Assessment of worst-case potential airborne asbestos exposure associated with the use of cosmetic talc: application of an exponential decay model.

Talc is used in cosmetic products to confer desirable properties, such as moisture absorption and smooth texture, to the finished products. Concerns have been raised about the potential presence of asbestos in products containing cosmetic talc. Reconstruction of potential asbestos exposure from the use of cosmetic talc products (assuming a trace level of asbestos) requires consideration of consumer use patterns. Although application generally only lasts seconds, exposure theoretically may continue if the consumer remains in the immediate vicinity. Most published exposure measurements have not adequately characterized the potential for continued exposure. In this analysis, estimates and measurements of airborne asbestos fiber concentrations associated with cosmetic talc use from 10 published studies were used as inputs to an exponential decay model to estimate "worst-case" exposure during and following application. The resulting geometric mean 30-min time-weighted average (TWA) concentrations were 0.006 f/cc for both puff and shaker application, for diapering, 0.0001 f/cc (adult applying baby powder) and 0.0002 f/cc (infant), and for makeup application, 0.0005 f/cc. Application of an exponential decay model to measured or estimated asbestos concentrations associated with the use of cosmetic talc products yields a conservative means to comprehensively reconstruct such exposures. Moreover, our results support that, if a cosmetic talc powder product contained a trace level of asbestos fibers, the "worst-case" airborne asbestos exposure associated with its application is low.

Holton et al., Characterization of asbestos exposures associated with the use of facial makeups. Risk Analysis, 42, 2129-2139.

Holton and colleagues have performed a risk assessment after measuring asbestos released from several samples of facial makeup. Unfortunately, it is not possible to interpret or generalize their findings because the authors have not described the source(s) of the talc tested or the asbestos concentrations of the samples. The concentration of amphiboles varies widely between sources, and the authors are urged to divulge the locations of the ore bodies providing the talc for their samples, as well as the asbestos concentration of the samples, so that the results may be interpreted and possibly generalized.

Analytic comparison of talc in commercially available baby powder and in pelvic tissues resected from ovarian carcinoma patients.

OBJECTIVE: Measure the size and shape of talc particles in talcum powder and compare this data to the size and shape of talc particles found in surgically resected tissues from patients with ovarian carcinoma. METHODS: Using polarized light microscopy (PLM) and scanning electron microscopy (SEM), we measured the size and shape of talc particles in samples of talc-containing baby powder (TCBP) and surgically resected pelvic tissues (hysterectomies) from talc-exposed patients with ovarian carcinoma. RESULTS: The most frequent class of particles in TCBP can be unequivocally identified as talc, using both polarized light microscopy and scanning electron microscopy with energy dispersive X-ray analysis (SEM/EDX). The talc particles found in resected tissues from ovarian carcinoma patients are similar in size and shape to the most abundant morphological class of particles in TCBP. CONCLUSIONS: This finding, combined with previous epidemiological literature and tissue-based analytical studies, provides further evidence that the small, isodiametric particles that dominate TCBP can migrate from the perineum and become lodged in distal structures in the female reproductive tract, where they may lead to an increased risk of developing ovarian carcinoma.

Malignant mesothelioma following repeated exposures to cosmetic talc: A case series of 75 patients.

BACKGROUND: Asbestos is the primary known cause of malignant mesothelioma. Some cosmetic talc products have been shown to contain asbestos. Recently, repeated exposures to cosmetic talc have been implicated as a cause of mesothelioma. METHODS: Seventy-five individuals (64 females; 11 males) with malignant mesothelioma, whose only known exposure to asbestos was repeated exposures to cosmetic talcum powders, were reviewed in medical-legal consultation. Out of the 75 cases, 11 were examined for asbestiform fibers. RESULTS: All subjects had pathologically confirmed malignant mesothelioma. The mean age at diagnosis was 61 ± 17 years. The mean latency from exposure to diagnosis was 50 ± 13 years. The mean exposure duration was 33 ± 16 years. Four mesotheliomas (5%) occurred in individuals working as barbers/cosmetologists, or in a family member who swept the barber shop. Twelve (16%) occurred in individuals less than 45 years old (10 females; 2 males). Forty-eight mesotheliomas were pleural (40 females; 8 males), 23 were peritoneal (21 females; 2 males). Two presented with concomitant pleural and peritoneal disease. There was one pericardial, and one testicular mesothelioma. The majority (51) were of the epithelioid histological subtype, followed by 13 biphasic, 8 sarcomatoid, 2 lymphohistiocytoid, and 1 poorly differentiated. Of the 11 individuals whose nontumorous tissues were analyzed for the presence of asbestiform fibers, all showed the presence of anthophyllite and/or tremolite asbestos. CONCLUSIONS: Mesotheliomas can develop following exposures to cosmetic talcum powders. These appear to be attributable to the presence of anthophyllite and tremolite contaminants in cosmetic talcum powder.

Talc and mesothelioma: mineral fiber analysis of 65 cases with clinicopathological correlation.

Malignant mesothelioma is strongly associated with prior asbestos exposure. Recently there has been interest in the role of talc exposure in the pathogenesis of mesothelioma. We have analyzed lung tissue samples from a large series of malignant mesothelioma patients. Asbestos bodies were counted by light microscopy and mineral fiber concentrations for fibers 5 µm or greater in length were determined by scanning electron microscopy equipped with an energy dispersive spectrometer. The values were compared with 20 previously published controls. Among 609 patients with mesothelioma, talc fibers were detected in 375 (62%) and exceeded our control values in 65 (11%). Elevated talc levels were found in 48/524 men (9.2%) and 17/85 women (20%). Parietal pleural plaques were identified in 30/51 informative cases (59%) and asbestosis in 5/62 informative cases (8%). Commercial amphiboles (amosite and/or crocidolite) were elevated in 52/65 (80%) and noncommercial amphiboles (tremolite, actinolite or anthophyllite) in 41/65 (63%). Both were elevated in 34/65 (52%). Asbestos body counts by light microscopy were elevated in 53/64 informative cases (83%). A history of working in industries associated with asbestos exposure and increased mesothelioma risk was identified in 36/48 cases in men, and a history of exposure as household contacts of an occupationally exposed individual was identified in 12/17 cases in women. We conclude that among patients with mesothelioma, the vast majority have talc levels indistinguishable from background. Of the remaining 11% with elevated talc levels, the vast majority (80%) have elevated levels of commercial amphibole fibers.

Asbestos in commercial indian talc.

BACKGROUND: Easily available commercial Indian talc products widely used in Southeast Asia were examined for the presence of asbestos. Asbestos in talc products carry all risks of asbestos-related disease. METHODS: Using polarizing light microscopy, transmission electron microscopy (TEM), electron diffraction, and X-ray analysis, multiple over-the-counter Indian talc products were examined for the presence of asbestos. RESULTS: Results In an initial group of five Indian talc products, one was found to contain tremolite asbestos. The second group of eight products was tested and six of eight contained tremolite asbestos as well. No other regulated amphibole was found. CONCLUSION: Large quantities of body talc products containing asbestos are used throughout Southeast Asia and are likely to pose a public health risk for asbestos-related diseases, especially for the cancers related to asbestos exposure. The country of origin in which the talc examined was sourced for production is unknown to the authors, and further investigation to measure associated public health risk is needed.

Magnesium/silicon atomic weight percent ratio standards for the tissue identification of talc by scanning electron microscopy and energy dispersive X-ray analysis.

Talc may lodge in human tissues through various routes, and has been associated with the development of ovarian carcinoma in case control epidemiologic studies. Talc is detected in tissues with scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDS), with expected magnesium (Mg) and silicon (Si) peaks. The theoretical atomic weight % Mg/Si ratio for talc is 0.649, and for diagnostic purposes, a range of ± 5% (~0.617 to 0.681) is often used as a standard. Our goal was to establish empirically the quantitative range for talc identification by SEM/EDS using two source materials: a Johnson's Baby PowderTM (cosmetic-grade) consumer sample, and talc from Sigma-Aldrich (particle-grade material intended for scientific use). We examined 401 Mg-Si particles with SEM/EDS across the two samples, using two different SEM microscopes. Overall, we found a mean Mg/Si atomic weight % ratio of 0.645, with minimal differences between study subsets. The standard deviation was 0.025; (± 1σ = 0.620-0.670). The currently used ± 5% diagnostic range (Mg/Si 0.617-0.681) is thus reasonably close to this study's ± 1σ range, and well within a ± 2 σ confidence interval span (Mg/Si 0.595-0.695). The ± 5% range is thus an appropriately conservative standard whose continued use seems justified.

Identification of Foreign Particles in Human Tissues Using Raman Microscopy.

The goal of this study was to precisely and unambiguously identify foreign particles in human tissues using a combination of polarized light microscopy and Raman microscopy, which provides chemical composition and microstructural characterization of complex materials with submicrometer spatial resolution. This identification for patient care and research has been traditionally studied using polarized light microscopy, electron microscopy with X-ray analysis, and electron diffraction, all with some limitations. We designed a model system of stained and unstained cells that contained birefringent talc particles and systematically investigated the influence of slide and coverslip materials, laser wavelengths, and mounting media on the Raman spectra obtained. Hematoxylin and eosin stained slides did not produce useful results because of fluorescence interference from the stains. Unstained cell samples prepared with standard slides and coverslips produce high quality Raman spectra when excited at 532 nm; the spectra are uniquely assigned to talc. We also obtain high quality Raman spectra specific for talc in unstained tissue samples (pleural tissue following talc pleurodesis and ovarian tissue following long-term perineal talc exposure). Raman microscopy is sufficiently sensitive and compositionally selective to identify particles as small as one micrometer in diameter. Raman spectra have been catalogued for thousands of substances, which suggests that this approach is likely to be successful in identifying other particles of interest in tissues, potentially making Raman microscopy a powerful new tool in pathology.

Assessment of Health Risk from Historical Use of Cosmetic Talcum Powder.

This study's objective is to assess the risk of asbestos-related disease being contracted by past users of cosmetic talcum powder.  To our knowledge, no risk assessment studies using exposure data from historical exposures or chamber simulations have been published. We conducted activity-based sampling with cosmetic talcum powder samples from five opened and previously used containers that are believed to have been first manufactured and sold in the 1960s and 1970s.  These samples had been subject to conflicting claims of asbestos content; samples with the highest claimed asbestos content were tested.  The tests were conducted in simulated-bathroom controlled chambers with volunteers who were talc users.  Air sampling filters were prepared by direct preparation techniques and analyzed by phase contrast microscopy (PCM), transmission electron microscopy (TEM) with energy-dispersive x-ray (EDX) spectra, and selective area diffraction (SAED).  TEM analysis for asbestos resulted in no confirmed asbestos fibers and only a single fiber classified as "ambiguous."  Hypothetical treatment of this fiber as if it were asbestos yields a risk of 9.6 × 10-7 (under one in one million) for a lifetime user of this cosmetic talcum powder.  The exposure levels associated with these results range from zero to levels far below those identified in the epidemiology literature as posing a risk for asbestos-related disease, and substantially below published historical environmental background levels.  The approaches used for this study have potential application to exposure evaluations of other talc or asbestos-containing materials and consumer products.

Asbestos in organochlorine insecticide powder sprinkled between pages of antiquarian books in a library in Japan.

Librarians at a university had planned to check the collection prior to the library renovations that began in 2015. They had previous knowledge of the presence of a light greyish-white powder with an unpleasant odour (hereinafter referred to as 'powder') sprinkled between the pages of antiquarian books in the library archive. The purpose of this study was to identify this powder with the help of experts from both inside and outside the university. The powder was qualitatively analysed using gas chromatography with mass spectrometry after hexane extraction. The powder was examined under a polarised light microscope and a field-emission scanning electron microscope equipped with an energy-dispersive X-ray spectrometer. Benzene hexachloride (BHC) was detected in the powder. Talc was the most abundant particle in the powder. The powder also contained 0.52 wt% asbestos, which belonged to the tremolite-actinolite series. No other types of asbestos were detected. The powder was presumed to be a bulking agent for BHC, and its major constituent was talc. This is the first report on asbestos-containing insecticides.

Identification and quantitative detection of illegal additives in wheat flour based on near-infrared spectroscopy combined with chemometrics.

As a common food raw material in daily life, the quality and safety of wheat flour are directly related to people's health. In this study, a model was developed for the rapid identification and detection of three illegal additives in flour, namely azodicarbonamide (ADA), talcum powder, and gypsum powder. This model utilized a combination of near-infrared spectroscopy with chemometric methods. A one-dimensional convolutional neural network was used to reduce data dimensionality, while a support vector machine was applied for non-linear classification to identify illegal additives in flour. The model achieved a calibration set F1 score of 99.38% and accuracy of 99.63%, with a validation set F1 score of 98.81% and accuracy of 98.89%. Two cascaded wavelength selection methods were introduced: The first method involved backward interval partial least squares (BiPLS) combined with an improved binary particle swarm optimization algorithm (IBPSO). The second method utilized the CARS-IBPSO algorithm, which integrated competitive adaptive reweighted sampling (CARS) with IBPSO. The two cascade wavelength selection methods were used to select feature wavelengths associated with additives and construct partial least squares quantitative detection models. The models constructed using CARS-IBPSO selected feature wavelengths for detecting ADA, talcum powder, and gypsum powder exhibited the highest overall performance. The model achieved validation set determination coefficients of 0.9786, 0.9102, and 0.9226, with corresponding to root mean square errors of 0.0024%, 1.3693%, and 1.6506% and residual predictive deviations of 6.8368, 3.5852, and 3.9253, respectively. Near-infrared spectroscopy in combination with convolutional neural network dimensionality reduction and support vector machine classification enabled rapid identification of various illegal additives. The combination of CARS-IBPSO feature wavelength selection and partial least squares regression models facilitated rapid quantitative detection of these additives. This study introduces a new approach for rapidly and accurately identifying and detecting illegal additives in flour.

Pneumoconiosis and malignant mesothelioma in a family operated metal casting business that used industrial talc from New York state.

BACKGROUND: The United States is second only to the People's Republic of China in annual talc production. U.S. talc is used in the production of ceramics, paint, paper, plastics, roofing, rubber, cosmetics, flooring, caulking, and agricultural applications. A number of U.S. talc deposits consistently contain talc intergrown with amphiboles such as tremolite and/or anthophyllite. It has long been recognized that miners and millers of talc deposits are at risk for pneumoconiosis and it has recently been reported that it is prudent, on the balance of probabilities, to conclude that dusts from New York State talc ores are capable of causing mesothelioma in exposed workers. This is a report of the diagnosis of pneumoconiosis and mesothelioma in a husband and wife who operated a small metal casting business that used industrial talc from New York as a parting agent. METHODS: Case reports, including medical records and exposure histories, were provided by an attorney who had also commissioned laboratory investigation of the industrial talc product used in the factory. RESULTS: Mrs X was diagnosed with pneumoconiosis characterized by interstitial fibrosis and heavily calcified pleural plaques. Mr X had calcified pleural plaques and developed a fatal pleural mesothelioma. Samples of the industrial talc contained fibrous tremolite and anthophyllite. CONCLUSIONS: The author concludes that end users of industrial talc from New York State may be at risk of pneumoconiosis and malignant disease. End users of talcs from other regions of the United States, where talc formation arose from processes driven by regional metamorphism, might also be at risk.

Evaluation of tremolite asbestos exposures associated with the use of commercial products.

Tremolite is a noncommercial form of amphibole mineral that is present in some chrysotile, talc, and vermiculite deposits. Inhalation of asbestiform tremolite is suspected to have caused or contributed to an increased incidence of mesothelioma in certain mining settings; however, very little is known about the magnitude of tremolite exposure that occurred at these locations, and even less is known regarding tremolite exposures that might have occurred during consumer use of chrysotile, talc, and vermiculite containing products. The purpose of this analysis is to evaluate the exposure-response relationship for tremolite asbestos and mesothelioma in high exposure settings (mining) and to develop estimates of tremolite asbestos exposure for various product use scenarios. Our interpretation of the tremolite asbestos exposure metrics reported for the Thetford chrysotile mines and the Libby vermiculite deposits suggests a lowest-observed-adverse-effect level (LOAEL) for mesothelioma of 35-73 f/cc-year. Using measured and estimated airborne tremolite asbestos concentrations for simulated and actual product use, we conservatively estimated the following cumulative tremolite asbestos exposures: career auto mechanic: 0.028 f/cc-year; non-occupational use of joint compound: 0.0006 f/cc-year; non-occupational use of vermiculite-containing gardening products: 0.034 f/cc-year; home-owner removal of Zonolite insulation: 0.0002 f/cc-year. While the estimated consumer tremolite exposures are far below the tremolite LOAELs derived herein, this analysis examines only a few of the hundreds of chrysotile- and talc-containing products.

Assessing potential nanoparticle release during nanocomposite shredding using direct-reading instruments.

This study was conducted to determine if engineered nanoparticles are released into the air when nanocomposite parts are shredded for recycling. Test plaques made from polypropylene resin reinforced with either montmorillonite nanoclay or talc and from the same resin with no reinforcing material were shredded by a granulator inside a test apparatus. As the plaques were shredded, an ultrafine condensation particle counter; a diffusion charger; a photometer; an electrical mobility analyzer; and an optical particle counter measured number, lung-deposited surface area, and mass concentrations and size distributions by number in real-time. Overall, the particle levels produced were both stable and lower than found in some occupational environments. Although the lowest particle concentrations were observed when the talc-filled plaques were shredded, fewer nanoparticles were generated from the nanocomposite plaques than when the plain resin plaques were shredded. For example, the average particle number concentrations measured using the ultrafine condensation particle counter were 1300 particles/cm(3) for the talc-reinforced resin, 4280 particles/cm(3) for the nanoclay-reinforced resin, and 12,600 particles/cm(3) for the plain resin. Similarly, the average alveolar-deposited particle surface area concentrations measured using the diffusion charger were 4.0 µm(2)/cm(3) for the talc-reinforced resin, 8.5 µm(2)/cm(3) for the nanoclay-reinforced resin, and 26 µm(2)/cm(3) for the plain resin. For all three materials, count median diameters were near 10 nm during tests, which is smaller than should be found from the reinforcing materials. These findings suggest that recycling of nanoclay-reinforced plastics does not have a strong potential to generate more airborne nanoparticles than recycling of conventional plastics.

The risk of asbestos exposure in South African diamond mine workers.

OBJECTIVES: Asbestos is associated with South African diamond mines due to the nature of kimberlite and the location of the diamond mines in relation to asbestos deposits. Very little is known about the health risks in the diamond mining industry. The objective of this study was to explore the possibility of asbestos exposure during the process of diamond mining. METHODS: Scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis were used to identify asbestos fibres in the lungs of diamond mine workers who had an autopsy for compensation purposes and in the tailings and soils from three South African diamond mines located close to asbestos deposits. The asbestos lung fibre burdens were calculated. We also documented asbestos-related pathological findings in diamond mine workers at autopsy. RESULTS: Tremolite-actinolite asbestos fibres were identified in the lungs of five men working on diamond mines. Tremolite-actinolite and/or chrysotile asbestos were present in the mine tailings of all three mines. Mesothelioma, asbestosis, and/or pleural plaques were diagnosed in six diamond mine workers at autopsy. CONCLUSIONS: These findings indicate that diamond mine workers are at risk of asbestos exposure and, thus, of developing asbestos-related diseases. South Africa is a mineral-rich country and, when mining one commodity, it is likely that other minerals, including asbestos, will be accidentally mined. Even at low concentrations, asbestos has the potential to cause disease, and mining companies should be aware of the health risk of accidentally mining it. Recording of comprehensive work histories should be mandatory to enable the risk to be quantified in future studies.

Measurement of talc in flour by the prompt-gamma ray neutron activation analysis method.

Prompt gamma-ray neutron activation analysis method (PGNAA) was used to measure the talc content in flour. Neutron activation prompt gamma spectrum measured by NaI(Tl) detector has complex components, poor energy resolution, and high Compton plateau, how to obtain accurate element content from the prompt γ spectrum is one of the core problems of PGNAA. To reduce the systematic uncertainty caused by the variation of the neutron energy spectrum and γ self-absorption in different samples, the spectral decomposition method based on library least-squares was improved. As a result, the average relative deviation between the calculated values from measured spectra and the theoretical values based on the known composition was reduced from 6.1% to 0.3%. The relative uncertainty of 30 measurements on the same sample was reduced from 4.8% to 3.0%. The detection time can be reduced to 1 min, which meets the requirement of on-line measurement for talc in flour.

Field performance of the CATHIA-T sampler and two cyclones against the standard Cowled sampler for thoracic fiber concentrations.

The performance of two thoracic samplers, the GK2.69 cyclone and the CATHIA-T sampler, and the GK3.51 cyclone was investigated in the field against the standard cowled sampler (current NIOSH 7400 method) to determine the effect of thoracic sampling. The CATHIA-T sampler and the GK2.69 cyclone were operated at 7 and 1.6 l min(-1), respectively. The GK3.51 sampler is related to the GK2.69 cyclone, but designed to give a thoracic cut at a flow rate of 3.2 l min(-1). A total of 136 area samples were obtained from a tremolitic talc processing mill and 148 area samples were obtained within a quarry in which metamorphosed volcanic rocks were being crushed for construction stone. Sample slides were prepared using the dimethyl formamide/Euparal technique and relocatable cover slips. NIOSH 7400 'A' counting rules were used to examine fibers. Additionally, counters were asked to record the number of fibers where a fiber meets the 'A' rules and is wider than 3-mum physical diameter in order to estimate the proportion of extra-thoracic fibers. A few slides from each sampler type were randomly selected and fiber widths for those fibers satisfying the counting rules were measured to determine median width ratios of each thoracic sampler to the cowled sampler. Overall, the combined results of this study and the previous study by the same authors (Lee et al., 2008) showed lower fiber concentrations for the CATHIA-T sampler and higher concentrations for the GK2.69 cyclone and the GK3.51 cyclone compared to the standard cowled sampler. The proportion of extra-thoracic fibers (>3-mum physical diameter) on the filters collected with each type of thoracic samplers was comparable to the proportion of such fibers collected with the cowled sampler. The most consistent result over this study and our previous study is that both cyclones gave higher fiber concentrations than the CATHIA-T sampler. However, the estimated width ratios of each cyclone type to the cowled sampler were similar to or equal to 1 indicating no separation of fiber bundles due to cyclone effects. An inverse relationship between the fiber concentration ratios of each thoracic sampler type to the cowled sampler and the relative sample loading rate compared to the cowled sampler was observed. The difference in fiber concentration ratios might be a function of sample loading rather than an effect of thoracic size selection. Therefore, it is not recommended that any of these samplers be used to replace the cowled sampler in measurements intended for comparison with limit values arising from risk assessments developed from cowled sampler measurements without considering this possible effect.

Analysis of Historical Worker Exposures to Respirable Dust from Talc Mining and Milling Operations in Vermont.

OBJECTIVES: Talc is mined and milled throughout the world for use in a variety of industrial and consumer products. Although prior studies have evaluated workplace exposures or health effects from talc operations, the primary emphasis of these investigations has been on certain mineral contaminants (e.g. crystalline silica and asbestos) rather than talc itself. The purpose of this analysis is to evaluate historical worker exposures to respirable dust (as a measure of talc exposures) in the Vermont talc mines and mills, which involved a relatively pure form of talc (i.e. no asbestos and <0.25% or <1% crystalline silica). METHODS: Respirable dust sampling data collected for workers in the Vermont mines and mills, which have not been previously published, were obtained from both mining company records and Mine Safety and Health Administration (MSHA) inspections. Because of differences in sampling design, the company and MSHA data were analyzed and reported separately. Overall, nearly 700 respirable dust samples collected for 44 job categories at 7 site locations over an approximate 30-year period were analyzed. RESULTS: Average respirable dust concentrations were found to exceed occupational exposure limits (OELs) in the United States and other countries for several job categories and site locations. Regardless of data source, the highest observed exposures were for mining jobs involving the operation of heavy equipment to break up, move, or load raw ore from the mines and milling or shipping jobs involving the crushing of raw ore, cleaning and drying of processed talc, and bagging and packaging of the final talc product. When analyzing the company data, the arithmetic mean respirable dust concentration was 2.73 mg m-3 for Muckerman at Hammondsville Mine, 3.18 mg m-3 for dosco operator at Ludlow mines, 1.35 mg m-3 for crusher operator at Gassetts Mill, 2.4 mg m-3 for palletizer at West Windsor Mill, and 2.68 mg m-3 for bagging operator at Columbia Shipping Center. When analyzing the MSHA data, the arithmetic mean respirable dust concentration was 3.5 mg m-3 for kiln/dryer operator at Hammondsville Mine, 1.27 mg m-3 for driller at Ludlow mines, 3.69 mg m-3 for ball mill operator at Columbia mill, 3.02 mg m-3 for flotation operator at West Windsor Mill, and 3.24 mg m-3 for bagging operator at Columbia Shipping Center. Worker exposures were found to decline over time for many, but not all, jobs. CONCLUSIONS: Our findings highlight potential high-risk jobs that might benefit from additional exposure control strategies at current or future talc manufacturing sites. The respirable dust measurements summarized here may also be used to reconstruct historical worker exposures at the Vermont sites or aid in subsequent epidemiology studies of this cohort focused on malignant or non-malignant respiratory disease.

Disordered biopyriboles, amphibole, and talc in the Allende meteorite: products of nebular or parent body aqueous alteration?

Transmission electron microscope observations of the Allende carbonaceous chondrite provided evidence of widespread hydrous phases replacing enstatite in chondrules. Calcic amphibole and talc occur in thin (less than 0.3 micrometer) crosscutting veins and as alteration products of primary chondrule glass in contraction cracks within the enstatite. In addition, talc and disordered biopyriboles were found replacing enstatite grains along cracks and fractures. Although rare hydrous phases have been reported in calcium- and aluminum-rich inclusions in the Allende meteorite, these observations suggest that aqueous fluids played a much more significant role in the mineralogical and geochemical evolution of Allende than has previously been thought.