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PubMed2005

High exposure to respirable dust and quartz in a labour-intensive coal mine in Tanzania.

Labour-intensive mines are numerous in several developing countries, but dust exposure in such mines has not been adequately characterized. The aim of this study was to identify and quantify the determinants of respirable dust and quartz exposure among underground coal mine workers in Tanzania. Personal respirable dust samples (n = 134) were collected from 90 underground workers in June-August 2003 and July-August 2004. The development team had higher exposure to respirable dust and quartz (geometric means 1.80 and 0.073 mg m(-3), respectively) than the mining team (0.47 and 0.013 mg m(-3)), the underground transport team (0.14 and 0.006 mg m(-3)) and the underground maintenance team (0.58 and 0.016 mg m(-3)). The percentages of samples above the threshold limit values (TLVs) of 0.9 mg m(-3) for respirable bituminous coal dust and 0.05 mg m(-3) for respirable quartz, respectively, were higher in the development team (55 and 47%) than in the mining team (20 and 9%). No sample for the underground transport team exceeded the TLV. Drilling in the development was the work task associated with the highest exposure to respirable dust and quartz (17.37 and 0.611 mg m(-3), respectively). Exposure models were constructed using multiple regression model analysis, with log-transformed data on either respirable dust or quartz as the dependent variable and tasks performed as the independent variables. The models for the development section showed that blasting and pneumatic drilling times were major determinants of respirable dust and quartz, explaining 45.2 and 40.7% of the variance, respectively. In the mining team, only blasting significantly determined respirable dust. Immediate actions for improvements are suggested to include implementing effective dust control together with improved training and education programmes for the workers. Dust and quartz in this underground mine should be controlled by giving priority to workers performing drilling and blasting in the development sections of the mine.

Coal Mining↗
PubMed1998

Differences between rat alveolar and interstitial macrophages 5 wk after quartz exposure.

Macrophages play an essential role in pulmonary host defense. We investigated differences between rat alveolar (AM) and interstitial (IM) macrophages after exposure in vivo to quartz, an inducer of intensive alveolitis. Rats were exposed to 0.5 ml of saline without (n = 8) or with (n = 8) 10 mg of quartz by intratracheal instillation. In a third group (n = 8), 10 mg of surfactant were added to the quartz mixture. Five weeks later, AM were recovered by bronchoalveolar lavage and IM by mechanical fragmentation of the lung, followed by enzymatic treatment. Contamination of AM to the IM fraction was calculated to be 12-15%. After quartz exposure, the expression of major histocompatibility complex class Ia was increased in both AM and IM fractions. The receptor corresponding to human complement receptor 3 increased in AM after quartz exposure, and AM from quartz-exposed animals had a lower metabolic activation. Our findings indicate that IM are immunocompetent cells and that differences between AM and IM fractions occur upon quartz-induced inflammation. This response is not affected by addition of surfactant.

Animals↗
PubMed1985

Fibrogenic potential of intratracheally instilled quartz, ferric oxide, fibrous glass, and hydrated alumina in hamsters.

As a first step in the development of an animal model for determining the role of pulmonary fibrosis in the etiology and pathogenesis of lung cancer, the fibrogenic potential of quartz, quartz and ferric oxide administered together, fibrous glass, and hydrated alumina were studied by multiple intratracheal instillation in groups of male Lak:LVG Syrian golden hamsters. Dose-related decreases in survival were evident for the groups instilled with the two highest doses of quartz or quartz and ferric oxide. Instillation of quartz or quartz and ferric oxide induced the greatest pulmonary fibrosis in response to the materials tested. However, the dense fibrous tissue present in the lungs in classical human silicosis and in experimental silicosis of rats was not observed in this study. The results of this study indicate that the Syrian golden hamster is not a suitable species for studying the role of quartz-induced pulmonary fibrosis in pulmonary carcinogenesis.

Aluminum↗
PubMed1995

Mathematical model of phagocytosis and inflammation after the inhalation of quartz at different concentrations.

A mathematical model was developed with several distinctive features to represent the various processes leading to silicosis. It assures the phagocytosis of quartz by the resident alveolar macrophages. It then models the necrosis of macrophages caused by the ingestion of quartz particles and the subsequent release of these clusters onto alveolar surfaces. The inflammatory recruitment of alveolar macrophages and neutrophils in response to the cell necrosis caused by the ingestion of quartz particles is described in a functional form and is included in the model. The model also describes the pathological and other biological reactions to quartz particles in the interstitium. Specifically, once the quartz particles arrive at the interstitium, they can be phagocytozed by interstitial macrophages. The pathological interaction between quartz and interstitial macrophages may lead to quartz particles being sequestered in silicotic nodules, and also cleared to the efferent lymph nodes.

Administration, Inhalation↗
PubMedDate not supplied

Studies on the toxic effects of quartz and a mycobacterial glycolipid, trehalose 6,6'-dimycolate.

Quartz and trehalose 6,6'-dimycolate (TDM) both potentiate tuberculosis and have toxicities that depend on surface crystalline structures. Investigations were undertaken to determine if TDM can kill macrophages and produce hemolysis in a fashion similar to that of quartz and if quartz can induce granulomas similar to those induced by TDM. Trehalose 6,6'-dimycolate was spread as a molecular monolayer on the surface of tissue culture dishes adjacent to areas of uncoated plastic for comparison. Murine peritoneal macrophages were killed within hours by contact with the TDM monolayer, while those on adjacent areas of uncoated plastic remained viable and spread normally. The membranes of erythrocytes were also damaged by contact with the monolayer of TDM. This damage was inhibited by poly-2-vinyl-pyridine-N-oxide, an inhibitor of hydrogen bonding that blocks quartz induced hemolysis. These data suggest that TDM damages membranes via an adhesive mechanism similar to that of quartz. Furthermore, injections of quartz particles into mice induce acute granulomatous reactions similar to those induced by TDM. These data indicate that TDM and quartz have certain similarities in their mechanisms of action and that these similarities may be of importance in the pathogenesis of tuberculosis.

Animals↗
PubMed2006

Modification of kaolinite surfaces through mechanochemical activation with quartz: A diffuse reflectance infrared fourier transform and chemometrics study.

Studies of kaolinite surfaces are of industrial importance. One useful method for studying the changes in kaolinite surface properties is to apply chemometric analyses to the kaolinite surface infrared spectra. A comparison is made between the mechanochemical activation of Kiralyhegy kaolinites with significant amounts of natural quartz and the mechanochemical activation of Zettlitz kaolinite with added quartz. Diffuse reflectance infrared Fourier transform (DRIFT) spectra were analyzed using principal component analysis (PCA) and multi-criteria decision making (MCDM) methods, the preference ranking organization method for enrichment evaluations (PROMETHEE) and geometrical analysis for interactive assistance (GAIA). The clear discrimination of the Kiralyhegy spectral objects on the two PC scores plots (400-800 and 800-2030 cm(-1)) indicated the dominance of quartz. Importantly, no ordering of any spectral objects appeared to be related to grinding time in the PC plots of these spectral regions. Thus, neither the kaolinite nor the quartz are systematically responsive to grinding time according to the spectral criteria investigated. The third spectral region (2600-3800 cm(-1), OH vibrations), showed apparent systematic ordering of the Kiralyhegy and, to a lesser extent, Zettlitz spectral objects with grinding time. This was attributed to the effect of the natural quartz on the delamination of kaolinite and the accompanying phenomena (i.e., formation of kaolinite spheres and water). The mechanochemical activation of kaolinite and quartz, through dry grinding, results in changes to the surface structure. Different grinding times were adopted to study the rate of destruction of the kaolinite and quartz structures. This relationship (i.e., grinding time) was classified using PROMETHEE and GAIA methodology.

Journal Article↗
PubMed2004

[The depolarization characteristic of quartz depolarizer in UV-VUV spectral region].

The quartz depolarizer consisting of two wedge-shaped quartz crystals was designed based on the Lyot depolarizer. The quartz depolarizer is used to reduce the polarization response of spectral instruments. The residual degree of polarization of the quartz depolarizer was derived by the method of matrix optics, so the variation regularity of its depolarization characteristic was analysed concerning its center thickness and the status of the incident radiation in the UV-VUV spectral range. Its depolarization effect was obvious for the radiation with some spectral bandwidth. Also, the depolarization characteristic of the quartz depolarizer was studied experimentally with 1-meter Seya-Namioka UV-VUV spectrometer, using LiF crystals as the polarizer and analyzer. The residual degree of polarization of the quartz depolarizer was less than 1%. Both the theoretical analysis and experimental results show that the quartz depolarizer we designed is appropriate to the spectral measurement with high accuracy.

English Abstract↗
PubMed2006

Robert Boyle's chiral crystal chemistry: computational re-evaluation of enantioselective adsorption on quartz.

While searching for early examples of interactions of organic chromophores with minerals in the context of a systematic study of the process of dyeing crystals, we came across Robert Boyle's description of an experiment that may have been evidence of the enantioselective adsorption of a natural product, carminic acid (7-beta-D-glucopyranosyl-9,10-dihydro-3,5,6,8-tetrahydroxy-1-methyl-9,10-dioxo-2-anthracenecarboxylic acid), to the chiral surfaces of alpha-quartz, three centuries before such interactions became the subject of active chemical investigations. In order to determine whether Boyle did indeed observe enantioselective adsorption--albeit unbeknownst to him--we attempted to dye quartz with carminic acid according to his recipe. Quartz adsorbs carminic acid only because on heating it develops a network of microfissures that adsorb dye. This process depends on capillarity, not on specific non-covalent interactions; there is no evidence of enantioselectivity adsorption to heated crystals or enantioselective epitaxy to unheated crystals. These failures changed the focus of our inquiry: Why have almost all attempts to demonstrate the enantioselective adsorption of additives to quartz crystal surfaces been generally confounding and equivocal? In order to answer this question, we complement our experimental historical re-investigation with contemporary computational techniques for modeling crystal surface structure and the adsorption of additives. Minimizations of the energies associated with the adsorption of carminic acid to relaxed, hydrated d- and l-quartz {10(-)0} surfaces are analyzed in light of quartz's abysmal record as an enantioselective stationary phase.

Adsorption↗
PubMed2001

Mitochondrial-derived oxidants and quartz activation of chemokine gene expression.

Macrophage inflammatory protein 2 (MIP-2) is a chemotactic cytokine which mediates neutrophil recruitment in the lung and other tissues. Pneumotoxic particles such as quartz increase MIP-2 expression in rat lung and rat alveolar type II epithelial cells. Deletion mutant analysis of the rat MIP-2 promoter demonstrated quartz-induction depended on a single NFkappaB consensus binding site. Quartz activation of NFkappaB and MIP-2 gene expression in RLE-6TN cells was inhibited by anti-oxidants suggesting the responses were dependent on oxidative stress. Consistent with anti-oxidant effects, quartz was demonstrated to increase RLE-6TN cell production of hydrogen peroxide. Rotenone treatment of RLE-6TN cells attenuated hydrogen peroxide production, NFkappaB activation and MIP-2 gene expression induced by quartz indicating that mitochondria-derived oxidants were contributing to these responses. Collectively, these findings indicate that quartz and crocidolite induction of MIP-2 gene expression in rat alveolar type II cells results from stimulation of an intracellular signaling pathway involving increased generation of hydrogen peroxide by mitochondria and subsequent activation of NFkappaB.

Animals↗
PubMed1991

Subchronic inhalation toxicity of amorphous silicas and quartz dust in rats.

The inhalation toxicity of three amorphous silicas (Aerosil 200, Aerosil R 974 and Sipernat 22S) was compared with that of quartz dust. Rats were exposed to 1, 6 or 30 mg Aerosil 200/m3, 30 mg Aerosil R 974/m3, 30 mg Sipernat 22S/m3 or 60 mg quartz/m3 for 6 hr/day, 5 days/wk for 13 wk. Some rats were killed at the end of the exposure period and some were killed 13, 26, 39 or 52 wk after the end of exposure. Clinical signs, body weight, haematology, biochemistry, urinalyses, organ weights, retention of test material in the lungs and regional lymph nodes, collagen content of the lungs, and gross and microscopic pathology were determined in order to disclose possible adverse effects and to study the reversibility, stability or progression of the effects. All test materials induced increases in lung weight, and pulmonary lesions such as accumulation of alveolar macrophages, inflammation, alveolar bronchiolization and fibrosis. In addition, rats exposed to Aerosil 200, Aerosil R 974 or quartz developed granulomatous lesions. Silicosis was observed only in quartz-exposed animals. At the end of the exposure period, Aerosil 200 and quartz had induced the most severe changes. Quartz dust was hardly cleared from the lungs and the changes in the lungs progressed during the post-treatment period, and eventually resulted in lesions resembling silicotic nodules and in one squamous cell carcinoma. Although Aerosil 200 was very quickly cleared from the lungs and regional lymph nodes, the changes in these organs were only partly reversed during the post-exposure period in rats exposed to 30 mg/m3. Aerosil R 974 and the lower levels of Aerosil 200 resulted in less severe, and mostly reversible, changes. The slightest changes were found after exposure to Sipernat 22S, notwithstanding the persistence of this silica in the lungs during the major part of the post-treatment period. The results of this study revealed that only quartz induced progressive lesions in the lungs resembling silicotic nodules. Of the amorphous silicas examined Aerosil 200 induced the most severe changes in the lungs, which only partly recovered, whereas Sipernat 22S induced the least severe, completely reversible lung changes.

Administration, Inhalation↗
PubMed1994

Combined influence of quartz dust, ozone and NO2 on chemotactic mobility, release of chemotactic factors and other cytokines by macrophages in vitro.

In this study the single as well as combined effects of quartz, ozone and nitrogen dioxide (NO2) on some immunofunctions of bovine alveolar macrophages (BAM) were investigated. After incubation with 10 micrograms/ml of particles the chemotactic response of BAM is increased nonspecifically, whereas after incubation with 100 micrograms/ml of quartz chemotaxis is specifically decreased. In addition, quartz induces tumor necrosis factor alpha (TNF-alpha) and chemokines to be released dependent on the concentration. Ozone by itself is also a very potent inducer of the release of chemokines and TNF-alpha, but in combination with ozone, quartz has not more than an additive effect. NO2 alone suppresses drastically the release of TNF-alpha. The results show that quartz, ozone and NO2 alter some immunofunctions of BAM and that by combining toxic particles such as quartz with these gases, additive but not synergistic effects might be expected.

Animals↗
PubMed1992

Oxidative stress in vivo and in vitro: modulation by quartz dust and hyperbaric atmosphere.

Changes in the oxidative status in the soluble proteins of bronchoalveolar lavage (BAL) fluid from monkeys were examined during 26 months of individual or combined exposure to quartz dust (5 mg/m3 of DQ12) and a hyperbaric atmosphere (2.5 bar). The oxidation of BAL proteins, assumed to be an indicator for oxidative stress in the lungs, was determined by measuring the amount of carbonyl groups in their amino acid side chains. The carbonyl content of BAL proteins (nmol carbonyl/mg protein) increased steadily to a maximum value of 156% of the control after 6 months exposure to hyperbaric atmosphere, and decreased below 50% of control levels in both the quartz alone exposed group and the group exposed to quartz in combination with a hyperbaric atmosphere. The effect of quartz on the production of reactive oxygen species by BAL cells was investigated in vitro. BAL cells from healthy monkeys preincubated with quartz and stimulated with phorbol-myristate acetate (PMA) produced reduced levels of extracellular superoxide anion and intracellular hydrogen peroxide compared with PMA-only stimulated cells. Thus the lowered carbonyl content of BAL proteins in the quartz exposed groups may have resulted from reduced production of the hydrogen peroxide which is essential for carbonyl formation by phagocytes. Changes in carbonyl content of BAL protein in vivo may be a new indicator for potential subsequent lung damage.

Animals↗
PubMed1993

The use of quartz patch pipettes for low noise single channel recording.

Quartz has a dissipation factor of approximately 10(-4), which is an order of magnitude less than that of the best glasses previously used to fabricate patch pipettes; it's dielectric constant of 3.8 is also lower than that of other glasses. On the basis of these electrical characteristics it is expected that patch pipettes pulled from quartz tubing will produce significantly less noise than pipettes made from other glasses. Our work confirms these expectations and we describe theoretical and practical aspects of the use of quartz pipettes for single channel patch voltage clamp measurements. Methods for pulling quartz pipettes with a laser-based puller and coating them with low-loss elastomers are discussed, as are precautions that are necessary to achieve low noise recordings. We have shown that quartz pipettes can be pulled from tubing with outer diameter to inner diameter ratios as large as 3 and a method of applying heavy elastomer coatings all the way to the tip of pipettes is presented. Noise sources arising from the pipette and its holder are described theoretically, and it is shown that measured noise is in good agreement with such predictions. With low noise capacitive feedback electronics, small geometry holders, and thick-walled quartz pipettes coated with low-loss elastomers we have been routinely able to achieve noise of 100 fA rms or less in a 5-kHz bandwidth with real cell patches and a pipette immersion depth of approximately 2 mm. On occasion we have achieved noise as low as 60 fA rms in this bandwidth.

Animals↗
PubMed2001

Ultrasensitive quartz crystal microbalance sensors for detection of M13-Phages in liquids.

Quartz crystal microbalance (QCM) sensors are widely used for determining liquid properties or probing interfacial processes. For some applications the sensitivity of the QCM sensors typically used (5-20 MHz) is limited compared with other biosensor methods. In this study ultrasensitive QCM sensors with resonant frequencies from 39 to 110 MHz for measurements in the liquid phase are presented. The fundamental sensor effect of a QCM is the decrease of the resonant frequency of an oscillating quartz crystal due to the binding of mass on a coated surface during the measurement. The sensitivity of QCM sensors increases strongly with an increasing resonant frequency and, therefore, with a decreasing thickness of the sensitive area. The new kind of ultrasensitive QCM sensors used in this study is based on chemically milled shear mode quartz crystals which are etched only in the center of the blank, forming a thin quartz membrane with a thick, mechanically stable outer ring. An immunoassay using a virus specific monoclonal antibody and a M13-Phage showed an increase in the signal to noise ratio by a factor of more than 6 for 56 MHz quartz crystals compared with standard 19 MHz quartz crystals, the detection limit was improved by a factor of 200. Probing of acoustic properties of glycerol/water mixtures resulted in an increase in sensitivity, which is in very good agreement with theory. Chemically milled QCM sensors strongly improve the sensitivity in biosensing and probing of acoustic properties and, therefore, offer interesting new application fields for QCM sensors.

Acoustics↗
PubMed1997

Surfactant prevents quartz induced down-regulation of complement receptor 1 in human granulocytes.

Quartz is known to induce an inflammatory response in the alveolar space by recruitment of different effector cells. We investigated the interaction between granulocytes and quartz with respect to expression of complement receptor type 1 (CR1) and CR3, with and without the presence of surfactant. Granulocytes from hemolyzed blood were stimulated by N-formyl-methionyl-leucyl-phenylalanine (fMLP), which mobilize the intracellular pool of CR1 to the surface, and the mean fluorescence intensity (MFI) measured by cytofluorometry was 47.4 (46-63.6) (median; interquartile range). Quartz exposure reduced the CR1 expression to 23.2 (22.8-30.6) MFI units (P < 0.01), a porcine surfactant preparation added during quartz exposure abolished the down-regulation completely, 47.7 (43.2-62.3) MFI units (P < 0.001). Similar results were obtained after preincubation of the cells with surfactant followed by quartz exposure. No significant influence on CR1 expression was found by a synthetic lipid mixture, nor was the CR3 expression affected. In conclusion, this study demonstrates that the presence of surfactant inhibits quartz induced down-regulation of CR1 on activated granulocytes.

Adolescent↗
PubMed2000

Diagenetic origin of quartz silt in mudstones and implications for silica cycling.

Mudstone--the most abundant sedimentary rock type, composed primarily of clay- or silt-sized particles--contains most of the quartz found in sedimentary rocks. These quartz grains, which are chemically and mechanically resistant and therefore preserve their characteristics well, have long been considered to be derived from the continental crust. Here we analyse quartz silt from black shales in the eastern USA, dating back to the Late Devonian period (about 370 million years ago), using backscattered electron and cathodoluminescence imaging and measure oxygen isotopes with an ion probe. Our results indicate that up to 100% of the quartz silt in our samples does not originate from the continental crust. Instead, it appears to have precipitated early in diagenesis in algal cysts and other pore spaces, with silica derived from the dissolution of opaline skeletons of planktonic organisms, such as radiolaria and diatoms. Transformation of early diatoms into in situ quartz silt might explain the time gap between the earliest fossil occurrences of diatoms about 120 Myr ago and molecular evidence for a much earlier appearance between 266 or even 500 Myr ago. Moreover, if many other mudstone successions show similarly high proportions of in situ precipitated--rather than detrital--quartz silt, the sedimentary record in mudstones may have been misinterpreted in the past, with consequences for our estimates of palaeoproductivity as well as our perceptions of the dynamics and magnitude of global biogeochemical cycling of silica.

Animals↗
PubMed2004

Different toxic, fibrogenic and mutagenic effects of four commercial quartz flours in the rat lung.

There is still intensive debate on the variability in the biological activities of different quartz species. Therefore we examined in a rat lung model the inflammatory, fibrogenic and genotoxic characteristics of four commercial quartz flours. The samples, two with probably low activity and two with probably high activity were selected from a panel of 16 samples on the basis of in vitro investigations. Rats were exposed by a single intratracheal injection of 0.6, 1.2 and 2.4 mg quartz samples per lung or with 1.2 mg standard quartz DQ12. After 90 days the inflammatory response was measured in the bronchoalveolar lavage fluid, as well as the content of 8-oxoguanine in the DNA of the lung cells. Additionally mutated p53 protein was determined. The four quartz samples revealed specific differences in all parameters investigated. In good agreement with the in vitro results the two samples expected as lowly active showed only weak inflammatory and no genotoxic reactions in the rat lungs. In contrast the two samples suspected as highly reactive induced a pronounced inflammatory response and for one of the samples genotoxic effects could be proven. The results raised here show a broad spectrum of biological activities dependent on the type of quartz from almost inert to genotoxic and highly inflammatory.

Animals↗
PubMed2004

Relationship between the state of the surface of four commercial quartz flours and their biological activity in vitro and in vivo.

Four commercial quartz dusts (flours), two inflammogenic in vivo and activating macrophages in vitro (Qz 2/1-c and Qz 3/1-c) and two mostly inert (Qz 5/1-c and Qz 11/1-c), have been compared regarding their surface properties, in order to detect chemical differences which may account for their different biological behaviour. The following features have been examined: 1) extent of the amorphous fraction (heat associated alpha<-->beta transition of quartz) and its solubility in HF; 2) potential to cleave a carbon-hydrogen bond with consequent generation of carbon centred radicals (spin trapping technique, EPR); 3) evolution of surface functionalities upon heating (FTIR spectroscopy); 4) mechanisms of adsorption of water on dusts outgassed at 150 degrees and at 800 degrees C (adsorption calorimetry). HCl treated samples have also been examined. The two "less toxic" quartzes are more resistant to HF attack, coordinate irreversibly H2O molecules and exhibit strong adsorption sites, which are absent in the other two and in a very pure quartz dust. Conversely all samples show the same potential to release free radicals. The different behaviour of the two sets of dust is consistent with a different level of impurities, namely aluminium ex kaolin, carbon and alkaline ions. The less inflammogenic quartzes appear to be covered by aluminium ions (and possibly iron) which strongly holds molecular water or carbonates, thus reducing the silanol patches to a large extent and changing the surface properties of the particles. We hypothesize that cellular response, and particularly macrophage activation and death, is mediated by strong interactions between silanol patches and some cell membrane components, but inhibited when the surface of the particle is modified by the presence of aluminium ions, surface carbonates and other metal contaminants. This hypothesis suggests that grinding procedures with little appropriate additives, e.g. kaolin, alumina, can reduce the biological activity of quartz dusts.

Adsorption↗