Effects of asbestos and smoking on the levels and rates of change of lung function in a crocidolite exposed cohort in Western Australia

Our plain-English summary of Effects of asbestos and smoking on the levels and rates of change of lung function in a crocidolite exposed cohort in Western Australia, by H.S. Alfonso, L. Fritschi, N.H. de Klerk, et al (Thorax, 2004).

The study

• Authors: H.S. Alfonso, L. Fritschi, N.H. de Klerk, N. Olsen, J. Sleith, A.W. Musk
• Journal: Thorax
• Published: 2004;59(12):1052-6
• Cited by: 22 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Increased rates of death from asbestos related diseases have been reported in former workers and residents exposed to crocidolite (blue asbestos) at Wittenoom, Western Australia. Exposure to asbestos is associated with reduced static lung volumes, gas transfer and lung compliance, and a restrictive ventilatory abnormality.

Methods: The effects of crocidolite exposure and smoking history on levels and rates of change of lung function were evaluated using a linear mixed model. Lung function was measured as forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and FEV1/FVC.

Results: Cumulative doses of asbestos and the presence of radiographic asbestosis were associated with lower levels of FEV1 and FVC and a steeper decline during the period of observation. Subjects exposed to asbestos at a younger age had lower levels of FEV1 and FVC. Current smokers had lower levels and a steeper decline in lung function than never smokers. No significant interactions between crocidolite exposure and smoking on the levels or rates of change of lung function were found.

Conclusions: The deleterious effects of crocidolite exposure on lung function persist in this population, despite asbestos exposure having ceased more than 30 years ago. No significant interactions were found in this population between asbestos and smoking at the first visit or longitudinally.

In plain English

This study followed 1392 former workers and residents of Wittenoom, Western Australia, where crocidolite (blue asbestos) was mined from 1943 until 1966. Participants, aged 25 or over and enrolled in a Vitamin A Program, had 6440 breathing tests from 1992 to 2002. Lung function was measured as FEV1 (air forcefully exhaled in one second), FVC (forced vital capacity: total air forcefully exhaled) and the FEV1/FVC ratio. Higher estimated cumulative crocidolite exposure was associated with lower FEV1 and FVC and faster decline. People with radiographic asbestosis had levels 313 ml lower for FEV1 and 381 ml lower for FVC than those without, and an extra yearly fall of 13 ml in FEV1 (95% CI 9 to 17) and 20 ml in FVC (95% CI 14 to 26). People first exposed at a younger age had lower levels. Current smokers had lower levels and steeper FEV1 decline than never smokers. No significant asbestos-smoking interaction was found. The authors concluded that crocidolite's harmful effects on lung function persisted more than 30 years after exposure ceased. They noted that smoking was self-reported and silica exposure was not assessed.

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: Longitudinal (repeated-measures) cohort analysis of spirometry in participants of a Vitamin A cancer-prevention program, analysed with a linear mixed model
• Who was studied: 1392 former workers (819) and former residents (573) of Wittenoom, Western Australia, aged 25 or over at entry. They had 6440 spirometry measurements from 1992 to September 2002.
• Exposure: Crocidolite (blue asbestos) from mining and milling at Wittenoom (1943 to 1966), or from living in the town. Exposure was estimated as cumulative fibre exposure in f/ml-years. Radiographic asbestosis (ILO profusion 1/0 or greater) and smoking status (never, ex-, current) were also studied.
• Main results:
  • Average decline across the cohort was 24 ml per year in FEV1 (95% CI 20 to 28) and 39 ml per year in FVC (95% CI 35 to 45).
  • Each additional f/ml-year of cumulative asbestos exposure was associated with a lower FEV1 level by 0.9 ml (95% CI 0.31 to 1.50) and a lower FVC level by 1.5 ml (95% CI 0.72 to 2.29).
  • People with higher cumulative asbestos exposure had greater declines in FEV1 and FVC over time.
  • Subjects with radiographic asbestosis had lower FEV1 (313 ml) and lower FVC (381 ml) than those without asbestosis.
  • Radiographic asbestosis was associated with an additional yearly decrease of 13 ml in FEV1 (95% CI 9 to 17) and 20 ml in FVC (95% CI 14 to 26). It was not associated with the level or rate of decline of FEV1/FVC.
  • People first exposed to asbestos at a younger age had lower FEV1 and FVC levels. Years since last exposure was not a significant predictor.
  • After adjustment, ex-residents had higher FEV1 (157 ml), FVC (110 ml) and FEV1/FVC (1.2%) than workers. There were no significant differences in annual change between the two groups.
  • Compared with never smokers, current smokers had a steeper FEV1 decline. The FEV1 decline in ex-smokers was not significantly different from never smokers.
  • No significant statistical interactions between asbestos exposure and smoking were found, either for lung function levels or for rate of decline.
• The authors' conclusion: The authors concluded that the harmful effects of crocidolite exposure on lung function persist in this population, more than 30 years after exposure ceased. They suggested that smoking and asbestos acted independently (additively) rather than synergistically.
• Limitations the authors state:
  • Smoking exposure was based on self-reporting.
  • Only smoking status at the start of follow up was analysed. Changes in smoking habits over time were not included.
  • Smoking was analysed in categories (never, current, ex-smokers), which raises the possibility of residual confounding by smoking.
  • Exposure to other mineral dusts, particularly silica, was not assessed, so its potential confounding effect could not be accounted for.
  • Dietary confounding factors were not accounted for.
  • Participants self-selected into the program and may not represent the whole Wittenoom cohort. Results may not apply to lower exposure levels or older age groups.
  • Ninety subjects (6.3%) dropped out. Those who left had lower FEV1, FVC and FEV1/FVC than those who remained.

Mines named here

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

• Wittenoom, Western Australia

All asbestos mines

Topics

The National Library of Medicine indexes this study under subjects our site covers: Crocidolite.

Medical terms in this study, explained in our Lexicon: Crocidolite, Wittenoom, FEV1, FEV1/FVC Ratio, Cumulative Exposure, Asbestos Exposure.

Related studies

• Plasma retinol, carotene and vitamin E concentrations and lung function in a crocidolite-exposed cohort from Wittenoom, Western Australia: a cohort study — H.S. Alfonso, L. Fritschi, et al. (2005)
• Effects of asbestos and smoking on gas diffusion in people exposed to crocidolite — H.S. Alfonso, L. Fritschi, et al. (2005)
• Plasma vitamin concentrations and incidence of mesothelioma and lung cancer in individuals exposed to crocidolite at Wittenoom, Western Australia — H.S. Alfonso, L. Fritschi, et al. (2006)
• Retinol supplementation and mesothelioma incidence in workers earlier exposed to blue asbestos (Crocidolite) at Wittenoom, Western Australia — H.S. Alfonso, A. Reid, et al. (2010)
• Malignant pleural and peritoneal mesotheliomas in former miners and millers of crocidolite at Wittenoom, Western Australia — G. Berry, N.H. de Klerk, et al. (2004)
• Malignant mesotheliomas in former miners and millers of crocidolite at Wittenoom (Western Australia) after more than 50 years follow-up — G. Berry, A. Reid, et al. (2012)

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