Respiratory impairment due to asbestos exposure in brake-lining workers

Our plain-English summary of Respiratory impairment due to asbestos exposure in brake-lining workers, by A. Franzblau, D.H. Garabrant (Environmental Research, 2004).

The study

• Authors: A. Franzblau, D.H. Garabrant
• Journal: Environmental Research
• Published: 2004;96(1):105-6; author reply 106-8
• Type of article: Letter, Comment
• Read it: PubMed · Publisher

In plain English

This is a letter to the editor, not a new study. In it, the authors criticized a 2003 study by Erdinç and colleagues. That study had followed workers at a single brake-lining production facility and concluded that chrysotile asbestos exposure may lower lung diffusion capacity. The authors argued that its study group was poorly described. Among its 86 subjects there were no ex-smokers, all 12 unexposed office workers were current smokers, and workers who missed the 1999 retesting were not mentioned. They noted that smokers were tested as little as 3 hours after smoking, while carbon monoxide's half-life in blood is about 4 hours, so smokers' diffusion results were likely biased toward looking more impaired. They called the reported 20% drop in percentage predicted diffusion capacity among unexposed smokers over 7 years a sign of measurement error. They also argued that a mean latency of about 10.7 years made a measurable asbestos effect exceedingly unlikely, and noted that no statistical comparisons were presented. The authors concluded that no valid scientific conclusions could be drawn from that study.

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: Letter to the editor criticizing a previously published study (Erdinç et al., 2003, Environmental Research); no new data were collected
• Who was studied: As described by the letter's authors, the criticized study involved active workers at a single brake-lining production facility, tested in 1992 and 1999: 74 asbestos-exposed workers (49 current smokers, 25 nonsmokers) and 12 unexposed office workers, all current smokers, for 86 subjects in total
• Exposure: Chrysotile asbestos exposure among workers processing asbestos brake linings in the criticized study; unexposed comparison workers were employed in offices
• Main results:
  • The letter's authors argued that the absence of ex-smokers among the 86 subjects suggested that a substantial number of workers had been excluded from the criticized study
  • The letter's authors noted that the unexposed group in the criticized study contained no nonsmokers
  • The letter's authors noted that the criticized study did not mention workers tested in 1992 who were not retested in 1999
  • Because diffusion testing was done as little as 3 hours after smoking, and carbon monoxide's half-life in blood is about 4 hours, the letter's authors argued that smokers' measurements were likely biased toward appearing more impaired
  • In the criticized study, the unexposed (non-asbestos-exposed) smokers showed a mean drop of 20% in percentage predicted diffusion capacity (TL,CO) over 7 years, almost 3% per year, which the letter's authors treated as a sign of measurement error
  • Based on a prediction equation for healthy male smokers (Miller et al., 1983), the letter's authors calculated that the expected age-related change over 7 years is 1.603 ml/mmHg/min, or only 5.4% of baseline (less than 1% per year)
  • The letter's authors stated that the overall mean latency of asbestos exposure in the criticized study was about 10.7 years, and argued that a measurable effect on lung function would be exceedingly unlikely after so short a latency
  • The letter's authors stated that the criticized study's five tables gave only descriptive statistics, with no statistical comparisons and no models adjusting for smoking or age
• The authors' conclusion: The authors concluded that, because of a poorly defined study population with unknown selection biases, flawed lung function testing and inadequate statistical analysis, no valid scientific conclusions could be drawn from the criticized study

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos Exposure.

Related studies

• Asbestos bodies in bronchoalveolar lavage fluids of brake lining and asbestos cement workers — P. Dumortier, P. De Vuyst, et al. (1990)
• Respiratory impairments due to dust exposure: a comparative study among workers exposed to silica, asbestos, and coalmine dust — X. Wang, E. Yano, et al. (1997)
• Asbestos exposure during brake lining maintenance and repair — A.N. Rohl, A.M. Langer, et al. (1976)
• Environmental and occupational health hazards associated with the presence of asbestos in brake linings and pads (1900 to present): a "state-of-the-art" review — D.J. Paustenbach, B.L. Finley, et al. (2004)
• Asbestos exposure during routine brake lining manufacture — H. Kakooei, M. Sameti, et al. (2007)
• Experimental studies on the effects of heated chrysotile asbestos and automobile brake lining dust injected into the body cavities of mice — J.M. Davis, S.W. Coniam (1973)

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