Decreased lung function in long-term asbestos cement workers: a cross-sectional study

Our plain-English summary of Decreased lung function in long-term asbestos cement workers: a cross-sectional study, by C.G. Ohlson, T. Rydman, L. Sundell, et al (American Journal of Industrial Medicine, 1984).

The study

• Authors: C.G. Ohlson, T. Rydman, L. Sundell, L. Bodin, C. Hogstedt
• Journal: American Journal of Industrial Medicine
• Published: 1984;5(5):359-66
• Cited by: 22 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000563).

Abstract

The effect on lung function of exposure in an asbestos cement plant was investigated in male workers, employed more than 10 years. The exposed group was selected to exclude subjects with pneumoconioses and ex-smokers and consisted of 77 smokers and 48 never-smokers. Referents were chosen from plants where asbestos had not been in use and restricted to those without X-ray signs of chest disease. The primary type of asbestos used was chrysotile and the general dust level in the two decades 1950-1970 seems to have been around 10 mg/m3 while the asbestos fiber concentration averaged 2 fibers/ml. The mean differences between exposed and referents were statistically significant for forced vital capacity and forced expiratory volume, -0.25 and -0.30 liters, respectively, after adjustment for age, height, tracheal area, and smoking category. No significant differences were detected between those with and without pleural plaques. Smokers and never-smokers were similarly affected. In conclusion, the group exposed to dust with comparatively low asbestos fiber concentration had a minor impairment of lung function, mainly due to obstructive changes.

In plain English

In this cross-sectional study from Sweden, the authors tested the lung function of 125 men (77 smokers, 48 never-smokers) actively employed at least 10 years at an asbestos cement plant that closed in 1976. They compared them with 76 men from three plants that did not use asbestos. Men with X-ray signs of silicosis or asbestosis, and ex-smokers, were excluded. The asbestos was mostly chrysotile, with a few hundred tons of crocidolite and amosite used in the 1960s. Fiber levels averaged 1 fiber/ml in 1970-1976 and were estimated at 2 fibers/ml earlier. After adjustment for age, height, tracheal area and smoking, the exposed men's forced vital capacity (FVC) was 0.25 liters lower and their forced expiratory volume in one second (FEV1) 0.30 liters lower than the referents'. These differences were statistically significant. The 42 men with pleural plaques did not differ significantly from those without. Smokers and never-smokers were similarly affected, and no statistically significant dose-effect relation was found. The authors judged the decrease statistically but probably not clinically significant.

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 study comparing spirometry results of asbestos cement workers with unexposed referents
• Who was studied: 125 male, actively employed workers (77 smokers, 48 never-smokers) with at least 10 years' employment at an asbestos cement plant in the middle part of Sweden, examined when production closed down in 1976. Ex-smokers, pensioners and 4 men with X-ray signs of silicosis or asbestosis were excluded. Referents were 76 men (40 smokers, 36 never-smokers) without radiographic signs of chest disease, from three plants not using asbestos (fertilizers, cement products, wood products).
• Exposure: Asbestos cement production dust. The asbestos was mostly chrysotile, with a few hundred tons of crocidolite and amosite used during the 1960s. The general dust level was about 10 mg/m3 in the 1950s and 1960s and half that in the 1970s. Fiber concentrations averaged 1 fiber/ml in 1970-1976 and were estimated at 2 fibers/ml in earlier decades. Small amounts of silica were also handled.
• Main results:
  • After adjustment for age, height, tracheal area and smoking, the mean differences between exposed workers and referents were -0.25 liters for FVC and -0.30 liters for FEV1.
  • The exposed workers' adjusted lung volumes were 95.4% (FVC) and 91.6% (FEV1) of values predicted from the referents. The differences were significant at the 1% level.
  • 42 exposed men had pleural plaques. Their lung function did not differ significantly from that of exposed workers without plaques.
  • Lung volumes were slightly lower at higher accumulated exposure, but the differences were not statistically significant. For 0-14, 15-22 and 23 or more fiber-years (41, 42 and 41 men), FVC was 96.1%, 95.4% and 94.6% of predicted, and FEV1 was 92.8%, 91.8% and 90.5% of predicted.
  • Both smokers and never-smokers were affected, with no interaction found between dust exposure and smoking.
  • Tracheal area added significantly to the prediction of FVC and FEV1 even after correction for height.
• The authors' conclusion: The authors concluded that the exposed group had a statistically, but probably not clinically, significant decrease in FEV1 and FVC. They described it as a minor impairment of lung function, mainly due to obstructive changes.
• Limitations the authors state:
  • About half of the referents were exposed to cement dust or irritating gases such as ammonia, which might have caused a slight underestimation of the decrease among the exposed workers.
  • Workers who may have developed asbestos-related disease and left their jobs were not in the study population, so the decrease may be a minimum estimate.
  • Effects of pure fibers, cement dust and cement-coated asbestos fibers could not be separated.
  • Silica exposure could not be evaluated separately.
  • Simple spirometry cannot detect small airways disorders.
  • Exposure estimates for the 1940s and 1950s were very rough. The 10-year minimum employment may have left too little variation for dose-effect calculations.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Cement, Chrysotile, Pleural Plaques.

Related studies

• Lung function among asbestos cement factory workers: cross-sectional and longitudinal study — A. Siracusa, C. Cicioni, et al. (1984)
• Asbestos-related disease in railroad workers. A cross-sectional study — L.C. Oliver, E.A. Eisen, et al. (1985)
• Lung function and respiratory symptoms in subjects with asbestos-related disorders: a cross-sectional study — B. Hilt, J.T. Lien, et al. (1987)
• Are the knowledge of non-malignant asbestos-related diseases and lung function impairment differentially associated with psychological well-being? A cross-sectional study in formerly asbestos-exposed workers in Germany — J. Lang, M.K. Felten, et al. (2019)
• Ventilatory decrements in former asbestos cement workers: a four year follow up — C.G. Ohlson, L. Bodin, et al. (1985)
• Modelling prevalence and incidence of fibrosis and pleural plaques in asbestos-exposed populations for screening and follow-up: a cross-sectional study — C. Paris, A. Martin, et al. (2008)

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