Exposure to asbestos-containing vermiculite ore and respiratory symptoms among individuals who were children while the mine was active in Libby, Montana

Our plain-English summary of Exposure to asbestos-containing vermiculite ore and respiratory symptoms among individuals who were children while the mine was active in Libby, Montana, by L.C. Vinikoor, T.C. Larson, T.F. Bateson, et al (Environmental Health Perspectives, 2010).

The study

• Authors: L.C. Vinikoor, T.C. Larson, T.F. Bateson, L. Birnbaum
• Journal: Environmental Health Perspectives
• Published: 2010;118(7):1033-28
• Cited by: 27 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Libby, Montana, was home to the largest vermiculite ore mine in the United States. The processing, use, and transport of the ore, which was contaminated with amphibole asbestos, led to generalized contamination of the community. The mine closed in 1990.

Objectives: We examined the prevalence of respiratory symptoms in 2000-2001 and their association with history of vermiculite exposure among people who were < or = 18 years of age when the mine closed.

Methods: Information on respiratory symptoms and exposure history was collected by questionnaire in 2000-2001, at which time participants were 10-29 years old. Logistic regression was used to model the associations between exposures and outcomes adjusted for age, sex, and tobacco smoke exposure.

Results: Of the 1,003 individuals included in the study, 10.8% reported usually having a cough, 14.5% reported experiencing shortness of breath when walking up a slight hill or hurrying on level ground, and 5.9% reported having coughed up bloody phlegm in the past year. These respiratory symptoms were positively associated with frequently handling vermiculite insulation compared with never handling vermiculite insulation. We found no association between vermiculite insulation in the house and respiratory symptoms. Respiratory symptoms were associated with other vermiculite exposures as well, and the number and frequency of these activities showed a positive trend with usually having a cough. We found no association between any of the activities and abnormal spirometry.

Conclusions: These data suggest that residents of Libby, Montana, who were children when the mine closed experienced some respiratory symptoms associated with asbestos-contaminated vermiculite exposure.

In plain English

This study analysed 2000–2001 questionnaire and breathing-test (spirometry) data in Libby, Montana, where vermiculite ore was contaminated with amphibole asbestos. It included 1,003 people aged 18 or younger when the mine closed in 1990. People reporting work for W.R. Grace or its contractors, or dust or vermiculite exposure at other jobs, were excluded. Usually having a cough was reported by 10.8% (95% CI 8.9 to 12.7%), versus 5.6% (4.1 to 7.0%) nationally; the authors said these were not directly comparable. Adjusting for age, sex and tobacco smoke, frequently versus never handling vermiculite insulation was associated with cough (odds ratio 3.38; 95% CI 1.56 to 7.31), shortness of breath (3.28; 1.63 to 6.63) and bloody phlegm (2.75; 1.07 to 7.09). Frequent recreation along Rainy Creek Road, heating vermiculite, and playing at ball fields near the expansion plant were each linked to some symptoms. Home vermiculite insulation showed no association with symptoms; no activity was associated with abnormal spirometry. The authors noted possible recall bias and volunteer participants. They concluded these residents experienced some self-reported respiratory symptoms associated with asbestos-contaminated vermiculite exposure.

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: Analysis of interview questionnaire and spirometry data from a 2000–2001 ATSDR community screening study in Libby, using logistic regression adjusted for age, sex and tobacco smoke exposure
• Who was studied: Of 1,224 ATSDR participants who were 18 or younger when the mine closed in 1990, 221 were excluded because they reported working for W.R. Grace or as a W.R. Grace contractor, or exposure to dust or vermiculite at other jobs. That left 1,003 people, 57.2% female, aged 10 to 29 when interviewed in 2000–2001 in Libby, Montana.
• Exposure: Community, non-occupational exposure to vermiculite contaminated with Libby amphibole asbestos (tremolite, winchite and richterite). It was measured by self-reported frequency (never, sometimes, frequently) of six activities: handling vermiculite insulation, recreation along Rainy Creek Road, playing at the ball fields near the expansion plant, playing in or around vermiculite piles, heating vermiculite to make it expand or pop, and other contact with vermiculite. The presence of vermiculite insulation in the home was also analysed.
• Main results:
  • In the Libby study group, 10.8% (95% CI 8.9 to 12.7%) reported usually having a cough, compared with 5.6% (95% CI 4.1 to 7.0%) in the national NHANES population.
  • The authors stated that the Libby and NHANES cough figures were not directly comparable, because the questions defined cough differently.
  • Compared with never handling vermiculite insulation, frequently handling it was associated with self-reported cough (OR 3.38; 95% CI 1.56 to 7.31), shortness of breath (OR 3.28; 95% CI 1.63 to 6.63) and coughing up bloody phlegm (OR 2.75; 95% CI 1.07 to 7.09).
  • Frequent recreation along Rainy Creek Road was associated with shortness of breath (OR 1.89; 95% CI 1.12 to 3.19) as well as with cough.
  • Frequently heating vermiculite to make it expand or pop was associated with cough only.
  • Frequently playing at the ball fields near the expansion plant was associated only with coughing up bloody phlegm (OR 2.46; 95% CI 1.04 to 5.79).
  • For usually having a cough, compared with never taking part in any activity, the odds ratios were 1.88 for taking part sometimes, 2.00 for one or two activities frequently, and 2.93 for three or more activities frequently. All of these confidence intervals included 1.
  • When adjusted only for age and sex, the odds ratio for usually having a cough was 3.62 (95% CI 1.17 to 11.16) for people who frequently took part in three or more activities, compared with people who never took part in any.
  • Having vermiculite insulation in the home was not associated with cough (OR 1.12), shortness of breath (OR 0.95) or lung disease (OR 0.65).
  • None of the activities was clearly associated with self-reported lung disease.
  • No exposure variable was associated with an abnormal spirometry result.
  • There were no cases of mesothelioma in the study population.
• The authors' conclusion: The authors concluded that Libby residents who were children when the mine closed experienced some self-reported respiratory symptoms in association with exposure to asbestos-contaminated vermiculite.
• Limitations the authors state:
  • The authors could not determine whether the higher levels of cough were due to the vermiculite or to some other exposure in Libby.
  • Higher particulate air pollution in Libby, for example from wood-burning stoves, may have contributed to the higher cough rates.
  • Residents' awareness of the contamination may have caused recall bias or exaggerated reporting of symptoms or of exposure frequency.
  • Participants were volunteers, not a random sample of the population.
  • Coughing up bloody phlegm may not represent outcomes as serious as this symptom usually indicates.
  • The data were self-reported and were not checked against medical records.
  • The cough definitions in the ATSDR survey and NHANES differed.

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: Talc and vermiculite.

Medical terms in this study, explained in our Lexicon: vermiculite, Amphibole Asbestos, Exposure History, Spirometry.

Related studies

• Vermiculite, respiratory disease, and asbestos exposure in Libby, Montana: update of a cohort mortality study — P.A. Sullivan (2007)
• 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)
• Mortality in a cohort of vermiculite miners exposed to fibrous amphibole in Libby, Montana — J.C. McDonald, J. Harris, et al. (2004)
• A clinical assessment and lung tissue burden from an individual who worked as a Libby vermiculite miner — B. Black, R.F. Dodson, et al. (2017)
• 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)
• An evaluation of potential occupational exposure to asbestiform amphiboles near a former vermiculite mine — J.F. Hart, T.M. Spear, et al. (2009)

Browse more research in Environmental Health Perspectives, or return to medical research.