Respiratory impairments due to dust exposure: a comparative study among workers exposed to silica, asbestos, and coalmine dust

Our plain-English summary of Respiratory impairments due to dust exposure: a comparative study among workers exposed to silica, asbestos, and coalmine dust, by X. Wang, E. Yano, K. Nonaka, et al (American Journal of Industrial Medicine, 1997).

The study

• Authors: X. Wang, E. Yano, K. Nonaka, M. Wang, Z. Wang
• Journal: American Journal of Industrial Medicine
• Published: 1997;31(5):495-502
• Cited by: 35 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

We conducted a comparative study of pulmonary dysfunction among workers who were exposed to silica, asbestos, or coalmine dust. The results showed that all three groups of dust-exposed workers, even those without radiographic signs of pneumoconiosis, had decreased spirometric parameters and diffusing capacity (DLco) in both nonsmokers and smokers. Pulmonary function was further decreased when pneumoconioses were present in the three groups. In accord with increasing radiographic categories, pulmonary function in the workers with either silicosis or asbestosis was even lower, whereas in those with coal workers' pneumoconiosis (CWP), it changed relatively little. Workers with mild to moderate (radiographic category I-II) silicosis or asbestosis showed similarly decreased DLco, but those with silicosis showed lower FEV1/FVC than those with abestosis. The workers with CWP also showed a lower FEV1/FVC than those with asbestosis. The major impairment patterns for silica workers, asbestos workers, and coal miners were mixed, restrictive and mixed, and obstructive, respectively. Smoking obviously increased the prevalence of obstruction for all the groups. We conclude from the present study that all the three dusts cause functional abnormalities that precede radiographic changes of pneumoconiosis. We should pay more attention to respiratory impairment in the initial stage of silicosis and CWP.

In plain English

This study reanalyzed data from a 1989 cross-sectional survey of 1,131 men in Chongqing, China. The groups were 219 silica workers, 248 asbestos workers from a factory that mainly used chrysotile to make asbestos textile, shingle and asbestos cement, 497 coal miners, and 167 unexposed control workers. Exposed workers had at least 3 years of direct dust exposure. Of the asbestos workers, 85 of 248 (34%) had asbestosis on X-ray, all in categories I to II. Asbestos workers without X-ray signs of disease had significantly lower diffusing capacity (DLco) and most breathing-test measures than controls. DLco was also significantly lower in silica workers and coal miners without X-ray signs. Among asbestos workers, DLco tended to fall as asbestosis appeared and progressed. In nonsmoking asbestos workers, restrictive impairment was the most common pattern. Smoking increased obstruction in all groups. Controls were younger than exposed workers. The authors concluded that all three dusts cause lung function abnormalities that come before X-ray changes. They noted that dust levels had not been regularly measured, so their influence could not be analyzed.

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: Reanalysis of data from a cross-sectional survey conducted in 1989, comparing lung function among workers exposed to different dusts and unexposed controls
• Who was studied: 1,131 men in Chongqing, China, surveyed in 1989: 219 silica workers (refractory brick workshop of an iron-steel plant), 248 asbestos workers (asbestos products factory), 497 underground coal miners, and 167 control workers from an electronic instrument and meter assembly plant with no dust exposure. Current and retired workers were included.
• Exposure: Silica, asbestos (chrysotile mainly used, to make asbestos textile, shingle and asbestos cement), or coalmine dust. Each worker had at least 3 years of direct exposure, and the mean exposure for asbestos workers was 18.6 years. Dust was not regularly measured, but total dust concentrations nearly always exceeded 2 mg/m3.
• Main results:
  • 85 of the 248 asbestos workers (34%) had asbestosis, all in radiographic categories I to II. None had category III.
  • Among asbestos workers without radiographic signs of pneumoconiosis, all spirometric measures were significantly decreased compared with controls in both nonsmokers and smokers. The exception was FVC in nonsmokers.
  • In workers without radiographic signs of pneumoconiosis, exposure to each of the three dusts (silica, asbestos, coalmine dust) was associated with a statistically significant decrease in DLco compared with controls, in both nonsmokers and smokers.
  • DLco tended to decrease with the appearance and progression of radiographic signs of silicosis and asbestosis, regardless of smoking history.
  • Workers with category I to II silicosis or asbestosis had similarly decreased DLco. Those with silicosis had lower FEV1/FVC than those with asbestosis.
  • Among nonsmokers, the most common impairment pattern was obstructive for coal miners, restrictive for asbestos workers, and mixed for silica workers.
  • Smoking increased the prevalence of obstruction in all groups. Among asbestos workers, total impairment was similar in smokers and nonsmokers, but obstruction predominated in smokers.
  • Control workers were younger and taller than the dust-exposed workers. Mean age was 38.3 years for controls and 55.6 years for asbestos workers.
• The authors' conclusion: The authors concluded that silica, asbestos and coalmine dusts all cause lung function abnormalities that precede radiographic changes of pneumoconiosis. They called for more attention to respiratory impairment in the early stage of silicosis and coal workers' pneumoconiosis.
• Limitations the authors state:
  • Dust concentrations had not been regularly measured, so the influence of dust concentration could not be analyzed.
  • Impairment prevalence was not statistically compared between workers with and without radiographic pneumoconiosis because subgroups were small.
  • The authors said their results could not settle whether asbestos-related impairment is mainly restrictive.
  • The rise in FEV1/FVC with asbestosis seen in nonsmoking asbestos workers, but not in smokers, needs further study to confirm.

Topics

Medical terms in this study, explained in our Lexicon: Pneumoconiosis, Diffusing Capacity (DLCO), Silicosis, FEV1/FVC Ratio.

Related studies

• Respiratory symptoms and functional status in workers exposed to silica, asbestos, and coal mine dusts — X.R. Wang, D.C. Christiani (2000)
• Surveillance of respiratory diseases among construction and trade workers at Department of Energy nuclear sites — J.M. Dement, L. Welch, et al. (2003)
• Relationship between chest X-ray findings and pulmonary function tests in dust workers — Y. Tonori, M. Niitsuya, et al. (2005)
• Plasma lipid peroxides among workers exposed to silica or asbestos dusts — A.A. Kamal, A. Gomaa, et al. (1989)
• Mortality from lung cancer and respiratory disease among pottery workers exposed to silica and talc — T.L. Thomas, P.A. Stewart (1987)
• Electron microscopic findings in the lungs of miners — G. Harrison, N.L. Lapp (1972)

Browse more research in American Journal of Industrial Medicine, or return to medical research.