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Alessandro Pacella - One of the best experts on this subject based on the ideXlab platform.

  • surface and bulk modifications of Amphibole Asbestos in mimicked gamble s solution at acidic ph
    Scientific Reports, 2021
    Co-Authors: Alessandro Pacella, Paolo Ballirano, Marzia Fantauzzi, Elisa Nardi, Antonella Rossi, Gian Carlo Capitani, Lorenzo Arrizza, Maria Rita Montereali
    Abstract:

    This study aimed at investigating the surface modifications occurring on Amphibole Asbestos (crocidolite and tremolite) during leaching in a mimicked Gamble’s solution at pH of 4.5 and T = 37 °C, from 1 h up to 720 h. Results showed that the fibre dissolution starts with the release of cations prevalently allocated at the various M- and (eventually) A-sites of the Amphibole structure (incongruent dissolution). The amount of released silicon, normalized to fibre surface area, highlighted a leaching faster for the crocidolite sample, about twenty times higher than that of tremolite. Besides, the fast alteration of crocidolite promotes the occurrence of Fe centres in proximity of the fibre surface, or possibly even exposed, particularly in the form of Fe(II), of which the bulk is enriched with respect to the oxidized surface. Conversely, for tremolite fibres the very slow fibre dissolution prevents the underlying cations of the bulk to be exposed on the mineral surface, and the iron oxidation, faster than the leaching process, significantly depletes the surface Fe(II) centres initially present. Results of this work may contribute to unravel possible correlations between surface properties of Amphibole Asbestos and its long-term toxicity.

  • towards a detailed comprehension of the inertisation processes of Amphibole Asbestos in situ high temperature behaviour of fibrous tremolite
    Mineralogical Magazine, 2020
    Co-Authors: Paolo Ballirano, Alessandro Pacella
    Abstract:

    Thermal behaviour of fibrous tremolite from Maryland, USA has been investigated in situ up to breakdown temperature. Tremolite can be found both as primary constituent and as contaminant in Asbestos Containing Materials (ACMs). The products of breakdown are subcalcic diopside and calcium-rich clinoenstatite in a 2:1 ratio, traces of hematite plus minor silica-rich amorphous material. Thermal expansion follows a regular trend up to 723 K before the onset of Fe2+ oxidation/OH– deprotonation which is completed at 1023 K. At 923 K the Fe3+ migration starts towards M(1) and the corresponding counter-migration of Mg to M(2) and M(3). At T close to structure breakdown, M(2) shows a significant site-scattering reduction possibly consistent with the occurrence of minor vacancies. In fully oxidised tremolite, Fe3+ is allocated prevalently at M(1) and subordinately at M(3). As it is well-known that M(1), along with M(2), is the most exposed octahedral site at the surface of Amphiboles, most of the Fe3+ is available for participating in the Fenton-like reactivity of oxidised tremolite, potentially making it dangerous for human health. This point should be properly taken into account in the evaluation of the safety of thermally decomposed tremolite-containing ACMs, in particular in the case of accidentally incomplete treatments.

  • Surface reactivity of Amphibole Asbestos: A comparison between two tremolite samples with different surface area
    Periodico Di Mineralogia, 2018
    Co-Authors: Alessandro Pacella, Maura Tomatis, Giovanni B. Andreozzi, Ingrid Corazzari, Francesco Turci
    Abstract:

    The present study investigates how the specific surface area modulates chemical reactivity of Amphibole Asbestos. Surface reactivity of a fibrous tremolite sample from Castelluccio Superiore (Italy) was investigated by means of free radical generation following incubation in an oxidant environment and compared with that of  another fibrous tremolite sample (from Maryland, USA), with much smaller surface area, previously studied by Andreozzi et al. (2017). Both samples were comparable in terms of bulk, crystal and surface chemistry and only differed for their surface area, namely 10.1 and 2.75 m 2 g -1 for Castelluccio and Maryland sample, respectively. Tremolite was incubated in H 2 O 2 solution buffered at pH 7.4 for several time points, ranging from 1 day to 1 month. Structural, morphological, and chemical alterations induced on tremolite by incubation were investigated by HR-TEM and EDS. The generation of HO • and COO -• radicals following reaction of tremolite with H 2 O 2 or formate ion was investigated by spin trapping/EPR spectroscopy. The dissolution process and surface modification were slower for the Maryland sample, with lowest surface area. Kinetics of fibre dissolution and surface modification indicated the occurrence of either low-coordinated or high-coordinated Fe centres on the surface, as well as the evolution of nuclearity of those Fe centres (preventing or enhancing the formation of clusters and nanoparticles). In turn, iron centres determine the reaction of fibre surface with hydrogen peroxide and formate ion and the yield of HO • and COO - • radical species. The evolution of radical reactivity over time was proved to be largely dependent on surface area, with the highest radical yield occurring for low-area tremolite incubated over long times. The experimental results obtained in this study as well as the comparison with previous studies further confirm that surface reactivity of mineral fibres and inorganic particles is not dependent on Fe tot content per se, but is likely due to surface properties and occurrence of specific iron sites.

  • surface reactivity of Amphibole Asbestos a comparison between crocidolite and tremolite
    Scientific Reports, 2017
    Co-Authors: Giovanni B. Andreozzi, Maura Tomatis, Alessandro Pacella, Ingrid Corazzari, Francesco Turci
    Abstract:

    Among Asbestos minerals, fibrous riebeckite (crocidolite) and tremolite share the Amphibole structure but largely differ in terms of their iron content and oxidation state. In Asbestos toxicology, iron-generated free radicals are largely held as one of the causes of Asbestos malignant effect. With the aim of clarifying i) the relationship between Fe occurrence and Asbestos surface reactivity, and ii) how free-radical generation is modulated by surface modifications of the minerals, UICC crocidolite and fibrous tremolite from Maryland were leached from 1 day to 1 month in an oxidative medium buffered at pH 7.4 to induce redox alterations and surface rearrangements that may occur in body fluids. Structural and chemical modifications and free radical generation were monitored by HR-TEM/EDS and spin trapping/EPR spectroscopy, respectively. Free radical yield resulted to be dependent on few specific Fe2+ and Fe3+ surface sites rather than total Fe content. The evolution of reactivity with time highlighted that low-coordinated Fe ions primarily contribute to the overall reactivity of the fibre. Current findings contribute to explain the causes of the severe Asbestos-induced oxidative stress at molecular level also for iron-poor Amphiboles, and demonstrate that Asbestos have a sustained surface radical activity even when highly altered by oxidative leaching.

  • surface alteration mechanism and topochemistry of iron in tremolite Asbestos a step toward understanding the potential hazard of Amphibole Asbestos
    Chemical Geology, 2015
    Co-Authors: Alessandro Pacella, Francesco Turci, Marzia Fantauzzi, Carlo Cremisini, Maria Rita Montereali, Elisa Nardi, Davide Atzei, Antonella Rossi, Giovanni B. Andreozzi
    Abstract:

    Abstract Non-occupational, environmental and unintentional exposure to fibrous tremolite, one of the most widespread naturally occurring Asbestos, represents a potentially significant geological risk in several parts of the world. The toxicity of Amphibole Asbestos is commonly related to iron content and oxidation state, but information available on surface iron topochemistry and Amphibole alteration mechanism is still rather poor. With the aim to shed a light on this mechanism, two tremolite samples, one from Italy (Castelluccio) and one from USA (Maryland), immersed in a buffer solution (pH 7.4) with H 2 O 2 were characterized by a multi-technique approach. X-ray photoelectron spectroscopy (XPS) and high resolution–transmission electron microscopy (HR-TEM) were used to investigate the surface chemistry of the incubated samples and to detect structural modifications of the fibres, while inductively coupled plasma optical emission spectrometry (ICP-OES) was used to determine the concentration of dissolved elements. An original four-step model for Amphibole alteration pathway is proposed. The alteration process starts with an incongruent dissolution of the Amphiboles that produces an amorphous, altered surface layer and that is followed by iron oxidation and formation of FeOOH species. Then the congruent dissolution of the altered layer starts and, subsequently, the residual Fe oxi-hydroxides aggregates and insoluble, Fe-rich, amorphous nanoparticles on top of the fibres are formed. The results are compared to those obtained on crocidolite, a highly toxic Amphibole Asbestos with a 10 to 20 times higher iron content than tremolite. The high chemical reactivity observed in the literature for tremolite appears to be related not only to its iron content and oxidation state, but also to the low nuclearity of iron on the altered surfaces, in contrast to pronounced Fe clusterization at crocidolite surfaces. This is a significant step toward a conceivable explanation of why Asbestos tremolite is potentially as toxic as crocidolite.

Tanis Hernandez - One of the best experts on this subject based on the ideXlab platform.

  • social support functions during a slowly evolving environmental disaster the case of Amphibole Asbestos exposure in libby montana
    Health Communication, 2015
    Co-Authors: Rebecca Welch J Cline, Tanis Hernandez, Heather Orom, Jeffrey T Child, Brad Black
    Abstract:

    Previous research concluded that victims of rapid-onset natural disasters (e.g., hurricanes) receive and provide high levels of instrumental support. However, different kinds of disasters (natural or human caused [technological, environmental, intentional/terrorism], rapid or slow onset, short or long duration) may create different stressors and thus influence the types of social support most needed and provided. We explored social support functions during an ongoing “slowly-evolving environmental disaster” in Libby, Montana due to widespread exposure to Amphibole Asbestos. Analyses of focus groups and in-depth interviews focused on the relative salience of support functions (emotional, informational, instrumental, and spiritual) identified as needed or provided. Dominant themes emerged around each function. Results indicated that informational support is particularly salient in this type of disaster. Although not all community members had experienced the disaster’s health consequences (Asbestos-related d...

  • The Role of Social Toxicity in Responses to a Slowly-Evolving Environmental Disaster: The Case of Amphibole Asbestos Exposure in Libby, Montana, USA
    American Journal of Community Psychology, 2014
    Co-Authors: Rebecca J. W. Cline, Heather Orom, Jae Eun Chung, Tanis Hernandez
    Abstract:

    Experiencing a disaster has significant negative effects on psychological adjustment. Case study accounts point to two consistent trends in slowly-evolving environmental disasters: (a) patterns of negative social dynamics, and (b) relatively worse psychological outcomes than in natural disasters. Researchers have begun to explicitly postulate that the social consequences of slowly-evolving environmental disasters (e.g., community conflict) have their own effects on victims’ psychological outcomes. This study tested a model of the relationship between those social consequences and psychological adjustment of victims of a slowly-evolving environmental disaster, specifically those whose health has been compromised by the Amphibole Asbestos disaster in Libby, MT. Results indicate that experiencing greater community conflict about the disaster was associated with greater family conflict about the disaster which, in turn, was associated with greater social constraints on talking with others about their disease, both directly and indirectly through experiencing stigmatization. Experiencing greater social constraints was associated with worse psychological adjustment, both directly and indirectly through failed social support. Findings have implications for understanding pathways by which social responses create negative effects on mental health in slowly-evolving environmental disasters. These pathways suggest points for prevention and response (e.g., social support, stigmatization of victims) for communities experiencing slowly-evolving environmental disasters.

  • psychosocial health status of persons seeking treatment for exposure to libby Amphibole Asbestos
    International Scholarly Research Notices, 2011
    Co-Authors: Clarann Weinert, Brad Black, Tanis Hernandez, Charlene A Winters, Wade G Hill, Kimberly Rowse, Sandra W Kuntz, Shirley Cudney
    Abstract:

    A cross-sectional exploratory study was conducted to describe the psychosocial health status of persons seeking health care for exposure to Libby Amphibole Asbestos (LAA). Health indicators including depression, stress, acceptance of illness, and satisfaction with access and financial aspects of care were obtained via electronic and paper-pencil survey. The exposure pathway and demographic data were gleaned from the health record. Of the 386 participants, more than one-third (34.5%) demonstrated significant levels of psychological distress. The oldest group of women had the lowest levels of depression and stress and the highest acceptance of illness. Gender, age, and satisfaction with financial resources were significantly related to depression, stress, and acceptance of illness. Satisfaction with access to care was significant only for stress. No differences in depression, stress, and acceptance of illness were found based on residence, exposure pathway, or insurance status.

  • Community-Level Social Support Responses in a Slow-Motion Technological Disaster: The Case of Libby, Montana
    American Journal of Community Psychology, 2010
    Co-Authors: Rebecca J. W. Cline, Heather Orom, Tanis Hernandez, Lisa Berry-bobovski, Ann G. Schwartz, C. Brad Black, John C. Ruckdeschel
    Abstract:

    Social support is an important resource for communities experiencing disasters. However, a disaster’s nature (rapid- versus slow-onset, natural versus technological) may influence community-level responses. Disaster research on social support focuses primarily on rapid-onset natural disasters and, to a lesser extent, rapid-onset technological disasters. Little research has addressed slow-onset disasters. This study explores social support processes in Libby, MT, a community experiencing a “slow-motion technological disaster” due to widespread Amphibole Asbestos exposure. A comprehensive social support coding system was applied to focus-group and in-depth-interview transcripts. Results reveal that, although the community has a history of normative supportiveness during community and individual crises, that norm has been violated in the Asbestos disaster context. Results are interpreted as a failure to achieve an “emergent altruistic community.” Specifically, community-level conflict appears to interfere with previously established social support patterns. The observed phenomenon can be understood as the deterioration of a previously supportive community.

Bice Fubini - One of the best experts on this subject based on the ideXlab platform.

  • loss of surface reactivity upon heating Amphibole Asbestos
    Langmuir, 2002
    Co-Authors: Maura Tomatis, Laura Prandi, Silvia Bodoardo, Bice Fubini
    Abstract:

    Two Amphibole Asbestos, crocidolite and amosite, have been heated at 400 and 800 °C in order to examine the variations in some surface properties relevant to Asbestos toxicity, such as iron mobility, free radical generation, and hydrophilicity. At 400 °C, only the surface is modified, while at 800 °C the crystalline structure partially collapses (X-ray diffraction) with loss in specific surface (Brunauer−Emmett−Teller). Two chelators, ferrozine and desferrioxamine, were employed to evaluate Fe(II) and Fe(III), respectively. More iron was extracted by deferoxamine from crocidolite than from amosite, but when compared per unit surface, the extent of iron removed from the two Asbestos was the same. Ferrozine removed more iron from unheated amosite than from crocidolite. Upon heating, because of the oxidation of Fe(II) to Fe(III), less (400 °C) or no (800 °C) iron is removed by ferrozine. The amount of iron removed by deferoxamine is virtually unaffected by heating at 400 °C but dramatically decreases after t...

  • spontaneous polymerisation on Amphibole Asbestos relevance to Asbestos removal
    Chemical Communications, 2001
    Co-Authors: Ivana Fenoglio, Maura Tomatis, Bice Fubini
    Abstract:

    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).

  • free radical activity of natural and heat treated Amphibole Asbestos
    Journal of Inorganic Biochemistry, 2001
    Co-Authors: Otero C Arean, Bice Fubini, Ivana Fenoglio, F Barcelo, F Llabres X I Xamena, Maura Tomatis
    Abstract:

    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.

  • reactive sites at the surface of crocidolite Asbestos
    Langmuir, 1999
    Co-Authors: Gianmario Martra, Elena Chiardola, Salvatore Coluccia, Leonardo Marchese, And Maura Tomatis, Bice Fubini
    Abstract:

    The reactive sites at the surface of crocidolite (Amphibole Asbestos) which may play a role in the toxicity of the fibrous mineral have been investigated by measuring the adsorption of nitric oxide (infrared spectroscopy and adsorption calorimetry) and the release of free radicals in aqueous suspensions. The fibers have been thermally modifiedprogressively heated in vacuo up to 800 °C, calcined in air at 400 °C, and kept under hydrothermal conditions at 200 °Cin order to mimic modifications likely to occur upon weathering. While the crystal structure, as revealed by XRD, was stable up to 600 °C, IR spectroscopy indicated that from 400 to 600 °C OH groups are eliminated and changes in the lattice vibrations occur. Calcination at 400 °C, which oxidizes part of Fe2+ to Fe3+, as evidenced by diffuse reflectance UV−vis spectroscopy, eliminates OH groups and modifies lattice vibrations. The hydrothermal treatment causes oxidation of Fe2+ only to a limited extent. Upon contact with deuterated water, irreversibly...

  • Chemical characterization and reactivity of iron chelator-treated Amphibole Asbestos.
    Environmental Health Perspectives, 1997
    Co-Authors: Julie Gold, Helena Amandusson, Anatol Krozer, Bengt Herbert Kasemo, Tore Ericsson, Giovanna Zanetti, Bice Fubini
    Abstract:

    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 ...

Brad Black - One of the best experts on this subject based on the ideXlab platform.

  • childhood exposure to libby Amphibole Asbestos and respiratory health in young adults
    Environmental Research, 2017
    Co-Authors: Brad Black, James E Lockey, Timothy J Hilbert, Linda Levin, Carol Rice, Patrick H Ryan, Jeff Burkle, Cole Brokamp, Roy T Mckay
    Abstract:

    Abstract Objectives Vermiculite ore containing Libby Amphibole Asbestos (LAA) was mined in Libby, MT, from the 1920s-1990. Recreational and residential areas in Libby were contaminated with LAA. This objective of this study was to characterize childhood exposure to LAA and investigate its association with respiratory health during young adulthood. Methods Young adults who resided in Libby prior to age 18 completed a health and activity questionnaire, pulmonary function testing, chest x-ray and HRCT scan. LAA exposure was estimated based on participant report of engaging in activities with potential LAA exposure. Quantitative LAA estimates for activities were derived from sampling data and literature reports. Results A total of 312 participants (mean age 25.1 years) were enrolled and reported respiratory symptoms in the past 12 months including pleuritic chest pain (23%), regular cough (17%), shortness of breath (18%), and wheezing or whistling in the chest (18%). Cumulative LAA exposure was significantly associated with shortness of breath (aOR = 1.12, 95% CI 1.01–1.25 per doubling of exposure). Engaging in recreational activities near Rainy Creek Road (near the former mine site) and the number of instances heating vermiculite ore to make it expand or pop were also significantly associated with respiratory symptoms. LAA exposure was not associated with pulmonary function or pleural or interstitial changes on either chest x-ray or HRCT. Conclusions Pleural or interstitial changes on x-ray or HRCT were not observed among this cohort of young adults. However, childhood exposure to LAA was significantly associated with respiratory symptoms during young adulthood. Pleuritic chest pain, in particular, has been identified as an early symptom associated with LAA exposure and therefore warrants continued follow-up given findings of progressive disease in other LAA exposed populations.

  • multiple pathway Asbestos exposure assessment for a superfund community
    Journal of Exposure Science and Environmental Epidemiology, 2015
    Co-Authors: Curtis W. Noonan, Kathrene Conway, Tracy Mcnew, Laura Linker, Brad Black, Jaime Szeinuk, Jean C. Pfau, Erin L Landguth, Raja M Flores
    Abstract:

    Libby, MT, USA, was the home to workers at a historical vermiculite mining facility and served as the processing and distribution center for this industrial product that was contaminated with Amphibole Asbestos. Several pathways of environmental Asbestos exposure to the general population have been identified. The local clinic and health screening program collects data from participants on past occupational and environmental exposures to vermiculite and Asbestos. Health studies among this population have demonstrated associations between Amphibole exposure and health outcomes, but critical questions regarding the nature and level of exposure associated with specific outcomes remain unanswered. The objective of this study was to develop a comprehensive exposure assessment approach that integrates information on individuals’ contact frequency with multiple exposure pathways. For 3031 participants, we describe cumulative exposure metrics for environmental exposures, occupational exposures, and residents’ contact with carry-home Asbestos from household workers. As expected, cumulative exposures for all three occupational categories were higher among men compared with women, and cumulative exposures for household contact and environmental pathways were higher among women. The comprehensive exposure assessment strategies will advance health studies and risk assessment approaches in this population with a complex history of both occupational and environmental Asbestos exposure.

  • social support functions during a slowly evolving environmental disaster the case of Amphibole Asbestos exposure in libby montana
    Health Communication, 2015
    Co-Authors: Rebecca Welch J Cline, Tanis Hernandez, Heather Orom, Jeffrey T Child, Brad Black
    Abstract:

    Previous research concluded that victims of rapid-onset natural disasters (e.g., hurricanes) receive and provide high levels of instrumental support. However, different kinds of disasters (natural or human caused [technological, environmental, intentional/terrorism], rapid or slow onset, short or long duration) may create different stressors and thus influence the types of social support most needed and provided. We explored social support functions during an ongoing “slowly-evolving environmental disaster” in Libby, Montana due to widespread exposure to Amphibole Asbestos. Analyses of focus groups and in-depth interviews focused on the relative salience of support functions (emotional, informational, instrumental, and spiritual) identified as needed or provided. Dominant themes emerged around each function. Results indicated that informational support is particularly salient in this type of disaster. Although not all community members had experienced the disaster’s health consequences (Asbestos-related d...

  • Amphibole Asbestos exposure metrics for a superfund community
    ISEE Conference Abstracts, 2014
    Co-Authors: Curtis W. Noonan, Tracy Mcnew, Laura Linker, Brad Black, Jaime Szeinuk, Jean C. Pfau, Erin L Landguth, Kathrene R Conway, Raja M Flores
    Abstract:

    Background: Libby, Montana, located in the Rocky Mountain region of the United States, was home to workers at a historical vermiculite mining facility. The material was contaminated with Amphibole ...

  • descriptive analysis of the respiratory health status of persons exposed to libby Amphibole Asbestos
    BMJ Open, 2012
    Co-Authors: Charlene A Winters, Brad Black, Wade G Hill, Kimberly Rowse, Sandra W Kuntz, Clarann Weinert
    Abstract:

    Objective: Describe respiratory health and quality of life in persons exposed to Libby Amphibole Asbestos (LAA) contaminated vermiculite. Design: Cross-sectional descriptive. Setting: Asbestos-related disease clinic in Libby,

David M Bernstein - One of the best experts on this subject based on the ideXlab platform.

  • the health risk of chrysotile Asbestos
    Current Opinion in Pulmonary Medicine, 2014
    Co-Authors: David M Bernstein
    Abstract:

    Purpose of review The word Asbestos is a poorly attributed term, as it refers to two very different minerals with very different characteristics. One is the serpentine mineral of which the white Asbestos, chrysotile, is the most common. The other is the Amphibole Asbestos, which includes the blue Asbestos crocidolite and the brown Asbestos amosite. Although today chrysotile is the only type used commercially, the legacy of past use of Amphibole Asbestos remains. This review clarifies the differences between the two mineral families referred to as Asbestos and summarizes the scientific basis for understanding the important differences in the toxicology and epidemiology of these two minerals. Recent findings Biopersistence and sub-chronic inhalation toxicology studies have shown that exposure to chrysotile at up to 5000 times the current threshold limit value (0.1 fibers/cm) produces no pathological response. These studies demonstrate as well that following short-term exposure the longer chrysotile fibers rapidly clear from the lung and are not observed in the pleural cavity. In contrast, short-term exposure to Amphibole Asbestos results quickly in the initiation of a pathological response in the lung and the pleural cavity. Summary Significant progress has been made in understanding the factors that influence inhalation toxicology studies of fibers and epidemiological studies of workers. Evaluation of the toxicology and epidemiology studies of chrysotile indicates that it can be used safely under controlled use. In contrast, even short-term exposure to Amphibole Asbestos can result in disease.

  • the health effects of chrysotile current perspective based upon recent data
    Regulatory Toxicology and Pharmacology, 2006
    Co-Authors: David M Bernstein, John A Hoskins
    Abstract:

    This review substantiates kinetically and pathologically the diVerences between chrysotile and Amphiboles. The serpentine chrysotile is a thin walled sheet silicate while the Amphiboles are double-chain silicates. These diVerent chemistries result in chrysotile clearing very rapidly from the lung (T1/2 D 0.3 to 11 days) while Amphiboles are among the slowest clearing Wbers known (T1/2 D 500 days to 1). Across the range of mineral Wber solubilities chrysotile lies towards the soluble end of the scale. Chronic inhalation toxicity studies with chrysotile in animals have unfortunately been performed at very high exposure concentrations resulting in lung overload. Consequently their relevance to human exposures is extremely limited. Chrysotile following subchronic inhalation at a mean exposure of 76 Wbers L >2 0m/ cm 3 (3413 total Wbers/cm 3 ) resulted in no Wbrosis (Wagner score 1.8–2.6), at any time point and no diVerence with controls in BrdU response or biochemical and cellular parameters. The long chrysotile Wbers were observed to break apart into small particles and smaller Wbers. Toxicologically, chrysotile which rapidly falls apart in the lung behaves more like non-Wbrous mineral dusts while response to Amphibole Asbestos reXects its insoluble Wbrous structure. Recent quantitative reviews of epidemiological studies of mineral Wbers have determined the potency of chrysotile and Amphibole Asbestos for causing lung cancer and mesothelioma in relation to Wber type have also diVerentiated between these two minerals. The most recent analyses also concluded that it is the longer, thinner Wbers that have the greatest potency as has been reported in animal inhalation toxicology studies. However, one of the major diYculties in interpreting these studies is that the original exposure estimates rarely diVerentiated between chrysotile and Amphiboles. Not unlike some other respirable particulates, to which humans are, or have been heavily occupationally exposed, there is evidence that heavy and prolonged exposure to chrysotile can produce lung cancer. The value of the present and other similar studies is that they show that low exposures to pure chrysotile do not present a detectable risk to health. Since total dose over time decides the likelihood of disease occurrence and progression, they also suggest that the risk of an adverse outcome may be low if even any high exposures experienced were of short duration.

  • the biopersistence of canadian chrysotile Asbestos following inhalation final results through 1 year after cessation of exposure
    Inhalation Toxicology, 2005
    Co-Authors: David M Bernstein, Rick A Rogers, Paul Smith
    Abstract:

    Chrysotile Asbestos, a serpentine mineral, has been shown to be notably different from Amphibole Asbestos such as amosite, crocidolite, and tremolite in that chrysotile once inhaled is rapidly removed from the lung while the Amphiboles persist. This has been demonstrated for three different chrysotile samples from Canada, the United States, and Brazil. The initial results of the inhalation biopersistence study on the Canadian chrysotile were reported earlier. This article presents the full results through 365 days after cessation of exposure. In order to fully understand the dynamics of the clearance of chrysotile from the lung, the study included a standardised inhalation biopersistence study following the recommendations of the European Commission (EC) Interim Protocol for the Inhalation Biopersistence of synthetic mineral fibers () in which the lungs were digested to evaluate fiber content remaining. In addition, confocal microscopy was used to examine lungs in three dimensions to determine where and w...

  • the biopersistence of brazilian chrysotile Asbestos following inhalation
    Inhalation Toxicology, 2003
    Co-Authors: David M Bernstein, Rick A Rogers
    Abstract:

    With the initial understanding of the relationship of Asbestos to disease, little information was available on whether the two different groups of minerals which are called Asbestos were of similar or different potency in causing disease. Asbestos was often described as a durable fiber which if inhaled would remain in the lung and cause disease. It has been only more recently with the development of a standardised protocol for evaluating the biopersistence of mineral fibers in the lung that the clearance kinetics of the serpentine chrysotile have been shown to be dramatically different from those of Amphibole Asbestos with chrysotile clearing rapidly from the lung. In addition, recent epidemiology studies also differentiate chrysotile form Amphibole Asbestos. The above mentioned biopersistence studies have indicated that chrysotile from Canada and California clear rapidly from the lung once inhaled. However, variations in chrysotile mineralogy have been reported depending upon the region. This is most likely associated with variations in the forces which created the chrysotile fibers centuries ago. In the present study, the dynamics and rate of clearance of chrysotile from the Cana Brava mine in central Brazil was evaluated in a comparable inhalation biopersistence study in the rat. For synthetic vitreous fibers, the biopersistence of the fibers longer than 20 µm has been found to be directly related to their potential to cause disease. This study was designed to determine lung clearance (biopersistence) and translocation and distribution within the lung. As the long fibers have been shown to have the greatest potential for pathogenicity, the chrysotile samples were specifically chosen to have more than 450 fibers/cm 3 longer than 20 µm in length present in the exposure aerosol.

  • comparison of calidria chrysotile Asbestos to pure tremolite inhalation biopersistence and histopathology following short term exposure
    Inhalation Toxicology, 2003
    Co-Authors: David M Bernstein, Jorg Chevalier, Paul Smith
    Abstract:

    The differences between chrysotile Asbestos, a serpentine mineral, and Amphibole Asbestos have been debated extensively. Many studies have shown that chrysotile is cleared from the lung more rapidly than Amphibole. In order to quantify the comparative clearance of chrysotile and the Amphibole Asbestos tremolite, both fibers were evaluated in an inhalation biopersistence study that followed the European Commission recommended guidelines. In addition, the histopathological response in the lung was evaluated following the short-term exposure. This article presents the results of this study through 90 days after cessation of exposure. Following the termination of the study, a subsequent article will provide the complete results through 12 mo after cessation of exposure. In order to quantify the dynamics and rate by which these fibers are removed from the lung, the biopersistence of a sample of commercial grade chrysotile from the Coalinga mine in New Idria, CA, of the type Calidria RG144 and of a long-fiber t...