Descriptive analysis of the respiratory health status of persons exposed to Libby amphibole asbestos

Our plain-English summary of Descriptive analysis of the respiratory health status of persons exposed to Libby amphibole asbestos, by C.A. Winters, W.G. Hill, K. Rowse, et al (BMJ Open, 2012).

The study

• Authors: C.A. Winters, W.G. Hill, K. Rowse, B. Black, S.W. Kuntz, C. Weinert
• Journal: BMJ Open
• Published: 2012;2(6)
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: Describe respiratory health and quality of life in persons exposed to Libby amphibole asbestos (LAA) contaminated vermiculite.

Design: Cross-sectional descriptive.

Setting: Asbestos-related disease clinic in Libby, Montana USA.

Participants: 329 individuals exposed to LAA; mostly men, married, between 50 and 69 years; two-thirds lived in the surrounding county; one-third lived elsewhere in the state and USA.

Primary Outcome Measures: Chest radiograph (CXR), pulmonary function data and the St George Respiratory Questionnaire (SGRQ).

Results: Exposure categories included vermiculite workers=7.6%; family/household contact of vermiculite worker=32%; and environmental exposure only=60%. Of the participants, 55% had only pleural abnormalities; 5.4% had only interstitial abnormalities; nearly 21% had both abnormalities and 18% had no lung abnormality on chest x-ray. Mean forced vital capacity (FVC) 95.3% (SD=18.7); forced expiratory volume (FEV(1)) mean 87% (SD=20.2); ratio of FEV1(1)/FVC 95.5% (SD=12.0); and diffusing capacity (DLCO) of 83% (SD=21.7) of the percent predicted. The mean total SGRQ (38.5; SD=22.1) indicated a lower quality of life than healthy persons and persons with other chronic conditions. SGRQ subscale means were Symptoms 52.1 (SD=24.9), activity 49.4 (SD=26.9) and impacts 27.5 (SD=21.9). Participants with normal CXR differed significantly from those with both interstitial and pleural abnormalities on total, activity and impacts scores. For activity alone, subjects with normal CXR differed significantly from those with pleural disease; no differences were found for those with interstitial disease. Significant findings were found for smoking history across all pulmonary measures, and for exposure status, radiographic findings, age and gender for select pulmonary parameters. Subjects with any smoking history had significantly worse average total and subscale scores on the SGRQ.

Conclusions: Of 329 persons exposed to LAA, the majority (182) had pleural abnormalities identified on CXR. SGRQ scores for persons with abnormalities (pleural, interstitial or both) (269) differed significantly from those with a normal CXR.

In plain English

This cross-sectional study described lung health and breathing-related quality of life in 329 Libby, Montana, clinic patients exposed to Libby amphibole asbestos in contaminated vermiculite. Of the participants, 25 were vermiculite workers, 106 were household contacts of workers and 198 had other, environmental-only exposure. On their most recent chest x-ray, 55% had only pleural abnormalities, 5.4% only interstitial abnormalities, nearly 21% both, and 18% none. Average lung function was 95.3% of predicted for FVC, 87% for FEV1 and 83% for DLCO. Those with a normal x-ray had better FVC, FEV1 and DLCO than those with both kinds of abnormality. The mean St George Respiratory Questionnaire total score was 38.5 (0 best, 100 worst), versus 8.41 in a Spanish general-population sample. Ever-smokers scored significantly worse on the questionnaire. The authors noted the cross-sectional design and insensitive chest x-rays as limits. They concluded that the group's quality of life was significantly lower than in healthy persons and appreciably worse than some people with COPD or interstitial lung disease.

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 descriptive study using a questionnaire plus chest x-ray and lung function results taken from medical records
• Who was studied: 329 patients aged 21 or older of the Center for Asbestos Related Disease (CARD) in Libby, Montana, USA. Primary data were collected on 485 patients, but 329 remained after excluding those with incomplete clinical data. There were 187 men and 142 women. Two-thirds lived in Lincoln County and one-third lived elsewhere in Montana or the USA. Data were collected February to December 2007.
• Exposure: Libby amphibole asbestos (LAA) in contaminated vermiculite. Exposure routes: vermiculite workers (25 people), family or household contacts of workers (106) and environmental exposure only (198). No exposure doses were measured.
• Main results:
  • On the most recent chest x-ray, out of 329 participants: 182 (55%) had only pleural abnormalities, 18 (5.4%) only interstitial abnormalities, 69 (nearly 21%) both, and 60 (18%) no abnormality.
  • For the whole group, mean lung function as percent of predicted was: FVC 95.3% (SD 18.7), FEV1 87% (SD 20.2), FEV1/FVC ratio 95.5% (SD 12) and DLCO 83% (SD 21.7).
  • Participants with a normal chest x-ray (n=60) had better FVC, FEV1 and DLCO than those with both interstitial and pleural abnormalities (n=69). Mean FVC was 103.8 vs 88.8, FEV1 92.8 vs 80.4, and DLCO 90.2 vs 73.7 percent predicted.
  • Smoking history was associated with statistically significant differences across the lung function measures.
  • For the whole group, the mean St George Respiratory Questionnaire total score was 38.5 (SD 22.1). Subscale means were symptoms 52.1 (SD 24.9), activity 49.4 (SD 26.9) and impacts 27.5 (SD 21.9). Scores run from 0 (no impairment) to 100 (worst).
  • For comparison, published population norms from a Spanish sample (n=862, from the IBERPOC study by Ferrer et al) had a mean total score of 8.41 (SD 11.33). Their subscale means were symptoms 9.67, activity 13.40 and impacts 4.73.
  • Participants with a normal chest x-ray differed significantly from those with both interstitial and pleural abnormalities on total, activity and impacts scores. For example, mean total score was 29.8 in the normal group vs 43.8 in the group with both.
  • Participants with any smoking history (n=215) had significantly worse average questionnaire scores, overall and on all three subscales, than never-smokers (n=114).
• The authors' conclusion: The authors concluded that the cohort's mean total questionnaire score of 38.5 indicated significantly lower respiratory-related quality of life than in healthy persons, and appreciably worse than some persons with COPD or interstitial lung disease.
• Limitations the authors state:
  • The cross-sectional design means results should be interpreted with caution.
  • It is not known how well the sample represents everyone with asbestos-related disease from Libby amphibole asbestos exposure.
  • Questionnaire data were collected at enrolment, but x-ray, lung function and exposure data came from the most recent health record entries, which may not reflect current status.
  • Standard chest x-rays are insensitive for detecting asbestos-related pleural and lung scarring. This is especially true for non-calcified pleural thickening, which the authors say predominates in the Libby population.
  • Participants were at varying stages of a disease that progresses over 10-plus years, so the results are a snapshot in time.

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

Medical terms in this study, explained in our Lexicon: Libby amphiboles, Quality of Life, vermiculite, Chest X-Ray, Environmental Exposure, Interstitial, FEV1, Diffusing Capacity (DLCO).

Related studies

• Psychosocial health status of persons seeking treatment for exposure to libby amphibole asbestos — C. Weinert, W.G. Hill, et al. (2011)
• Determining satisfaction with access and financial aspects of care for persons exposed to Libby amphibole asbestos: rural and national environmental policy implications — C.A. Winters, W. Hill, et al. (2011)
• Childhood exposure to Libby amphibole asbestos and respiratory health in young adults — P.H. Ryan, C.H. Rice, et al. (2017)
• A review of scientific literature examining the mining history, geology, mineralogy, and amphibole asbestos health effects of the Rainy Creek igneous complex, Libby, Montana, USA — B.R. Bandli, M.E. Gunter (2006)
• Exposure to airborne amphibole structures and health risks: Libby, Montana — B. Price (2008)
• Comparative health effects in mice of Libby amphibole asbestos and a fibrous amphibole from Arizona — J.C. Pfau, B. Buck, et al. (2017)

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