Determinants of respiratory symptoms in insulation workers exposed to asbestos and synthetic mineral fibres

Our plain-English summary of Determinants of respiratory symptoms in insulation workers exposed to asbestos and synthetic mineral fibres, by P. Ernst, S. Shapiro, R.E. Dales, et al (British Journal of Industrial Medicine, 1987).

The study

• Authors: P. Ernst, S. Shapiro, R.E. Dales, M.R. Becklake
• Journal: British Journal of Industrial Medicine
• Published: 1987;44(2):90-5
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000314).

Abstract

The determinants of respiratory symptoms were studied in an active workforce of insulation workers exposed to asbestos and synthetic mineral fibres. Responses to a mailed respiratory symptom questionnaire from 537 insulation workers without diagnosed asbestosis were analysed using logistic regression. Wheezing complaints and breathlessness were related primarily to current cigarette smoking and to symptoms suggesting an asthmatic predisposition antedating work in the trade. There was also evidence that these complaints were related to occupational exposure (estimated by number of hours worked in the trade) in subjects with prior airways hyperreactivity. An asthmatic predisposition antedating work in the trade was the major determinant of acute respiratory symptoms in the workplace. The effects of workplace exposures on respiratory symptoms may have been underestimated due to selective withdrawal from the active workforce and due to inaccuracies in the measure of exposure used.

In plain English

This questionnaire survey studied Quebec insulation workers, whose trade involved asbestos and, more recently, synthetic mineral fibres. Of 644 union insulators, 558 replied; 21 receiving asbestosis compensation were excluded, leaving 537. Exposure was estimated only as total hours worked in the trade. The authors also scored asthmatic tendency predating work in the trade. Compared with never smokers, current smokers had higher odds of wheeze apart from colds (more than threefold), chronic cough, chronic phlegm and symptoms at work, but not breathlessness. A higher score was linked to wheeze and to symptoms during dusty work. Across all workers, no independent effect of hours worked could be identified, though a small increase with exposure was suggested among those with higher scores. Among 294 current smokers, the odds of persistent wheeze were 1.06 times higher per 1000 hours worked (95% confidence interval 1.01 to 1.13). The authors concluded that smoking and asthmatic predisposition chiefly determined chronic symptoms, and asthmatic predisposition acute symptoms at work. They noted workplace effects may have been underestimated: only current workers were surveyed and exposure was crudely measured.

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 mailed respiratory symptom questionnaire survey, analysed with logistic regression
• Who was studied: Insulators working in Quebec in 1982 who were members of union local 58 of the International Association of Heat and Frost Insulators and Asbestos Workers. The target population was 644 men alive in January 1983. Of these, 558 responded (87%). Twenty-one receiving compensation for asbestosis were excluded, leaving 537 in the analysis.
• Exposure: Work in the insulation trade, with exposure to asbestos fibres and synthetic mineral fibres. Exposure was estimated only by duration, as cumulative total hours worked in the trade, with no measure of intensity.
• Main results:
  • Among all 537 workers, current smokers were more than three times as likely as never smokers to report wheeze apart from colds (odds ratio 3.24).
  • Compared with never smokers, current smokers had about a sixfold increase in risk for chronic cough, a fourfold increase for chronic phlegm, and a twofold increase for acute symptoms at work.
  • Current smoking was not associated with an increased risk of dyspnoea (breathlessness).
  • Each one-unit increase in the score for asthmatic predisposition before employment raised the risk of wheeze apart from colds by a factor of 1.16. It raised the risk of acute respiratory symptoms during dusty work by a factor of 1.28.
  • In the whole group, no independent effect of workplace exposure (hours worked) on symptoms could be identified. The authors said this did not clear the dust exposure of contributing to symptoms.
  • A statistically significant positive interaction between exposure and the reactivity score suggested a small increase in risk with exposure among workers with more evidence of an asthmatic predisposition.
  • Among the 294 current smokers, exposure was significantly related to persistent wheeze. The odds ratio was 1.06 per 1000 hours of work, with a 95% confidence interval of 1.01 to 1.13; table 5 prints these with hyphens for decimal points. This increase did not depend on a history suggesting increased airway reactivity.
  • Among current smokers, no dose-response relation was found between amount smoked (in units of 10 pack-years) and current respiratory symptoms.
  • Wheezing syndromes before employment predicted current wheezing. Dyspnoea grade 2 was related to a history of chronic rhinitis, and less so to urticaria (p = 0.1).
• The authors' conclusion: The authors concluded that cigarette smoking and an asthmatic predisposition were the major determinants of chronic respiratory symptoms in these insulation workers. They also concluded that an asthmatic predisposition before entering the trade was the main determinant of acute symptoms at work.
• Limitations the authors state:
  • Only current workers were questioned. Former workers, who may have had the most severe symptoms and the most intense exposure, were excluded.
  • The exposure measure was crude. It counted duration but not intensity, and involved assumptions for work before 1963. The authors said this would likely weaken rather than exaggerate any association.
  • Hygiene surveys were mostly unavailable because many employers were small firms.
  • The association between asthmatic predisposition and wheezing may partly reflect biased recall of earlier symptoms.

Topics

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

Related studies

• Respiratory cancer incidence in Swedish construction workers exposed to man-made mineral fibres and asbestos — G. Engholm, A. Englund, et al. (1987)
• Correlation between respiratory symptoms and pulmonary function in asbestos-exposed workers — C.A. Brodkin, S. Barnhart, et al. (1993)
• Longitudinal pattern of reported respiratory symptoms and accelerated ventilatory loss in asbestos-exposed workers — C.A. Brodkin, S. Barnhart, et al. (1996)
• Pleural determinants of restrictive lung function and respiratory symptoms in an asbestos-exposed population — A. Broderick, L.J. Fuortes, et al. (1992)
• Pleural determinants of restrictive lung function and respiratory symptoms in an asbestos-exposed population — P.H. Wright (1993)
• Relation of occupational exposure to respiratory symptoms and asthma in a general population sample: self-reported versus interview-based exposure data — P.S. Bakke, R. Hanoa, et al. (2001)

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