1
|
Bernstein DM. The health effects of short fiber chrysotile and amphibole asbestos. Crit Rev Toxicol 2022; 52:89-112. [PMID: 35703172 DOI: 10.1080/10408444.2022.2056430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The potential toxic effects of short chrysotile and amphibole asbestos fibers with lengths <5 to ∼10 µm have been debated over the years. This stems from the large database of epidemiology, toxicology, and in-vitro studies, each of which often provides different information in understanding and differentiating the effects of short fibers. The epidemiology studies in which the cancer potency estimates were based upon relatively high exposure concentrations provide a conservative assessment that shorter fibers would have little if any effect, especially under controlled exposure or environmental conditions that may occur today. The QSAR models have shown that fiber aspect ratio and Mg content are excellent predictors of cancer potency and that short fibers/particles of amphibole would have no effect. The studies of motor vehicle mechanics and in particular workers who serviced chrysotile containing brakes with the majority of the fibers being short provides evidence that motor vehicle mechanics, including workers who were engaged in brake repair, are not at an increased risk of mesothelioma. Several inhalation toxicology studies clearly differentiated that short chrysotile and amphibole asbestos fibers did not produce a significant carcinogenic effect in the lung or pleural cavity. Because of dosing and lack of sensitivity to biosolubility, in vitro studies can be difficult to interpret; however, a number have differentiated short chrysotile and amphibole asbestos fibers from long fibers. Integral to understanding the importance of fiber length in determining possible health effects is an understanding of the biological and physiological function of the respiratory system. Short asbestos fibers, like innocuous dust, can be cleared through the tracheobronchial ciliated mucous transport, phagocytized by macrophages and cleared via the bronchial tree, and can also be removed through the lymphatic system. While the first two methods can remove them from the lung, with lymphatic transport through one-way valves, fibers are removed from the active area of the lung where the fiber-related disease has been shown to develop and can accumulate in lymphatic sumps and lymph nodes. While short asbestos fibers are present in most occupational or environmental exposures, the large body of studies strongly supports that they do not contribute to the health effects of asbestos exposure.
Collapse
Affiliation(s)
- David M Bernstein
- Consultant in Toxicology, 40 Chemin de la Petite-Boissière, Geneva, Switzerland
| |
Collapse
|
2
|
Moitra S, Farshchi Tabrizi A, Idrissi Machichi K, Kamravaei S, Miandashti N, Henderson L, Mukherjee M, Khadour F, Naseem MT, Lacy P, Melenka L. Non-Malignant Respiratory Illnesses in Association with Occupational Exposure to Asbestos and Other Insulating Materials: Findings from the Alberta Insulator Cohort. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2020; 17:ijerph17197085. [PMID: 32998195 PMCID: PMC7579178 DOI: 10.3390/ijerph17197085] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 09/25/2020] [Accepted: 09/25/2020] [Indexed: 12/23/2022]
Abstract
Many insulating materials are used in construction, although few have been reported to cause non-malignant respiratory illnesses. We aimed to investigate associations between exposures to insulating materials and non-malignant respiratory illnesses in insulators. In this cross-sectional study, 990 insulators (45 ± 14 years) were screened from 2011-2017 in Alberta. All participants underwent pulmonary function tests and chest radiography. Demographics, work history, and history of chest infections were obtained through questionnaires. Chronic obstructive pulmonary disease (COPD) was diagnosed according to established guidelines. Associations between exposures and respiratory illnesses were assessed by modified Poisson regression. Of those screened, 875 (88%) were males. 457 (46%) participants reported having ≥ 1 chest infection in the past 3 years, while 156 (16%) were diagnosed with COPD. In multivariate models, all materials (asbestos, calcium silicate, carbon fibers, fiberglass, and refractory ceramic fibers) except aerogels and mineral fibers were associated with recurrent chest infections (prevalence ratio [PR] range: 1.18-1.42). Only asbestos was associated with COPD (PR: 1.44; 95% confidence interval [CI]: 1.01, 2.05). Therefore, occupational exposure to insulating materials was associated with non-malignant respiratory illnesses, specifically, recurrent chest infections and COPD. Longitudinal studies are urgently needed to assess the risk of exposure to these newly implemented insulation materials.
Collapse
Affiliation(s)
- Subhabrata Moitra
- Alberta Respiratory Centre, Department of Medicine, University of Alberta, Edmonton, AB T6G 2R3, Canada; (S.M.); (A.F.T.); (K.I.M.); (S.K.); (N.M.); (L.M.)
| | - Ali Farshchi Tabrizi
- Alberta Respiratory Centre, Department of Medicine, University of Alberta, Edmonton, AB T6G 2R3, Canada; (S.M.); (A.F.T.); (K.I.M.); (S.K.); (N.M.); (L.M.)
| | - Kawtar Idrissi Machichi
- Alberta Respiratory Centre, Department of Medicine, University of Alberta, Edmonton, AB T6G 2R3, Canada; (S.M.); (A.F.T.); (K.I.M.); (S.K.); (N.M.); (L.M.)
| | - Samineh Kamravaei
- Alberta Respiratory Centre, Department of Medicine, University of Alberta, Edmonton, AB T6G 2R3, Canada; (S.M.); (A.F.T.); (K.I.M.); (S.K.); (N.M.); (L.M.)
| | - Noushin Miandashti
- Alberta Respiratory Centre, Department of Medicine, University of Alberta, Edmonton, AB T6G 2R3, Canada; (S.M.); (A.F.T.); (K.I.M.); (S.K.); (N.M.); (L.M.)
| | - Linda Henderson
- Synergy Respiratory & Cardiac Care, Sherwood Park, AB T8H 0N2, Canada; (L.H.); (F.K.); (M.T.N.)
| | - Manali Mukherjee
- Department of Medicine, McMaster University & Firestone Institute for Respiratory Health, St. Joseph’s Healthcare, Hamilton, ON L8N 4A6, Canada;
| | - Fadi Khadour
- Synergy Respiratory & Cardiac Care, Sherwood Park, AB T8H 0N2, Canada; (L.H.); (F.K.); (M.T.N.)
| | - Muhammad T. Naseem
- Synergy Respiratory & Cardiac Care, Sherwood Park, AB T8H 0N2, Canada; (L.H.); (F.K.); (M.T.N.)
| | - Paige Lacy
- Alberta Respiratory Centre, Department of Medicine, University of Alberta, Edmonton, AB T6G 2R3, Canada; (S.M.); (A.F.T.); (K.I.M.); (S.K.); (N.M.); (L.M.)
- Correspondence: ; Tel.: +1-780-492-6085
| | - Lyle Melenka
- Alberta Respiratory Centre, Department of Medicine, University of Alberta, Edmonton, AB T6G 2R3, Canada; (S.M.); (A.F.T.); (K.I.M.); (S.K.); (N.M.); (L.M.)
- Synergy Respiratory & Cardiac Care, Sherwood Park, AB T8H 0N2, Canada; (L.H.); (F.K.); (M.T.N.)
| |
Collapse
|
3
|
Germine M, Puffer JH. Analytical Transmission Electron Microscopy of Amphibole Fibers From the Lungs of Quebec Miners. ARCHIVES OF ENVIRONMENTAL & OCCUPATIONAL HEALTH 2015; 70:323-331. [PMID: 25386835 DOI: 10.1080/19338244.2014.918928] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The objective of this study is to describe the morphology, molecular structure, and chemistry of amphibole fibers from lung samples from workers in the chrysotile mines at Asbestos and Thetford Mines, Quebec. A fibrous tremolite-actinolite contaminant in an asbestos ore sample from the deposit at Asbestos was used for comparison. Lattice imaging was performed using high-resolution transmission electron microscopy (HRTEM). Silica-rich amorphous coatings (SIRA) that may be related to carcinogenesis are noted on all of the HRTEM photographs of fibers retained in lung, but not on fiber surfaces of the bulk comparison sample. Fibers found in lung samples and in a bulk comparison sample are produced primarily by splitting of thicker crystals and, as such, might not be considered asbestos fibers on the basis of certain mineralogical criteria. Implications of SIRA coatings with respect to carcinogenesis are worthy of further study.
Collapse
Affiliation(s)
- Mark Germine
- a Department of Earth and Environmental Sciences Rutgers University , Newark , New Jersey , USA
| | - John H Puffer
- a Department of Earth and Environmental Sciences Rutgers University , Newark , New Jersey , USA
| |
Collapse
|
4
|
Case BW, Abraham JL, Meeker G, Pooley FD, Pinkerton KE. Applying definitions of "asbestos" to environmental and "low-dose" exposure levels and health effects, particularly malignant mesothelioma. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2011; 14:3-39. [PMID: 21534084 PMCID: PMC3118487 DOI: 10.1080/10937404.2011.556045] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Although asbestos research has been ongoing for decades, this increased knowledge has not led to consensus in many areas of the field. Two such areas of controversy include the specific definitions of asbestos, and limitations in understanding exposure-response relationships for various asbestos types and exposure levels and disease. This document reviews the current regulatory and mineralogical definitions and how variability in these definitions has led to difficulties in the discussion and comparison of both experimental laboratory and human epidemiological studies for asbestos. This review also examines the issues of exposure measurement in both animal and human studies, and discusses the impact of these issues on determination of cause for asbestos-related diseases. Limitations include the lack of detailed characterization and limited quantification of the fibers in most studies. Associated data gaps and research needs are also enumerated in this review.
Collapse
Affiliation(s)
- B W Case
- Department of Pathology and School of Environment, McGill University, Montreal, Quebec, Canada.
| | | | | | | | | |
Collapse
|
5
|
|
6
|
Dodson RF, Brooks DR, O'Sullivan M, Hammar SP. Quantitative Analysis of Asbestos Burden in a Series of Individuals with Lung Cancer and a History of Exposure to Asbestos. Inhal Toxicol 2008; 16:637-47. [PMID: 16036755 DOI: 10.1080/08958370490464652] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Asbestos is recognized as a lung carcinogen. In the present study, tissue from 20 individuals who died from lung cancer and who had a history of exposure to asbestos was evaluated for the presence of asbestos bodies and uncoated asbestos fibers. A digestion procedure was used to isolate the particulates from the tissue. The samples were evaluated by light microcopy to quantify the numbers of ferruginous bodies in the tissue. The uncoated fibers (which included all fibers equal to or greater than 0.5 microm) were analyzed by analytical transmission electron microscopy. Seventeen of the 20 cases were positive for ferruginous bodies (which were morphologically consistent with asbestos bodies). Five of these were found to have concentrations within the range used in our laboratory for the general population (<20 ferruginous bodies/g wet tissue). Nineteen of the 20 cases were found to have asbestos fibers in the higher magnification scan (either 16 K or 20 K). Some of the asbestos fibers identified were specific for the types of exposures that were reported. Most individuals in this study were found to have mixed populations of asbestos fibers in the lung tissue. This suggests that when there are exposures to products containing commercial asbestos there are likely exposures to dust containing noncommercial asbestos. A contrast exists in the dust burden within the lung of these individuals as compared to samples from the general population in that occupational or "occupational-like" exposures such as in these cases are often reflected by the presence of longer fibers of asbestos in the tissue.
Collapse
Affiliation(s)
- Ronald F Dodson
- University of Texas Health Center at Tyler, Tyler, Texas 75708, USA.
| | | | | | | |
Collapse
|
7
|
Response to Letter to the Editor. Inhal Toxicol 2008. [DOI: 10.1080/08958370802320814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
|
8
|
Ansari FA, Ahmad I, Ashquin M, Yunus M, Rahman Q. Monitoring and identification of airborne asbestos in unorganized sectors, India. CHEMOSPHERE 2007; 68:716-23. [PMID: 17337034 DOI: 10.1016/j.chemosphere.2007.01.040] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2006] [Revised: 12/20/2006] [Accepted: 01/17/2007] [Indexed: 05/14/2023]
Abstract
Rajasthan state in India is credited to cater more than 90% of total production of asbestos in this country, of which around 60% is processed there in unorganized sectors including milling and manufacturing of asbestos-based products. Unorganized asbestos units particularly mills showed unhealthy occupational conditions, therefore industrial hygiene study was carried out focusing on the prevalence of asbestos fibres in air at work zone area of asbestos milling units. Fibre levels were in the range of 2.00-5.09f/cm(3) and 4.07-15.60f/cm(3) in unorganized asbestos mills of Rajasthan located at Beawer and Deogarh districts, respectively. Like asbestos concentration, fibre type and length are also vital factors in the health risk assessment of industrial workers. Phase contrast and polarized light microscopic study of asbestos fibres showed their amphibole nature registering about 90% as tremolite and rest as anthophyllite. Fibre length measured micrometrically were sub-grouped in <10microm, 11-20microm, 21-30microm and >30microm. About 30-40% fibres belonged to sub-group <10microm. It is concluded that unorganized asbestos mills bear poor industrial unhygienic conditions reflected specifically from their manyfold higher fibre concentrations than the Indian and International standards. Poor industrial unhygienic conditions are attributable to obsolete milling technology, lack of pollution control devices and escape from regulatory control.
Collapse
Affiliation(s)
- Furquan Ahmad Ansari
- Industrial Toxicology Research Centre, Mahatma Gandhi Marg, Post Box No. 80, Lucknow 226 001, India
| | | | | | | | | |
Collapse
|
9
|
Wood SA, Taunton AE, Normand C, Gunter ME. Mineral-fluid interaction in the lungs: insights from reaction-path modeling. Inhal Toxicol 2006; 18:975-84. [PMID: 16920671 DOI: 10.1080/08958370600835252] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Thermodynamic modeling, in conjunction with available kinetic information, has been employed to investigate the fate of chrysotile and tremolite in the human lung. In particular, we focus on mineral-fluid reactions using techniques borrowed from geochemistry, including calculation of saturation indices, activity-ratio phase diagrams, and reaction-path modeling. Saturation index calculations show that fresh lung fluid is undersaturated with respect to both tremolite and chrysotile and these minerals should dissolve, in accordance with conclusions from previous work described in the literature. Modeling of reaction paths in both closed and open systems confirms previous suggestions that chrysotile dissolves faster than tremolite in lung fluid, which offers an explanation for the apparent increase in tremolite/chrysotile ratios in lungs of miners and millers over time. However, examination of activity-ratio phase diagrams and reaction-path model calculations raises the possibility not only that minerals dissolve congruently in lung fluid, but that secondary minerals such as talc or various Ca-Mg carbonates might potentially form in lung fluid as asbestiform minerals dissolve.
Collapse
Affiliation(s)
- Scott A Wood
- Department of Geological Sciences, University of Idaho, Moscow, Idaho 83844-3022, USA.
| | | | | | | |
Collapse
|
10
|
Nayebzadeh A, Case BW, Massé J, Dufresne A. Mineralogical and exposure determinants of pulmonary fibrosis among Québec chrysotile miners and millers. Int Arch Occup Environ Health 2005; 79:227-36. [PMID: 16283364 DOI: 10.1007/s00420-005-0046-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Accepted: 09/08/2005] [Indexed: 11/27/2022]
Abstract
OBJECTIVES Lung fibre content was determined for 86 former chrysotile miners and millers in two Québec mining regions: Thetford mines (TM) and the Asbestos region (AR). METHODS Fibres were assessed using transmission electron microscopy (TEM) and energy dispersive X-ray spectrometry (EDS). Asbestos body (AB) concentrations were assessed by microscopy of tissue digests. Corresponding histological lung tissue sections were quantitatively graded for the severity of interstitial fibrosis on a 12-point scale. Fibrosis score and its associations with (1) fibre concentrations and fibre dimensions within three fibre length intervals (less than 5 microm, 5-10 microm, and over 10 microm), and (2) several exposure variables were evaluated using correlation coefficients and regression techniques. RESULTS Concentration of short (<5 microm) tremolite fibres was the best predictor of fibrosis grade in both mining groups (r=0.44, P<0.01 and r=0.39, P<0.01 for TM and AR, respectively). Chrysotile fibre concentration showed a lower correlation with the fibrosis grade for subjects from TM only. Long (>10 microm) amosite fibre concentration showed a linear relationship with the fibrosis score in miners and millers from AR. Exposure variables, including smoking, had no predictive value for fibrosis grade. Within fibre length categories, fibre dimension was not related to the fibrosis score. CONCLUSION Lung fibre concentration as measured by TEM/EDS, especially that of short (<5 microm) tremolite fibres, is a better predictor of fibrosis grade in these two groups of chrysotile miners than either the concentration of ABs or the duration of exposure. Due to the limitation of our counting method, almost all fibres longer than 10 microm observed in this study were shorter than 14 microm. Thus, if length plays a role in fibrogenesis, it may be related to fibres of greater length than those covered in this study.
Collapse
Affiliation(s)
- Ataollah Nayebzadeh
- McGill University Health Centre, Montréal General Hospital, 1650 Cedar Ave. Suite T6-204, Montréal, QC, Canada H3G 1A4.
| | | | | | | |
Collapse
|
11
|
Abstract
Asbestos has been incorporated into friction products since the early 1900s. Epidemiological studies have been equivocal in their analysis of the incidence of disease among mechanics servicing brakes. Decomposition of asbestos occurs during the normal usage of the brake due to thermal decomposition into forsterite, although not all asbestos is so converted. Short fibers, below 5 microm in length, are also found in brake products. Several facts are discussed including the toxicity of the remaining asbestos fibers, short asbestos fibers, and the health implications of exposure to forsterite. Control methodologies, when used appropriately, have reduced exposure to asbestos during brake servicing, but have not been able to entirely eliminate exposure to asbestos, thus bring into question the controlled use of asbestos for friction product such as brakes. Even the so called "controlled" use of asbestos containing brakes poses a health risk to workers, users, and their families.
Collapse
|
12
|
Egilman D, Fehnel C, Bohme SR. Exposing the "myth" of ABC, "anything but chrysotile": a critique of the Canadian asbestos mining industry and McGill University chrysotile studies. Am J Ind Med 2003; 44:540-57. [PMID: 14571518 DOI: 10.1002/ajim.10300] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BACKGROUND Beginning in the 1930s, the Canadian asbestos industry created and advanced the idea that chrysotile asbestos is safer than asbestos of other fiber types. METHODS We critically evaluate published and unpublished studies funded by the Quebec Asbestos Mining Association (QAMA) and performed by researchers at McGill University. RESULTS QAMA-funded researchers put forth several myths purporting that Quebec-mined chrysotile was harmless, and contended that the contamination of chrysotile with oils, tremolite, or crocidolite was the source of occupational health risk. In addition, QAMA-funded researchers manipulated data and used unsound sampling and analysis techniques to back up their contention that chrysotile was "essentially innocuous." CONCLUSIONS These studies were used to promote the marketing and sales of asbestos, and have had a substantial effect on policy and occupational health litigation. Asbestos manufacturing companies and the Canadian government continue to use them to promote the use of asbestos in Europe and in developing countries. Am. J. Ind. Med. 44:540-557, 2003.
Collapse
Affiliation(s)
- David Egilman
- Clinical Associate Professor, Brown University, Department of Community Health, Providence, Rhode Island, USA
| | | | | |
Collapse
|