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

Our plain-English summary of 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, by A.C. Whitehouse (American Journal of Industrial Medicine, 2004).

The study

• Author: A.C. Whitehouse
• Journal: American Journal of Industrial Medicine
• Published: 2004;46(3):219-25
• Cited by: 50 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: The community of Libby, Montana has recently been the focus of national attention secondary to widespread amphibole contamination associated with vermiculite mining and processing.

Methods: Patients who had occupational and non-occupational exposure to amphibole asbestos in Libby, Montana were evaluated for progressive loss of pulmonary function.

Results: Of the 123 patients evaluated, 94 demonstrated average age-corrected accelerated loss per year of vital capacity at 3.2%, total lung capacity (TLC) 2.3%, and DLCO 3.3%. All patients all had predominantly pleural changes with minimal to no interstitial disease.

Conclusions: The study demonstrates a progressive loss of pulmonary function in patients exposed to tremolite asbestos.

In plain English

This study reviewed repeated lung function tests of patients of a lung disease practice who were exposed to the amphibole asbestos in Libby, Montana vermiculite, which the author calls tremolite. The 123 patients included 86 former W.R. Grace employees, 27 family members of employees, and 10 with only environmental exposure. Most had pleural changes only; 67 showed no interstitial changes on chest X-ray or HRCT. Results were age-corrected against predicted normal values, so changes reflected decline beyond normal aging. Across all 123 patients, followed for an average of 35 months, the average yearly loss was 2.2% for forced vital capacity (FVC), 2.3% for total lung capacity and 3.0% for diffusing capacity (DLCO). Ninety-four (76%) had an accelerated loss of FVC, averaging 3.2% per year. The extent of pleural changes on chest X-ray was not statistically correlated with the loss. The author concluded that pleural changes related to Libby tremolite exposure are associated with progressive loss of lung function. The author noted that only about half the patients had HRCT scans and that exposure histories were complex.

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: Retrospective analysis of serial (first versus last) pulmonary function tests in patients of a clinical practice, with no comparison group
• Who was studied: 123 patients from Libby, Montana, out of a practice group of 491. Of the 123, 86 (70%) were former W.R. Grace employees, 27 (22%) were family members of employees, and 10 (8%) had Libby environmental exposure only. 99 were male and 24 female, with an average age of 66 at the first test. Of 153 patients with at least two sets of tests, 30 were excluded.
• Exposure: Occupational, household and community exposure to the amphibole in Libby vermiculite. Mineralogists characterized it as a tremolite–actinolite–richterite–winchite transition fiber, which the author calls tremolite. The author describes the exposure period as approximately 1950 to 1975.
• Main results:
  • All lung function values were age-corrected against normative predicted values. Changes in percent of predicted over time therefore reflected decline beyond that accounted for by aging.
  • In all 123 patients, the average yearly age-corrected loss was 2.2% for FVC, 2.3% for TLC and 3.0% for DLCO, calculated over an average of 35 months.
  • 94 of the 123 patients (76%) had an accelerated loss of FVC.
  • In the 94 patients with progressive FVC loss, the yearly age-corrected loss was 3.2% for FVC, 2.3% for TLC and 3.3% for DLCO.
  • In the 79 of 123 patients with greater than 1% FVC loss per year, the average yearly loss was 3.6% for FVC, 2.5% for TLC and 3.5% for DLCO.
  • 67 of 123 patients (55%) had no evidence of interstitial changes on chest X-ray or HRCT.
  • In the 67 patients with pleural changes alone and no interstitial changes, the average yearly FVC loss was 2.2%.
  • The other 56 patients had minimal irregular interstitial changes at the lung bases, at profusion category 0/1 or 1/0.
  • There did not appear to be a difference between patients with pleural changes plus minor interstitial changes and those with no interstitial changes.
  • The declines were reported as statistically significant. The comparison symbol before .01 is missing from the text.
  • In the entire group, diffusing capacity (DLCO) declined faster than FVC or TLC.
  • The extent of pleural changes on chest X-ray was not statistically correlated with loss of lung function.
• The authors' conclusion: The author concluded that pleural changes related to Libby tremolite exposure are associated with progressive loss of lung function in this group, exposed from approximately 1950 to 1975.
• Limitations the authors state:
  • Only about half the patients had HRCT scans, so pleural plaques could not be reliably distinguished from diffuse pleural thickening.
  • Exposure histories were complex, with exposure largely continuous throughout residence in Libby.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Libby vermiculite mine, Montana

All asbestos mines

Topics

The National Library of Medicine indexes this study under subjects our site covers: Pleural plaques and thickening, Tremolite.

Medical terms in this study, explained in our Lexicon: Asbestos-Related Pleural Disease, Tremolite, Amphibole Group, vermiculite, Non-Occupational Exposure, Amphibole Asbestos, Total Lung Capacity (TLC), Diffusing Capacity (DLCO).

Related studies

• Libby Amphibole Disease: Pulmonary Function and CT Abnormalities in Vermiculite Miners — A. Miller, J. Szeinuk, et al. (2018)
• Case-fatality study of workers and residents with radiographic asbestos disease in Libby, Montana — A. Miller, C.B. Black, et al. (2022)
• Mortality in a cohort of vermiculite miners exposed to fibrous amphibole in Libby, Montana — J.C. McDonald, J. Harris, et al. (2004)
• Lung function, radiological changes and exposure: analysis of ATSDR data from Libby, MT, USA — D. Weill, G. Dhillon, et al. (2011)
• Rapid progression of pleural disease due to exposure to Libby amphibole: "Not your grandfather's asbestos related disease" — B. Black, J. Szeinuk, et al. (2014)
• Exposure to asbestos-containing vermiculite ore and respiratory symptoms among individuals who were children while the mine was active in Libby, Montana — L.C. Vinikoor, T.C. Larson, et al. (2010)

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