Ventilatory function after exposure to various respirable hazards in a population of former coal miners

Our plain-English summary of Ventilatory function after exposure to various respirable hazards in a population of former coal miners, by G.M. Calvert, M. Moore, S.M. Hessl (British Journal of Industrial Medicine, 1991).

The study

• Authors: G.M. Calvert, M. Moore, S.M. Hessl
• Journal: British Journal of Industrial Medicine
• Published: 1991;48(1):38-40
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The ventilatory function of 406 male former coal miners who had presented at the Cook County Hospital occupational medicine clinic between January 1976 and April 1987 was studied to determine whether subsequent exposure to respiratory hazards after leaving the coal mines adversely affected lung function. The miners were divided into five exposure groups based on their exposure to respirable hazards. These were coal dust only, coal dust plus asbestos dust, coal dust plus silica dust, coal dust plus another respirable hazard and coal dust plus two other respirable dust exposures. Duration of employment in coal mines, race, smoking history, and mean age were not significantly different between the various exposure groups. No significant difference was found in the per cent of predicted forced expiratory volume in one second (FEV1), per cent of predicted forced vital capacity (FVC), and FEV1/FVC when the coal dust only group was compared with each of the other four exposure groups using ANOVA. Among former coal miners who present for a respiratory disability determination, therefore, exposure to respirable hazards subsequent to employment in coal mines is not associated with a statistically significant deterioration in ventilatory function.

In plain English

The authors reviewed the charts of 406 male former coal miners assessed for Black Lung disability benefits at the Cook County Hospital clinic in Chicago between January 1976 and April 1987. They wanted to see whether breathing hazards in jobs held after leaving the mines were linked to worse lung function. The miners were sorted into five groups: coal dust only (268), coal dust plus asbestos dust (37), coal dust plus silica dust (50), coal dust plus another hazard such as welding fumes (44), and coal dust plus two or more hazards (7). The groups were similar in race, age, height, smoking and years of coal dust exposure. No statistically significant differences in breathing test results were found between the groups. In the asbestos group, the air blown out in one second was 74.3% of the predicted value, compared with 71.5% in the coal-only group. The authors concluded that later exposure was not associated with a statistically significant decline in lung function. They noted a self-selected sample, no control group and no cumulative dust exposure data, and said further investigation is warranted.

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: Retrospective review of clinic charts (cross-sectional comparison of lung function between exposure groups)
• Who was studied: 406 male former coal miners assessed for Black Lung disability benefits at the Cook County Hospital occupational medicine clinic, Chicago, USA, between January 1976 and April 1987. A further 158 miners were excluded because their lung tests did not meet American Thoracic Society standards.
• Exposure: Coal dust in the mines, plus jobs held afterwards with exposure to asbestos dust, silica dust, or other hazards (welding fumes, plastic fumes, or cotton dust). The type of asbestos is not stated. Cumulative dust exposure was not recorded.
• Main results:
  • Group sizes: coal only 268; coal plus asbestos 37; coal plus silica 50; coal plus miscellaneous hazard 44; coal plus two hazards 7.
  • All five exposure groups were similar for race, mean age, mean height, smoking state, pack-years smoked and mean duration of coal dust exposure.
  • No statistically significant differences in ventilatory (breathing) function were found between the exposure groups, either by analysis of variance or by linear regression.
  • The coal plus asbestos group (group 2) had a mean of 20.4 years of non-coal hazard exposure and 14.0 years of coal dust exposure. Its mean FEV1 was 2.39 litres (74.3% of predicted), its mean FVC 3.46 litres (83.4% of predicted), and its FEV1/FVC 68.3%. The coal-only group (group 1) had a mean FEV1 of 2.41 litres (71.5% of predicted), a mean FVC of 3.61 litres (84.3% of predicted), and an FEV1/FVC of 66.6%.
  • Neither adding the 158 excluded miners back into the analysis nor analysing non-smokers only produced any significant differences.
• The authors' conclusion: The authors concluded that among former coal miners presenting for a black lung disability determination, exposure to respiratory hazards after leaving the coal mines was not associated with a statistically significant deterioration in ventilatory function. They suggested that the lack of a difference in the asbestos group may mean asbestos exposure was not high enough to affect lung function, though they could not confirm this. Because of the study's limitations, they said further investigation is warranted.
• Limitations the authors state:
  • The sample was non-randomised and self-selected, and so prone to selection bias.
  • The authors could not determine the effect of selection factors such as survival, socioeconomic status, or the exclusion of workers not sick enough to seek a disability determination.
  • No control group was used; findings were based on comparisons between the five exposure groups.
  • Data on cumulative dust exposure were not available, so the authors could not confirm whether asbestos exposure was too low to affect lung function.

Topics

Medical terms in this study, explained in our Lexicon: FEV1, FEV1/FVC Ratio.

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