Short, fine and WHO asbestos fibers in the lungs of quebec workers with an asbestos-related disease

Our plain-English summary of Short, fine and WHO asbestos fibers in the lungs of quebec workers with an asbestos-related disease, by G. Adib, F. Labrèche, L. De Guire, et al (American Journal of Industrial Medicine, 2013).

The study

• Authors: G. Adib, F. Labrèche, L. De Guire, C. Dion, A. Dufresne
• Journal: American Journal of Industrial Medicine
• Published: 2013;56(9):1001-14
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: The possible role of short asbestos fibers in the development of asbestos-related diseases and availability of lung fiber burden data prompted this study on the relationships between fiber characteristics and asbestos-related diseases among compensated workers.

Methods: Data collected between 1988 and 2007 for compensation purposes were used; lung asbestos fibers content of 123 Quebec workers are described according to socio-demographic characteristics, job histories and diseases (asbestosis, mesothelioma, lung cancer).

Results: Most workers (85%) presented chrysotile fibers in their lungs, and respectively 76%, 64%, and 43% had tremolite, amosite, and crocidolite. Half of the total fibers were short, 30% were thin fibers and 20% corresponded to the World Health Organization definition of fibers (length ≥ 5 μm, diameter ≥ 0.2 and <3 μm). Chrysotile fibers were still observed in the lungs of workers 30 years or more after last exposure.

Conclusion: Our findings stress the relevance of considering several dimensional criteria to characterize health risks associated with asbestos inhalation.

© 2013 Wiley Periodicals, Inc.

In plain English

This brief report described asbestos fibers in lung tissue from 123 Quebec workers with asbestosis, pleural mesothelioma or lung cancer recognized as occupational diseases. It used lung analyses done for compensation between 1988 and 2007. Chrysotile was found in the lungs of 85% of the workers, tremolite in 76%, amosite in 64% and crocidolite in 43%. Of fibers measured in 97 workers, 50% were short (under 5 micrometers long) and 30% were fine (at least 5 micrometers long and under 0.2 micrometers wide). The other 20% met the World Health Organization counting definition, and few chrysotile fibers met it. Concentrations of chrysotile, crocidolite and tremolite were statistically significantly higher in workers with longer durations of exposure. Chrysotile was still found in some workers 30 years or more after exposure ended, above published levels for unexposed Quebec people. The authors concluded that several fiber-size criteria should be considered when characterizing asbestos health risks. They noted that they had no unexposed comparison group of workers, and that the workers studied were probably a less exposed subgroup. For that reason, the results cannot easily be extended to all exposed workers.

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: Descriptive study (brief report) of existing lung fiber burden data collected for workers' compensation purposes
• Who was studied: 123 Quebec workers (122 men) whose asbestos-related disease was recognized as an occupational lung disease and whose lung fiber content was analyzed between 1988 and 2007. Of 135 cases with a requested analysis, 12 were excluded. Diagnoses: 23 asbestosis, 27 mesothelioma, 58 lung cancer, 3 both asbestosis and mesothelioma, and 12 both asbestosis and lung cancer. Counted once per disease, this gives 38 asbestosis, 30 pleural mesothelioma and 70 lung cancer. Average age at disease recognition was 68.7 years.
• Exposure: Occupational asbestos exposure, mainly in chrysotile asbestos mining, maintenance and repair, and construction. Lung tissue was analyzed by electron microscopy for chrysotile, amosite, crocidolite and tremolite fibers. Anthophyllite was not counted.
• Main results:
  • Across all 123 workers, chrysotile fibers were found in the lungs of 85%, tremolite in 76%, amosite in 64% and crocidolite in 43%.
  • Chrysotile and tremolite fibers were found in almost all workers whose main industry was chrysotile asbestos mining. Amosite was found in more than 80% of workers in every other industry, but in 26.2% (11 of 42) of chrysotile mining workers.
  • For all subjects, diseases and fiber types together (fiber dimensions available for 97 workers), 50% of fibers were short, 30% fine and 20% WHO fibers. Short meant longer than 0.5 and under 5 micrometers long and under 3 micrometers wide. Fine meant at least 5 micrometers long and under 0.2 micrometers wide. WHO fibers were at least 5 micrometers long and from 0.2 to under 3 micrometers wide. All categories required a length-to-width ratio of at least 3 to 1.
  • Proportions of WHO chrysotile fibers were low regardless of disease or industry: 27 of 2,932 chrysotile fibers (0.9%) for all cases.
  • Lung concentrations of chrysotile, crocidolite and tremolite were statistically significantly higher in workers with exposure durations above the median.
  • Concentrations were statistically significantly lower when more time had passed between last exposure and lung analysis. This applied to chrysotile fibers of all lengths and to crocidolite fibers shorter than 5 micrometers.
  • Among 24 workers analyzed 30 years or more after their last exposure, chrysotile was found in 2 of 3 with asbestosis, 4 of 8 with mesothelioma and all 13 with lung cancer.
  • In some workers 30 years or more after exposure stopped, chrysotile concentrations were above those published for an unexposed Quebec population.
• The authors' conclusion: The authors concluded that their findings stress the relevance of considering several fiber-size criteria, not only the WHO definition, to characterize health risks from asbestos inhalation. They also concluded that chrysotile fibers can still be found in the lungs decades after occupational exposure ends.
• Limitations the authors state:
  • No lung tissue from an unexposed reference population of workers was available; comparisons used only published reference counts.
  • Lung analyses were requested mainly when exposure was unclear or seemed insufficient, so the study group was probably a less exposed subgroup.
  • The proportion of lung cancer cases was larger than usual, which influenced the pooled results, and these cases were mostly smokers.
  • Results cannot easily be extrapolated to all claimants, all recognized cases or all Quebec workers exposed to asbestos.
  • The data were already collected, with no control over biopsy site, number of tissue blocks or analytical protocol, so representativeness of total lung burden is unknown.
  • No detailed exposure data, such as initial exposure intensity or specific tasks, were available.
  • Anthophyllite fibers were not counted because they are hard to distinguish chemically from talc.

Topics

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

Medical terms in this study, explained in our Lexicon: Fiber Burden, Mesothelioma, Lung Cancer, Chrysotile, Tremolite, Amosite, Crocidolite.

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