Effects of asbestos and smoking on gas diffusion in people exposed to crocidolite

Our plain-English summary of Effects of asbestos and smoking on gas diffusion in people exposed to crocidolite, by H.S. Alfonso, L. Fritschi, N.H. de Klerk, et al (The Medical Journal of Australia, 2005).

The study

• Authors: H.S. Alfonso, L. Fritschi, N.H. de Klerk, N. Olsen, J. Sleith, A.B. Musk
• Journal: The Medical Journal of Australia
• Published: 2005;183(4):184-7
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: To examine the effects of asbestos exposure and tobacco smoking on the level and rate of change of the diffusing capacity of the lung for carbon monoxide (DLCO).

Design And Participants: A cohort study of 934 people (including both mine workers and town residents) exposed to crocidolite (blue asbestos) at the asbestos mines and in the town of Wittenoom, Western Australia, between 1943 and 1966. DLCO measurements were taken during a follow-up period from 1992 to 2002.

Main Outcome Measures: Baseline levels of DLCO and change in levels over time.

Results: 2980 DLCO measurements were done on 934 people (of whom 818 were men and 724 were workers) who underwent a median of 2 (range, 1-17) measurements during the follow-up period. Radiographic asbestosis at baseline and asbestos exposure at a younger age were associated with lower DLCO values. The average rate of decline in DLCO was 0.33 (95% CI, 0.31-0.35) units per year, plus an additional decrement of 0.22 (95% CI, 0.12-0.32) units per year if the participant had radiographic asbestosis at the beginning of the follow-up period. Compared with never-smokers, current smokers and ex-smokers had lower DLCO at baseline, but smoking status did not affect the change in DLCO during the follow-up period.

Conclusions: Our results confirm a continuous deleterious effect of crocidolite on DLCO, especially on people with asbestosis. Smoking was associated with lower DLCO levels, but was not a significant predictor of rate of change in DLCO. Smoking status did not affect the relationships between crocidolite exposure and the level or rate of change of DLCO in this population.

In plain English

This study followed 934 former mine workers and town residents, aged 25 or older, exposed to crocidolite (blue asbestos) at Wittenoom, Western Australia, between 1943 and 1966. The authors analysed 2980 DLCO measurements, a test of how well gas passes from lungs into blood, taken 1992 to 2002 in a vitamin A program. DLCO fell by an average 0.33 (95% CI, 0.31–0.35) units per year, plus 0.22 (95% CI, 0.12–0.32) units more per year in people whose first chest x-ray showed asbestosis. People with asbestosis on x-ray started 3.0 (95% CI, 2.2–3.8) units lower than those without; people first exposed at a younger age also started lower. Cumulative asbestos exposure was not a significant predictor. Compared with never-smokers, current smokers started 5.1 (95% CI, 4.7–5.5) units lower and ex-smokers 1.4 (95% CI, 1.1–1.7) units lower. Smoking did not change the rate of decline or significantly interact with asbestos exposure. The authors concluded that their study confirms the harmful effect of crocidolite on DLCO. They noted that participants may not represent everyone exposed, and that withdrawals (29.8% of participants) may have biased follow-up.

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 cohort study of repeated lung-function (DLCO) tests carried out annually within a vitamin A supplementation program, analysed with a random-effects model
• Who was studied: 934 former workers and residents of Wittenoom, Western Australia (818 men, 116 women), aged 25 or older at baseline, with at least one DLCO test between 1992 and 23 September 2002; 2980 measurements in total
• Exposure: Crocidolite (blue asbestos) from the Wittenoom mine and town between 1943 and 1966. Cumulative exposure was estimated in fibre/mL years, from employment records and air measurements for workers and from town measurements for residents. The authors also studied radiographic asbestosis at baseline (ILO profusion 1/0 or greater) and self-reported smoking status.
• Main results:
  • Across all participants, DLCO declined on average by 0.33 (95% CI, 0.31–0.35) units (mL/min per mmHg) per year of follow-up
  • People with radiographic asbestosis at the start of follow-up had an additional decline of 0.22 (95% CI, 0.12–0.32) units per year
  • People with radiographic asbestosis at baseline had baseline DLCO 3.0 (95% CI, 2.2–3.8) units lower on average than people without asbestosis
  • People first exposed to asbestos at a younger age had significantly lower baseline DLCO
  • Years since last exposure, exposure category (worker or resident) and cumulative asbestos exposure were not significant predictors of change in DLCO over time
  • Compared with never-smokers, baseline DLCO was 5.1 (95% CI, 4.7–5.5) units lower in current smokers and 1.4 (95% CI, 1.1–1.7) units lower in ex-smokers
  • Smoking status did not affect the change in DLCO over follow-up, and there was no significant interaction between smoking and asbestos exposure on DLCO level or change
  • Apart from 146 participants who died, 29.8% of all participants dropped out without giving reasons; those who withdrew had higher average DLCO and tended to have had less asbestos exposure
• The authors' conclusion: The authors concluded that their study confirms the harmful effect of crocidolite on DLCO. They also stated that this damage persists and worsens over time, and that the effects of smoking appeared independent of those of asbestos exposure.
• Limitations the authors state:
  • The sample may not represent the whole asbestos-exposed Wittenoom population: program participants were younger and had higher asbestos exposures than non-participants
  • Participants could not be asked to stop smoking for 24 hours before testing. The authors said this is likely to have affected DLCO measurements and to have accentuated differences between current smokers and others.
  • Missing data due to withdrawals may have caused follow-up bias
  • Exposure estimates for former residents were based on few town measurements and are more uncertain than those for workers

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, Asbestos Exposure, Diffusing Capacity (DLCO), Cohort Study, Wittenoom.

Related studies

• Effects of asbestos and smoking on the levels and rates of change of lung function in a crocidolite exposed cohort in Western Australia — H.S. Alfonso, L. Fritschi, et al. (2004)
• 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)
• The risk of lung cancer with increasing time since ceasing exposure to asbestos and quitting smoking — A. Reid, N.H. de Klerk, et al. (2006)
• 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)
• Age and sex differences in malignant mesothelioma after residential exposure to blue asbestos (crocidolite) — A. Reid, G. Berry, et al. (2007)
• 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)

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