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Synthesis of Knowledge on Tremolite in Talc

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Chemical Substances and Biological Agents Studies and Research Projects REPORT R-755 Synthesis of Knowledge on Tremolite in Talc Chantal Dion Guy Perrault Mounia Rhazi Established in Québec since 1980, the Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST) is a scientific research organization known for the quality of its work and the expertise of its personnel. OUR RESEARCH is working for you ! Mission To contribute, through research, to the prevention of industrial accidents and occupational diseases as well as to the rehabilitation of affected workers. To offer the laboratory services and expertise necessary for the activities of the public occupational health and safety prevention network. To disseminate knowledge, and to act as scientific benchmark and expert. Funded by the Commission de la santé et de la sécurité du travail, the IRSST has a board of directors made up of an equal number of employer and worker representatives. To find out more Visit our Web site for complete up-to-date information about the IRSST. All our publications can be downloaded at no charge. www.irsst.qc.ca To obtain the latest information on the research carried out or funded by the IRSST, subscribe to Prévention au travail, the free magazine published jointly by the IRSST and the CSST. Subscription: 1-877-221-7046 Legal Deposit Bibliothèque et Archives nationales du Québec 2012 ISBN: 978-2-89631-640-3 (PDF) ISSN: 0820-8395 IRSST – Communications and Knowledge Transfer Division 505 De Maisonneuve Blvd. West Montréal, Québec H3A 3C2 Phone: 514 288-1551 Fax: 514 288-7636 [email protected] www.irsst.qc.ca © Institut de recherche Robert-Sauvé en santé et en sécurité du travail, October 2012 Chemical Substances and Biological Agents Studies and Research Projects REPORT R-755 Synthesis of Knowledge on Tremolite in Talc Disclaimer Chantal Dion The IRSST makes no guarantee Chemical and Biological Hazards Prevention, IRSST regarding the accuracy, reliability or completeness of the information Guy Perrault contained in this document. Under no circumstances shall the IRSST be held Consultant liable for any physical or Mounia Rhazi psychological injury or material damage resulting from the use of Institut Armand-Frappier this information. Note that the content of the docu- ments is protected by Canadian intellectual property legislation. This publication is available free of charge on the Web site. This study was financed by the IRSST. The conclusions and recommendations are those of the authors. This publication has been translated; only the original version (R-724) is authoritative. IN CONFORMITY WITH THE IRSST’S POLICIES The results of the research work published in this document have been peer-reviewed. IRSST – Synthesis of Knowledge on Tremolite in Talc i ACKNOWLEDGEMENTS The authors would like to thank André Dufresne, from the Université de Montréal, for his important contribution to the development of the design of the study and for relevant discussions and comments throughout the project. Our thanks also go to librarians Jacques Blain and Maryse Gagnon at the Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST) for their contribution to the literature search, as well as to secretaries France C. Lafontaine and Diane Laprés for their assistance in the layout of this document. In addition, we thank Helen Fleischauer for the translation of the document. We also want to highlight the financial contribution of the Agence nationale de sécurité sanitaire de l'alimentation, de l'environnement et du travail (ANSES, France) and to thank the experts in the “Tremolitic talc” working group for constructive discussions and comments in the finalization of this report. IRSST - Synthesis of Knowledge on Tremolite in Talc iii SUMMARY Talc is widely used in different workplaces, mainly in the ceramics, paint (antirust paint), gypsum joint compound, cosmetics, plastics and rubber industries. Since some talcs can contain amphiboles, namely tremolite, possibly with asbestiform (or fibrous) and non-asbestiform (cleavage fragments) morphology, it is important to know the origin and composition of the talcs to be able to implement exposure monitoring strategies and means of prevention appropriate for workers and other users. Several definitions and applications of the term asbestos are used to classify amphiboles, whether it is in studies on health effects, in exposure monitoring, or for regulatory purposes. Considering the different opinions and contradictory studies regarding definitions, analytical methods, regulations, and the health effects of non-asbestiform tremolite, the CSST (Québec workers’ compensation board) asked the IRSST to carry out a literature review on tremolite, present in talc and vermiculite, in order to clarify the impacts on worker health and safety and to facilitate the implementation of means of prevention in the Québec context. This report covers the synthesis of the results obtained for tremolite in talc. Vermiculite and its components will be the subject of another study. The primary objective of this study is to produce a review and a synthesis of the knowledge on tremolitic talc in relation to the different morphologies, asbestiform (asbestos) and non- asbestiform (cleavage fragments), and in relation to the following parameters: • Metrology (definitions, characterization of the materials, sampling and exposure); • Regulations (standards and regulatory criteria applied in the different countries); • Epidemiological data on the health effects. Since the early 1990s, numerous studies have focused on the elongate mineral particles (EMPs) generated from the milling and fracturing of non-asbestiform amphibole minerals, defined as cleavage fragments. More particularly, the studies have focused on tremolite, occurring naturally in certain talc and vermiculite deposits, ores that are used in different consumer products. However, information is still limited on the exposures and health effects of these EMPs. Experts, analysts, researchers and government scientists have not reached a consensus on the definition or differentiation of asbestiform and non-asbestiform amphiboles (cleavage fragments). While the distinction between cleavage fragments and fibres is theoretically clear, it is rather obscure from the analytical standpoint. With the use of complementary analytical methods such as phase contrast microscopy, scanning electron microscopy, transmission electron microscopy with selected area electron diffraction (SAED), or analytical electron transmission microscopy (SAED coupled with energy dispersion X-ray spectrometry), it would be possible to confirm the presence of asbestos fibres in an ore or a material and, more specifically, to determine the concentration in the air of fibres, asbestiform tremolite fibres, cleavage fragments of tremolite and talc fibres, if there was a consensus on the differentiation criteria to be used. Most of the studies describing the health effects related to talc exposure contain very little information on the characterization of the talc involved. Even if the analytical methods iv Synthesis of Knowledge on Tremolite in Talc - IRSST characterized the presence of amphiboles beyond any doubt, and quantified the asbestiform and non-asbestiform portions, it is rather unlikely that toxicology studies can be performed on completely pure products because talcs are generally a mixture of different minerals of variable concentration. However, this information would be invaluable in epidemiology for establishing better dose-response relationships. Talc dust exposure is associated with respiratory disease such as NMRD (non-malignant respiratory disease), particularly pneumoconioses, and lung cancer, in the presence of other carcinogenic agents. In fact, talc ore dust can cause silicosis, talcosis, and mixed pneumoconiosis, but the causal share between talc, quartz and the other silicotic agents cannot be determined. Millers do not present a significant increase in lung cancer risk, but miners could show significant tendencies or increases in risk in the presence of other carcinogens such as radon, quartz or asbestos. Use of the weighted concentration (dust or respirable dust) as exposure metric is a poor predictor of the fibre or elongate mineral particle concentration. The result is a possibly incorrect classification of cases, which complicates the establishment of a dose-response relationship. The possibility of mesothelioma related to talc dust exposure remains a controversial subject. Mesotheliomas present diagnostic and causal recognition difficulties. With the current state of knowledge, there is no proof linking mesothelioma and exposure to talc not containing asbestos or asbestiform fibre. From the results of epidemiological studies, it is difficult to answer definitively, with supporting proof, the question about the health risk of non-asbestiform tremolite (cleavage fragments), due to deficiencies in exposure characterization. In fact, no study had well characterized and well sampled cleavage fragment concentration results for the workers’ breathing zones. With all these uncertainties about exposures and health effects, research is still necessary in both toxicology and epidemiology as well as on exposure measurements, sampling, and on analytical methods. Furthermore, mineralogic studies of lung tissue (biometrology) could identify abnormal burdens and characterize the fibres and EMPs. These studies could help in defining the analytical and sampling methods
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