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Fubini B, Aust AE, Bolton RE, Borm PJ, Bruch J, Ciapetti G, Donaldson K, Elias Z, Gold J, Jaurand MC, Kane AB, Lison D, Muhle H. Non-animal Tests for Evaluating the Toxicity of Solid Xenobiotics. Altern Lab Anim 2020. [DOI: 10.1177/026119299802600505] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Bice Fubini
- Central Science Laboratory, Sand Hutton, North Yorkshire YO4 1LZ, UK
| | - Ann E. Aust
- Department of Health Risk Analysis, University of Limburg, 6200 MD Maastricht, The Netherlands
| | - Robert E. Bolton
- Institut für Hygiene und Arbeitsmedizin, Universitäts-klinikum Essen, Hufelandstrasse 55, 4300 Essen, Germany
| | - Paul J.A. Borm
- Laboratorio di Biocompatibilità dei Materiali da Impianto, Istituti Ortopedici Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy
| | - Joachim Bruch
- Department of Biological Sciences, Napier University, 10 Golinton Road, Edinburgh EH10 5DT, UK
| | - Gabriela Ciapetti
- INRS Laboratoire de Carcinogenèse In Vitro, Avenue de Bourgogne, 54501 Vandoeuvre Les Nancy Cedex, France
| | - Ken Donaldson
- Department of Applied Physics, Chalmers University of Technology, University of Gothenburg, 412 96 Gothenburg, Sweden
| | - Zoe Elias
- INSERM, U139, Faculté de Medicine, 8 rue du General Sarrail, 94010 Créteil Cedex, France
| | - Julie Gold
- Department of Pathology and Laboratory Medicine, Division of Biology and Medicine, Brown University, Providence, RI 02912, USA
| | - Marie Claude Jaurand
- INSERM, U139, Faculté de Medicine, 8 rue du General Sarrail, 94010 Créteil Cedex, France
| | - Agnes B. Kane
- Department of Pathology and Laboratory Medicine, Division of Biology and Medicine, Brown University, Providence, RI 02912, USA
| | - Dominique Lison
- Industrial Toxicology and Occupational Medicine, Catholic University of Louvain, Clos Chapelle-aux-Champs 30.54, 1200 Brussels, Belgium
| | - Hartwig Muhle
- Fraunhofer Institut Toxikologie und Aerosol-forschung, Nikolai-Fuchs-Strasse 1, 30625 Hannover, Germany
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Boyles MSP, Brown D, Knox J, Horobin M, Miller MR, Johnston HJ, Stone V. Assessing the bioactivity of crystalline silica in heated high-temperature insulation wools. Inhal Toxicol 2018; 30:255-272. [PMID: 30328741 PMCID: PMC6334780 DOI: 10.1080/08958378.2018.1513610] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
High-Temperature Insulation Wools (HTIW), such as alumino silicate wools (Refractory Ceramic Fibers) and Alkaline Earth Silicate wools, are used in high-temperature industries for thermal insulation. These materials have an amorphous glass-like structure. In some applications, exposure to high temperatures causes devitrification resulting in the formation of crystalline species including crystalline silica. The formation of this potentially carcinogenic material raises safety concerns regarding after-use handling and disposal. This study aims to determine whether cristobalite formed in HTIW is bioactive in vitro. Mouse macrophage (J774A.1) and human alveolar epithelial (A549) cell lines were exposed to pristine HTIW of different compositions, and corresponding heat-treated samples. Cell death, cytokine release, and reactive oxygen species (ROS) formation were assessed in both cell types. Cell responses to aluminum lactate-coated fibers were assessed to determine if responses were caused by crystalline silica. DQ12 α-quartz was used as positive control, and TiO2 as negative control. HTIW did not induce cell death or intracellular ROS, and their ability to induce pro-inflammatory mediator release was low. In contrast, DQ12 induced cytotoxicity, a strong pro-inflammatory response and ROS generation. The modest pro-inflammatory mediator responses of HTIW did not always coincide with the formation of cristobalite in heated fibers; therefore, we cannot confirm that devitrification of HTIW results in bioactive cristobalite in vitro. In conclusion, the biological responses to HTIW observed were not attributable to a single physicochemical characteristic; instead, a combination of physicochemical characteristics (cristobalite content, fiber chemistry, dimensions and material solubility) appear to contribute to induction of cellular responses.
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Affiliation(s)
- Matthew S P Boyles
- a Nano Safety Research Group, School of Engineering and Physical Sciences, Institute of Biological Chemistry, Biophysics and Bioengineering, Heriot-Watt University , Edinburgh , UK
| | - David Brown
- a Nano Safety Research Group, School of Engineering and Physical Sciences, Institute of Biological Chemistry, Biophysics and Bioengineering, Heriot-Watt University , Edinburgh , UK
| | - Jilly Knox
- b Morgan Advanced Materials, Thermal Ceramics , Bromborough, UK
| | - Michael Horobin
- b Morgan Advanced Materials, Thermal Ceramics , Bromborough, UK
| | - Mark R Miller
- c Centre for Cardiovascular Science , University of Edinburgh , Edinburgh , UK
| | - Helinor J Johnston
- a Nano Safety Research Group, School of Engineering and Physical Sciences, Institute of Biological Chemistry, Biophysics and Bioengineering, Heriot-Watt University , Edinburgh , UK
| | - Vicki Stone
- a Nano Safety Research Group, School of Engineering and Physical Sciences, Institute of Biological Chemistry, Biophysics and Bioengineering, Heriot-Watt University , Edinburgh , UK
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Huang SXL, Jaurand MC, Kamp DW, Whysner J, Hei TK. Role of mutagenicity in asbestos fiber-induced carcinogenicity and other diseases. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2011; 14:179-245. [PMID: 21534089 PMCID: PMC3118525 DOI: 10.1080/10937404.2011.556051] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The cellular and molecular mechanisms of how asbestos fibers induce cancers and other diseases are not well understood. Both serpentine and amphibole asbestos fibers have been shown to induce oxidative stress, inflammatory responses, cellular toxicity and tissue injuries, genetic changes, and epigenetic alterations in target cells in vitro and tissues in vivo. Most of these mechanisms are believe to be shared by both fiber-induced cancers and noncancerous diseases. This article summarizes the findings from existing literature with a focus on genetic changes, specifically, mutagenicity of asbestos fibers. Thus far, experimental evidence suggesting the involvement of mutagenesis in asbestos carcinogenicity is more convincing than asbestos-induced fibrotic diseases. The potential contributions of mutagenicity to asbestos-induced diseases, with an emphasis on carcinogenicity, are reviewed from five aspects: (1) whether there is a mutagenic mode of action (MOA) in fiber-induced carcinogenesis; (2) mutagenicity/carcinogenicity at low dose; (3) biological activities that contribute to mutagenicity and impact of target tissue/cell type; (4) health endpoints with or without mutagenicity as a key event; and finally, (5) determinant factors of toxicity in mutagenicity. At the end of this review, a consensus statement of what is known, what is believed to be factual but requires confirmation, and existing data gaps, as well as future research needs and directions, is provided.
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Affiliation(s)
- Sarah X. L. Huang
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York, USA
| | - Marie-Claude Jaurand
- INSERM (Institut National de la Santé et de la Recherche Médicale), Paris, France
| | - David W. Kamp
- Pulmonary & Critical Care Medicine, Northwestern University Feinberg School of Medicine, Jesse Brown VA Medical Center, Chicago, Illinois, USA
| | - John Whysner
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York, USA
| | - Tom K. Hei
- Address correspondence to Tom K. Hei, Center for Radiological Research, College of Physicians and Surgeons, Columbia University. 630 West 168th Street, New York, NY 10032, USA. E-mail:
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4
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Kudo Y, Kotani M, Aizawa Y. Evaluation of hazardousness of refractory fibers by cell magnetometry. J Toxicol Sci 2010; 35:807-15. [PMID: 21139330 DOI: 10.2131/jts.35.807] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
This study was carried out to assess the cytotoxicity of three kinds of refractory fibers (RFs), RF1, RF2, and RF3, by cell magnetometry, lactate dehydrogenase (LDH) assay and morphological observation by scanning electron microscopy, using a mouse-derived cultured cell line, RAW264.7. As an indicator for cell magnetometry, Fe(3)O(4) was added to RAW264.7 cells. RF1, RF2 and RF3 were each added to an aliquot of this solution to make final concentrations of 250, 500 and 1,000 µg/ml in the experimental group. Phosphate buffered solution was added to make the control solution (n = 6). After culturing for 48 hr, the solution was magnetized from outside using a cell magnetometric apparatus, and the remnant magnetic field was measured for 20 min postmagnetization. In cell magnetometry, a significant delay of relaxation compared to that of the control was observed. In the LDH assay, LDH release into the culture medium was observed by addition of RFs. Furthermore, a quantity-dependent relationship was found between the quantity of RF added and the cytotoxicity in cell magnetometry and LDH assay. Morphological examination revealed incomplete phagocytosis of fibers and a decrease of microvilli in the experimental groups. These results suggest that RFs are cytotoxic to RAW264.7 cells, showing concentration-dependent cytotoxicity, and have a possible risk of cytotoxicity similar to that of asbestos. Further studies by pulmonary magnetometry are necessary to assess the hazardousness of RFs.
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Affiliation(s)
- Yuichiro Kudo
- Department of Preventive Medicine and Public Health, Kitasato University School of Medicine, Japan.
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Mast RW, McConnell EE, Anderson R, Chevalier J, Kotin P, Bernstein DM, Thevenaz P, Glass LR, Miiller WC, Hesterberg TW. Studies on the Chronic Toxicity (Inhalation) Of Four Types of Refractory Ceramic Fiber in Male Fischer 344 Rats. Inhal Toxicol 2008; 7:425-67. [DOI: 10.3109/08958379509015208] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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McConnell EE, Mast RW, Hesterberg TW, Chevalier J, Kotin P, Bernstein DM, Thevenaz P, Glass LR, Anderson R. Chronic Inhalation Toxicity of a Kaolin-Based Refractory Ceramic Fiber in Syrian Golden Hamsters. Inhal Toxicol 2008. [DOI: 10.3109/08958379509015210] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Andujar P, Lecomte C, Renier A, Fleury-Feith J, Kheuang L, Daubriac J, Janin A, Jaurand MC. Clinico-pathological features and somatic gene alterations in refractory ceramic fibre-induced murine mesothelioma reveal mineral fibre-induced mesothelioma identities. Carcinogenesis 2007; 28:1599-605. [PMID: 17272307 PMCID: PMC4749665 DOI: 10.1093/carcin/bgm023] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Although human malignant mesothelioma (HMM) is mainly caused by asbestos exposure, refractory ceramic fibres (RCFs) have been classified as possibly carcinogenic to humans on the basis of their biological effects in rodents' lung and pleura and in cultured cells. Hence, further investigations are needed to clarify the mechanism of fibre-induced carcinogenicity and to prevent use of harmful particles. In a previous study, mesotheliomas were found in hemizygous Nf2 (Nf2(+/-)) mice exposed to asbestos fibres, and showed similar alterations in genes at the Ink4 locus and in Trp53 as described in HMM. Here we found that Nf2(+/-) mice developed mesotheliomas after intra-peritoneal inoculation of a RCF sample (RCF1). Clinical features in exposed mice were similar to those observed in HMM, showing association between ascite and mesothelioma. Early passages of 12 mesothelioma cell cultures from ascites developed in RCF1-exposed Nf2(+/-) mice demonstrated frequent inactivation by deletion of genes at the Ink4 locus, and low rate of Trp53 point and insertion mutations. Nf2 gene was inactivated in all cultures. In most cases, co-inactivation of genes at the Ink4 locus and Nf2 was found and, at a lower rate, of Trp53 and Nf2. These results are the first to identify mutations in RCF-induced mesothelioma. They suggest that nf2 mutation is complementary of p15(Ink4b), p16(Ink4a) and p19(Arf) or p53 mutations and show similar profile of gene alterations resulting from exposure to ceramic or asbestos fibres in Nf2(+/-) mice, also consistent with the one found in HMM. These somatic genetic changes define different pathways of mesothelial cell transformation.
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Affiliation(s)
- Pascal Andujar
- IMRB, Institut Mondor de recherche biomédicale
INSERMUniversité Paris-Est Créteil Val-de-Marne - Paris 12Hôpital Henri Mondor 51 Avenue du Mal de Lattre de Tassigny 94010 Creteil Cedex
| | - Céline Lecomte
- Genomique Fonctionnelle des Tumeurs Solides
INSERMUniversité Paris Diderot - Paris 7IFR105Université Paris Descartes - Paris 5Hopital Saint-Louis - IFR 105 Paris VII 27 Rue Juliette Dodu 75010 Paris
| | - Annie Renier
- Genomique Fonctionnelle des Tumeurs Solides
INSERMUniversité Paris Diderot - Paris 7IFR105Université Paris Descartes - Paris 5Hopital Saint-Louis - IFR 105 Paris VII 27 Rue Juliette Dodu 75010 Paris
| | - Jocelyne Fleury-Feith
- Genomique Fonctionnelle des Tumeurs Solides
INSERMUniversité Paris Diderot - Paris 7IFR105Université Paris Descartes - Paris 5Hopital Saint-Louis - IFR 105 Paris VII 27 Rue Juliette Dodu 75010 Paris
- Laboratoire d'Histologie et de Biologie Tumorale
Université Pierre et Marie Curie - Paris 6Assistance Publique - Hôpitaux de Paris (AP-HP)Hôpital TenonParis
| | - Laurence Kheuang
- IMRB, Institut Mondor de recherche biomédicale
INSERMUniversité Paris-Est Créteil Val-de-Marne - Paris 12Hôpital Henri Mondor 51 Avenue du Mal de Lattre de Tassigny 94010 Creteil Cedex
| | - Julien Daubriac
- Genomique Fonctionnelle des Tumeurs Solides
INSERMUniversité Paris Diderot - Paris 7IFR105Université Paris Descartes - Paris 5Hopital Saint-Louis - IFR 105 Paris VII 27 Rue Juliette Dodu 75010 Paris
- Laboratoire d'Histologie et de Biologie Tumorale
Université Pierre et Marie Curie - Paris 6Assistance Publique - Hôpitaux de Paris (AP-HP)Hôpital TenonParis
| | - Anne Janin
- Service de Pathologie
Assistance Publique - Hôpitaux de Paris (AP-HP)Hôpital Saint-LouisParis
- Gvh et Gvl : Physiopathologie Chez l'Homme et Chez l'Animal, Incidence et Rôle Thérapeutique
INSERMUniversité Paris Diderot - Paris 7Hopital Saint-Louis - Centre Hayem Paris VII 1 Avenue Claude Vellefaux 75475 Paris Cedex 10
| | - Marie-Claude Jaurand
- Genomique Fonctionnelle des Tumeurs Solides
INSERMUniversité Paris Diderot - Paris 7IFR105Université Paris Descartes - Paris 5Hopital Saint-Louis - IFR 105 Paris VII 27 Rue Juliette Dodu 75010 Paris
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8
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Elias Z, Poirot O, Danière MC, Terzetti F, Binet S, Tomatis M, Fubini B. Surface reactivity, cytotoxicity, and transforming potency of iron-covered compared to untreated refractory ceramic fibers. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2002; 65:2007-2027. [PMID: 12490045 DOI: 10.1080/00984100290071360] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Untreated and iron-coated refractory ceramic fibers (RCFs) 1, 3, and 4 were examined for their potential to generate free radicals and to catalyze hydrogen peroxide decomposition in cell-free assays and were compared for cytotoxic and transforming potencies in Syrian hamster embryo (SHE) cell system. Coating with a high quantity of iron increased the capability of RCFs to generate hydroxyl radicals and to catalyze the decomposition of hydrogen peroxide. In the SHE cells, the untreated RCFs had varying ability to induce inhibition of cell proliferation, cytotoxicity (as measured by the colony-forming efficiency, CE) and morphological transformation, in a concentration-dependent manner. According to cytotoxic and transforming potencies, they ranged as follows: RCF3 > RCF1 > RCF4. The lethal concentration 50 (LC50; decrease of CE to 50% of controls after 7 d of treatment) expressed per number of RCF3 and RCF1/cm(2) of culture dish was 2.5 x 10(4) and 3.7 x 10(4), respectively, whereas RCF4 was not cytotoxic up to the highest concentration tested (23.7 x 10(4) fibers/cm(2)). At LC50, RCF3 was 1.4-fold more transforming than RCF1, and the weakest, RCF4, induced less than 1% transformation. Iron coating of RCF1 and RCF3 markedly attenuated their cytostatic, cytotoxic, and transforming potencies without a linear concentration-transformation relationship. In contrast, iron coating of RCF4 affected slightly its low transforming potency, although the growth inhibitory effect was reduced. The observed decrease rather than increase in the cytotoxic and transforming potencies of the active samples RCF1 and RCF3 by their coating with large amounts of ferric iron suggests that it is not the quantity or any form of iron on the surface of fibers but the iron, even in trace, in a particular redox and coordinate state that might play a role in the fiber's surface reactivity with regard to the biological material. Surface chemical functions involved in the interaction with the cell could be inactivated by the deposition of a high quantity of Fe(III) on the surface of fibers. Physicochemical studies correlated to biological effects is an approach for understanding the properties of solids related to a given biological response and for elucidating the cellular and molecular mechanisms.
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Affiliation(s)
- Zoé Elias
- Institut National de Recherche et de Sécurité, Vandoeuvre-lès-Nancy, France.
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Mast RW, Maxim LD, Utell MJ, Walker AM. Refractory ceramic fiber: toxicology, epidemiology, and risk analyses--a review. Inhal Toxicol 2000; 12:359-99. [PMID: 10880135 DOI: 10.1080/089583700196103] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Refractory ceramic fiber (RCF) is an energy-efficient, high-temperature insulation, used principally in industrial furnaces, heaters, and reactors. Prior to the 1980s, there were few publications dealing with the potential health effects of this material. However, with the advent of higher energy costs and the need for thermally efficient high-temperature insulating materials, production of RCF grew rapidly, as did interest in its potential health effects. This article provides a comprehensive and integrated review of the toxicology (in vitro and in vivo), epidemiology, and risk analysis literature of RCF. Based on the available literature, we conclude that an occupational exposure of 0.5 fibers per cubic centimeter (cm(3)) [8-h time-weighted average (8-h TWA)] results in an occupational health risk no greater than 9.1 x 10(-5).
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Affiliation(s)
- R W Mast
- Everest Consulting Associates, Inc., 15 North Main Street, Cranbury, NJ 08512, USA
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10
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Warheit DB, Hart GA, Hesterberg TW. Fibers. Toxicology 1999. [DOI: 10.1016/b978-012473270-4/50093-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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11
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Hart GA, Hesterberg TW. In vitro toxicity of respirable-size particles of diatomaceous earth and crystalline silica compared with asbestos and titanium dioxide. J Occup Environ Med 1998; 40:29-42. [PMID: 9467118 DOI: 10.1097/00043764-199801000-00008] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The relationship between particle characteristics and in vitro toxicity was investigated using Chinese hamster ovary cells. Test dusts included respirable natural (Nat) and flux-calcined (FC) diatomaceous earth (DE), quartz, cristobalite, TiO2, and chrysotile and crocidolite asbestos. All dusts elicited a qualitatively similar, concentration-dependent response: particle uptake, induction of micro- and polynuclei, and reduction in cell proliferation. However, similar mass concentrations of the dusts yielded a 35-fold range of toxicity: chrysotile > crocidolite > Nat DE > FC DE > quartz > Cristobalite > TiO2. In vitro toxicity did not correlate with crystalline silica content, surface area, composition, volume, particles/cm2, or fibrous geometry. Toxicity was closely associated with the number of particles/cm2 culture surface that had at least one dimension > 7.5 mu. Thus particle size but not shape could be a determinant of in vitro toxicity. Particle size might also impact in vivo pathogenesis.
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Affiliation(s)
- G A Hart
- Johns Manville Corporation Technical Center, Littleton, CO 80162-5005, USA
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12
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McClellan RO, Miller FJ, Hesterberg TW, Warheit DB, Bunn WB, Kane AB, Lippmann M, Mast RW, McConnell EE, Reinhardt CF. Approaches to evaluating the toxicity and carcinogenicity of man-made fibers: summary of a workshop held November 11-13, 1991, Durham, North Carolina. Regul Toxicol Pharmacol 1992; 16:321-64. [PMID: 1293648 DOI: 10.1016/0273-2300(92)90011-w] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The Workshop on Approaches to Evaluating the Toxicity and Carcinogenicity of Man-Made Fibers (MMF) was held in Durham, North Carolina, on November 11-13, 1991. The goal of the workshop was to reach a consensus, or to determine the extent to which a consensus existed, in two areas. Participants were asked to identify scientifically sound approaches for evaluating the toxicity and carcinogenicity of man-made fibers based on today's science and to determine research appropriate for study during the next 5 years that can provide an improved scientific basis for future revisions of approaches used to evaluate man-made fiber toxicity and carcinogenicity. During the first day, a series of "state of knowledge" presentations were made to provide all participants with a common data base from which to interact and discuss scientific issues. The workshop participants were assigned to one of four discussion groups, which met separately in three half-day sessions following the first day of presentations. All groups discussed the same topics: exposure assessment, hazard identification, and dose-response information needed to integrate to characterize risk in the first session; approaches to obtaining the needed information in the second session; and recommended approaches and guidelines for evaluating the toxicity and carcinogenicity of MMF and research needs in the third session. The workshop participants reconvened as a whole after each discussion session, and one member from each group reported the group's conclusions. A closure period was also included at the end of the workshop for review and discussion of items that had been considered during the workshop. The primary conclusions reached were the following: -All fiber types capable of depositing in the thorax are not alike in their pathogenic potential. -Only fiber samples with dimensions similar to those to which humans can inhale should be tested. -A complete characterization (i.e., dimensions, fiber number, mass, and aerodynamic diameter) of the fiber aerosol and retained dose is essential. -Appropriate aerosol generation methods must be used for inhalation studies in order to preserve fiber lengths. -A tiered approach to toxicity evaluation is recommended that includes: 1. In vitro screening for durability, surface properties, cytotoxicity, and similar properties, etc; 2. Short-term inhalation or other in vivo studies; 3. That chronic inhalation studies are the "gold standard" (i.e., provide most appropriate data for risk characterization). -The rat is the most appropriate species for inhalation studies. -In chronic inhalation studies, animals should be retained to at least 20% survival after 2-year exposure. -Serial lung burden analyses are an essential component of inhalation studies and are essential for understanding exposure-dose-response relationships. -Studies oriented to understanding mechanisms of toxicity and carcinogenicity are important adjuncts to traditional toxicity studies. -Histopathological analyses of tissues of the respiratory tract represent primary endpoints for evaluating effects of inhaled fibers. Major effects include pulmonary fibrosis, lung tumors, and mesotheliomas. Experimental tissues should be archived for future studies; wherever possible, handling and preservation of tissues should be done in a way that maximizes their future use in mechanistic studies. -Potential human exposures throughout the entire life-cycle of the fiber must be considered and fibrous material for toxicologic studies prepared accordingly. -Intracavity studies are inappropriate for risk characterization but can play a useful screening role in assessing fiber toxicity.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- R O McClellan
- Chemical Industry Institute of Toxicology, Research Triangle Park, North Carolina 27709
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