Patterns of pulmonary dysfunction in asbestos workers: a cross-sectional study

Our plain-English summary of Patterns of pulmonary dysfunction in asbestos workers: a cross-sectional study, by B.A. Abejie, X. Wang, S.N. Kales, et al (Journal of Occupational Medicine and Toxicology, 2010).

The study

• Authors: B.A. Abejie, X. Wang, S.N. Kales, D.C. Christiani
• Journal: Journal of Occupational Medicine and Toxicology
• Published: 2010;5:12
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Restrictive patterns of pulmonary function abnormalities associated with asbestos exposure are well described. Studies are less consistent, however, regarding the association of asbestos inhalation with airway dysfunction and obstructive impairment.

Methods: We compared pulmonary function test results between 277 chrysotile exposed workers (22% non-smokers) and 177 unexposed controls (50.3% non-smokers). Information on exposure and smoking were collected using a standardized questionnaire. Standardized spirometric and DCLO Measurement methods were utilized. CXRs were read based on ILO pneumoconiosis guidelines.

Results: Asbestos exposed subjects had significantly reduced FVC, FEV1, FEV1/FVC and DLCO. Restricting the analysis to non-smokers, asbestos workers still had about 3% lower FEV1/FVC ratio than controls, but this difference did not reach statistical significance. Among exposed workers, the presence of radiographic evidence of asbestosis further lowered FVC and DLCO but not FEV1/FVC compared to asbestos exposure without radiographic asbestosis. Additionally, smoking asbestos workers had significantly lower DLCO compared to non-smoking workers.

Conclusion: Asbestos exposure, especially when radiographic evidence of interstitial fibrosis from asbestosis is present, leads to significant decreases in FVC, FEV1 and the DLCO. However, asbestos exposure alone is not significantly associated with a reduction of the FEV1/FVC. Smoking-asbestos workers had significantly lower DLCO than their non-smoking counterparts. Whether asbestos interacts with smoking additively or synergistically on DLCO needs further investigation. Similarly, further studies are needed to assess the progression and clinical significance of asbestos induced airway dysfunction.

In plain English

This cross-sectional study compared lung function in 277 chrysotile-exposed men from an asbestos textile factory in Southwest China, surveyed in 1989, with 177 unexposed male electronics workers from the same area. The asbestos workers were older and smoked more. More than 80% of controls had normal lung function, compared with about half of the asbestos workers. The authors then excluded workers with asbestosis on X-ray and accounted for age and smoking. In that analysis, exposure was significantly associated with lower breathing volumes (FVC, FEV1) and gas transfer (DLCO), but not with the FEV1/FVC ratio, a measure of airflow obstruction. Among non-smokers, the asbestos workers' ratio was close to 3% lower, but not significantly. Among exposed workers without emphysema on X-ray, those with asbestosis had significantly lower FVC and DLCO, but no significant difference in the ratio. Among exposed workers with neither asbestosis nor emphysema on X-ray, more pack-years of smoking went with significantly lower DLCO. The authors called for further study of whether asbestos and smoking act additively or synergistically. They noted that the testing technicians knew who was exposed and that there were no area or personal asbestos measurements.

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 lung function tests (spirometry and DLCO) and chest X-rays in asbestos-exposed workers and unexposed controls, analyzed with multiple regression
• Who was studied: 277 male workers (current workers and retired workers living nearby) from an asbestos textile factory in Southwest China, surveyed in 1989, with at least 2 years of direct asbestos exposure. Controls were 177 male electronics industry workers from the same area with no asbestos or other dust exposure. Mean age was 55.1 years in the exposed group and 37.2 years in controls. Ever smokers were 78.0% of the exposed group and 49.7% of controls.
• Exposure: Chrysotile in a factory making asbestos textile products. Area sample concentrations in most cases still exceeded 2 mg/m3, the Chinese maximum allowable concentration at that time, and workers used no personal protective equipment. Mean exposure duration was 16.7 years. Cumulative duration of work in exposed areas was used as a stand-in for total exposure.
• Main results:
  • More than 80% of controls had normal lung function, compared with only half of the asbestos workers.
  • Unadjusted mean DLCO (percent predicted) was 97.1 in exposed workers and 124.6 in controls (p .0001). Mean FEV1/FVC was 71.3 in exposed workers and 78.3 in controls (p .0001).
  • In controls plus exposed workers without radiographic asbestosis (N = 369), adjusted for age and pack-years, exposure was significantly associated with lower FEV1 (coefficient -6.69), FVC (-5.72) and DLCO (-19.30). It was not significantly associated with the FEV1/FVC ratio (0.25).
  • Among non-smokers only (N = 130), exposure was significantly associated with lower FEV1 (-11.67), FVC (-6.58) and DLCO (-31.87) percent predicted. Non-smoking asbestos workers had close to 3% lower FEV1/FVC (-2.79), which was not statistically significant.
  • Among exposed workers without radiographic emphysema (N = 175), those with radiographic asbestosis had significantly lower FVC (-5.66) and DLCO (-9.76). FEV1 (-1.85) and FEV1/FVC (0.75) did not differ significantly.
  • Among exposed workers without radiographic asbestosis or emphysema (N = 132), pack-years of smoking were significantly associated with lower DLCO, FEV1 and FEV1/FVC, but not significantly with FVC.
• The authors' conclusion: The authors concluded that asbestos exposure, with or without radiographic asbestosis, was significantly associated with reduced DLCO and restrictive lung impairment, but not significantly with reduced FEV1/FVC. They called for further study of whether asbestos and smoking act additively or synergistically, and of the progression and clinical significance of asbestos-induced airway impairment.
• Limitations the authors state:
  • The asbestos workers were significantly older than the controls; age was adjusted for in the prediction equations and the regression models.
  • The lung function technicians were not blinded to exposure status.
  • Controls had no chest films, and there was no pleural radiographic information on the asbestos workers.
  • There were no area or personal asbestos measurements for exposure assessment.
  • Different smoking habits between the groups may explain some of the difference in obstructive impairment.
  • The authors believe the FEV1/FVC difference in non-smokers did not reach significance because of limited sample size.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Pulmonary Function Test (PFT), Chrysotile, Pneumoconiosis, FEV1, FEV1/FVC Ratio, Diffusing Capacity (DLCO), Statistical Significance.

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