc miners and millers exposed to asbestos-containing talc dusts (21). Lung tissues from workmen exposed to talc dust have been analyzed in our laboratory. Both amphibole and chrysotile asbestos fibers were observed in these tissues by electron microscopy (22). Several recent studies, involving experimen tal animals and observations on human materials, have shown that exposure to asbestos and talc may be associated with tumors of the ovary and cervix (23. 21,). In addition, the use of such talcum products as lubricants, drying agents, and excipients in a number of food and food packaging products may pose a hazard in terms of an increased neoplastic risk in the gas trointestinal system through ingestion (25). December 1974 97 Asbestos Content of Consumer Talcum Products Because the mining of talc almost invariably includes the mining of asbestos as well, this natural asbestos contaminant in talc may be carried over into the consumer product. Since asbestos has been suspected as the pathogenic agent in talc workmen, low levels of asbestos in consumer talcs have been the focus of many re cent studies. These data and observations lead to an important public health question: is asbestos present in consumer talcs, and, if pre sent, which fiber type and in what concen trations? Instrumental Methods of Identification of Asbes tos in Talc There are a number of standard mineralogical techniques which may be used for identification and quantitation of asbestos fibers in talc. These include light optical methods, electron optical techniques, and x-ray diffraction techniques. Light Microscopy The most widely used and inexpensive instrumental technique for the analysis of mineralogical specimens is optical microscopy. A microscope which employs polarized light op tics has been a standard technique for iden tification of minerals for the past century. When used with immersion oils, not only may phases be identified, but the bulk chemistries of the phases may be determined with remarkable accuracy. The field of optical mineralogy has been properly termed optical crystallography, in that the information obtained may be elegant and quantitative. The analyses of the light visi ble mineral phases within talcs may be made with this method. We have examined numerous talcs by means of light microscopy. Powders from different sources (ca. 0.5 mg) both natural and man made, were placed on precleaned glass slides and immersed in mounting nD = 1.500, 1.550, 1.600. Several splits from each sample were ex amined for their optical properties. The microscope employed in all cases was equipped with bright field illumination and polarized light optics. An overall view of various proper ties of the material was obtained at this level of investigation: relative relief, birefringence, gross morphology, and extinction angles of fibers were observed or measured. The relative purity of each sample was observed, and the general size distributions of the mineral phases were determined fFig. 1). The identified mineral phases tended to be coarse-grained. However, when the talc samples are fine-grained, and con tain talc fibers, some problems are encountered. Specifically, the normal birefringence characteristics may not be present (for the fibers); indices of refraction are difficult to measure (differentiation of internal reflec tance and' Becke line when viewed with central illumination); talc fibers have higher indices of refraction than talc plates, and may be confused with amphiboles (especially small fibers of tremolite); fibers are difficult to routinely resolve from talc plates when the latter are oriented on edge (especially at high magnifications); many fibers are too small to see by light microscopy. In summary, light microscopy, employing polarized light optics, has severe limitations for critical analysis of talc specimens for asbestos fibers. The inherent limitation of optical microscopic resolution may so restrict the analysis that large numbers of small fibers may go undetected. It is a paradox, however, that op tical microscopy is well suited for determining the presence of other contaminants in talc, e.g., the carbonate minerals and other silicate phases (quartz, feldspar, micas, etc.). Also, it is remarkably sensitive for the determination of trace mineral phases, if they are present in sizes resolvable by light optical systems. This method, although limited, is recommend as a preliminary tool of investigation (26). X-Ray Diffraction One of the standard mineralogical techniques used in the analysis of solid crystalline phases is x-ray powder diffractometry. With this method, those phases with crystallite sizes greater than 2000 A may be subjected to x-ray bombardment and made to reflect from their atomic planes an x-ray spectrum characteristic of their in teratomic distances and chemical makeup. This, in effect, is a structural "fingerprint" and serves to identify, in most cases uniquely, the nature of the phases present in the sample. Additional in formation may be obtained by x-ray powder dif- 98 Environmentai Health Perspectives Figure 1. Photomicrographs of a talc sample from New York State: (A) talc in plane polarized light) shows "granularity" and small size of pulverized sample; (B-D) consecutive photos of pulverized samples between crossed potars) show the presence of prismatic crystals. Several on-edge plates may be confused with fibers. Some of the larger crystals, on the basis of their optical properties, were identified as tremolite. fractometry, including quantitation of the in dividual phases present in a crystalline matrix and their average particle size. (27). X-ray diffraction is considered to be a more sophisticated tool than the polarizing microscope. Although less sensitiv^than the electron microscope for the detection of trace quantities of materials present in a matrix, this instrumental technique is commonly used for the analysis of talcs. The difficulties and nuances involved in the x-ray analysis of talc for trace asbestos fiber are many. We describe these below and outline what we consider to be an acceptable analytical technique. This technique consists of the preparation of talc standards (talc matrices admixed with known quantities of fiber), the selection of characteristic x-ray reflections to be scanned, sample preparation to insure homogeneity and reproducibility, and in strumental technique. Preparation of Standard Dilution of Asbestos Minerals in Talc for the Purpose of Quan titative X-Ray Analysis The identification and quantitation of asbestos fiber in talc by x-ray diffraction techniques may be achieved by comparison of known dilutions (fiber type and quantity) of asbestos in a talc matrix with unknowns. The preparation of standard (known) dilutions of asbestos minerals in talc for quantitative analysis requires: (1) a talc matrix completely free of contaminating asbestos minerals; (2) pure asbestos fiber as the sought contaminant phase; (3) a preparation method for insuring homogeneity and reproducibility of the stan dard dilution material, i.e., identical aggregate December 1974 99 various other techniques (27-31). Several such preparation methods were tested for use in the present study. None were found to give satisfactory reproducibility, as indicated by the variation (deviation) of reflection intensity of duplicate dilution standards which had been un iformly prepared and mounted. The lack of success in this regard was taken to indicate that, in mixtures of minerals with piaty or fibrous habit, a statistically random distribution of orientations is extremely difficult, if not im possible, to achieve. Accordingly, a technique was developed which was intended to obtain a high degree of sensitivity for substances present in minute quantities, and more important, which had a greater degree of reproducibility of reflection in tensities. Binary systems of chrysotile, tremolite, and anthophyllite in talc were prepared at varying levels of dilution on a vyeight per weight basis. The following per cent concentrations of fibers in talc were initially prepared for each binary system: 5.0, 4.0, 2.0, 1.0, 0.5, 0.25, 0.20,0.10%. The standard weight of the total sample was 50 mg. The weighed talc-asbestos mixtures were prepared in 10 ml of filtered water (to avoid any possible contamination) utilizing a surfactant and ultrasonic energy to disperse the phases homogeneously. This slurry was poured im mediately into a 30-cc hypodermic syringe and filtered through a 37-mm diameter, 0.22 tini effective pore size membrane filter. [A standard filler holder for attachment to a hypodermic syringe is available (Fig. 3) from the Millipore Co.] In the course of filtering, the syringe is held in a horizontal position and is frequently rotated and shaken. This action helps to prevent size and density separation of the suspended particles. The residue forms a cake of uniform thickness of about 0.5 mm on the membrane filter, and the resulting surface of the filter cake is flat. The cake is allowed to dry and then is glued to a glass microscope slide for x-ray powder diffraction analysis. X-ray analysis of the dried cake on repeated preparations shows that the mineral phases are homogeneously dis tributed throughout. This technique has the ad vantage of uniformly preparing, mounting, and measuring the talc-asbestos dilutions under identical conditions. The reproducibility and sensitivity of the technique is demonstrated by a comparison of the measured areas of index reflections for a number of samples (Table 3). Figure 3. Device used to prepare filter cakes of stan dard dilutions of asbestos fibers in talc: (A; holder which accommodates the membrane filter: (B) holder and gasket attachment to syringe; <C) syringe; tD) plunger. Selection of X-Ray Reflections: In order to detect the weak reflections of dilution com ponents it was necessary to scan in a stepwise manner across a preselected area of the x-ray profile. Because of structural similarities in the minerals under examination, there was much "overlapping" or interference in many reflec tions (Table 2; Fig. 4). The similarities in crystal structure and the consequent overlapping and interference of the x-ray diffraction reflections of talc, chrysotile, anthophyllite, and tremolite have been mentioned. This condition made it necessary to select a reflection or set of reflec tions for each mineral component which could be used unambiguously as an index or indices of Table 2. Diagnostic reflections of asbestos minerals used in standard dilutions. Mineral rf.A hkl I/h 26 Scan 29 Anthophyllite Chrysotile Tremolite 8.26 3.66 8.38 r210) (004) (110) 55 10.65" 10.1-11.1" 80 24.31" 23.5- 27.5" 100 10.55" 10.0-11.1" "For each characteristic interplanar spacing given, the Miller Index, relative intensity, Bragg reflection angle, and step-scan interval are included. December 1974 101 Table 3. Replicate measurements of areas of diagnostic peaks of chrysotile in chrysotile-talc dilutions.1 Specimen Peak areas, in.3 A 0' 99.5% Talc-0.57c chrysotile Avg. 2.20 2.17 2.18 2.18 2.19 2.17 2.19 2.18 99.75% Talc-0.25% chrysotile Avg. 0.84 0.88 0.84 0.84 0.88 0.88 0.88 0.88 99.9% Talc-0.10 chrysotile Not detected Not detected 4 Measured with compensating polar planimeter; peaks plotted on same scale on step-scan runs under constant settings (2 x 103 cps; 0.02 29: 45 kV/20 mA). 16 12 8 4 Figure 4. X-ray diffraction tracings of fibrous talc samples from New York State, in the 8--16 29 region of reflections: (SI serpentine (includes the minerals chrvsotile, lizardite, antigorite); (A) anthophyflite; (Tr) tremolite; (T) talc; (Ml mica (phlogopite); (Cl chlorite. Note that the anthophyllite peak at 8.9 A (020) is often masked by a strong talc peak at 9.3 A (002); the anthophyllite 8.26 A (210) peak is often masked by the tremolite 8.38 A (110) peak. The tremolite peak in this figure masked almost 5% anthophyllite. I/h = intensity. the amount of that mineral present in a mix ture. This was done by a comparison of the ASTM X-Ray Powder Data File for each of the minerals and by indexing the diffractograms of each of the UICC asbestos minerals and the reference talc. When this data was assembled and compared, it was possible to select reflec tions unique in d spacing and strong enough in intensity to be used as quantitative indices (Table 2). In this way, certain diagnostic or in dex reflections for each of the dilution com ponents were selected and these angular inter vals were x-ray step-scanned at 0.01 and 0.02 28. A digital printout of elapsed time in a fixedcount determination was used to prepare precise positions and profiles of the diagnostic reflec tions. In the fixed count mode, the diffrac tometer scans equal angular intervals (0.02 20), accumulating fixed counts at each point with equal accuracy. Although weak reflections re quire longer times than higher intensity reflec tions, all points are determined with equal precision. In this method the statistical ac curacy of any measured count depends only on the total number of counts recorded. The number of counts was calculated by taking the reciprocal of counting times. The counting rates w'ere selected to give a uniform percentage probable error of about 2.0%. When the number of counts is plotted as a function of 28 a profile of the diagnostic reflection is found (Fig. 5). The area above background, determined with a com pensating polar planimeter, is taken to be proportional to the reflection intensity. Factors Affecting the Limits of Detectability of Substances by X-Ray Diffraction In a mixture of powders, the resulting x-ray diffraction pattern consists of the superposition 102 Environmental Health Perspectives 3.63 X (5o0 oCHR 004 z 3 0 u O 0 >- < O O' 1 O '0 X 0'o poo o 3.53 X b o CHL 004 yr 9 oy 20 24 25 26 Figure 5. Step-scan profile obtained on a standard dilution of 1% chrvsotile in a 99% talc matrix. Note the contamination of talc with a trace of chlorite (3.53 A reflection). Step-scan obtained at 0.05 2S for 2000 counts. of diffraction patterns of the constituent com pounds (Fig. 4). The intensity of each com pound's pattern is proportional to, but not necessarily a linear function of, its concentration (29). Aside from instrumental factors (e.g., change in x-ray output from target tube) which may influence the profiles of diffraction max ima, there are a number of other factors to be considered. These are related primarily to the material, including sample homogeneity, chemical makeup, particle size, preferred orien tation, sample thickness and flatness, and ab sorption characteristics. General Factors: The components of a mix ture and their relative amounts may be deter mined by the intensity measurements of the dif fraction patterns, if all these factors are con sidered. However, it is necessary that certain conditions be satisfied. The component sought must be homogeneously mixed in its matrix and consist of randomly oriented small particles to insure that a large proportion of them will satisfy the Bragg geometry for reflection. It has been shown that with materials of intermediate atomic number (Z=12-30), particle sizes in the range of 2-10 Mm will give a reproducibility of greater than 1% (27, 29). A uniformly smalt par ticle size will also help to minimize particle orientation and microabsorption effects. Com parative intensity measurements also require that the porosity of the specimen is constant and that the specimen is thick enough to diffract xrays with maximum intensity. The powdered materials used in this study and the filter-mounting technique of specimen preparation were selected in order to fulfill these basic requirements of quantitative x-ray diffraction analysis. Special Factors: An important factor which affects the ability to detect small amounts of material by x-ray diffraction analysis is specimen x-ray absorption. This oc curs when two substances with different mass absorption coefficients are mixed. The mass ab sorption coefficient (m/p) is a measure of the fraction of the energy in the incident x-ray beam absorbed when a beam of unit cross section traverses a unit mass of material. It is useful because it is characteristic of the chemical elements in the absorbing material and is essen tially independent of their chemical or physical aggregate state. It is a function only of the wavelength of the absorbed radiation and the atomic number of the absorbing element. The sensitivity of detection of a component may vary considerably, depending on p/p for the component relative to that of the matrix. The mass absorption coefficients of talc, chrysotile, anthophyllite, and tremolite for the wavelength of copper x-radiation (1.542 A ) are given in Table 1. Chrysotile has the lowest p/p of the four minerals, about 717, which is about 7/10 that of talc, 1032. Thus, the sensitivity of detec tion of chrysotile in talc is greater than that of the other two asbestos minerals, neglecting the effects of such variables as particle size and degree of crystallinity which may have equal or greater influences on the sensitivity of detec tion. The precision (reproducibility) of intensity measurements obtained in x-ray diffraction analysis can be optimized by a suitable counting strategy. If an accumulated count of December 1974 103 4Xl05-5xl05 is obtained, the precision of the relative intensity measurement due to counting statistics alone is X 1/2. The determination is also related to specimen preparation reproduc ibility. With specimens having an average par ticle size of 1-2/im. the range in intensity measurements is from 0.1 to 0.5%. The overall precision of quantitative x-ray analysis will probably lie in the range of 0.5 to 1.0% (27). The accuracy of x-ray analysis depends in large measure on the degree of preferred orien tation of particles in the sample. The materials used in this study, sheet silicates and fibers, can be expected to have a high degree of preferred orientation. This inescapable physical limitation is the main factor in controlling the level of ac curacy. Standard Dilutions Chrysotile in Talc: The presence of chlorite in the talc standard used in preparation of chrysotile-talc dilutions may preclude the use of the (002) reflection of chrvsotiie as a diagnostic reflection. The chlorite reflection at about 12.6 28 overlaps and masks the latter reflection. When the intensities of these two reflections are about the same, the peaks can be resolved with a step-scanning rate of 0.01 per degree 28. Except for this special condition, the peak-tobackground ratio of the chrysotile (002) does not permit it to be measured with precision. If chrysotile and chlorite are both present in the sample, but chrysotile predominates, then the 1002) peak of chrysotile can be used as an in dicator of the relative amount of chrysotile pre sent. Another mineral which may interfere with the detection or quantitation of chrysotile is kaolinite. This mineral is the most common member of the kaolin group of hydrous aluminum silicate clay minerals. Although kaolinite has not been reported in talc or serpen tine rock, particularly because the modes of for mation and geochemical environment are quite dissimilar, this fact does not preclude the presence of kaolinite in industrial or consumer talcum by admixing. The mechanical and physical properties of kaolinite would be in har mony with those of talc. In fact, it has been identified as a.component of some cosmetic talcum products. Because there are close struc tural similarities between chrysotile and kaolinite, their x-ray diffraction patterns are similar in many respects. The first-order basal reflection of kaolinite at 7.15 A may thus overlap or mask the chrysotile (002) reflection at 7.24 A . Depending on the relative amounts of these two minerals present, chrysotile may be neither detectable nor quantitatively deter mined with precision by use of the 7.24 A reflec tion. It has been found that the 3.63 A (004) reflection of chrysotile at 24.3 28 is more useful than the (002) reflection for detecting the dilutions of that mineral in talc matrices. This chrysotile reflection is better resolved from reflections of associated minerals, particularly from the 3.53 A (004) reflection of chlorite at 25.1 28. The peak-to-background ratio of the chrysotile (004) line, which has an intensity of about 8/10 of the (002) reflection, is thus used to determine the minimum detectable amount of chrysotile. in talc standard samples. The samples are step-scanned at a rate of 0.02 per degree 26 from an angle of 23.0 to 27.0 28 in order to achieve maximum peak and minimum background intensities in the same region of the spectrum. A minimum of 0.25% by weight of chrysotile in standard talc has been detected consistently. Chrysotile at lower levels of dilu tion cannot be detected. Tremolite in Talc: A few specimens, la beled as tremolite, were prepared for x-ray powder diffraction analysis and continuously scanned from 3 to 60 28 at a rate of l/min. When these spectra were indexed, it was found that only one tremolite sample was free of con taminants. That is, the positions and relative in tensities of all of its reflections compared exact ly with the data given for an ASTM reference tremolite (American Society for Testing Materials standard powder diffraction file, #13- 437). As indicated in Table 2, the 8.38 A reflec tion of tremolite, which has a relative intensity of 100, was selected as the diagnostic reflection for the tremolite-talc dilution series. The 3.12 A tremolite reflection, which also has a relative in tensity of 100, was not used because it overlaps with the 3.12 A reflection of talc. Dilution levels from 99.0% talc-1.0% tremolite through 99.95% talc-0.05% tremolite were prepared and stepscanned under constant instrumental con ditions. The diagnostic reflection of tremolite was detected at all levels of dilution up to, and 104 Environmental Health Perspectives including, the 99.9% talc--0.1% tremolite level. Less than 0.1% tremolite was not detected above background. Replicate dilution mixtures at the 0.1% and 0.05% tremolite levels were prepared and step-scanned to confirm these observations. The results were consistent and reproducible. Anthophyllite in Talc: The anthophyllite used in preparing dilution mixtures of fiber in talc was from the UICC standard asbestos reference mineral collection, previously characterized (28). A specimen of this material was continuously scanned by x-ray diffraction from 3 to 70 26 at l/min. When the peaks on the diffraction pattern were assigned d spacings, it was found that the anthophyllite was contaminated by talc, chlorite, and phlogopite. However, these intrinsic con taminants do not preclude use of the material as a dilution standard. A more serious limiting condition pertains to the similarities between the diffraction patterns of "pure" anthophyllite and talc (see Fig. 4). Among the most intense reflections of anthophyllite are the 3.05 A (obscured by the superposition of the talc 3.12 A, I/h = 40); the 4.50 A (obscured by the 4.53 A, I/h = 12 and the 4.56 A , I/h = 45 both of talc) and the 3.23 A (obscured by the 3.33 A mica contaminant of talc, I/h = 100). Since the peak-to-background ratio of the most intense reflections of the powder pattern is the most im portant single factor in determining the minimum detectable amount of a substance, the interference between similarly spaced strong reflections of talc and anthophyllite significant ly diminishes the possibility of detecting minute amounts of anthophyllite asbestos in talc. The S.26 A reflection of anthophyllite, with the relative intensity of 55, was selected as the most useful diagnostic reflection for the anthophyllite--talc dilution series. Dilution mixtures ranging from 95.0% talc --5.0% anthophyllite through 99.5% talc-0.5% anthophyllite w-ere prepared. When stepscanned under constant conditions, anthophyllite was not detected at concen trations below 2.0% in repeated samples. With continuous scanning, anthophyllite was not detected at or below the 4.0% dilution level when the 8.26 A reflection was used as an index (see Fig. 4). Preparation and Analysis of Chrysotile--Talc Dilu tion Samples by Electron Microscopy Aliquot portions of various chrysotile-talc dilution levels which had been analyzed by x-ray diffraction were prepared for transmission elec tron microscopy by a "rubout" procedure (32). Standard weights (0.01 mgi of each of the dilu tion standards are dispersed in a nitrocellulose film and mounted on Formvar-coated electron microscope grids. The dispersal is accomplished by mounting the sample in a drop of nitrocellulose-amyl acetate solution on a microscope slide and grinding it with the edge of a clean watch glass to reduce the sample into submicron-sized particles. This procedure breaks apart the fiber bundles of chrysotile, already greatly comminuted by triple air jet-milling and sonification, into unit fibrils or into smail fiber bundles. At the same time, large aggregates of talc particles are reduced in size and dispersed to allow all asbestos fibers to be seen and counted. After dispersing the sample, a drop of amyl acetate is placed on a second clean side. The two slides are placed in contact and the ground residue and nitrocellulose solution is further dispersed. The residue is typically spread over the slide for a length of 5 cm. The two slides are then pulled apart, leaving two films with the powder uniformly distributed in them. The films quickly dry. The edges of the slide with at tached film are scraped with a scalpel blade; then by dipping the slide into water, the film can be floated onto the surface of the water. Electron microscope grids are placed on top of segments of the film and covered with a strip of filter paper. The grid is retrieved by lifting the filter paper out of the water. After drying, the grids can be picked off the filter paper and mounted in the electron microscope for scan ning. Typically, three grids are prepared for each dilution level of chrysotile-talc and six squares of each grid are scanned at about 10.000X magnification to obtain a number of represen tative fields for study. A large number of fields are photographed and enlarged prints are then made. From the photographic enlargements the number of long unit fibrils per field are counted December 1974 105 and the results are tabulated. When multiple fibril bundles are encountered, the number of unit fibrils in the bundles is estimated by counting the number of visible central capillaries and by judging the optical density of the fiber bundle. The electron microscopic fiber counts show a fairly good correlation with levels of chrysotile dilution. For example, the average number of chrysotile fibrils per field, scanned at 7100X magnification was counted at the follow ing dilution levels: 5% chrysotile-95% talc, 92 fibrils per field 10%; 1% chrysotile-99% talc 22 fibrils per field 10%; 0.5% chrysotile--99.5% talc 8 fibrils per field 10%; 0.25% chrysotile-99.75% talc 6 fibrils per field 10%. It is evident that there are considerable numbers of chrysotile fibers present in talc even at very low dilution levels. By using the fiber count data for the various dilution levels it is possible to calculate the number of fibrils con tained in a unit weight of sample. The area of the nitrocellulose film is known, as is the magnification factor. From these and a measurement of the area of the photographs, a conversion factor is calculated. Allowing for an error as large as one magnitude the calculations show that there are 2iV x 10 fibrils/mg of sam ple, the value N being the average number of fibrils per field. Thus, in a 1% dilution of chrysotile in talc, there would be about 4 X 109 fibrils/mg. At the lowest level of detection of chrysotile by x-ray diffraction, i.e., 0.25%, there would be about a 10* fibrils/mg. It is clear that in issuing regulations specify ing the absence or absolute limits of asbestos in talc, close attention must be paid to the capabilities of the analytical technique used for determining whether, or how much, asbestos is present. X-ray diffraction can provide positive answers to these questions only at the 0.25% lev el for chrysotile which has been shown to be a crude and inaccurate measure of the potential contamination and possible hazard involved. In addition, as much as 2.0% of anthophyllite in talc may not be detected by this method. On the other hand, electron microscopic analysis can be a sensitive tool for detecting extremely minute amounts of chrysotile and other asbestos minerals in talc. Application of Transmission Electron Microscopy Methods (Including Selected Area Electron Dif fraction) in Detection of Asbestos in Consumer Talcs Consumer talcs have been prepared and examined by means of transmission electron microscopy. Representative sample aliquots were sonically dispersed in filtered water and pipetted onto Formvar-carbon 200-mesh copper electron microscope grids. After these preparations were dry they were again carbon coated to insure a thermally and electrically stable preparation. Samples were scanned at magnification in excess of 20,000 and examined for their fiber content. A representative piaty and fibrous talc is shown in Figure 6. The asbestos content of talc may be directly es timated utilizing transmission electron microscopy. Each fiber type may be identified. For example, chrysotile asbestos is morphologically unique. Its internal capillary, fibril dimensions, susceptibility to electron beam damage, and unique electron diffraction pattern, all make the fiber easily recognizable (33). Fibers which are electron-dense and which possess the morphological characteristics of amphiboles, were examined by selected area electron diffraction for confirmation. We have done this on many particles in numerous samples and are able to differentiate fibrous talc from fibers of asbestos quite easily (Fig. 7) (33). However, this method is not sufficiently sensitive to distinguish among the amphiboles. Here, microchemical characterization is necessary (31). Electron microscopy is an ex cellent qualitative tool for determining the presence or absence of asbestos fibers in talc. Microchemical Analysts by Electron Microprobe Analysis By means of microchemical analysis, it is possible to differentiate among.the amphibole asbestos fiber types. We have examined talc samples obtained from a mill in which anthophyllite and tremolite fibers occurred within the talc. These samples were examined on an ARL electron microprobe analyzer equipped with crystal spectometers. The instru- 106 Environmental Health Perspectives Figure 6. Transmission electron micrographs of (A) a "platy" talc and fB) a "fibrous" talc. The platy talcs tend to be made up of a mixture of well-formed polygonal and "ragged" edged sheets. Fibers visible are laic fibers. The fibers in (B) are made up of tremolite, anthophyllite. and talc. Fibrous components and nonfibrous objects are common. Magnification for (A) and (B). as marked. ment and technique have been described elsewhere (30. 31). Tremolite may be easily differentiated from fibrous talc on the basis of its high calcium con tent and Si-Mg ratio, but anthophyllite, de pending on its iron content, may not be (Fig. 8). These latter amphiboles may be differentiated from fibrous talc only on the basis of electron diffraction characteristics. Also, where fiber ends are visible, it is possible to differentiate talc from anthophyllite morphologically. Talc fibers tend to have prism truncation, whereas anthophyllite does not (Fig. 7). Microchemical Figure 7. Selected area electron diffraction patterns obtained on (A) a tale plate and (marked TF in B) a talc fiber. Tale fibers are not confused with amphi boles. They are often curvilinear, possess irregular diffraction contrast contours as do talc plates, tend towards prismatic truncations, and have identical diffraction patterns as compared with piate9. techniques may be of limited use because of the time involved in analysis. Samples with a large number of fibers may be subjected to microchemical analysis to define the types of particles present. This requires the definition of standards and the analyses of several hundred representative fibers in the sample. The technique is excellent for characterization, but is not recommended as a routine analytical method (3i). Summary and Conclusions Talc because of its composition, conditions of formation and geological occurrence, is fre quently contaminated with asbestos fibers. The presence- of fibers may be determined by a number of instrumental techniques. Some in- December 1974 107 FlCl'RE 8. Electron microprobe analyses of 95 particles observed in a fibrous talc from New York State. A-Crepresent scanning micrographs (obtained monitoring backscattered electrons) of a fibrous talc dust: (A) an amphibole fiber in the dust: <Bl analyzed as tremolite: and iC) a "talc" grain. The complex intergrowth of many phases invariably yields an analysis outside of the ideal compositional fields: (D) talc, anthophyilite, tremolite emission fields in the system Ca-Si-Mg. These analyses are scattered about these fields. Chemical analysis based on elemental emission, termed "pseudo-analysis" by Rubin and Maggiore fJi), show the presence of talc, tremolite. anthophyilite, quartz, feldspar, and carbonate phases. Differentiation between amphibole minerals is easily achieved; talc and anthophyilite fibers generally require structural characterization by selected area electron diffraction as well. struments provide direct visualization of the fibrous objects. Although light microscopy and electron microscopy are excellent tools for qualitative analysis, each has distinct disadvan tages. Use of light microscopy is restricted to analysis of objects larger than 1 ttm. Electron microscopy requires extensive sample prepara tion and instrument time. Both techniques re quire homogeneous sampling to achieve quan titation or even estimates of fiber content. Uni que characterization of amphibole fibers by transmission electron microscopy {anthophyilite and tremolite versus fibrous talc) requires structural analysis (selected area elec tron diffraction) and microchemical characterization. Quantitative analysis for fiber may be achieved by x-ray diffraction techniques employing step-scanning modes of operation on selected characteristic reflections. Preparation by slurry filtration yields "cakes" which provide homogeneous samples for analysis. Samples thus prepared yield reproducible x-ray counting results. Each fiber type has its own level of sen sitivity related to matrix and x-ray sorbtion effects. Anthophyilite may be detected at levels of 2.0"; chrysotile, 0.25^; and tremolite at 108 Environmental Health Perspectives 0.10% by weight in a talc matrix. Quantitative analysis of mineral systems more complex than two phases in composition may be compared with binary standards, with limitations. We recommend the use of both x-ray diffrac tion analysis by step-scan mode of operation and transmissin microscopy with selected area electron diffraction for analysis of consumer talcs for their asbestos fiber content. Acknowledgement The authors wish to acknowledge support under a NIEHS Center Grant, ES 00928. One of us (AML) wishes to acknowledge support under a NIEHS Career Scientist Award, ES 44812. REFERENCES 1. Ford, W. E. Dana's Textbook of Mineralogy, Wilev, New York, 1957, P. 851. 2. Deer. W. A., Howie. R. A., and Zussman, J. Rock Forming Minerals. The Sheet Silicates. Wiley, New York, 1962. 3. Bowen, N. L., and Tuttle, 0. F. The system MgOSiOj--H2O. Bull. Geol. Soc. Amer. 60: 439 11949). 4. Yoder, H. S. The MgO--AliOa-SiOj--HjO system and related metamorphic facies. Amer. J. Sci., Bowen Memorial Vol. 569 (1952). 5. Ross, M., Smith, W. L., and Ashton, W. Triclinic talc and associated amphiboies from Gouverneur Mining District, N. Y. Am. Mineralogist. 53: 751 (1968). 6. Wells. J. R. Soapstone and pyrophyllite. In: U.S. Bureau of Mines Bull. 630, Mineral Facts and Prob lems U S. Government Printing Office, Washington, D.C., 1965, p. 919. 7 Schulz, R. Z., and Williams, C. R. Commercial talc, animal and mineral studies. J. Ind. Hyg. 24:75 (1942). 8. Kleinfeld, M,, Messite, J., and Langer, A. M. A study of workers exposed to asbestiform minerals in com mercial talc manufacture. Environ. Res. 6:132 (1973). 9. Cralley, L. J., et al. Fibrous and mineral content of cosmetic talcum products. J. Amer. Ind. Hyg. Assn. 29:350 (1968). 10. Dreesen, W. C. and Dalla Valle, J. M. The effects of exposure to dust in two Georgia talc mills and mines. Publ. Health Repts. No. 5. U.S. Public Health Service, Washington, D.C., 1935, p. 131. 11. Porro, F. W,, Patton. J. R., and Hobbs, A. A. Pneumoconiosis in the talc industry. Amer. J. Roentgenol. 47: 507 (19421. 12. Siegal, W., Smith, A. R,, and Greenburg, L. The dust hazard in tremolite talc mining, including roentgenological findings in talc workers. Amer. J. Roentgenol. 49: 11 U943). 13. Kleinfeld. M., Messite. J.. and Tabershaw, I. R. Talc pneumoconiosis. Arch. Ind. Health. 12: 66 (1955). 14. Dreesen. W. C. Effects of certain silicate dusts on the lungs. J. Ind, Hyg. Toxicol. 15: 66 (1933). 15. Hunt. A. C. Massive pulmonary fibrosis from the fibrosis from the inhalation of talc. Thorax 11: 287 (1956). 16. Alivisatos. G. P.. Pontikakis. A. E., and Terzis, B. Talcosis of unusuailv rapid development. Brit. J. Ind. Med. 24: 25 (19421. ' 17. Graham. W. G. B.. and Gaensler. E. A. Talco-silicosis in a rubber worker. Med. Thorac. 22: 590 (1965). 16, Hobbs, A. A. A type of pneumoconiosis. Amer. J. Roentgenol. 58: 488(1950). 19. Kleinfeld, M., and Messite, J. Problem areas in pneumoconiosis. Arch. Env. Health 5: 428 (1960). 20. Schepers. G. W. H., and Durkan, T. M. An experi mental study of the effects of talc dust on animal tissue. Arch. Ind. Health 12: 317 (1955). 21. Kleinfeld, M,, et al. Mortality among talc miners and millers in New York State. Arch. Environ. Health 14: 663 (1967). 22. Moskowiu. R. L. Talc pneumoconiosis: a treated case. Chest 58: 37 (1970). 23. Graham, J., and Graham. R. Ovarian cancer and asbestos. Environ. Res. 1: 115 (1967). 24. Henderson, W. J., et al. Talc and carcinoma of the ovary and cervix. J. Obst. Gyn. Brit. Comm. 78: 266 (19711. 25. Blejer, H. P. and Arlon. R. Talc: a possible occu pational and environmental carcinogen. J. Occup. Med, 15: (1973). 26. McCrone. W. C. Detection and identification of asbestos by microscopical dispersion staining. Environ. Health Perspect. 9: 57 (1974) 27. Bragg, R. H. Quantitative analysis by powder dif fraction. In Handbook of X-Rays, McGraw-Hill, New York, (1967).. 28. Timbrell. V. Characteristics of the International Union Against Cancer standard reference samples of asbestos. In; Pneumoconiosis, Proc. Inti. Conf. Johnannesburg 1969. H. A. Shapiro, ed., Oxford Univ. Press. London, 1970, pp. 28. 29. Klug, H. P., and Alexander, L. E. X-Ray Diffraction Procedures. Wiley, New York. 1954. 30. Cullity, B. D. Elements of X-Ray Diffraction. Addison- Weslev. Reading, Mass., 1956 31. Brindiey, G. W. and Kurtossy, S. S. Quantitative deter mination of kaolinite by X-Ray diffraction. Am. Mineralogist 46: 1205 (1961). 32. Leineweber. J. P. A method for determination of the fiber content of water. Johns-Manvilie Research and Engineering Center Rept. No. E404-37, 1968. 33. Langer. A. M., Mackler, A. D., and Pooley, F. D. Electron microscopical investigation of asbestos fibers. Environ. Health Perspect. 9: 63 (1974). 34. Rubin. I. B.. and Maggiore, C. J. Elemental analysis of asbestos fibers by means of electron-probe techniques. Environ. Health Perspect. 9: 81 (1974). December 1974 109 CONSUMER TALCUMS AND POWDERS: MINERAL AND CHEMICAL CHARACTERIZATION A. N. Rohl, A. M. Langer, I. j. Selikoff, A. Tordini, R. Klimentidis Eavironmenial Sciences Laboratory. Mount Sinai School of Medicine of the City University of New York New York, New York D. R. Bowes, D. L. Skinner Department of Geology, The University of Glasgow, Glasgow, Scotland . Representative consumer talcums and powders, including 20 body powders, baby powders, facial talcums, and also one pharmaceutical talc, were analyzed ro determine their mineraicgical and chemical composition. Where known, all were formulated prior to 1973. Of the 20 products 10 contained detectable amounts of tremolite and cnthopnyllite, principally asbestiform, while some also contained fragmented forms of these minerals. The amounts ranged from tenths of a percent to over i*% by weight; two contained detectable amounts of chrysotile asbestos fiber. Eight contained quartz, seven ranging from 2 to 5H, with one as high as 3396. The analyses showed that the consumer products examined were rarely the pure mineral talc, but rather were mixtures of various minerals; seme samples consisted of three to five minerals, only one of which was talc. Other common mineral phases included chlorite, platy serpentine, pyrophyllite, mica, and carbonate minerals. Kaolin additive was identified in two products. The single pharmaceutical talc examined contained only a trace amount of quartz. The chemical composition of these products, including both ma/or onae and trace element content, correlated with their mineral components. Four samples contained substantial concentrations of nickel, cobalt, and chromium, suggesting lattice substitu tion or the presence of trace mineral Phases, Geological provenance of the talcs may be ascertained on the basis of chemistry. Possible adverse health effects from intermittent use of these products, especially those that contain asbestiform and fragmented anthaphyilite and tremolite, chrysotile, auartz, and trace metais, are presently unknown and warrant evaluafon. INTRODUCTION Consumer talcums and powders are considered by the general public to be talc, an impression that is conveyed and strengthened by the product This stuov was supDortea in part bv grant tS 0092S r'om tne National institute of Environmenta. Health Sciences. One of us ,'AMLl 'eceivea support under Career Scientist A*ard 5 "STI, .National Institute of Environmental Health Sciences. Reauests for reprints should be sent to A. N. Ronl. Environmental Sciences _aooratorv, Mount Sinai School of Medicine of the City University of New Yorx. New York, Ne.\ Sons 10029. 255 Journal of Toxicology and Environmental Health, 2:255-2&4, 1976 Copvright 1976 by Hemisphere Publishing Corporation 256 A. N. SOHL ET AL. names and ingredients 'isted on the container labels. However, knowledge of the geological occurrence and mineralogical cnaracter of source materials suggests the nature of talc to be highly variable and complex. Twenty-one consumer talcums and powders (Table 1) were mineralogically and chemically analyzed to determine whether these products are actually talc mineral. Talc is a defined mineral entity, based on specific chemical, crystalline, and physical properties (Ford, 1957). The empirical chemical formula, Mg^SuOu^OHJj, is seldom observed in nature as a result of cation substitution. For example, magnesium is frequently replaced by iron, nickei, chromium, or manganese in the crystal structure. Talc is a sheet silicate, with a structural unit consisting of three layers; a sheet of octahedrallv coordinated magnesium hydroxide groups is sandwiched between two layers of tetrahedraily linked silica layers. The Van der Waals bond between the talc sheets are of low energy accounting for the ease with which talc as well as other sheet silicate minerals (micas, clays) cleave TABLE 1. Designation of Contents in Brand Name or Label Sample no. Date of formulation Products designated as talcs 3 Not available 8 Not available ' 2 Approximately 1972 7 September 1972 17 Not available 5 April 16, 1973 19 May 1973 2\ Not available Products designated as powders dale on laoeil 4 December 1 970 18 Not available 2Q Decemoer 1970 5 February 1973 16 Not available Products designated as powders (or dust) ; Between January 1968 and |ulv 1970 } 4 October 3, 1970 IS 8etween October 1 970 and Marcn i 973 9 February or March 1973 * i luly 1969 13 |uly 16. 1970 n Not available ID Approximatelv 1 972 CONSUMER, TALCUMS AND POWDERS 257 or break into plary fragments. This facile cleavage, with resultant high surface area, and its softness, small particle size, and whiteness confer uoon talc its usefulness as a cosmetic material. GEOLOGICAL OCCURRENCE OF TALC Talc rocks (including those commercially worked) are formed by several comolex geological processes reacting upon many possible, chem ically diverse preexisting rock types. Hydrothermal alteration of magnesiaand silica-rich ultramafic rocks, under a range of low-to-moderate tempera tures and pressures, may produce talc. Thermal metamorphism of silicarich dolomite [CaMg(C03)2] will produce talc as well. These processes, however, also commonly result in the formation of a number of other coexisting mineral phases, predominantly hydrous magnesium silicates. Some of these, for example, anthophyilite, tremolite, and serpentine minerals (including chrvsotile), occur as microscopic intergrowths with talc, as macroscopic nodules, or even as discrete zones within or adjacent to talc (Table 2). Talc rock is therefore generally not monominerallic but is often a mixture of minerals that may vary widely with respect to kind and quantitv. Phlogopite, a magnesium mica, and chlorite, a group of minerals related to the micas, are also commonly associated with talc. Some of these associated mineral phases are asbestiform amphiboles and chrysotile (see discussion of the terms asbestos and asbestiform in Appendix A). Conversely, talc has been described as a common accessory mineral in commercial asbestos deposits (Hurlbut and Williams, 1935). Talc deposits may be zoned, with different mineral assemblages physically changing in occurrence and proportions over extremely variable TABLE 2. Minerals that Commonly Occur in Talc Deposits Mineral group Phase Formula Carbonates Amphiboles Serpentine Calcite Dolomite Magnesite T remolite2 Anthophyilite*7 Antigorite CHrysotile (uncommon) uzardiie (uncommon; Quartz Mica, e g., phlogopite Cmorite, e.g., penmnite ^vropnv Hite CaCO, CaMgjCO,), MgCO, Ca. Mg,Si, 0.. ;0H). (FeMg). Si, O.. iOHi. Mg,Si.O,|OH, Mg, Si; 0, (0H|, Mg, Si. O, (OH1, SiO. K.(Mg,Fei, |Si, Ai.O,0 , ,OH). iMg.Ai.Fei,.jfsi.Ai (b.,;ioh;,, ai, i (ohi . ^Occurring as t'iprous and nonfiprous forms. Otner trace mineral or.ases are Dtten present Out are noi included. 258 A. N. ROHL T AL. distances, ranging from centimeters to tens of meters. Mineral phases in such deposits mav include talc plates and fibers, tremolite and anthophyllite fibers, intergrowths of amphibole and talc, serpentine minerals (which may include chrvsotiie), and free silica (quartz) ( Rqss et al.. 1968). The fiber intergrowth is often such that even extensive beneficiation may not yield, a pure product. Thus, where fine-grained intergrowths of taic and tremolite occur, the processed product will likely contain residual tremo lite. Further details concerning the crystal chemistry, structure, synthesis, and geological occurrence of talc are found in Appendix B. INDUSTRIAL AND COSMETIC GRADE TALCS It is generally recognized that various commercial grades of talc are marketed in the United States (Appendix C). Hildick-Smith (1976) has stated that a talc suitable for pharmaceutical purposes, used in cosmetic and toiletry products, contains at least 90% talc mineral and no detectable asbestos. Such stated compositional restrictions are not placed on indus trial grade talcs. One study demonstrated that a number of industrial talcs contained substantial Quantities of tremolite, up to 87% by weight of the samoie (Schulz and Williams, 1942). in 1968, a study (Cralley et at., 1968) of 22 cosmetic talcum products demonstrated fiber contents ranging from 8 to 30% by count with an average of 19%. The fibrous material was predominately talc but probably contained minor amounts of tremolite, anthophyllite and chrysotile as these are often present in fibrous talc mineral deposits. With the exception of 4 of the 22 cosmetic talcum products analyzed, the levels of free silica, cobalt, nickei, chromium, and manganese were generally of a low magnitude and within a narrow range. . . . The levels of silica, chromium, and nickel in tnese four products are sufficiently high, however, to be of concern in their potential to cause disease. Thus, as late as 1968 some consumer talcum products marketed in the United States contained asbestiform minerals, free silica, and trace metais. HUMAN DISEASE ASSOCIATED WITH TALC EXPOSURE For nearly half a century a number of reports have shown that occupational exposure to talc dust is associated with a fine diffuse interstitial lung scarring known as talcosis. -ibrous talcs appeared to be more pathogenic than platy talcs, producing in addition to talcosis, increased risk of malignant tumors in exposed workers (Kieinfeld and CONSUMER talcums a,no powders 259 Messite, 1960; Kleinfeld et al.p 1967). Studies concerning the biological consequences associated with talc dust exposure, including cancer, are referred to in Appendix D. OBJECTIVES OF THE PRESENT STUDY Twenty-one samples of consumer talcums and powders, including baby powders, body powders, facial powders, and a pharmaceutical talcum, were obtained at retail stores in the New York City area. These samples were acquired and studied during the period 1971-1975 (Table 1). The major purpose of the study was to determine the mineraiogical and chemical composition, with particular emphasis on the quantitative determination of tremolite, anthophyllite, serpentine minerals, and quartz. Another objective was to establish a base line for consumer talcums and powders, based on a sampling of products available during the period 1971-1975. This base line provides an index for evaluating possible changes in subsequent formu lations. .METHODOLOGY AND RESULTS OF MINERAL AND CHEMICAL CHARACTERIZATION The analytical techniques employed for mineral identification and quantification included optical microscopy, transmission electron micro scopy with selected area electron diffraction, X-ray diffraction, and scanning electron microscopy with X-ray analysis capabilities. Chemical determinations (bulk chemistry and trace metals) were made with a number of standard instruments and geochemical techniques, including spectrophotometry (Si02, TiO;, AU03, total Fe (Fe203 by difference from FeO), P2Os]; atomic absorption (MnO, MgO, CaO); flame photo metry (Na20, KjO); wet chemical assay (FeO); weight loss, volatiles (H20, C02 , organics). X-ray fluorescence was used for all trace metals (Bowes and Langer, 1974). . Optical Microscopy Optical microscopy is a conventional technique for the identification of minerals and for the study of mineral relationships. A microscope equipped with bright field illumination and polarized light optics was used to analyze the cosmetic powders. Approximately 0.5 mg of powder was placed on a precleaned glass slide and immersed in index oils of known refractive indices. These were checked on a refractometer. The information obtained on particles with this method included most of the measurable optical properties, including indices of refraction, extinction angles of fibers, general morphology, and size characteristics of mineral phases (Fig. 1). In coarse-grained powders, fibers couid be identified (tremolite, anthophyllite. talc). Two samples contained cornstarch, easily recognized FIGURE 1. Ootical photomicrographs of cosmetic talcums and powders grosslv contaminated with isbesti'orm minerals. Photos oouined in plane polarized light fA--F) anp oetwee.n crossed polars 1G1. Scale in i'AI for ail Dnotos. Fibers shown have ootical properties consistent with tremolite .'Tri ind ar.thophvllite iAni. Quartz grains (Qul and calcite fragments iCai are also shown. Most tremolite fibers tend to possess smaller length-to-width ratios than anthophyiiue. Tremoiite is observeo as fragments ,C',. Photo ootained between crossed polars iG| also demonstrates tne presence of fleers in tne matrix material. Asbestiform lengtn-to-wcatrt ratios measures up to 20:i {Fi. 160 CONSUMER TALCUMS AND POWDERS 261 bv morphological and optical characteristics. One product consisted entirely of cornstarch. In most samples, however, the powders were too fine grained, with particle dimensions significantly less than 1.0 am, for the technique to be useful. The limiting factor for determination of optical constants, and hence for identification of particles, is the resolving power of the microscope. The presence of talc fibers, which may have indices of refraction similar to amphibole (tremolite, anthophyilite) fibers, also confounds analysis. Therefore, although this technique is an excellent diagnostic instrument in some instances these restrictions limited its usefulness. Other investigators have experienced similar difficulties. For example, in a study of the asbestos content of talc (Stanlev and Norwood, 1973), there was difficulty in applying optical microscopv to the problem. The authors concluded that optical microscopy while it works well on pure samples of fairly massive fiber length from 3 to 5 microns, our observations by transmission electron microscopy have shown that naturally occurring asbestiform minerals often lie below the working resolution capabilities of the light microscope and furthermore while massive fiber bundles can often be observed by either light or electron microscopy the observation of individual fibers smaller than 0,5 by 0.2 micrometers often will require the high resolution capability of the transmission electron microscope (emphasis added). It is further stated that "light microscopy was helpful only in screening sampies with large particles and high concentrations of objectionable fibers." By comparing the results of optical microscopy with those of quantita tive X-ray diffraction and electron microscopy, we observed that large numbers of fibers go undetected. In addition to the restraints of resolution imposed by light microscopy, another major drawback relates to the strong tendency of asbestiform minerals to cleave or break along planes of weakness when they are crushed, producing large numbers of small fibers. For example, light microscopic examination of a talc sample (no. 8), which contains over 7% tremolite (see Table 4), demonstrates the presence of mineral fragments that are primarily not asbestiform (Fig. 1C). How ever, electron microscopic examination of the same sample demonstrates that many of the submicroscopic tremoiite particles are fibrous (see Fig. 3E). The problem involving the determination of the relative proportions of each of these morphological phases in the same sample (mass vs. number) is presently unresolved. Basically, the large fibers are broken during milling yielding a new size distribution in the submicroscopic range. 262 A. N. ROHL ET AL. X-ray Diffraction The application of X-rav diffraction analysis in step-scan mode for quantitative determination of asbestos in talc has been described in detail (Rohl and Danger, 1974), including the selection of talc and asbestos reference materials, the preparation of standard dilutions of asbestos minerals in talc to ensure sensitivity and reproducibility, the selection of characteristic X-ray reflections to be scanned, and instrumental technique. Selection of talc mineral standard. Screening of various types of talcs for use as reference material was made by X-ray diffraction and trans mission electron microscopic analysis. A continuous scan was first made to identify the major mineral phases present. Talcs that showed the presence of any serpentine mineral, tremolite, or anthophyllite were eliminated as reference materials. The possibility of false negatives for these minerals was checked by step scanning the diagnostic reflections (Table 3). Further verification of the absence of asbestiform minerals was made by trans mission electron microscopy. These techniques permitted the selection of a matrix talc that was completely free of asbestiform minerals. Chlorite minerals are hydrous iron-magnesium silicates, frequently associated with talcs. Their presence may interfere with the detection of serpentine minerals, both platy (antigorite) and fibrous (chrysotile). This is particularly true if they are present in equal or larger amounts than these latter minerals. Two intense basal reflections at 14.2 A (001) and 7.1 A (002) are characteristic of chlorite minerals. The latter reflection occurs close to the (002) reflection of serpentine minerals (7.3 A). The 3.66 A (004) reflection of serpentine was selected as diagnostic (Table 3), since the lower intensity (004) reflection of chlorite (3.53 A) in this region was found not to cause interference. Selection of the asbestos standard. Reference samples of pure asbestos minerals were obtained from various mineral collections and from the International Association for Research on Cancer (IARC). These were screened for purity and particularly for the presence of interfering contaminants according to the procedures previously describee for talc. Two different specimens of chrysotile were used as reference materials: a triple air-jet milled sample from the Jeffrey Mine, Quebec (provided by the Jonns-Manville Corp.) and a specimen from Coalinga, California (provided by the Calidria Division, Union Carbide Corp.). Sample preparation. Among the variables that strongly influence the precision and accuracy of quantitative X-ray diffractometrv are particle size, preferred orientation, and surface flatness. Variation due to particle size can be minimized by crushing and screening the asbestos and talc standards to ensure a uniform size distribution, with an effective crvstallite dimension on the order of 5 pm or less. The effect of preferred orientation is more difficult to control. The tendency fqr preferred orientation is largely the function of mineral cleavage properties. Both the talc and the asbestos minerals have excellent cleavages, platy in talc and I i. CONSUMER TALCUMS AND POWDERS 263 TABLE 3. Czi.oration Curve Data for the Determination of Asoestiform Minerals ana Quart' n Taic ov X-rav Analysis'1 Mineral ohase Parameter AmhODhyilite Chrvsotne Quartz Miller maex of augnostic reflection Corresponding cf-spJCing (A) Relative intensity Step-scan interval 12 theta) cio) S.26 55 10.0-1 1.0 (004) 3.66 30 23.5-25.0 (211) 1.54 15 59.5-60.5 Percent mineral in talc and corresponding area of reflection T remoiite (110) a.38 100 10.0-1 1.0 Anthophvllite % ,n.3C 5.0 10.0 15.0 20.0 25.0 30.0 35.0 - 0.92 2.35 3.99 4.65 5.12 7.22 9.92 - Chrvsotile % in.1 0.25 0.5 1.0 2.0 5.0 7.0 8.5 8.9 0.01 0.03 0.08 0.22 0.94 1.52 2.21 2.34 Quartz % in.3 5.0 10.0 20.0 25.0 30.0 40.0 - 2.75 3.75 7.11 9.30 13.20 16.90 - T remoiite % in.: 0.1 0.5 2.2 2.7 4.3 5.0 7.0 10.0 0.13 0.30 0.4 3 0.67 1.25 1.65 2.08 2.80 Detection limit Wt % Anthophvllite = Area (210) = 0.27 |%An)-0.52 R3 = 0.95 Wt % Chrvsotile = Area (004) = 0.27 (%Ch) -0.50 R' = 0.98 Wt % Quartz = Area (211) ~ 0.43 (%Q) -0.60 R3 = 0.96 Wt % Tremolite = Area (110) = 0.28 (%Tr) -0.04 R3 = 0.98 2.0% 0.7% 1.4% 0.1% 3lnstrumental settings: target/filter, Cu/Ni, 45 kV/20 mA; scintillation counter. 1450 VDC; monochromator, graphite; puise-time analvzer, 20 V, 5 V (width, level); continuous scan, i* 2 9/ min; step-scan. 0.02" 2 S at 2,000 counts fixed. ^ Rhomoonedrai index. -Repeated measurements of areas under curves with a polar planimeter indicated average deviation of ^ 0.02-0.05 m.'. fibrous in the case of tremolite, anthophvllite, and chrvsotile (see Rohl and Langer, 1974, Fig. 2). In attempting to reduce or eliminate the effects of preferred orientation in X-ray analysis, a number of sample preparation and instrumental techniques have been developed (8ragg, 1967; Brindley and Kurtossy, 1961; Cullity, 1956; Klug and Alexander, 1954). In the present study these techniques were tested, but none was found tc provide adequate precision (reproducibility). Accordingly, a sample preparation technique was developed that was successfully used, in conjunction with X-rav diffraction in the step-scan mode, to detect diagnostic reflections of these minerals in a talc matrix over a range of concentrations ,Taoie 3). 264 A. N. ROHL T AL. The reproducibility of reflection intensities was also greater than other preparation techniques tested. Binary dilution standards of chrysotile, anrhophyllite. and tremolite in talc were prepared gravimetricaily. Asbestos fiber concentrations were prepared initially at 5.0, 4.0, 2.0, 1.0, 0.5, 0.2, and 0.1%. Fifty milligrams of the talc-asbestos mixtures were homogenized in 10 ml filtered water utilizing ultrasonic energy. This slurry was poured into a 30 cc syringe and filtered through a 0.22 /am pore size membrane filter. To prevent stratification due to differential particle size and density, effects, the syringe is held in a horizontal position, rotated, and shaken during filtration. The residue forms a flat cake of about 0.5 mm uniform thickness on the membrane filter. When dried, the sample is affixed to a glass slide for X-ray diffraction analysis (Rohl and Langer, 1974). Selection of X-ray reflections. Because of crystal structure similarities in the minerals being studied (i.e., tremolite and anthophyllite), consider able overlapping and interference of X-ray reflections occur. The low symmetry and consequent complex X-ray diffractograms of such minerals as talc, chlorite, and mica, as well as possible interferences from admixed phases such as kaolinite, make it necessary to select a reflection or set of reflections for each mineral component thac couid be used as an index of the amount of that mineral in a mixture. Such diagnostic reflections were selected by referring to standard X-ray powder diffraction data. These diagnostic reflections were step-scanned at 0.02 2 theta in a fixed count mode (2 X 103 counts). Precise positions and profiles of the diagnostic reflections were determined. In the fixed count mode, each of the angular intervals selected are scanned with equal accuracy. Thus weak reflections can be determined with equal precision as high intensity reflections. The statistical accuracy depends only on the total number of counts recorded, and the counting rate selected gives a percentage probable error of about 2%. Profiles of the diagnostic reflections, plotted as a function of number of counts vs. 2 theta, are measured with a compensating polar planimeter. The intensity of a reflection is proportional to, but not necessarily a linear function of, its concentration. Other factors that may influence reflection intensities include instrumental conditions, particle size, degree of pre ferred orientation, sample thickness and flatness, and absorption character istics (Klug and Alexander, 1954; Rohl and Langer, 1974). Figure 2 shows calibration curves obtained for chrysotiie, anthophyl lite, tremolite, and quartz using the step-scan technique. Measured areas of diagnostic reflections are plotted against percent dilution in talc. As indicated in Table 3 tremolite may be determined at levels as low as 0.1 0% by weight, chrvsotile from 0.25 to 0.50%, and anthophyllite, as low as 2% in talc. It is important to note that the limits of detection given in Table 3 are higher and based on a best fit regression analvsis. For example, regression analvsis indicates that the detection limit for chryso tile is 0.7%, whereas from 0.25 to 0.5% can be actualK detected, CONSUMER TALCUMS AND POWDERS 265 FIGURE 2. Calibration of isbestiform amphiboles and guana in talc. depending on particle size, degree of crystallinity, etc. The changes in slope at the lower end of the curves are not reflected so that axial intercepts are exaggerated on the high end of the abscissa. By using X-ray diffraction in the step-scan mode, Stanley and Nor wood (1973) were able to detect a minimum of 0.25% tremolite in talc and a minimum of 0.5% chrysotile and the other asbestiform minerals. However, such low levels of chrysotile were not detected when chiorite was present. Step scanning. The contents of the containers were thoroughly mixed with a sample splitter to avoid stratification effects. Aliquots of each, weighing 50 mg, were prepared using the identical methodology described for preparation of the dilution standards. The filter-mounted samples were then step scanned over the goniometric intervals diagnostic for the standard asbestiform minerals and quartz, instrument operating conditions were identical with those used for analyzing the dilution standards. Profiles plotted for the diagnostic intervals and reflection areas after peak stripping were measured by polar planimetry. The weight percents of anthophyllite. tremoiite, and quartz contents were estimated by referring to the appropriate regression curve. The quantities of asbestiform materials in the 21 talcums and powders found by this technique are shown in Table 4. The results show that 10 of the 21 samples contain amphibole 66 CONSUMER TALCUMS AND POWDERS 26 7 minerals, ranging in amounts from a few tenths of a percent to over 14%. Tremolite was the most commonly found (9 of the 21), and anthophvllite occurred with tremolite in 6 of the 21. A serpentine mineral phase was indicated .n two samples, in amounts at or near the lower limits of detection. Verification of the serpentine phase as chrvsotile in the two samples in amounts corresponding to the observed concentrations was made by electron microscopy. Continuous scanning. In order to study the presence of all mineralogical (and possibly other crystalline) components the samples were scanned from 5 to 70 2 theta at a scanning rate of 1 2 theta per minute. This technique, as expected, proved satisfactory for the identification of major components, but it was generally found to be incapable of detecting tremolite, anthophyllite, or serpentine minerals except in cases of gross contamination. The high noise level (low peak-to-background ratio) often prevents the detection of quantities on the order of 4-6% or less and also excludes this technique for quantitative analysis. As a result of high noise level three false positives, as indicated by continuous scanning, were subsequently shown to be negative for amphibole by step scanning and electron microscopy. In addition, continuous scanning may not generally detect serpentine minerals in the presence of chlorite or kaolinite. Electron Microscopy and Electron Diffraction The transmission electron microscope has been shown to possess the sensitivity required for fiber identification and for determination of particle size distribution of submicroscopic particles (Langer and Pooley, 1973; Langer et at., 1973). Accordingly, aliquots of talcum samples were prepared for electron microscopic analysis by a technique that disperses particles in a drop of nitrocellulose solution on a glass slide. A second glass slide is placed on the first and the two are drawn lightly apart, leaving a film. This technique is intended to minimize the alteration of particle size distribu tion. The film is mounted on electron microscope grids and scanned at magnifications of X20,000. Morphologically, amphibole minerals are generally quite dissimilar from other silicate minerals. Both anthophyliite and tremolite are rectilinear, often with amphibole-type step cleavage or, infrequently, with prismatic terminations. Tremolite fibers tend to be electron dense and shorter than anthophyllite (Fig. 3), while the latter has a tendency to be electron translucent and to show diffraction contrast figures (Langer and Pooley. 19731. Sheet silicate minerals (talc, chlorite, micas) tend to be equiaimensionai in shape, often with pseudohexagonal outlines (Fig. 4). Curled taic plates or talc fibers on edge may superficially resemble asbestiform minerals, but selected area electron diffraction patterns easily distinguish between the two (compare Fig. 5A, C, and D). Electron microscopy, in combination with selected area diffraction, FIGURE 3. Transmission electron micrographs showing range in morohological characteristics of asoestiform tremolite and anthoonyllite in talc. The entire range of morpnoiogical variations observed for tnese minerals -s observed in the asbestos stannaras: rectilinear fibers witn parallel ends and eages \A); steo-cieavage enos (B); unit fibrils protruding from fiber bods, 1C;curvilinear loer with amonibole cleavage end ID); high length-to-width ratio fibers IE); fibers protruding from nteriors of talc plates iFl. All of these morphological sanations and forms iA-E| nave been described .r, antnoDhvilite anc tremoiite asebestos samples. The amphibole structure was confirmed r. all cases cs selected area electron diffraction cnaracteriration. Scale as marked. Micrographs ootamed on a |EOL JEM I2C U with an accelerating voltage at ! 20 kV. 268 CONSUMER TALCUMS AND POWDERS 269 FIGURE 4. Transmission electron micrographs of cosmetic talc samples composed primarily of plates with an occasional large ulc fiber talc with maftv talc fibers !0h, Scale is tne same in (A) and iBI and in (C) and (O). All selected area electron diffraction patterns optamed on fibers vieioed those consistent for talc plates (see Fig. S, A and 3). In all talc-containing samples examined bv electron microscopy talc grains tenoed to range from IS to 0.2 urn in greatest dimension. Micrograph obtained on a JEOL ]M 120 U with an acceleration voltage at 120 kV. was used to verify the presence of ampniboie in the 10 samples shown to be positive bv X-rav diffraction. Electron microscopy, while not quantitative, also showed that amphibole fibers were present in relative amounts that corresponded to their percentages as shown by X-rav diffraction. The oresence of traces of chrvsotiie. rather than piatv serpentine, in sampies i2 and ii was verified by electron microscooy J Fig. 6). Bv ....... - ---------- la .. ~ ^2T A. FIGURE 5. Transmission electron micrographs ana accompanying selected area electron infraction ,SA.ED> patterns for cosmetic talc samples. The taic plate 'TP) in (A' shows typical poivgonai cleavage and diffraction contrast contours for tne mineral species. The accompanying SAED pattern displays the characteristic reciprocal ab* plane pseuaohexagpnai svmmetrv for talc. Ta<c a" and b' Directions indicated on IA|. Measurement of pattern indicates a 5.3 A repeat along a" and a 9." a repeat 'or b* imeasured at [110|). Talc fiber (TF) in IB) displays irregular ends and nonrectilinear edges. The SAED pattern is aiso pseudohexagonai. but some reflection intensities (e.g., the i060.. .C.T Z.Ci are more pronounced. This mav be pue to ooth orientation and structural effects. Tne curies tj.c plate (CT1 in (C) dispiavs an incipient DeDve-Scnerrer ring pattern ithe effects of ooth folding oser of talc and small associated grains/. The ampmbole fiber ;0 was diffractec onl\ or one oi tne protruding unit fibrils. The c* axis is shown, wan repeat measured at 5.3 \. Areas wnere diffraction patterns were ootamed are .ndicated bv location circles: particles we'S pnotograonea it the SAED magnification X26.5QC. Scaie is the same m A-C. scaie, in D as marked. Micrographs obtained on a IEOL .IEM 120U witn an accelerating voitae; a: 130 XV. 270 Q.25um 'T FIGURE 6. Transmission electron micrographs of asbestiform minerals m cosmetic talc, other than ampmbole. {A and B) Two chrvsotile fibers witn moronoiogicii characteristics induced bv electron beam aamage. No diffraction pattern was obtained on either fiber. Arrow markers lA and B) indicate areas where these oeam-damaged features are most prominent. Botn fiber Bundles appear to rest on talc plate substrates. Free chrysolite fibers and fibrns iCi were `ound in a sample found negative for asbestos bv all other techniques. Scaie as marxed. Micrographs obtained on a |EOL ; EM r 20 U with an accelerating voltage at 120 kV. A. N. ROHL ET AL. comparison with known dilution levels of chrysotile in taic observed by electron microscopy, the levels of contamination of chrysotile in the two samples correspond to about 0.25-0-5% chrysotile, wnich was suggested by the X-rav diffraction results. The chrysotile fibers were all shorter than 2 /om and the diameters less than 0.2 ^m, explaining why they were not visible by optical microscopy. Chemistry of Consumer Talcums and Powders The bulk chemistry (Table 5) and mineral contents (Table 4) of the talcums and powders complement each other in that one data set implies limits for the other. For example, analysis of sample I shows the presence of FeO and CaO (Table 5). Recalculation of these oxides into values for the empirical formulas for tremolite and anthophyllite indicates that sufficient quantities are present to account for the presence of these minerals (Table 4). An appreciable decrease in Si02, which should normally occur, was not observed, because of the occurrence of over 5% quartz content. The Al203, Na20, and K20 are reflected by the presence of chlorite (probably the penninite phase). Variations in oxides were also observed in the other samples that contain amphibole minerals (6-8, 11, 12, 15-17, and 21). In these samples, a number of other factors account for the wide variations in oxide percentages: in 5, the presence of chlorite TABLE 5. Major Oxide Content of 21 Consumer Taicum and Powders0 Sample no. Major oxide 1 2 3C 4 5 6 " a 9 10 11 SiO- no. 41.0, Fe ; O, FeO MnO NieO CaO Sa-O k.o ?;os Volamev Total o! .95 0.10 0.82 O.OO 1.5S 0.00 29-60 C.40 0.0- o.c: CO 1 5.36 99.38 0.00 0.00 : .30 0.00 o.oc o.oc 9.00 0.00 0.00 0.00 0.00 98.70 100.00 62.63 0.M 0.37 0.08 0.3 2 0.00 29.83 0.04 0.03 0.02 0.03 4.66 98.00 38.72 0.04 0.24 0.04 3.03 0.00 2S.2S 0.10 0.03 0.02 0.03 3.38 95.88 61.94 0.03 0.45 0.03 0.51 0.01 30.19 0.04 o.os 0.02 0.01 5.51 98.79 52-95 0.17 1.16 0.02 0.86 0.00 29.02 3.46 0.00 0.05 0,13 10.32 55.67 1.40 3.57 0.18 0.54 0.00 29.23 0.90 o.os 0.05 C. -4 5.64 98.14 98.?- 71.93 0.19 15.73 0.10 0.34 0.00 2.95 2.37 0.43 1.37 0.05 5.25 '00.-6 58.68 0.08 0.58 0.12 3.12 0.00 29.23 0.17 0.00 0.00 C.0Q 5.34 97.32 5 T .65 0.71 ; .45 0.09 0.34 0.00 27.90 4.75 0.03 0.00 O.OS 9.72 96.69 49.48 0.22 2-32 1.23 0.07 0.00 25.67 1.61 0.42 0.19 0.01 10.41 91.63 "We rent percer 'ecatcuia; ea as oxides, following standard oetrocnemicai broceaures. T~e cal k analysis of he oowoers re fie c:s :r>e camoined mineral con: ent after aedrttves were e xtfictec using ware', j*.u:e HG acetone, benzene, and ether. " sis of 2. ?$. -- sca'c.n - organics and vena tiles. .3% =* m -O, saluminum cniornv crate'.. c Standard taic used as matrix *cr fiber stanoard dilutions. CONSUMER TALCUMS AND POWDERS sharply reduces the SiO; content and elevates the Al203 content. The presence or the carbonate mineral calcite increases the expected CaO and volatile contents (the latter includes C02); in 7, the high Ti02 is reflected by the presence of the mineral rutiie (Ti02l; in 11, the high CaO. moderately high Al2 03, and low Si02 contents reflect the presence of calcite, chlorite, and tremolite. Several of the above samples (numbers 8, 12, and 15) require special evaluation. Sample 8 is extremely high in Si02, Al203, Na20, and K20 and extremely low in MgO content. The chemistry indicates that this material was not derived from a talc rock, but rather from one rich in alumina and silica. The mineralogy reflects this, as do the trace metals (see trace metal section). The amphibole minerals in sample 8 are associated with both pvrophyllite [AI4Si80;; (OH) ] and quartz, both present in substantial quantities. The mica phase is not phlogopite, but muscovite, accounting for the presence of substantial quantities of K20 and Na:0. A plagioclase feldspar was also detected in the mineral phase. Sample 12 is very high in Al203 but extremely low in SiCU, apparently the result of high chlorite content as well as substantial amounts of pvrophyllite. Sample 15 is low in Si02 and extremely high in volatile content, reflecting the presence of both carbonate phases and organic additives. The trace element analyses (Tabie 6) show distributions that are in accordance with the known behavior of trace elements in minerals. With TABLE 5 icontinued) Major Oxipe Conlent of Cl Consumer Talcu m and Powders^ Sample no. :: 13 u 15 16 T 7 18 19 20 21 B* 4 7.3 2 Q.18 9-34 0.05 1> . A"1A^ 0.00 29.S3 0.69 0.03 0.05 j.Z 1 .:.:6 99. IS 53.83 0.11 ; .74 0.03 0.70 0.00 27.14 5.49 0.07 0.00 0.14 10.81 '. CO.06 57.47 0.11 1.65 0.02 0.55 0.00 26.98 5.52 0.05 0.02 0.13 10.41 44.83 0.07 0.69 0.00 0.52 0.00 23.88 3.67 0.35 0.07 0.10 21.34 98.01 95.62 62.26 0.06 0.45 0.18 1.04 0.00 30.00 0.13 0.09 0.05 0.01 5.92 54.45 0.10 4.26 0.04 1.41 0.00 30.79 1.13 0.09 0.02 0.04 7.54 59.93 0.10 0.79 0.00 0.84 0.00 30.40 0.50 0.09 0.02 0.13 5.65 100.1 s 99. S7 95.^5 58.54 0.18 1 11 0.00 1.38 0.01 29.33 1.13 0.00 0.00 0.00 5 94 62.19 0.08 0.69 0.00 0.81 0.00 30.19 0.43 0.07 0.00 0.13 5.14 9S.21 99.73 56.34 rt ' -u 1.35 0.02 1.39 0.00 27.90 1.53 0.07 0.00 0.02 9.99 ?S." 57.34 0.21 2.30 0.1 * 1.05 0.00 ::.44 1.69 0.10 0.10 0.70 S.03 9S.20 61.49 0.Q1 1.20 0.38 1.07 0.00 30.54 0.46 5.00 100.11 J Average or 20 talc $amo*es. * Average of 3 taic analyses m Deer et al. v T 962). ' Volatiles are lost on ignition i total H. 0, CQ:, or games, ana other volatiles/. , a 3 A CM * -- 3 A- A *N 1 v y /V-- / " IA a A A ^ -, ^ a 3 O A A O A A. --. A LA A O A --L 3 r*i . -- (N V rv -- A, - -. 1 / /" " " -J cl oc V V. 30 y^ 4^ "N v O' 30 rv <30 LA A Q "" o A ^ -- 3 y 39 a a a r-"l at a A ^ a CN A O A x O O--y -- ~V o O m fM .a --"T V^ y\ a * 'A 3 a a r<. 3 *- --- V A* y 'N A j "** 'O a v a \ LA -- n a r 'A i" - TM V LA ^7 v A A3* "1 3 -- V A v A **- -- v LA 9 o o A - ^ O Vi o a A A 3 a 3 -- y ^ -- A1 -- r* rN y a* -- VV AV W". m o do - O A. r*\ V V '' T J rsi A A 3 A -- o CL ^ y -- -- AV r*l o o a a; >/l r* - A* A A AA -- " -A y -* V v y r*^ ^ Vv y V rv ; ~, Q o CN "i ^ V^ lh a V" 00 V V" V _ a a A "1 OJ W " O S3 ---- " v-- v -- VJ V' A A O VH i a v 90 -- V -- fN V A 3 A 43 -- V --o v - 3 a LA 1 A A -- a p-. A LA, A A A A a -- C y V v -- V '* V v V ^-- a o A 00 LA -- 3 a a -- >** -- IN V V -- -- V V 00 V 1 CN A AoA o V A. --* V (T\ TM wV V i a a A** U-1 fj\ o a ** * LA -- V 7* "* tr -- 1 ~V A A 30 Tr o -n 3 rA "* " r o a a a> rf a -- o a 3 vA A a O *A A - -- y fN y y * n, A A' V--------- i vv V 1 a a m m la -- y cn y v y ra A O O A "v 3 V CM V -- CL a ; i ; a -- >/ a "- LA X -- A v O " JQ y V r- Ai W" V 3 ->( t"s 3A X 3 V i 00^ i a a A A A -- oe fN LA A A i*^ 3 -- -- n"i V V y V *N VV V j A 1 a a a a ca v*, ^ 3 30 -- " r-* V ^ V -- A. 3 3 A A 3 *A -- V - I A H ! I. <) I i. iic I.Il ij u iiI 4 'o u le n l i>l \1 LiMksumci f jlc n m u n t l ftnvtJcrb' AA -- or*-3aCA 274 > ^ - N- CONSUMER TALCUMS AND POWDERS 275 the crystal lattice of a mineral acting as a sorting mechanism for cations, the cations can enter a crystal structure providing they have appropriate size and charge. These phenomena apply to major as well as minor elements. Thus, barium is present in large amounts in sample 8, which has a high KjO content (1.37%). Since barium and potassium have similar ionic radii, barium is easily admitted into potassium minerals, such as micas and feldspars (both found in 8). Rubidium and strontium are also enriched in sample 8, since these metals also easily substitute for potassium. Gallium is found in large amounts in samples 8, 12, and 17. These samples are also very high in ALO3. Gallium has the same ionic charge and radius as aluminum and, in fact, is found only in aluminum bearing minerals. In four samples (1, 4, 9, and 16) there are significantly higher concentrations of cobalt, chromium, and nickel than found in the other samples. These four samples also have high contents of FeO (Table 5). The association of these four transition metals has been observed before in certain geochemical environments, particularly in ultramafic rocks. Since talcs derived from the metamorphism of serpentines and peridotites (ultramafic rocks) are considerably enriched in FeO (Deer et al., 1962), it is likely that the divalent cations are substituting for iron in the brucite layer of the talc. DISCUSSION AND CONCLUSIONS Talc used in the United States represents a wide range of mineralogical substances. Industrial grade talcs are obtained from different rock types of highly variable mineral composition with the result that the mineral talc may actually be a minor constituent. However, it has been stated that consumer talcum products should contain at least 90% of the mineral of the same name and no asbestos fiber (Hildick-Smith, 1976). Review of the literature suggests that at least until 1968, materials that were marketed as cosmetic talcum products did not necessarily conform to these criteria. Talc mineral may occur in a platy form or in a fibrous form. Talc fiber may occur as a small proportion of the mineral desposit or as a major constituent. Intergrowths of talc with other mineral phases are common. These phases may be simply macroscopic zones adjoining talc mineral or may occur as microscopic intergrowths within the talc. Of the many minerals that may coexist with talc, a number of asbestiform phases commonly occur: tremolite, anthophvliite, and chrysotile have been identified in these deposits. In addition, free siiica (quartz) is a freauent constituent. The trace metal content may include elevated levels of nickel, chromium, and cobalt. There is general agreement between the mineral composition and the major and trace element content of the consumer talcum products. On the 276 V iN. ROHL ET AL. basis of mineral and chemical contents, the type of geological provenance may be ascertained. Methodology has been developed for quantitative X-ray diffraction determination of anchophyllite, tremolite, serpentine, and quartz in con sumer talcums and powders. Important factors in the calibration standard development include selection of talc and reference minerals and the selection of diagnostic X-ray reflections. The sample preparation technique is sensitive and reproducible. Dilution standards are step scanned over diagnostic reflection areas, peak areas are measured, and a set of standard calibration curves is developed by regression analysis. Samples of consumer talcums and powders are prepared and analyzed under identical conditions and compared with the calibration curves, permitting quantitative analysis of these minerals. X-ray diffraction alone cannot distinguish between asbestiform and fragmented forms of anthophyllite and tremolite nor between asbestiform and platy serpentine varieties. Electron microscopic analysis was used to distinguish between these forms. Mineralogicai characterization of 21 consumer talcums and powders showed that 10 contained measurable concentrations of asbestiform tremo lite and anthophyllite, and some also contained fragmented forms of these minerals. Two samples contained trace quantities of chrysotile (0.25-0.5%). These observations were confirmed by transmission electron microscopy. The amphibole phases present in these talcum products ranged in amounts from several tenths of a percent to over 14% by weight. Quartz was present in eight consumer talcs in amounts ranging from 1.6 to 35.1% by weight. Consumer talcum products are for the most part complex mineral assemblages, which confer X-ray sorbing and fluorescing effects that are not equivalent to, and are usually greater than, those of the binary systems used in preparing the dilution standards. In consumer talcum pro ducts minerals such as talc, micas, chlorite, caicite, dolomite, and others tend to diminish reflection intensities of asbestiform minerals by sorbing X-rays or by contributing to background noise. Also, repeat runs on some selected specimens have demonstrated greater peak areas due to slight modifications in instrumental sellings (e.g., increase in receiving slit width). Therefore, the values for weight percent concentrations given in this report are conservative. Examination of the same consumer talcum products by both optical and transmission electron microscopy indicates that not all of the mater ials fall within the definition of fiber or asbestiform. For example, one consumer talcum product that contained more than 7% tremolite was observed to contain ooth fragmented tremolite grains by optical micro scopy and asbestiform fiber with 3:1 or greater iength-to-width ratio by transmission electron microscopy. Optical microscopy may provide useful information. However, more complete characterization can be obtained by electron microscopy and selected area electron diffraction. Using electron CONSUMER TALCUMS AND POWDERS 277 microscopy, for example, several samples of consumer talcum products exhibited both free amphibole fiber, discrete from talc grains, and, in addition, numerous small amphibole fibers were visible, apparently interlayered between talc or chlorite plates (see Fig. 6A). Preliminary examination of the asbestiform amphiboles by an electron microprobe technique has demonstrated that individual fiber chemistry is identical to those fibers encountered in the IARC Asbestos Standards (Timbrell and Rendall, 1971). On the basis of the mineralogicaf and chemical characterization of these products, all formulated prior to June 1973, we conclude that cosmetic grade talc was not used exclusively. The presence in these products of asbestiform anthophyllite and tremolite, chrysotile, and quartz indicates the need for a regulatory standard for cosmetic talc. This standard should be cognizant of talc complexities, mineralogica! and chemical in nature, and should provide for adequate analytical protocols to ensure monitoring. We also recommend that evaluation be made to determine possible health hazards associated with the use of these products. APPENDIX A: DEFINITIONS OF TERMS USED IN TEXT Asbestos "A name applied to a group of naturally fibrous minerals" (chrysotile, amosite, crocidolite, tremolite, anthophyllite cited by name) (Bureau of Mines, 1968). The term asbestos has also been applied to commercially exploited fibrous days, including attapulgite and palvgorskite (Whittaker, 1968). Asbestos implies current or possible exploitation, based on the presence of special physical and chemical properties, determined on the bulk sample level. For example, high fiber tensile strength, flexibility, low heat conductivity, high electrical resistance, and chem ical inertness are properties of asbestos. Noncommercial varieties of the same mineral may not possess the same qualities on the bulk level. For example, amosite has been considered to be the economically exploited variety of grunerite (Deer et al., 1962). If so, and even this is contested among mineralogists today, large macrocrystals are signifi cantly different physically and structurally. Grunerite fiber is rigid, amosite fiber is flexible; grunerite yieids well-defined single X-ray reflections with nonrotational film techniques, amosite yields multiple reflections as if rotated in the X-rav beam; grunerite appears to be a single crystal, amosite splays as if composed of strands. However, when ooth substances are pulverized, the resultant powder yields submicroscopic fibers, many of which are virtually indistinguishable on the basis of morphology, structure (determined bv selected area electron diffraction), and chemistry (determined by an electron probe 278 A. N. ROHL ET AL. technique). Amosite may be considered as an aggregate of unoriented, discrete, grunerite crystals with only the c axis in common alignment. Comminution of such aggregates produces fibers with character istics identical to those of single crystals of grunerite that have been similarly pulverized. Some workers have suggested that mechanical size reduction of amosite yields fibers with crystal growth surfaces rather than cleavage surfaces. Since amphibole cleavage tends to parallel prominent crystal face planes, such distinctions on the submicroscopic level may disappear. This appears to be the case for tremolite and anthophyllite as well. However, because no methods exist to distin guish between possible differences in fiber surface, we do not refer to anthophyllite and tremolite fibers in these talcums as asbestos. Instead they are referred to as asbestiform. It should be stressed, however, that evidence does not exist that would indicate that fibers with crystal growth surfaces or cleavage surfaces possess lesser or greater biological potential than fibers from commercial asbestos deposits. Asbestiform "Formed like or resembling asbestos; fibrous;.... (Bureau of Mines, 1968). The term is used herein for amphiboles (anthophyllite and tremolite) seen on both light and submicroscopic examination, which resemble comminuted asbestos varieties, on the basis of morphology. Essentially, when these fibers are derived from commer cial deposits we term them "asbestos" and when analytically identical fibers are found as noncommercial intrusions with the mineral taic, we term them "asbestiform." The use of two terms does not imply differences that can be analytically determined. Fiber "The smallest single strand of asbestos or other fibrous materials" (Bureau of Mines, 1968). We use this term in a broader sense. For example, chrysotile fibers are called fibrils, possessing unit diameters of about 200-400 A. Coherent bundles of fibrils are also called fibers. Fiber in the present text is used to denote any elongated single mineral unit visible on the light or electron microscopic level. The Occuoational Safetv and Health Administration has applied a 3:1 length-to-width ratio to distinguish fiber from mineral fragment. APPENDIX B: CRYSTAL CHEMISTRY, CRYSTAL STRUCTURE, AND GEOLOGICAL OCCURRENCE OF TALC Chemistry of Talc The empirical chemical formula of talc is Mgj Si4 O10 (OH):, but ferrous and ferric oxides, alumina, titania, soda, lime, and oxides of manganese have been reported in quantities up to several percents by CONSUMER TALCUMS AND POWDERS 279 weight. Titanium and aluminum appear to substitute for silicon, whereas iron, nickel, and manganese substitute for magnesium. Alkali metals are not readily accommodated in the structure and evidently occur as inter layer ions or as components of mineral impurities. For example, excess calcium may reflect the presence of the interlayer mineral phase tremoiite (Deer et al., 1962; Stemple and Brindley, 1960). One major talc deposit in the eastern United States contains substantial amounts of nickel, as much as 0.2%. Notwithstanding these minor components, talc is essentially (by weight) 32% MgO, 63% SiO-, and 5% structurally bound water. Talc Structure and Crystal Habit The three-layered crystal structure comprises a sheet of octahedrally coordinated Mg(OH)2 groups (the brucite layer) sandwiched between two planes of tetrahedrally linked Si04 groups (silica layers). Apical oxygens of the silica sheets are directed toward the brucite layer and in part re placed by hydroxyl groups, which form a portion of the inner structural unit. Valence balance is accomplished within the structure, so that there is a net zero charge on juxtaposed unit layers at the silica base interfaces. The basic unit of the talc structure was determined over 40 yr ago (Gruner, 1934; Hendricks, 1938), yet the repeated ceil geometry and space group were only recently resolved. X-ray single crystal patterns now indicate taic to be triclinic (Rayner and Brown, 1966; Ross et al., 1968). In addition to chemical and structural complexities, talc occurs with both plate and fiber habits (Ford, 1957). The development of the fibrous cyrstal form, with an elongated crystallographic 7-axis, may be a mani festation of ionic substitution since its refractive index is higher than platy talc (Fleischer and Osborn, 1957; Gruner, 1944). Talc that contains substantial amounts of these elongated forms is referred to in the mineralogical literature as fibrous talc. Similar observations with regard to the mineral brucite have been reported (Liebling and Langer, 1972) in which high iron content in the normally platy brucite is associated with the development of a fibrous habit. It is of interest to note that minnesotaite, considered by some to be an iron-rich form of talc, always occurs with a fibrous, or even a needle-like, habit (Gruner, 1944). Formation of Talc in the Laboratory of Nature In closely controlled experimental systems, talc has been synthesized (Bowen and Tuttle, 1949; Yoder, 1952). Bulk chemistry, water fugacitv, temperature, and pressure parameters are defined within extremely restrict ed limits and ranges to produce relatively pure crystallization products. However, in laboratory synthesis, just as in nature, coexisting mineral phases are produced if slight variations in any of the parameters are introduced. These phases include amhophylfite, serpentine, and in some instances tremoiite. ISO A. N. ROHL ET AL. Nature of Talc Plates Electron microscopic examination of talc minerals demonstrates that single talc grains consist of contiguous single crystals, mosaics of dis oriented crystallites, and intergrowths with other mineral phases, particu larly tremolite (Kleinfeid et al., 1973; Stemple and Brindley, 1960; Wright, 1960). Selected area electron diffraction patterns obtained on these objects display, in order, single crystal arrays, Debye-Scherrer rings, and superimposed complex patterns characteristic of intergrown single crystal phases. Talc and Mineral Intergrowths Tremolite is one common intergrowth in talc, and it requires relatively little energy thermodynamically to occur. Replacement of magnesium by calcium in the brucite layer may lead to structural as well as chemical modification (Bragg and Claringbull, 1965). Rotation of unit tetrahedra in talc forms double chains from sheets, readily accomplished by substitution of Mg(OH)2 by Ca(OH)2. The bulk chemistry is thereby changed from Mg6SigO:o)(OH)4 to Ca2MgsSigOI2(OH)j. The final structural array is remarkably similar in both materials; the crystallographic o-axis of talc is approximately 5.26 A, which corresponds with the c-crystallographic axis of tremolite (approximately 5.24 A); the b-axis for talc is approximately 9.10 A, which is equal to the /2-axis of tremolite; the c-axis of talc, approximately 18.8 A, is about equal to twice the p-dimension of tremolite (approximately 18.2 A). The monoclinic stacking angles, the beta-angle, are within a few degrees of each other. Intergrowths may form in which amphibole formation is not complete so that a mixed phase exists, referred to mineralogically as "talcboles." These are not as rare as once believed and may even be common in the more complex talc deposits. APPENDIX C: INDUSTRIAL AND COSMETIC GRADE TALCS Studies have demonstrated that industrial talc often consists of a variety of minerals, the utilization of which is based on physical properties rather than mineral composition (Hogue and Mallette, 1949; Schulz and Williams, 1942; Thompson, 1974; Wells, 1965). Early analyses of cosmetic talc also showed a wide range in mineral composition. Of six such products examined in one study, only 6-47% by weight of the inorganic material that constituted the product was the mineral talc; 14-51%, serpentine minerals; 5-77% carbonate minerals; 0-trace, quartz; 0-trace, tremolite; 3-12%, other minerals (Schulz and Williams, 1942). I CONSUMER TALCUMS AND POWOERS 281 APPENDIX D: BIOLOGICAL HAZARDS ASSOCIATED WITH TALC EXPOSURE A fine, diffuse, bilateral, progressive fibrosis was observed among miners and millers of tremolite talc in Georgia (Dreessen, 1933; Dreessen and. Dalla Valle, 1935). Siegal et al. (1943) studied a population of workers mining and milling tremolite and anthophvllite-bearing talc deposits in New York state. In addition to the bilateral fibrosis, pleural piaques, similar to those encountered in asoestos workers, were observed. Review of postmortem material in this study indicated that asbestos bodies were present in lung tissue. These findings were also reported in cases of severe pneumoconiosis in tremolite millers by Daymon (1946), and by Porro and Levine (1946). Millman (1947) reported that exposure to cosmetic-grade talc pro duced nodular fibrosis in workers. No quartz was detected in the dust. The author concluded that talc itself was capable of producing scarring. The observation was supported in studies by Reichman (1944) and by Wyers (1949) and in a study of talc miners and millers in Italy where exposure to pure talc produced a 10% incidence of pneumoconiosis in workers (Parmeggiani, 1948). Excess deaths attributed to pneumoconiosis have been reported among workers in northern Italy mining talc con sidered to be free of asbestiform fibers (Rubino et ai., 1976). Some investigators have held that fibrous talcs (not differentiated as talc or asbestos fiber) are biologically more hazardous than platy talcs. For example, in a review of the literature by Porro et al. (1942), Gloyne and Gardner are referred to as considering that the clinical, radiological, and pathological disease states of asbestosis and talcosis are very similar. There are several reports of the occurrence of asbestos bodies in the lung tissue of workers exposed to talc (Daymon, 19^6; Hobbs, 1950; Kleinfeld et al.. 1973; McLaughlin et a!., 1949; Porro et al., 1942). Several studies suggest, that fibrous tales are more dangerous as a result of the included asbestos fiber. For example, McLaughlin et al. (1949) compared fibers in talc with the proportion of fibers recovered from the lung tissue of an exposed worker. A larger concentration of fibers was found in the tissues as compared with the raw talc. Talc pneumoconiosis was reaffirmed by Kleinfeld and Messite (I960) in their study of the New York state talc workers. In a study by Kleinfeld et al. (1967) it was demonstrated that talc pneumoconiosis accounted for almost 30% of excess deaths among the talc miners and millers. Most of these were due to the complication of pneumoconiosis, cor pulmonale. However, 21% of the 91 deaths recorded were due to malignant tumors: lung carcinoma, pleural fibrosarcoma, and stomach, colon, rectum, and pancreatic cancers. A peritoneal meso thelioma was reported as well. In addition to these tumors, retroperitoneal sarcoma, hepatoma, and leukemia were also found. Statistical evaluation of 282 4.. N. ROHL ET AL. these data indicated that a 3- to 4-fold excess of cancers existed in this group, as compared to a matched control population. The biological activity of both tremolite and anthophyliite fibers has been known for some time, and both have been cited as asbestos minerals by Merewether (1930) and Noro (1946). Asbestos disease among workers (and others exposed to anthophyliite and tremolite) has been reported (Burilkov and Badajov, 1970; Kiviluoto, 1960; Meurman, 1968; Meurman et al., 1974; Schepers, 1965; Wegelius, 1947; Weiss and Boettner, 1967). Recent experimental data also indicate that tremolite fibers are biologically active (Graham and Graham, 1967). Some investigators have suggested that inorganic fiber frbrogenicity and carcinogenicity is limited only by its ability to reach the alveolar space (Holt et al., 1965; Pott and Friedrichs, 1972; Pott et al., 1974; Robock and Klosterkotter, 1976; Stanton and Wrench, 1972). Wagner et al. (1975) reported lung scarring in Wistar rats with pure talc, exposed by inhalation. The severity and extent of the lung scarring was comparable to that produced by chrysolite asbestos under identical experimental conditions. In addition to lung scarring, ingestion of talc was reported to be associated with leiomyosarcoma of the stomach as well as one adenoma and several sarcomas of the uterus. However, the exposure levels were high and the numbers of observed tumors small, so that statistical validation of the carcinogenic potential of pure talc and its relevance to human exposures were not achieved. There are also extensive data concerning hazards associated with exposure to silica or trace metals, particularly nickel and chromium (National Research Council, 1975). Analytical data are presented here that suggest possible disease potential and the need for investigation in these areas. REFERENCES Bowen, N. L. and Tuttie, 0. F. 1949. The system MgO-SiO,-H,O: Bull. Geo/. Soc. Am. 60:439-460. Bowes, 0. R. and Linger, A. M. 1974. Petrochemistry of the Manhattan Formation. Kristalinikum 10:39-52. Bragg, R. H. 1967. Quantitative analysis by powder diffraction. In Handbook of X-rays. New York: McGraw-Hill. Bragg, L. and Ciaringbull, G- F. 1965. The crystal structure of minerals. London: Bell and Sons. Brindley. G. W. and Kurtossy, S. S. 1961. Quantitative determination of kaoLmte by x-ray diffraction. Am. Mineral. 46:1205-1215. Bureau of Mines. 1968. Dictionary of mining, mineral and related terms, ed. F. W. Thrush. Washington, D.C: U.S. Government Printing Office. Burilkov. T. and Badajov, L- 1970. Ein Beitrag zum endemischen Auftreten doppelsettiger Pleuraverkalkungen. Prax. Pneumal. 24:433-438. C.-alley, Key, M. M., Groth, O. H., Lainnart, W. S. and Ligo R. M. 1968. Fibrous and mineral content of cosmetic talcum oroducts. Am. Ind. Hyg. Assoc, j. 29:350-354. Cullitv, B. D. 1956. Siements of X-ray diffraction. Reading, Mass.: Addison-Weslev. Oaymon. H. 1946. Latent silicosis and tuberculosis. Am. Rev. Tuberculosis 53.5S4-559. CONSUMER TALCUMS AND POWDERS 283 Deer, W, A.. Howie, R. A. and Zussman, ). 1962. Rock-forming minerals, vot. 3, Sheet silicates, Op. 203-374, Mew York: Wiley. Oreessen, W. C. 1533. Effeeis of certain silicate dusts irs the lungs. /. Inaust. Hvg. 15:66-78. Oreessen, W. C. and Oalla Valle, |. M, 1935, The effects of exposure to dust in two Georgia talc mills and mines. Publ. Health Repts. 50:1405-141S. Fleischer, S. S. and Osborn, E. F. 1957. Studies of the system iron oxide-silica-water at low oxygen partial pressures. Scan. Geol. 52:923-943. Ford, IV. E. 195*. Dana's textbooR of mineralogy. New York: Wilev. Granam, j. and Graham, R. 1967, Ovarian cancer and asbestos. Environ. Res. 1:115-128. Gruner, |. W. 1934. The crystal structure of talc and pyrophyllite. Zeit. Krist. 88:412-119. Gruner, J. W. 1944. The composition and structure of minnesotaite, a common iron silicate in iron formations. Am. Mineral. 29:363-372. Hendricks, S. B. 1938. On the crystal structure of talc and ovroohvllite. Zeit. Krist. 99:264-274. Hildick-Smith. G. 1976. Talc: Review of epidemiologic studies. Proc. Br. Occup. Health Sac., Edinburgh, Sept. 19 75. In press. Hobbs, A. A. 1950. A type of pneumoconiosis. Am. J. Roentgenol. Radiol. Therap. 58:488-497. Hogue, W. L and Mallelte, F. S. 1949. A study of workers exposed to talc and other dusting compounds in the rubber industry. /. Indust. Hyg. Toxicol. 31:359-364. Holt, P. F., Mills, J, and Young, 0. X. 1965. Experimental asbestosis with four types of fibers: Importance of small particles. Ann. N.Y, Acad. 5ci. 132:87-98. Hurlbut, C. S.. |r. and Williams, O. R. 1935. The mineralogy of asbestos dust. / Indust. Hyg. 17:289-293. " Kiviluoto, R. 1960. Pleural calcification as a roentgenologic sign of non-occupationai endemic amhopnyllite asbestosis: Aero Rod. Scand. 194:1-67. Kleinfeld. M. and Messite, J. 1960. Problem areas in pneumoconiosis. Arch. Environ. Health 5:428-437. Kleinfeld, M., Messite, )., Kooyman, O. and Zaki. M. H. 1967. Mortality among talc miners and millers in New York State. Arch. Environ. Health 14:663-667. Kleinfeld, M., Messite, |. and Langer, A. M. 1973- A study of workers exposed to asbestiform minerals in commercial talc manufacture. Environ. Res. 6:132-143. Klug, H. P. and Alexander. L. E. 1954. X-roy diffraction procedures. New York: Wilev. Langer, A. M. and Poolev, F. D. 1973. Identification of single asbestos fibers in human tissues. In Proceedings on tne biological effects of asbestos, ed. Bogovskv et ai., pp. IIS-125. Lyon: IARC. Langer, A, M.. tt al. 1973. Identification of asbestos in human tissues. /. Occup. Med. ' 5i 3): 287-295. Liebiing, R. S. and Langer, A. M. 1972. Optical properties of 'ibrous brucite from Asbestos, Quebec. Am. Mineral. 57:857-864. McLaughlin, A., Rogers, E. and Dunham, K. C. T949. Talc pneumoconiosis- Br. /. indust. Vfecr. 6:184-194. Merewetner, E. R. 4. 1930. The occurrence of pulmonary fiorosis and other culmonarv affections in asbestos workers. /. Ind. Hyg. 12:198-222, 239-257. Meurman, L- Q. 1968. Pleural fibrocalcific plaques and asbestos exposure. Environ. Res. 2:30-46. Meurman, L. O., Kiviluoto. R. and Hakama, M. 1974. Mortaiin and morbidity among working populations of anthophvllite asbestos miners in Finland. Sr. i. Indust. Med. 31:105-1 12. Miliman. N. 1974. Pneumoconiosis due to talc in the cosmetic industry. Occup. Med. 4-391-394. National Researcn Council. 1975. HieMel. Washington. D.C.: National Academy of Sciences. Noro, L. 1946. On the history of asbestosis. Acra Pathol. Microa-'o . Scand. 23:53-59. Pirmeggiam. L. 1948. Le pneumocomost dei mmatort e aei mugr.ai del talco nei Pinerolese. P.ass. 1led. Ind. 17-16-17. Porro. F. W. ana Levine, N. M. 1946. Pathology of talc pneumoconiosis with report of an autopsy. form. V. Y. State Med. /. 3:23-25. 284 A. N. ROHL ETAL. Porro, F. W., Patton, R. and Hobbs, A. A. 1942. Pneumoconiosis in the talc industry. Am. j. Roentgenol. 47:507-524. Pott, F. and Friedrichs, K. H. 1972. Tumoren der Ratte nach i.p. Injektion faserformiger Staube. Naturwissenschaften 59:318. Pott, F., Huth, F. and Friedrichs, K. H. 1974. Tumorigenic effects of fibrous dust in experimental animals. Environ. Health Persp. 9:313-315. Ravner, J. H. and Brown, G. 1966. Triclinie form of taic. Nature 212:1352-1353. Reichman, V. 1944. Uber Talkumstaublunge. Arch. Cewerbepathoi. Gewerbehyg. 12:319-322. Robock, K. and Klosterkbtter, W, 1976. The biological effect of dusts of asbestos and asbestos cement products. Proc. 3r. Occup. Health Soc., Edinburgh, Sept. 1975. In press. Roht, A. N. and Langer, A. M. 1974. Identification and Quantitation of asbestos in talc. Environ. Health Persp. 9:95-109. Ross, M., Smith, W. l_ and Ashton, W. H. 1968. Tridinic talc and associated amphiboles from Gauverneur Mining Oistrict, New York. Am. Mineral. S3:7S1-769. Rubino, G. F., Scansetti, G., Piolatto, G. and Romano, C A. 1976. Mortality study of talc miners and millers. /. Occup. Med. 18:186-193. Schepers, G. W. H. 1965. Discussion. Epidemiology of mesotheliai tumors in the London area. Ann. .V. Y. Acad. 5c/. 1 32:579-602. Schulz, R. Z. and Williams, C R. 1942. Commercial taic, animal and mineral studies./. Ind. Hyg. 24:75-82. .. Siegal, W., Smith, A. R. and Greenburg, L 1943. The dust hazard in tremolite taic mining, including roentgenological findings in talc workers. Am. /. Roentgenol. 4:11-29. Stanley, H. D. and Norwood, R. E. 1973. The detection and identification of asbestos and asbestiform materials m taic. Unpublished report for Pfizer, Inc, Stanton, M. F. and Wrench, C. 197X Mechanisms of mesothelioma induction with asbestos and fibrous glass. /. Natl. Cancer Inst. 48:797-821. Stemple. I. 5. and Brindley, G. W. I960. Structural study of talc and talc-tremolite relations. /. Am. Ceramic Soc. 43:34-42. Thompson, C. S. 1974. Discussion of the mineralogy of industrial tales. US. Bur. Mines Cite. 1C-363. 22-44. Timrell, V. and Rendall, R. E. G. 1971. Preparation of the LfICC (IARC) standard reference samples of asbestos. Powder Techno!. 5:279-287. Wagner, J. C, Berry, G., Cooke, T. J., Hill, R. )., Pooley, F. D. and Skidmore, J. W. 1975. Animal experiments with ale. Proc. Sr. Occup. Health Soc., Edinburgh, Sept. J975. In press. Wegelius, C- 1947. Changes in the lungs in 126 cases of asbestosis observed in Finland. Acta Radiol. 28:139-152. Weiss, S. and Boettner, E. 1967. Commercial talc and talcosis. Arch. Environ. Health 14:304-308. Wells, ). R. 1965. Talc, soapstone and pyrophvllite. In Mineral facts and problems. Washington, D.C.: Government Printing Office. Whittaker, E. ). W. 1968. The crystal chemistry of the amphiboles. Acta Crystal. 13:291-298. Wright. H. D. 1960. Optical study of talc-tremolite relations. /. Am. Ceramic Soc. 43:42-43. Wvers, H. 1949. Asbestos. Postgrad. Med. /. 631-638. Yoder, H. S. 1952. The MgO-AI, 0,-SiQ, -H, 0 system and related metamorphie facies. Am. /. Sci., Bowen Mem. Vo1. 569-627. Received April 26, 197$ Accepted August 13, 1976 Asbestos in Talc by Arthur N. Rohr Environmental Health Perspective! Vol. 9. pp. U9-IU. 1971 Talc deposit* include asbestos minerals such as chrysotile and amphiboles that may be carried over into consumer products. Optical microscopy and x-ray diffraction analyses may not reveal their presence. Examples are given of electron microscopy procedures that permit detection and measurement. The mineral talc is a hydrous magnesium sheet silicate that occurs in both platy and fibrous crystal forms. Talc tends to occur in rock masses coexisting with a number of other hydrous magnesium silicate minerals. Typical ly, talc deposits consists of fine-grained, intergrown mixtures of minerals which may con tain considerable amounts of asbestos. In addi tion, talc deposits often show complex mineral zonation, which adds to the difficulty of selec tive mining. For example, in the talc deposits of the Gouveneur District of New York State, talc occurs with the asbestos minerals chrysotile, tremolite, and anthophyllite in addition to other silicate minerals. Since the mining of talc rock almost in variably includes the mining of asbestos as well, the asbestos contaminant may be carried over into the consumer product and thus introduce the risk of asbestos disease. This possibility leads to an important public health question: is asbestos present in consumer talcs, and if pre sent, which mineral fibers and in what concen trations? Among the standard mineralogies! tech niques which may be used for identification and quantitation of asbestos in talc are optical microscopy, x-ray diffraction, and electron microscopy (EM). Optical microscopy, employing polarized light optics, is useful for determining the optical Environmental Sciences Laboratory, Mount Sinai School of Medicine, New York, N.Y. 10029 properties of particles. However, in the instance of talc, the extremely fine grained intergrowths of different minerals and the extensive overlap ping and similarities of their optical properities limit this technique to a preliminary or screen ing function. Since large numbers of fibers may go undetected, optical microscopy would not be capable of quantitative analysis. X-ray powder diffraction is a routine tech nique for analyzing crystalline materials. It is relatively simple in principle, but the results may be difficult to interpret. The limitations of precision and accuracy must be given careful consideration. The identification and quantitation of asbestos fibers in talc by x-ray diffraction may be achieved by comparison of known dilutions (fiber type and quantity) of asbestos in a talc matrix with unknowns. The preparation of stan dard dilutions of asbestos minerals in talc for quantitative analysis requires: (1) a talc matrix completely free of contaminating asbestos minerals, (2) pure asbestos fiber as the sought adventitious phase, (3) a preparation method for insuring homogeneity and reproducibility of the standard dilution material, and (4) selection of x-ray reflections with no superimposed in terferences. Condition (1) requires the selection of pure talc matrix material. In the first stage of screening, material was first scanned by x-ray diffraction to identify the major mineral phases rapidly, especially asbestos minerals. If no asbestos phases were detected, the material was December 1974 re-examined in a more sensitive mode of x-ray diffraction called step scanning, and finally by electron microscopy. In this way a pure talc was selected (pure with respect to asbestos; small amounts of chlorite and phlogopite mica were tolerated). In a similar way, pure samples of anthophyllite, tremolite, and chrysotile were screened and selected for use in preparing the talc-asbestos standard dilutions. In x-ray diffraction the reproducibility of reflection intensities is strongly influenced by the degree of cleavage of crystalline powders. The minerals under investigation exhibit a high degree of platy and fibrous cleavage. A number of preparation techniques have been developed for reducing preferred orientation effects. These were tested, but none were found to give satisfactory reproducibility. Accordingly a technique was developed and employed which gives a high degree of sensitivity for substances present in minute quantities and with a greater level of reproducibility of reflection intensities. Binary systems of three asbestos minerals in talc were prepared at varying levels of dilution concentrations. Standard weights of these mix tures were dispersed in water with ultrasonic energy to disperse the phases homogeneously. This slurry was filtered through a membrane filter by use of a hypodermic syringe (Fig. 1). The residue forms a flat cake which is mounted for x-ray analysis. This technique has the ad vantage of uniformly preparing, mounting and measuring the talc-asbestos dilutions under identical conditions. Because of the structural similarities between some of the minerals, there was considerable overlapping or interference in many reflections, and this made it necessary to select reflections which could be unambiguously used as indices of the amount of each mineral present. These diagnostic reflections were step-scanned at 0. 01 29, in a fixed-count mode. This permits the weak reflections produced at low dilution levels to be determined with precision. From the fixedcount data a profile of the diagnostic reflection is obtained and the area above background is taken to be proportional to the reflection inten sity. The results of these analyses are given in Table 1, which shows that: chrysotile at dilution levels less than 0.25% was not detected, tremolite was detected down to 0.1% dilution level, and anthophyllite was not detected at com centrations below 2.0% (diagnostic reflection is at 8.26 A; I/I. = 55). In order to determine the number of chrysotile fibers present at various dilution levels, aliquots of the various dilutions were prepared for EM scanning. A fairly standard technique called the rubout method was used. For each dilution level, 20 fields from three EM grids are photographed at constant magnifica tion and the number of long unit fibrils per field are counted from printed enlargements (Figs. 2 and 3). These fiber counts show fairly good correlation with levels of chrysotile dilution. By using the fiber count data, it is possible to calculate the number of fibers in a unit weight of sample. Thus, at a 1% dilution level there would be about 40 X 10s fibers/mg. Even at the lowest level of detection by x-ray diffraction, 1. e., 0.25%, there would be about 10* fibers/mg. Cosmetic talcum powder, for example, which had been step-scanned and chrysotile not found might contain billions of fibers released during dusting with a half-gram dose. Thus, very large numbers of asbestos fibers may be present in talc end products, yet they re main undetected if only optical microscopy and x-ray diffraction are used. On the other hand, EM can be a very sensitive method for detecting extremely minute amounts of asbestos in talc. , Figure 1. Membrane filter holder-hypodermic syringe system of sample preparation. 130 Environmental Health Perspectives Table I. Comparison of lower limits of detection of asbestos minerals in talc by step scanning and continuous scanning. Asbestos Diagnostic mineral reflection, A Chrysotiie 3.66 Tremolite 8.38 Anthophyllite 8.26 Detection limit concentration.% Step scanning Continuous scanning (o.or 20)J d' 20/mini1' 0.25 2.0 0.10 2.0 2.0 4.0 ` Operating conditions: fixed count rate = 2000; 45 kV, 20 mA. 11 Operating conditions: 500 counts/sec; time constant = 2.0; 45 kV, 20 mA. Figure 2. Electron photomicrograph of chrysotile-talc (99% talc, 1% chrysotiie). December 1974 131 3 El""" - h, ,. ,, dm>uirt 132 Environmental Health Perspectives