Radiographic abnormalities and exposure to asbestos-contaminated vermiculite in the community of Libby, Montana, USA

Our plain-English summary of Radiographic abnormalities and exposure to asbestos-contaminated vermiculite in the community of Libby, Montana, USA, by L.A. Peipins, M. Lewin, S. Campolucci, et al (Environmental Health Perspectives, 2003).

The study

• Authors: L.A. Peipins, M. Lewin, S. Campolucci, J.A. Lybarger, A. Miller, D. Middleton, C. Weis, M. Spence, B. Black, V. Kapil
• Journal: Environmental Health Perspectives
• Published: 2003;111(14):1753-9
• Cited by: 118 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Mining, handling, processing, and personal or commercial use of asbestos-contaminated vermiculite have led to widespread contamination of the Libby, Montana, area. We initiated a medical testing program in response to reports of respiratory illness in the community. The purpose of this analysis was to identify and quantify asbestos-related radiographic abnormalities among persons exposed to vermiculite in Libby and to examine associations between these outcomes and participants' self-reported exposures. A cross-sectional interview and medical testing were conducted in Libby from July through November 2000 and from July through September 2001. A total of 7,307 persons who had lived, worked, or played in Libby for at least 6 months before 31 December 1990 completed the interview. Of those, 6,668 participants > or = 18 years of age received chest radiographs to assess the prevalence of pleural and interstitial abnormalities. We observed pleural abnormalities in 17.8% of participants and interstitial abnormalities in < 1% of participants undergoing chest radiography. We examined 29 occupational, recreational, household, and other exposure pathways in the analysis. The prevalence of pleural abnormalities increased with increasing number of exposure pathways, ranging from 6.7% for those who reported no apparent exposures to 34.6% for those who reported > or = 12 pathways. The factors most strongly associated with pleural abnormalities were being a former W.R. Grace worker, being older, having been a household contact of a W.R. Grace worker, and being a male. In addition to being a former W.R. Grace worker, environmental exposures and other nonoccupational risk factors were also important predictors of asbestos-related radiographic abnormalities.

In plain English

This cross-sectional study tested people connected to the Libby, Montana, area, where asbestos-contaminated vermiculite was mined and processed. In 2000 and 2001, 7,307 people who had lived, worked or spent time there for at least 6 months before 31 December 1990 were interviewed about 29 possible exposure pathways. Of these, 6,668 adults had chest X-rays classified by three certified readers. Pleural abnormalities were found in 1,186 (17.8%) and interstitial (lung tissue) abnormalities in 54 (0.8%). Among former W.R. Grace workers, 51.0% had pleural abnormalities. Pleural abnormalities rose with the number of pathways reported, from 6.7% among people reporting none to almost 35% among those reporting 12 or more (adjusted odds ratio 3.75, 95% CI 1.65–8.50). In adjusted analyses, pleural abnormalities were associated with several factors, including being male, being older, being a former worker, being a household contact of a worker, and playing in vermiculite piles. The authors concluded that environmental and other nonoccupational factors, as well as W.R. Grace work, predicted these abnormalities. They noted that participants were self-selected volunteers and that the study was cross-sectional.

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: Cross-sectional interview and chest X-ray screening study (community medical testing program)
• Who was studied: 7,307 current and former residents of the Libby, Montana, area who had lived, worked, attended school or done other activities there for at least 6 months before 31 December 1990. Of these, 6,668 aged 18 or older had chest X-rays. Testing took place in 2000 and 2001, and the participation rate was 78.6%.
• Exposure: Self-reported exposure to asbestos-contaminated vermiculite through 29 pathways. These covered occupational pathways (including work for W.R. Grace or Zonolite, and trades such as pipe fitter, insulator and welder), household contact with a W.R. Grace worker, home uses (insulation, gardening), and recreational pathways (playing in vermiculite piles, popping vermiculite, playing at the ball field near the expansion plant, activities along Rainey Creek Road). The study did not measure fibers.
• Main results:
  • Among all 6,668 adults X-rayed, 1,186 (17.8%) had pleural abnormalities and 54 (0.8%) had interstitial abnormalities.
  • Among former W.R. Grace workers, 186 of 365 (51.0%) had pleural abnormalities, the highest unadjusted rate of any pathway. 14 (3.8%) of these workers had interstitial abnormalities.
  • Pleural abnormalities were found in 6.7% of those reporting no exposure pathways and in almost 35% of those reporting 12 or more pathways.
  • After adjusting for age, sex, BMI, smoking and residential duration, odds ratios for pleural abnormalities (compared with no apparent exposure) ranged from 1.40 (95% CI 0.60–3.26) for one pathway to 3.75 (95% CI 1.65–8.50) for 12 or more pathways. The trend was statistically significant.
  • With former W.R. Grace workers removed from the analysis, 30.1% of those reporting 12 or more pathways still had pleural abnormalities.
  • Compared with nonworkers, the adjusted odds ratio for pleural abnormalities in former W.R. Grace workers was 4.18 (95% CI 2.20–7.94) at age 30. It fell with age to 1.14 (95% CI 0.53–2.44) at age 90.
  • Among people who were not household contacts, males had an adjusted odds ratio for pleural abnormalities of 4.84 (95% CI 3.83–6.11) compared with females.
  • Female household contacts of former W.R. Grace workers had an adjusted odds ratio of 3.62 (95% CI 2.70–4.83) compared with females who were not contacts. For male household contacts the figure was 1.71 (95% CI 1.32–2.22).
  • Those who frequently played in vermiculite piles had an adjusted odds ratio for pleural abnormalities of 2.02 (95% CI 1.59–2.57) compared with those who never played in the piles.
  • For interstitial abnormalities, the strongest adjusted predictors were being a former W.R. Grace worker (OR 2.71, 95% CI 1.26–5.87) and being male (OR 2.48, 95% CI 1.08–5.68). Interstitial abnormalities showed no exposure–response pattern with number of pathways.
• The authors' conclusion: The authors concluded that, in addition to being a former W.R. Grace worker, environmental exposures and other nonoccupational risk factors were also, in their words, important predictors of asbestos-related radiographic abnormalities.
• Limitations the authors state:
  • The authors called the cross-sectional design and the self-selection of volunteer participants, rather than random selection, the principal limitations.
  • The cross-sectional design may have left out a disproportionate number of people who were ill or had died from more severe disease.
  • The X-ray readers knew the films came from the Libby program, and no control films were included.
  • The 'no apparent exposure' group was based on answers to specific questions and probably missed some exposure pathways.
  • A heavier BMI can make it harder to tell pleural abnormalities apart from fat on X-rays.

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, Talc and vermiculite.

Medical terms in this study, explained in our Lexicon: vermiculite, Chest X-Ray, Interstitial, W.R. Grace, Environmental Exposure.

Related studies

• Radiographic abnormalities and asbestos exposure: Libby, Montana — B. Price (2004)
• Select mortality and cancer incidence among residents in various U.S. communities that received asbestos-contaminated vermiculite ore from Libby, Montana — D.K. Horton, F. Bove, et al. (2008)
• 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)
• Low-level fiber-induced radiographic changes caused by Libby vermiculite: a 25-year follow-up study — A.M. Rohs, J.E. Lockey, et al. (2008)
• Libby Amphibole Disease: Pulmonary Function and CT Abnormalities in Vermiculite Miners — A. Miller, J. Szeinuk, et al. (2018)
• A review of the federal government's health activities in response to asbestos-contaminated ore found in Libby, Montana — K. Horton, V. Kapil, et al. (2006)

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