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1.
Inhal Toxicol ; 31(8): 325-342, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31690138

RESUMO

Grinding and drilling of chrysotile asbestos-containing brake pads during the 20th century led to release of chrysotile, resulting in varying levels of workplace exposures of mechanics. Despite exposures, excess risk of mesothelioma remains in doubt. Objectives: The toxicity of particulates is primarily derived through a combination of physicochemical properties and dose and as such this study aimed to determine properties of asbestos-containing brake debris (BD) which may influence pathogenicity and potential of mesothelioma. Materials and Methods: Chrysotile-containing brake pads were ground - to reflect occupational activities, aerosolized, and size-fractionated to isolate respirable fractions. Analysis of morphology, biodurability, surface charge, and interactions with macrophages were undertaken. Results: The respirable fraction of BD contained ∼15-17% free chrysotile fibers thereby constituting a small but relevant potential long fiber dose. Acellular biodurability studies showed rapid dissolution and fragmentation of chrysotile fibers that was consistent for pure chrysotile control and BD samples. Conclusions: The long, free, respirable chrysotile fibers were present in BD, yet were of low bio-durability; incubation in artificial lysosomal fluid led to destruction of free fibers.


Assuntos
Poluentes Ocupacionais do Ar/química , Asbestos Serpentinas/química , Macrófagos/efeitos dos fármacos , Automóveis , Humanos , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Espécies Reativas de Oxigênio/análise , Células THP-1
2.
Environ Sci Pollut Res Int ; 26(18): 18708-18718, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31055741

RESUMO

Chrysotile accounts for some 90% to 95% of all the asbestos used worldwide. Scientific evidences have shown that asbestos (including chrysotile) exposure is associated with increased rates of lung cancer, asbestosis, and mesothelioma. However, molecular mechanisms underlying the toxicity effects of chrysotile are not clear. This study evaluated the oxidative stress in chronic lung toxicity caused by the intratracheal instillation (IT) of four kinds China representative chrysotile once a month for 12 months in Wistar rats. These results indicated that chrysotile exposure led to an obvious increase in lung mass and slowed the growth of body mass. Inflammation and fibrosis were observed by hematoxylin-eosin (HE) staining. Exposure to chrysotile significantly increased the accumulation of reactive oxygen species (ROS) and the level of lipid peroxidation and decreased antioxidant capacity in lung tissues. Furthermore, 1-6-month chrysotile exposure activated heme oxygenase-1 (HO-1) and heat shock protein 70 (HSP70) expression, whereas 12-month exposure caused significant decreases of two-factor expression levels in XK and MN groups when compared to negative control group. Therefore, our results suggested that chronic chrysotile pulmonary injury in Wistar rats is triggered by oxidative damage. Meanwhile, the oxidative damage of MN and XK was stronger than that of SSX and AKS, and the difference of oxidative damage in four chrysotile could have been brought by its properties, morphology, chemical composition, and particle size. With all the above mentioned in view, we hope that the revealed data in the experiment could contribute to the progress of further researches on the toxicity and mechanism of chrysotile.


Assuntos
Asbestos Serpentinas/toxicidade , Lesão Pulmonar/induzido quimicamente , Pulmão/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Animais , Asbestos Serpentinas/química , China , Heme Oxigenase-1/metabolismo , Peroxidação de Lipídeos/efeitos dos fármacos , Pulmão/metabolismo , Lesão Pulmonar/metabolismo , Masculino , Tamanho da Partícula , Ratos , Ratos Wistar
3.
ISME J ; 13(7): 1750-1762, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-30872803

RESUMO

Hydration of ultramafic rock during the geologic process of serpentinization can generate reduced substrates that microorganisms may use to fuel their carbon and energy metabolisms. However, serpentinizing environments also place multiple constraints on microbial life by generating highly reduced hyperalkaline waters that are limited in dissolved inorganic carbon. To better understand how microbial life persists under these conditions, we performed geochemical measurements on waters from a serpentinizing environment and subjected planktonic microbial cells to metagenomic and physiological analyses. Metabolic potential inferred from metagenomes correlated with fluid type, and genes involved in anaerobic metabolisms were enriched in hyperalkaline waters. The abundance of planktonic cells and their rates of utilization of select single-carbon compounds were lower in hyperalkaline waters than alkaline waters. However, the ratios of substrate assimilation to dissimilation were higher in hyperalkaline waters than alkaline waters, which may represent adaptation to minimize energetic and physiologic stress imposed by highly reducing, carbon-limited conditions. Consistent with this hypothesis, estimated genome sizes and average oxidation states of carbon in inferred proteomes were lower in hyperalkaline waters than in alkaline waters. These data suggest that microorganisms inhabiting serpentinized waters exhibit a unique suite of physiological adaptations that allow for their persistence under these polyextremophilic conditions.


Assuntos
Asbestos Serpentinas/química , Fenômenos Fisiológicos Bacterianos , Sedimentos Geológicos/microbiologia , Adaptação Fisiológica , Anaerobiose , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Carbono/metabolismo , Metagenômica , Omã , Oxirredução , Microbiologia da Água
4.
Nano Lett ; 19(2): 921-929, 2019 02 13.
Artigo em Inglês | MEDLINE | ID: mdl-30484321

RESUMO

We have recently shown that nanopore zero-mode waveguides are effective tools for capturing picogram levels of long DNA fragments for single-molecule DNA sequencing. Despite these key advantages, the manufacturing of large arrays is not practical due to the need for serial nanopore fabrication. To overcome this challenge, we have developed an approach for the wafer-scale fabrication of waveguide arrays on low-cost porous membranes, which are deposited using molecular-layer deposition. The membrane at each waveguide base contains a network of serpentine pores that allows for efficient electrophoretic DNA capture at picogram levels while eliminating the need for prohibitive serial pore milling. Here, we show that the loading efficiency of these porous waveguides is up to 2 orders of magnitude greater than their nanopore predecessors. This new device facilitates the scaling-up of the process, greatly reducing the cost and effort of manufacturing. Furthermore, the porous zero-mode waveguides can be used for applications that benefit from low-input single-molecule real-time sequencing.


Assuntos
DNA/química , Nanoporos/ultraestrutura , Nanotecnologia/instrumentação , Análise de Sequência de DNA/instrumentação , Asbestos Serpentinas/química , DNA/isolamento & purificação , Desenho de Equipamento , Membranas Artificiais , Porosidade
5.
Toxicol Appl Pharmacol ; 361: 118-126, 2018 12 15.
Artigo em Inglês | MEDLINE | ID: mdl-30381243

RESUMO

Chrysotile asbestos was reacted with phosphorus oxychloride (POC) gas to produce a chemically modified fiber referred to as chrysophosphate. The presence of phosphorus and chlorine on the fiber surface and in small fiber bundles was verified by means of energy dispersive x-ray spectrometry and laser mass spectrometry. The altered fiber exhibits different physical-chemical properties when compared with the unaltered precursor material. In addition to marked surface changes, fibrils of the reacted material appear to be cross-linked increasing the size of particulates, fiber bundles and increasing their mechanical stability. The reacted specimens exhibit fewer fibrils reducing their surface area. In vitro testing using the human erythrocyte model showed the membranolytic activity of the reacted fiber to be substantially reduced to the background level measured for mechanical membrane breakage during manipulation. Membranolytic activity of unreacted chrysotile displayed values reported previously in the literature. These data support the observation made in other studies that fiber surface modification by means of an industrial process may be a method for reducing the biological potential of mineral particles. The membrane model is considered a useful and preliminary examination. These materials will require further testing in more complex in vivo systems. Some in vivo assays were performed on chrysophosphate with results that appeared to differ from our membrane tests. These differences are described and the variation of batch chemistry, stability of the reacted surface, and the resulting surface chemistry, are discussed.


Assuntos
Asbestos Serpentinas/química , Asbestos Serpentinas/toxicidade , Carcinógenos/química , Carcinógenos/toxicidade , Fósforo/química , Fósforo/toxicidade , Animais , Membrana Eritrocítica/efeitos dos fármacos , Eritrócitos/efeitos dos fármacos , Humanos , Propriedades de Superfície
6.
Am J Ind Med ; 61(7): 625-630, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29733442

RESUMO

BACKGROUND: Although antigorite is generally described as platy, its fibrous (asbestiform) variant is present widespread in serpentinite rocks. In addition to its primarily fibrous occurrence, asbestiform antigorite may also be formed from serpentinite with massive appearance during tunneling and mining. It is not of commercial interest, but exposure may occur in the certain environments. METHODS AND RESULTS: Detailed studies of the structural features of this antigorite type revealed characteristics closely related to those of chrysotile. Therefore, it is plausible that this serpentine mineral may present a similar health risk for exposed subjects. This is in agreement with results from clinical and animal studies, as well as in vitro experiments showing the cytotoxic, fibrogenic, and carcinogenic potential of antigorite, similar to that of chrysotile and amphibole asbestos. CONCLUSIONS: Current evidence supports a need for an update to existing regulations to include unregulated asbestiform antigorite, similar to regulatory measures taken for asbestos.


Assuntos
Asbestos Serpentinas/efeitos adversos , Asbestose/etiologia , Neoplasias Pulmonares/induzido quimicamente , Mesotelioma/induzido quimicamente , Mineração , Exposição Ocupacional/efeitos adversos , Animais , Asbestos Serpentinas/química , Asbestos Serpentinas/toxicidade , Asbestose/epidemiologia , Humanos , Neoplasias Pulmonares/epidemiologia , Mesotelioma/epidemiologia , Exposição Ocupacional/estatística & dados numéricos
7.
J Occup Environ Hyg ; 15(6): 466-473, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29580193

RESUMO

Chrysotile asbestos fibers were added to roofing products, including roof cement, for several decades. The fibers were described as "encapsulated" and therefore incapable of being released, an assertion that is disproved by the study reported herein. Three test panels of roof cement from the original container were exposed to ambient weathering in 2015 and 2016. Two panels were then sampled using the ASTM D5755 microvacuum method. Sampling revealed a light brown sub-layer under the dark brown surface layer, both of which crumbled and became friable during sampling. Analysis of the microvacuum samples with transmission electron microscopy showed that the material on the 2 panels contained 4,432,000 and 3,320,000 asbestos structures per cm² with nearly all of the structures consisting of fibers less than 5 µm long. Energy dispersive spectrometry determined that none of the fibers reported were coated with asphalt. The presence of free fibers was confirmed by direct examination of the surfaces of the panels and of dust released from handling the panels via scanning electron microscopy. This study confirmed the releasability of uncoated asbestos fibers from dried roof cement that was indicated in 2 previous studies published in 2007 and 2010. These results suggest that the finding of the Fifth Circuit Court in 1997 that uncoated airborne asbestos fibers cannot be released from roof cement, and therefore do not present a potential exposure by inhalation, was erroneous in retrospect. The exemption of roof cement from regulation under the Occupational Safety and Health Administration Construction Industry Standard for asbestos by the Court should not be relied on by employers of workers who remove weathered asbestos-containing roof cement, and precautions should be taken against exposure to airborne asbestos fibers during this work.


Assuntos
Asbestos Serpentinas/análise , Materiais de Construção/análise , Asbestos Serpentinas/química , Poeira/análise , Hidrocarbonetos/química , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Fibras Minerais/análise , Tempo (Meteorologia)
8.
Environ Sci Pollut Res Int ; 25(23): 22356-22367, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28766145

RESUMO

The wide use of asbestos and its substitutes has given rise to studies on their possible harmful effects on human health and environment. However, their toxic effects remain unclear. The present study was aimed to disclose the coupled effects of dissolved high-valence ions and oxide radicals using the in vitro cytotoxicity and genotoxicity of chrysotile (CA), nano-SiO2 (NS), ceramic fiber (CF), glass fiber (GF), and rock wool (RW) on Chinese hamster lung cells V79. All samples induced cell mortality correlated well with the chemical SiO2 content of asbestos substitutes and the amount of dissolved Si. Alkali or alkaline earth metal elements relieved mortality of V79 cells; Al2O3 reinforced toxicity of materials. Asbestos substitutes generated lasting, increasing amount of acellular ·OH which formed at the fiber surface at sites with loose/unsaturated bonds, as well as by catalytic reaction through dissolved iron. Accumulated mechanical and radical stimulation induced the intracellular reactive oxygen species (ROS) elevation, morphology change, and deviating trans-membrane ion flux. The cellular ROS appeared as NS > GF > CF ≈ CA > RW, consistent with cell mortality rather than with acellular ·OH generation. Chromosomal and DNA lesions in V79 cells were not directly associated with the cellular ROS, while influenced by dissolved high-valence irons in the co-culture medium. In conclusion, ions from short-time dissolution of dust samples and the generation of extracellular ·OH presented combined effects in the elevation of intracellular ROS, which further synergistically induced cytotoxicity and genotoxicity.


Assuntos
Asbestos Serpentinas/toxicidade , Fibras Minerais/toxicidade , Testes de Mutagenicidade/métodos , Dióxido de Silício/toxicidade , Animais , Asbestos , Asbestos Serpentinas/química , Linhagem Celular , Cerâmica/toxicidade , Cricetulus , Dano ao DNA/efeitos dos fármacos , Radicais Livres/química , Vidro , Íons/química , Ferro/química , Pulmão/citologia , Pulmão/efeitos dos fármacos , Nanoestruturas/toxicidade , Óxidos/química , Espécies Reativas de Oxigênio/metabolismo
9.
J Hazard Mater ; 341: 290-296, 2018 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-28797944

RESUMO

Asbestos fibers are highly toxic (Group 1 carcinogen) due to their high aspect ratio, durability, and the presence of iron. In nature, plants, fungi, and microorganisms release exudates, which can alter the physical and chemical properties of soil minerals including asbestos minerals. We examined whether exudates from bacteria and fungi at environmentally relevant concentrations can alter chrysotile, the most widely used asbestos mineral, and lower its toxicity. We monitored the release of iron from chrysotile in the presence of organic acid ligands and iron-specific siderophores derived from bacteria and fungi and measured any change in fiber toxicity toward peritoneal macrophages harvested from mice. Both fungal and bacterial siderophores increased the removal of iron from asbestos fibers. In contrast, organic acid ligands at environmentally relevant concentrations neither released iron from fibers nor helped in siderophore-mediated iron removal. Removal of plant-available or exchangeable iron did not diminish iron dissolution by both types of siderophores, which indicates that siderophores can effectively remove structural iron from chrysotile fibers. Removal of iron by siderophore lowered the fiber toxicity; fungal siderophore appears to be more effective than bacterial siderophore in lowering the toxicity. These results indicate that prolonged exposure to siderophores, not organic acids, in the soil environment decreases asbestos fiber toxicity and possibly lowers the health risks. Thus, bioremediation should be explored as a viable strategy to manage asbestos-contaminated sites such as Brownfield sites, which are currently left untreated despite dangers to surrounding communities.


Assuntos
Asbestos Serpentinas/química , Ferro/química , Sideróforos/química , Animais , Asbestos Serpentinas/toxicidade , Bactérias/química , Biodegradação Ambiental , Fungos/química , Macrófagos Peritoneais/efeitos dos fármacos , Malonatos/química , Camundongos , Ácido Oxálico/química
10.
Environ Sci Pollut Res Int ; 25(23): 22389-22399, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28963651

RESUMO

Chrysotile products were widely used in daily life, and a large amount of respirable dust was produced in the process of production and application. At present, there was seldom research on the safety of chrysotile fiber dust, and whether its long-term inhalation can lead to lung cancer was unknown. In order to determine whether respirable chrysotile fiber dust of China caused lung cancer, four major chrysotile-producing mine areas in China were selected for this study. Chrysotile fibers were prepared into respirable dust. Particle size was measured by laser particle analysis, morphology was observed by scanning electron microscope, chrysotile fiber phase was analyzed by X-ray diffraction, trace chemical elements were identified by X-ray fluorescence, and the structure and the active groups of the dust were determined after grinding by Fourier transform infrared spectroscopy. Male Wistar rats were exposed to non-exposed intratracheal instillation with different concentrations of chrysotile fiber dust. The rats were weighed after 1, 3, and 6 months, then the lung tissues were separated, the lung morphology was observed, and the pulmonary index was calculated. Pathological changes in lung tissues were observed by optical microscope after the HE staining of tissues, and the gene expression of p53 and p16 was determined by reverse transcription polymerase chain reaction. First, the results showed that the particle sizes of the four fibers were less than 10 µm. Four primary areas of chrysotile had similar fibrous structure, arranged in fascicles, or mixed with thin chunks of material. Second, the elementary composition of the four fibers was mainly chrysotile, and the structure and the active groups of the grinding dust were not damaged. Third, the weights of the treated rats were obviously lower, and the lung weights and the pulmonary index increased significantly (P < 0.05). Fourth, the treated Wistar rat lung tissues revealed different degrees of congestion, edema, inflammatory cell infiltration, and mild fibrosis. Fifth, the p53 and p16 genes decreased in the Mangnai group after 1 month of exposure, and the other groups increased. The expression of p53 and p16 in each group decreased significantly after 6 months (P < 0.05). In conclusion, the respirable chrysotile fiber dust from the four primary areas of China had the risk of causing lung injury, and these changes may be related to the physical and chemical characteristics of chrysotile from different production areas.


Assuntos
Asbestos Serpentinas/toxicidade , Inibidor p16 de Quinase Dependente de Ciclina/genética , Poeira , Lesão Pulmonar/induzido quimicamente , Proteína Supressora de Tumor p53/genética , Animais , Asbestos Serpentinas/química , China , Regulação da Expressão Gênica/efeitos dos fármacos , Exposição por Inalação/efeitos adversos , Pulmão/efeitos dos fármacos , Pulmão/patologia , Pulmão/fisiologia , Lesão Pulmonar/patologia , Masculino , Microscopia Eletrônica de Varredura , Mineração , Tamanho da Partícula , Ratos Wistar , Difração de Raios X
11.
Astrobiology ; 17(11): 1138-1160, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28910143

RESUMO

Low-temperature serpentinization is a critical process with respect to Earth's habitability and the Solar System. Exothermic serpentinization reactions commonly produce hydrogen as a direct by-product and typically produce short-chained organic compounds indirectly. Here, we present the spectral and mineralogical variability in rocks from the serpentine-driven Lost City Hydrothermal Field on Earth and the olivine-rich region of Nili Fossae on Mars. Near- and thermal-infrared spectral measurements were made from a suite of Lost City rocks at wavelengths similar to those for instruments collecting measurements of the martian surface. Results from Lost City show a spectrally distinguishable suite of Mg-rich serpentine, Ca carbonates, talc, and amphibole minerals. Aggregated detections of low-grade metamorphic minerals in rocks from Nili Fossae were mapped and yielded a previously undetected serpentine exposure in the region. Direct comparison of the two spectral suites indicates similar mineralogy at both Lost City and in the Noachian (4-3.7 Ga) bedrock of Nili Fossae, Mars. Based on mapping of these spectral phases, the implied mineralogical suite appears to be extensive across the region. These results suggest that serpentinization was once an active process, indicating that water and energy sources were available, as well as a means for prebiotic chemistry during a time period when life was first emerging on Earth. Although the mineralogical assemblages identified on Mars are unlikely to be directly analogous to rocks that underlie the Lost City Hydrothermal Field, related geochemical processes (and associated sources of biologically accessible energy) were once present in the subsurface, making Nili Fossae a compelling candidate for a once-habitable environment on Mars. Key Words: Mars-Habitability-Serpentinization-Analogue. Astrobiology 17, 1138-1160.


Assuntos
Planeta Terra , Exobiologia/métodos , Meio Ambiente Extraterreno/química , Compostos de Ferro/análise , Compostos de Magnésio/análise , Marte , Silicatos/análise , Asbestos Serpentinas/análise , Asbestos Serpentinas/química , Ecossistema , Fontes Geradoras de Energia , Hidrogênio/química , Compostos de Ferro/química , Compostos de Magnésio/química , Silicatos/química , Espectroscopia de Luz Próxima ao Infravermelho/instrumentação , Espectroscopia de Luz Próxima ao Infravermelho/métodos , Água/química
12.
Inhal Toxicol ; 28(14): 698-705, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27884072

RESUMO

Functional groups on the surface of fibrous silicates can complex iron. We tested the postulate that (1) asbestos complexes and sequesters host cell iron resulting in a disruption of metal homeostasis and (2) this loss of essential metal results in an oxidative stress and biological effect in respiratory epithelial cells. Exposure of BEAS-2B cells to 50 µg/mL chrysotile resulted in diminished concentrations of mitochondrial iron. Preincubation of these cells with 200 µM ferric ammonium citrate (FAC) prevented significant mitochondrial iron loss following the same exposure. The host response to chrysotile included increased expression of the importer divalent metal transporter-1 (DMT1) supporting a functional iron deficiency. Incubation of BEAS-2B cells with both 200 µM FAC and 50 µg/mL chrysotile was associated with a greater cell accumulation of iron relative to either iron or chrysotile alone reflecting increased import to correct metal deficiency immediately following fiber exposure. Cellular oxidant generation was elevated after chrysotile exposure and this signal was diminished by co-incubation with 200 µM FAC. Similarly, exposure of BEAS-2B cells to 50 µg/mL chrysotile was associated with release of the proinflammatory mediators interleukin (IL)-6 and IL-8, and these changes were diminished by co-incubation with 200 µM FAC. We conclude that (1) the biological response following exposure to chrysotile is associated with complexation and sequestration of cell iron and (2) increasing available iron in the cell diminished the effects of asbestos exposure.


Assuntos
Asbestos Serpentinas/química , Asbestos Serpentinas/toxicidade , Ferro/química , Linhagem Celular , Ferritinas/metabolismo , Homeostase , Humanos , Interleucina-6/metabolismo , Interleucina-8/metabolismo , Ferro/metabolismo , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Sulfatos/química , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Zinco/química
13.
Chemosphere ; 164: 547-557, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27619065

RESUMO

Relevant mineral fibres of social and economic importance (chrysotile UICC, crocidolite UICC and a fibrous erionite from Jersey, Nevada, USA) were put in contact with cultured diploid human non-tumorigenic bronchial epithelial (Beas2B) and pleural transformed mesothelial (MeT5A) cells to test their cytotoxicity. Slides of each sample at different contact times up to 96 h were studied in situ using synchrotron XRF, µ-XRD and µ-XAS (I18 beamline, Diamond Light Source, UK) and TEM investigations. XRF maps of samples treated for 96 h evidenced that iron is still present within the chrysotile and crocidolite fibres and retained at the surface of the erionite fibres, indicating its null to minor mobilization in contact with cell media; this picture was confirmed by the results of XANES pre-edge analyses. µ-XRD and TEM data indicate greater morphological and crystallinity modifications occurring in chrysotile, whereas crocidolite and erionite show to be resistant in the biological environment. The contact of chrysotile with the cell cultures seems to lead to earlier amorphization, interpreted as the first dissolution step of these fibres. The formation of such silica-rich fibre skeleton may prompt the production of HO in synergy with surface iron species and could indicate that chrysotile may be much more reactive and cytotoxic in vitro in the (very) short term whereas the activity of crocidolite and erionite would be much more sluggish but persistent in the long term.


Assuntos
Asbesto Crocidolita/química , Asbestos Serpentinas/química , Ferro/análise , Fibras Minerais/análise , Zeolitas/química , Animais , Asbesto Crocidolita/toxicidade , Asbestos Serpentinas/toxicidade , Brônquios/efeitos dos fármacos , Carcinogênese/induzido quimicamente , Linhagem Celular , Humanos , Ferro/toxicidade , Fibras Minerais/toxicidade , Mucosa Respiratória/efeitos dos fármacos , Zeolitas/toxicidade
14.
Chemosphere ; 159: 602-609, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27343867

RESUMO

Amphiphilic magnetic composites were produced based on chrysotile mineral and carbon structures by chemical vapor deposition at different temperatures (600-900 °C) and cobalt as catalyst. The materials were characterized by elemental analysis, X-ray diffraction, vibrating sample magnetometry, adsorption and desorption of N2, Raman spectroscopy, scanning electronic microscopy, and thermal analysis showed an effective growth of carbon structures in all temperatures. It was observed that at 800 and 900 °C, a large amount of carbon structures are formed with fewer defects than at 600 and 700 °C, what contributes to their stability. In addition, the materials present magnetic phases that are important for their application as catalysts and adsorbents. The materials have shown to be very active to remove the oil dispersed in a real sample of emulsified wastewater from biodiesel production and to remove methylene blue by adsorption and oxidation via heterogeneous Fenton mechanism.


Assuntos
Asbestos Serpentinas/química , Carbono/química , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Poluentes Químicos da Água/análise , Adsorção , Catálise , Azul de Metileno/química , Oxirredução , Análise Espectral Raman , Propriedades de Superfície , Difração de Raios X
15.
Inhal Toxicol ; 28(8): 357-63, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-27151190

RESUMO

The purpose of this work is to define a sample preparation protocol that allows inorganic fibers and particulate matter extracted from different biological samples to be characterized morphologically, crystallographically and chemically by transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS). The method does not damage or create artifacts through chemical attacks of the target material. A fairly rapid specimen preparation is applied with the aim of performing as few steps as possible to transfer the withdrawn inorganic matter onto the TEM grid. The biological sample is previously digested chemically by NaClO. The salt is then removed through a series of centrifugation and rinse cycles in deionized water, thus drastically reducing the digestive power of the NaClO and concentrating the fibers for TEM analysis. The concept of equivalent hydrodynamic diameter is introduced to calculate the settling velocity during the centrifugation cycles. This technique is applicable to lung tissues and can be extended to a wide range of organic materials. The procedure does not appear to cause morphological damage to the fibers or modify their chemistry or degree of crystallinity. The extrapolated data can be used in interdisciplinary studies to understand the pathological effects caused by inorganic materials.


Assuntos
Amiantos Anfibólicos/análise , Asbestos Serpentinas/análise , Manejo de Espécimes/métodos , Amiantos Anfibólicos/química , Asbestos Serpentinas/química , Humanos , Pulmão , Microscopia Eletrônica de Transmissão , Hipoclorito de Sódio/química
16.
Artigo em Inglês | MEDLINE | ID: mdl-26778506

RESUMO

Crystalline silica particles and asbestos have both been classified as carcinogenic by the International Agency for Research on Cancer (IARC). However, because of the limited data available, amorphous silica was not classifiable. In vitro, the carcinogenic potential of natural crystalline and amorphous silica particles has been revealed by the Syrian Hamster Embryo (SHE) cell transformation assay. On the other hand, the genotoxic potential of those substances has not been investigated in SHE cells. And yet, genotoxicity assays are commonly used for hazard evaluation and they are often used as in vitro assays of reference to predict a possible carcinogenic potential. The main objective of this study was to compare the genotoxic potential and the carcinogenic potential of different crystalline and amorphous silica particles in SHE cells. Three silica samples of different crystallinity were used: natural amorphous silica, partially crystallized silica and quartz silica particles. Their genotoxicity were tested through the in vitro micronucleus assay and the comet assay in SHE, and their carcinogenic potential through the SHE transformation assay. In addition, silica samples were also tested with the same genotoxicity assays in V79 hamster-lung cells, a common in vitro model for particle exposure. Results obtained in the micronucleus and the comet assays show that none of the silica was capable of inducing genotoxic effects in SHE cells and only the amorphous silica induced genotoxic effects in V79 cells. However in the SHE cell transformation assays, the partially crystallized and quartz silica were able to induce morphological cell transformation. Together, these data suggest that, in vitro, the short-term genotoxic assays alone are not sufficient to predict the hazard and the carcinogenic potential of this type of particles; SHE transformation assay appears a more reliable tool for this purpose and should be included in the "in vitro battery assays" for hazard assessment.


Assuntos
Ensaio Cometa/métodos , Dano ao DNA/efeitos dos fármacos , Testes para Micronúcleos/métodos , Dióxido de Silício/toxicidade , Animais , Asbestos Serpentinas/química , Asbestos Serpentinas/toxicidade , Carcinógenos/química , Carcinógenos/toxicidade , Proliferação de Células/efeitos dos fármacos , Transformação Celular Neoplásica/efeitos dos fármacos , Células Cultivadas , Fenômenos Químicos , Clonagem Molecular , Cricetinae/embriologia , Relação Dose-Resposta a Droga , Pulmão/citologia , Pulmão/efeitos dos fármacos , Pulmão/embriologia , Tamanho da Partícula , Dióxido de Silício/química , Difração de Raios X
17.
J Immunotoxicol ; 13(3): 335-48, 2016 05.
Artigo em Inglês | MEDLINE | ID: mdl-26484633

RESUMO

Calcined Serpentine (CS) is used in various formulations of alternative systems of medicine as a tonic to vital organs and as an anti-inflammatory agent. The process of calcination or incineration is believed to render non-toxic, gently absorbable, adaptable and digestible properties to the mineral compounds. The present study characterized CS and also evaluated its immunostimulatory potential. CS was characterized by using transmission electron microscopy (TEM), X-ray powder diffraction, atomic absorption spectroscopy and CHNS analysis. The characterized CS was further evaluated for its immunomodulatory potential in Swiss mice. X-Ray diffraction analysis revealed that the CS contained silicates of magnesium, calcium and iron as major minerals. Elemental composition and heavy metal analyses showed a presence of various inorganic elements/heavy metals, albeit at levels well below daily permissive intake values. TEM analysis of the test CS revealed a presence of nano particles with an average size of 10-20 nm (≈ 26% of total material). Oral administration of CS to mice at 50, 75, 100 or 200 µg/kg body weight for 10 days led to enhanced levels of total IgG, IgG1, IgG2a and IgG2b in ovalbumin-immunized mice as well as ex vivo lymphocyte proliferation and levels of TH1 (IL-2, IFNγ) and TH2 (IL-4, IL-10) cytokines produced by their cultured splenocytes. Similarly, CS treatment resulted in enhanced delayed-type hypersensitivity responses in GRBC-primed hosts. CS also activated host peritoneal macrophages, as indicated by increases in phagocytic activity and in TLR-2, CD80 and CD86 expression. The CS did not affect liver, kidney and spleen histology. Taken together, the results indicated that absorbed CS was stimulatory of host cell-mediated immune responses. It is hypothesized for now that the immunomodulatory effect of CS may have been due, in part, to a presence of nanoparticles on the CS; further study is required to validate this viewpoint.


Assuntos
Asbestos Serpentinas/imunologia , Macrófagos Peritoneais/imunologia , Silicatos/imunologia , Células Th1/imunologia , Células Th2/imunologia , Administração Oral , Animais , Asbestos Serpentinas/administração & dosagem , Asbestos Serpentinas/química , Proliferação de Células , Células Cultivadas , Terapias Complementares , Citocinas/metabolismo , Temperatura Alta , Humanos , Hipersensibilidade Tardia , Imunidade Humoral , Imunização , Camundongos , Microscopia Eletrônica de Transmissão , Nanopartículas/química , Silicatos/química , Difração de Raios X
18.
J Hazard Mater ; 305: 164-170, 2016 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-26685063

RESUMO

This study was primarily imposed by the ever increasing need for detoxification of asbestos and asbestos containing materials (ACM), with potential application onsite. The present work investigates potential detoxification of pure chrysotile (Chr) asbestos via a combined treatment of oxalic acid dihydrate (Oxac) (Η2C2Ο4·2Η2Ο) with silicates, such as tetraethoxysilane (TEOS) (SiH20C8O4) and pure water glass (WG) (potassium silicate) (K2SiO3). These reagents used in the experimental procedure, do not cause adverse effects on the environment and are cost effective. The results of FTIR, XRD, optical and scanning microscopy coupled with EDS analyses indicated that all of the applied treatments destructed the Chr structure and yielded silica of amorphous phase and the biomaterial glushinskite from the Oxac reacted with brucite [Mg(OH)2] layer. Each of the proposed formulations can be applied for the detoxification of asbestos, according to priorities related to the specific products of the recovery treatment. Therefore, Oxac acid leaching followed by the TEOS addition is preferred in cases of glushinskite recovery; TEOS treatment of asbestos with subsequent Oxac addition produced amorphous silica production; finally Oxac acid leaching followed by WG encapsulated the asbestos fibers and can be used in cases of onsite asbestos and ACM detoxification.


Assuntos
Asbestos Serpentinas/química , Ácido Oxálico/química , Dióxido de Silício/química , Microscopia Eletrônica de Varredura , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
19.
Inhal Toxicol ; 27(14): 787-801, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26671197

RESUMO

CONTEXT: Industrial hygiene assessments often focus on activity-based airborne asbestos concentration measurements, but few empirical data exist regarding the fiber removal rate from air after activities cease. OBJECTIVE: Grade 7T chrysotile indoor fiber settling (FS) rates were characterized using air sampling (NIOSH Method 7402). MATERIALS AND METHODS: Six replicate events were conducted in a 58 m(3) study chamber (ventilation 3.5 ACH), in which chrysotile-contaminated work clothing was manipulated for 15 min followed by 30 min of no activity. The fiber concentration decay constant and removal rate were characterized using an exponential decay model based on the measurements. RESULTS: Breathing zone airborne chrysotile concentrations decreased by 86% within 15-30 min after fiber disturbance, compared to concentrations during active disturbance (p < 0.05). Estimated mean time required for 99% of the phase contrast microscopy-equivalent (PCME) fibers to be removed from air was approximately 30 min (95% CI: 22-57 min). The observed effective FS velocity was 0.0034 m/s. This settling velocity was between 4.5-fold and 180-fold faster than predicted by two different particulate gravitational settling models. Additionally, PCME concentrations decreased approximately 2.5-fold faster than predicted due to air exchange alone (32 versus 79 min to 99% decrease in concentration). DISCUSSION: Other measurement studies have reported similar airborne fiber removal rates, supporting the finding that factors other than gravitational settling and dilution ventilation contribute measurably to PCM fiber removal from air (e.g. impaction, agglomeration). CONCLUSION: Overall, the scientific weight of evidence indicates that the time necessary for removal of 99% of fibers greater than 5 µm in length (with aspect ratios greater than 3:1) is approximately 20-80 min.


Assuntos
Poluentes Atmosféricos/química , Asbestos Serpentinas/química , Carcinógenos Ambientais , Monitoramento Ambiental , Gravitação , Modelos Teóricos , Ventilação
20.
Environ Sci Technol ; 49(22): 13340-9, 2015 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-26461183

RESUMO

We present real-time observations of the diffusion of individual asbestos fibers in water. We first scaled up a technique for fluorescent tagging and imaging of chrysotile asbestos fibers and prepared samples with a distribution of fiber lengths ranging from 1 to 20 µm. Experiments were then conducted by placing a 20, 100, or 150 ppm solution of these fibers in a liquid cell mounted on a spinning-disk confocal microscope. Using automated elliptical-particle detection methods, we determined the translation and rotation and two-dimensional (2D) trajectories of thousands of diffusing chrysotile fibers. We find that fiber diffusion is size-dependent and in reasonable agreement with theoretical predictions for the Brownian motion of rods. This agreement is remarkable given that experiments involved non-idealized particles at environmentally relevant concentrations in a confined cell, in which particle-particle and particle-wall interactions might be expected to cause deviations from theory. Experiments also confirmed that highly elongated chrysotile fibers exhibit anisotropic diffusion at short time scales, a predicted effect that may have consequences for aggregate formation and transport of asbestos in confined spaces. The examined fibers vary greatly in their lengths and were prepared from natural chrysotile. Our findings thus indicate that the diffusion rates of a wide range of natural colloidal particles can be predicted from theory, so long as the particle aspect ratio is properly taken into account. This is an important first step for understanding aggregate formation and transport of non-spherical contaminant particles, in the environment and in vivo.


Assuntos
Asbestos/análise , Microscopia Confocal/métodos , Asbestos/química , Asbestos Serpentinas/análise , Asbestos Serpentinas/química , Difusão , Microscopia Confocal/instrumentação , Água/química
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