Asbestos-related disease associated with exposure to asbestiform tremolite

Our plain-English summary of Asbestos-related disease associated with exposure to asbestiform tremolite, by S.H. Srebro, V.L. Roggli (American Journal of Industrial Medicine, 1994).

The study

• Authors: S.H. Srebro, V.L. Roggli
• Journal: American Journal of Industrial Medicine
• Published: 1994;26(6):809-19
• Type of article: Case report
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Tremolite is nearly ubiquitous and represents the most common amphibole fiber in the lungs of urbanites. Tremolite asbestos is not mined or used commercially but is a frequent contaminant of chrysotile asbestos, vermiculite, and talc. Therefore, individuals exposed to these materials or to end-products containing these materials may be exposed to tremolite. We have had the opportunity to do asbestos body counts and mineral fiber analysis on pulmonary tissue from five mesothelioma cases and two asbestosis cases with pulmonary tremolite burdens greater than background levels. There were no uncoated amosite or crocidolite fibers detected in any of these cases. Three patients were occupationally exposed to chrysotile asbestos; two patients had environmental exposures (one to vermiculite and one to chrysotile and talc) and one was a household contact of a shipyard worker. The tremolite burdens for the asbestosis cases were one to two orders of magnitude greater than those for the mesothelioma cases. Our study confirms the relationship between tremolite exposure and the development of asbestos-associated diseases. Furthermore, the finding of relatively modest elevations of tremolite content in some of our mesothelioma cases suggests that, at least for some susceptible individuals, moderate exposures to tremolite-contaminated dust can produce malignant pleural mesothelioma.

In plain English

This case series described seven patients from one author's consultation files. Five had malignant pleural mesothelioma and two had asbestosis, one of whom also had lung adenocarcinoma. Cases were chosen because scanning electron microscopy found two things in their lung tissue: no uncoated amosite or crocidolite fibers at least 5 micrometers long, and uncoated tremolite above a control upper limit of 2,540 fibers per gram of wet lung, a limit based on 19 control cases. Three patients had occupational exposure, including seven years making chrysotile asbestos blankets and gaskets. Others had lived near a vermiculite processing plant as a child, were the wife of a shipyard worker, or worked 18 years in a building with chrysotile and tremolite in acoustical tile. One more, a dry-cleaning plant assembler, worked in an occupation with no known asbestos exposure. Tremolite was the main fiber type in all seven. The asbestosis cases had about one to two orders of magnitude more tremolite than the mesothelioma cases. The authors concluded that the study confirms a relationship between tremolite exposure and asbestos-associated disease. They also suggested that moderate exposure to tremolite-contaminated dust can produce pleural mesothelioma in some susceptible individuals.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Case series: seven patients with asbestos-related disease whose lung tissue was analyzed for asbestos bodies by light microscopy and for mineral fibers by scanning electron microscopy, compared with 19 control cases
• Who was studied: Seven patients from the consultation files of one author (V.L.R.). The authors were from the Department of Pathology, Durham Veterans' Administration and Duke University Medical Centers. The article does not say where the patients were treated, or when.

Five had malignant pleural mesothelioma (three women and two men, aged 44 to 62). Two men had asbestosis, one of whom also had lung adenocarcinoma.

Selection required three things:

• a diagnosis of asbestos-related disease
• no uncoated amosite or crocidolite fibers detected by SEM
• uncoated tremolite (fibers 5 micrometers or longer) above control levels

The comparison group was 19 male control cases with no asbestos-related disease and no documented asbestos exposure.

• Exposure: Tremolite found in lung tissue. Reported exposure histories were:
• Three patients (cases 1, 3 and 4) had occupational exposure to asbestos or asbestos-containing products. These were chrysotile asbestos blanket and gasket manufacturing for 7 years, painter/spackler for 38 years, and an engineer at a power plant.
• One man lived near a vermiculite processing plant for his first 20 years and played in vermiculite tailings.
• One woman was the wife of a shipyard worker.
• One woman was a teacher's aide for 18 years in a building with chrysotile and tremolite in the acoustical tile.
• One woman was an assembler in a dry-cleaning plant, an occupation with no known exposure to asbestos.
• Main results:
  • In all seven cases, tremolite was the predominant fiber type detected by scanning electron microscopy.
  • Scanning electron microscopy detected no uncoated amosite or crocidolite fibers 5 micrometers or longer in any of the seven cases.
  • The five mesothelioma cases (cases 3 to 7) had tremolite counts of 8,100, 5,940, 5,440, 4,860 and 4,330 uncoated fibers per gram of wet lung. The control upper limit was 2,540.
  • Tremolite fiber burdens in the two asbestosis cases were about one to two orders of magnitude greater than in the mesothelioma cases. Asbestos body counts in the asbestosis cases were two orders of magnitude greater than in the mesothelioma cases.
  • Light-microscopy asbestos body counts for three of the seven cases were within the laboratory's normal range. The authors still considered these cases probably asbestos related because their tremolite counts exceeded the control upper limit.
  • Uncoated chrysotile fibers were detected in only two of the seven cases. In those two cases, tremolite concentrations were four to five times the chrysotile concentrations.
  • Four of the seven cases contained fibrous talc, which the authors note is frequently contaminated with tremolite.
  • Women made up 3 of the 7 cases (43%), compared with 8% of the 153 mesothelioma cases with tissue analyses in one author's files. The authors suggested cosmetic talc as a potential source of exposure for these women.
  • The man who lived near the vermiculite plant had the longest tremolite fibers in the study, many longer than 100 micrometers.
• The authors' conclusion: The authors concluded that their study confirms a relationship between tremolite exposure and asbestos-associated diseases. They also concluded that the modest tremolite elevations seen in some mesothelioma cases suggest that, at least for some susceptible individuals, moderate exposure to tremolite-contaminated dust can produce malignant pleural mesothelioma.
• Limitations the authors state:
  • The method mainly detects fibers 0.2 micrometers or more in diameter, so thinner fibers could have been missed. The authors judged this unlikely to change their results for amosite or crocidolite.
  • The analysis likely underestimated chrysotile fibers, because chrysotile splits into very thin fibers.
  • All 19 controls were men, so it is not known whether women in the general population have higher background tremolite levels.
  • Telling asbestos fibers apart from cleavage fragments can be difficult.
  • Only 5 to 30 fibers per case were chemically classified, and detection limits for each fiber type varied from case to case.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma, Tremolite.

Medical terms in this study, explained in our Lexicon: Asbestiform Tremolite, Tremolite, Amphibole Group, Chrysotile, vermiculite, Talc, Asbestos Body Formation, Mineral Fiber.

Related studies

• Asbestos-related pleural disease due to tremolite associated with progressive loss of lung function: serial observations in 123 miners, family members, and residents of Libby, Montana — A.C. Whitehouse (2004)
• Pulmonary fibrosis in workers exposed to non-asbestiform tremolite asbestos minerals — H.Y. Yang, R.H. Shie, et al. (2013)
• Carving of non-asbestiform tremolite and the risk of lung cancer: a follow-up mortality study in a historical nephrite processing cohort — H.Y. Yang, R.H. Shie, et al. (2013)
• The role of environmental and occupational exposures in Turkish immigrants with fibre-related disease — P. Dumortier, A. Göcmen, et al. (2001)
• Environmental exposure to tremolite and respiratory cancer in New Caledonia: a case-control study — D. Luce, I. Bugel, et al. (2000)
• Environmental airborne tremolite asbestos pollution and pleural plaques in Afghanistan — C. Voisin, I. Marin, et al. (1994)

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