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At least 19 recordsLinked to original sources
PubMed2004

Behaviour of the new asbestos amphibole fluor-edenite in different lung cell systems.

The aim of the present research was to determine whether the recently identified and characterized new fibrous amphibole fluoro-edenite may induce a cytopathic response in cultured cells. The final goal was to gain suggestions on the potentiality of fluoro-edenite to be harmful to human beings. Epidemiological studies, in fact, have shown an excess of developing mesothelioma among residents in Biancavilla, a town in eastern Sicily located in the Etna volcanic area. Therefore, we treated human lung fibroblasts, human lung alveolar epithelial cancer cell line A549 and monocyte-macrophage cell line J774 with fluoro-edenite or crocidolite; the latter used as a highly toxic amphibole asbestos reference. Our results show that fluoro-edenite may induce functional modifications and affects some biochemical parameters in tested cell cultures in a concentration and time dependent manner. However, the observed functional modifications induced by fluoro-edenite are generally less dramatic than those induced by crocidolite and more evident on human lung alveolar epithelial cancer cell line A549 with respect to those obtained on human lung fibroblasts or monocyte-macrophage cell line J774. The sequence of the damage is hypothesised to be as follows: at increasing fluoro-edenite concentrations, and/or treatment times, the increase in reactive oxygen species (ROS) production could trigger significant DNA damage in cell cultures, concomitantly with drop in cell metabolism and increase in lactic dehydrogenase release. In conclusion, according to our data, fluoro-edenite appears as a probable carcinogenic agent, responsible for the high incidence of malignant pleural mesothelioma in Biancavilla.

Animals↗
PubMed1997

Chemical characterization and reactivity of iron chelator-treated amphibole asbestos.

Iron in amphibole asbestos is implicated in the pathogenicity of inhaled fibers. Evidence includes the observation that iron chelators can suppress fiber-induced tissue damage. This is believed to occur via the diminished production of fiber-associated reactive oxygen species. The purpose of this study was to explore possible mechanisms for the reduction of fiber toxicity by iron chelator treatments. We studied changes in the amount and the oxidation states of bulk and surface iron in crocidolite and amosite asbestos that were treated with iron-chelating desferrioxamine, ferrozine, sodium ascorbate, and phosphate buffer solutions. The results have been compared with the ability of the fibers to produce free radicals and decompose hydrogen peroxide in a cell-free system in vitro. We found that chelators can affect the amount of iron at the surface of the asbestos fibers and its valence, and that they can modify the chemical reactivity of these surfaces. However, we found no obvious or direct correlations between fiber reactivity and the amount of iron removed, the amount of iron at the fiber surface, or the oxidation state of surface iron. Our results suggest that surface Fe3+ ions may play a role in fiber-related carboxylate radical formation, and that desferrioxamine and phosphate groups detected at treated fiber surfaces may play a role in diminishing and enhancing, respectively, fiber redox activity. It is proposed that iron mobility in the silicate structure may play a larger role in the chemical reactivity of asbestos than previously assumed.

Asbestos, Amphibole↗
PubMed2001

Free radical activity of natural and heat treated amphibole asbestos.

The amphibole minerals amosite and crocidolite were subjected to calcination and to hydrothermal treatment in order to study the effect of these heat treatments on the ability of the minerals to trigger formation of free radicals, which is known to be a main factor causing asbestosis and other asbestos-induced diseases. Free radical activity of the natural and heat treated minerals was studied by using supercoiled DNA (pUC18 plasmid) as a target molecule, and also by means of EPR spectroscopy. It was shown that after calcination of the natural minerals at 1073 K their free radical activity was strongly decreased These results, which may have relevant consequences for asbestos technology, were correlated with concomitant alteration of the structure and surface chemistry of the minerals during calcination.

Asbestos, Amosite↗
PubMed1998

On the mechanism of cogenotoxic action between ingested amphibole asbestos fibres and benzo[a]pyrene: I. Urinary and serum mutagenicity studies with rats.

Recently, there has been concern that ingested asbestos may cause an increase in cancer incidence in populations exposed to fibre-contaminated drinking water. Although animal experiments failed to demonstrate carcinogenicity of the oral asbestos exposure, the high adsorption capacity of the fibres creates the possibility of cocarcinogenic action with adsorbed organics. In a simple in vivo model we demonstrated earlier that UICC crocidolite and anthophyllite asbestos fibres were able to adsorb carcinogen molecules from aqueous solutions. When orally administered, these fibres increased the sister chromatid exchange frequency in bone marrow cells of rats. In the present study we tried to follow the desorption and metabolization processes of carcinogenic benzo[a]pyrene molecules transported by the ingested fibres using the highly sensitive Salmonella/Ames mutagenicity assay. The bacterial test was performed on concentrated serum and urine samples of the treated animals by using the TA98 and 100 strains in the presence and absence of liver microsomal and deconjugating enzymes. All sets of urine and serum samples failed to show mutagenic activity indicating a lack of both desorption in the serum and the ability of the liver to metabolize. Considering our results, the cytogenetic impact demonstrated earlier in the bone marrow can be explained by a local action of accumulated and transported carcinogen molecules.

Animals↗
PubMed1989

Relation between asbestosis and bronchial cancer in amphibole asbestos miners.

In a necropsy series of 339 amphibole asbestos miners heavy smoking, age, and the presence of asbestosis were significantly associated with the presence of bronchial cancer. Of the 35 cases of bronchial cancer, 24 were associated with asbestosis. Eleven cases of bronchial cancer occurred in men without asbestosis; all were smokers. Standardised proportional mortality rates indicated no excess of bronchial cancer in 302 exposed men without asbestosis whereas these rates were progressively raised in men with slight or moderate/severe asbestosis. Of the four exposure variables introduced separately into a logistic regression model, "years of exposure" made a small but significant contribution; "residence time" marginally failed to achieve a 5% level of significance. Two other exposure variables tested including cumulative fibre exposure (fibre years) made no significant contribution. In the absence of asbestosis at necropsy a bronchial cancer in a man exposed to asbestos is unlikely to be due to asbestos.

Asbestos↗
PubMed1991

Biological activity of synthetic amphibole asbestos.

The carcinogenic and fibrogenic activity of four samples of synthetic amphibole asbestos with different chemical structure was examined in white rats. Pleural mesotheliomas were found: in 11 out of 27 rats (37.8%) treated with magnesium asbestos; in 4 out of 24 animals (6.7%) for nickel asbestos; 13 out of 22 (59.1%) for cobalt asbestos; and in the experiment with asbestos where germanium was substituted for silicon pleural mesotheliomas were observed in 2 out of 55 rats (3.6%). No tumours of this kind were found in the control group. As revealed by the study results, all the examined samples of synthetic amphibole asbestos exhibited carcinogenic potentials. Correlation between the carcinogenic and fibrogenic activity could also be observed. The replacement of silicon with germanium produced considerable decrease in the carcinogenic and fibrogenic potentials of asbestos.

Animals↗
PubMed1992

Tumor incidence was not related to the thickness of visceral pleural in female Syrian hamsters intratracheally administered amphibole asbestos or manmade fibers.

Histological observations were performed on female Syrian hamsters 2 years after the intratracheal administration of amphibole asbestos, amosite, and crocidolite to evaluate the tumorigenicity of six types of fine manmade fibers (reported previously). A mesothelioma and a lung tumor were induced in 20 animals administered amosite, but no tumors were found in the crocidolite group. Because this incidence is not higher than that of manmade fibers, such as basic magnesium sulfate fiber [9 tumor-bearing hamsters in 20 hamsters (9/20)], metaphosphate fiber (5/20), calcium sulfate fiber (3/20), and fiberglass (2/20), it is suggested that some types of manmade fibers have a greater ability than asbestos to induce tumors. Moreover, as a specific observation in manmade fiber groups, tumors were induced at intracelial organs rather than at the pleural cavity. On the other hand, the average thickness of visceral pleura was higher in all asbestos and manmade fiber groups than in the control (2.9 microns), for instance, 36.95 microns in potassium titanate fiber group, 15.90 microns crocidolite group, 13.00 microns basic magnesium sulfate fiber group, and 10.45 microns in the rockwool group. Although both pleural thickening and mesothelioma are known as peculiar lesions in asbestos-exposed people, it might also be suggested that these lesions could be induced by different mechanisms from the result that there was no relation between the pleural thickening and mesothelioma incidence in hamsters.

Adenoma↗
PubMed1999

On the mechanism of cogenotoxic action between ingested amphibole asbestos fibres and benzo[a]pyrene: II. Tissue specificity studies using comet assay.

Epidemiological data seem to be equivocal on the probable increase in cancer incidence in populations exposed to asbestos-fibre contaminated drinking water. Although animal experiments failed to demonstrate carcinogenicity of oral asbestos exposure, the large surface area of the fibres, however, creates the possibility of cogenotoxic action with adsorbed water-borne organics. In our animal model, rats were gavaged with untreated UICC crocidolite and anthophyllite fibres and fibres that had been allowed to adsorb benzo[a]pyrene molecules from aqueous solutions. Peritoneal macrophages and intestine, parietal peritoneum and omentum samples were obtained from the animals after 24 h. The alkaline single-cell microgel electrophoresis assay (comet assay) was performed on cells isolated from the solid tissues. Tail moment was applied as a basis of evaluation following image analysis. Our results indicate high levels of DNA strand breaks in the cells prepared from the omentum and intestine. We could also demonstrate a significant potentiating effect of the adsorbed carcinogen on the induction of DNA damage in the omentum. The parietal peritoneum and macrophages were not involved in the early genotoxic alterations under study. Our results support the molecular model of asbestos cocarcinogenesis, including both asbestos-induced deletions and mutations caused by a mutagen carried by the same fibres.

Animals↗
PubMed2001

Spontaneous polymerisation on amphibole asbestos: relevance to asbestos removal.

Taking advantage of the spontaneous polymerisation of eugenol to lignin-like species catalysed by the surface of crocidolite fibres, a procedure is proposed, possibly useful in asbestos removal and disposal, where the polymer avoids the release of airborne fibres and also scavenges ROS (reactive oxygen species).

Air Pollutants↗
PubMed1978

The effect of fibre size on the in vitro biological activity of three types of amphibole asbestos.

Three standard (UICC) samples of amphibole asbestos were subjected to ball-milling; the main effect of this procedure was to reduce the length of the fibres present in each sample. The numbers of fibres in unit masses, and the distribution of fibre sizes in all the samples, both parent and milled, were estimated from electron micrographs. The ability of all the samples to reduce the plating efficiency of V79-4 cells is compared, on the basis of mass, fibre number and fibre number number above various length thresholds. This biological activity of all the samples correlated best with the number of fibres above a threshold length of 6.5 micron. This is compared with the sizes of fibre previously reported to induce mesotheliomata when implanted into the pleural cavities of rats.

Asbestos↗
PubMed2006

A review of scientific literature examining the mining history, geology, mineralogy, and amphibole asbestos health effects of the Rainy Creek igneous complex, Libby, Montana, USA.

This article reviews the past 90 yr of scientific research directed on multiple aspects of the unique geology and environmental health issues surrounding the vermiculite deposit found at Libby, MT. Hydrothermal alteration and extensive weathering of the ultramafic units resulted in the formation of a rich deposit of vermiculite that was mined for 67 yr and used in numerous consumer products in its expanded form. Later intrusions of alkaline units caused hydrothermal alteration of the pyroxenes, resulting in formation of amphiboles. Some of these amphiboles occur in the asbestiform habit and have been associated with pulmonary disease in former miners and mill workers. Identification of these amphibole asbestos minerals has received little attention in the past, but recent work shows that the majority of the amphibole mineral species present may not be any of the amphibole species currently regulated by government agencies. Epidemiological studies on former miners have, nevertheless, shown that the amphibole asbestos from the Rainy Creek igneous complex is harmful; also, a recent study by the Agency for Toxic Substances and Disease Registry shows that residents of Libby who had not been employed in the vermiculite mining or milling operations also appear to have developed asbestos-related pulmonary diseases at a higher rate than the general public elsewhere. Since November 1999, the U.S. Environmental Protection Agency has been involved in the cleanup of asbestos-contaminated sites in and around Libby associated with the mining and processing of vermiculite.

Aluminum Silicates↗
PubMed1990

Analysis of amphibole asbestos in chrysotile and other minerals.

Chrysotile asbestos and many other mineral raw materials contain amphibole minerals which may be asbestiform. There is currently no analytical method which will detect the presence of amphibole at sufficiently low limits to preclude the possibility of inadvertent exposure of persons handling these materials to hazardous airborne fibre concentrations. A method of chemical digestion of chrysotiles has been tested with regard to the determination of their tremolite contaminant content and this has been applied to a range of chrysotile and other minerals. The method improves the sensitivity of the amphibole analysis at least 10-fold giving detection limits of 0.01-0.05% in chrysotile by X-ray diffractometry (XRD). The difficulties arising from compositional and morphological variations are discussed in the context of the potential hazards from airborne fibres and the relative values of analyses by XRD, infrared spectrophotometry (IR) and electron microscopy. It is concluded that XRD and IR are useful as screening methods for the detection of amphibole in chrysotile but other materials should be analysed by optical or electron microscopy.

Asbestos↗
PubMed1990

Evidence for an amphibole asbestos threshold exposure for asbestosis assessed by autopsy in South African asbestos miners.

In an attempt to determine whether there exists a threshold asbestos dose below which asbestosis does not occur, data on 807 men who had worked on amphibole asbestos mines and undergone autopsy were analysed. When exposure was expressed as fibre-years no asbestosis was found at autopsy when exposure was up to 2 fibre-years, even after 31-45 years of residence time. In the group exposed to greater than 2-5 fibre-years asbestosis was found. When exposure was expressed as average fibre concentration asbestosis occurred below 2 fibres per ml (f ml-1) and the prevalence increased with residence time. In conclusion, if a threshold dose for asbestosis does exist it is at approximately 2 fibre-years if off-shift exposure is ignored.

Adolescent↗
PubMedDate not supplied

Mesothelioma and exposure to mixtures of chrysotile and amphibole asbestos.

This paper provides a new analysis of previously published work and draws attention to the possibility that mixtures of amphiboles and chrysotile appear more commonly in the lungs of mesothelioma patients compared to controls than do either of the main types of fiber alone. The possibility that these results may indicate a synergistic interaction between chrysotile and the amphiboles is discussed in the light of the epidemiological data.

Asbestos↗