Respiratory symptoms and functional status in workers exposed to silica, asbestos, and coal mine dusts

Our plain-English summary of Respiratory symptoms and functional status in workers exposed to silica, asbestos, and coal mine dusts, by X.R. Wang, D.C. Christiani (Journal of Occupational and Environmental Medicine, 2000).

The study

• Authors: X.R. Wang, D.C. Christiani
• Journal: Journal of Occupational and Environmental Medicine
• Published: 2000;42(11):1076-84
• Cited by: 40 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

This study aims to provide further understanding of physiologic and symptomatic changes and radiographic abnormalities due to exposure to silica, asbestos, and coal dusts. Questionnaires and pulmonary function tests were given to 220 silica, 277 asbestos, and 511 coal workers from three different industries in China. Posteroanterior chest radiographs were classified as stages 0, I, II, and III according to degree of parenchymal fibrosis. Significantly poorer pulmonary function and a higher prevalence of dyspnea and chronic cough were observed in workers with pneumoconiosis than those without, irrespective of dust type. Workers with stages II and III silicosis had worse pulmonary function and more common symptoms relative to workers with equivalent coal workers' pneumoconiosis or asbestosis. After adjusting for relevant confounders, reductions in the spirometric parameters and single breath diffusing capacity for carbon monoxide (DLCO) and the occurrence of respiratory symptoms were associated with increasing stage of silicosis, whereas lower DLCO and the occurrence of symptoms were associated with increasing stage of asbestosis and coal workers' pneumoconiosis. The study suggests that despite the differences in degree and pattern due to exposure to different fibrogenic dusts, respiratory impairments of all of the workers are associated with the presence and progression of parenchymal fibrosis and smoking.

In plain English

This 1989 cross-sectional survey in China studied 220 male workers from a refractory brick plant using silica sand, 277 from an asbestos products plant that mainly used chrysotile, and 511 from an underground coal mine. Workers answered symptom questions, had breathing tests, and had chest X-rays graded from stage 0 to III. Of the asbestos workers, 85 had asbestosis, none at stage III. Asbestos workers with asbestosis had significantly lower vital capacity and DLco, a measure of lung gas transfer, than those without. For every dust type, chronic cough and shortness of breath (dyspnea) were more common in workers with pneumoconiosis. After adjustment, higher asbestosis stage was associated with lower DLco; each one-stage increase was associated with chronic cough (odds ratio 2.0, 95% confidence interval 1.67 to 3.36) and dyspnea (odds ratio 2.9, 95% CI 1.35 to 6.30). Odds ratios were greatest among silica workers. Smoking also contributed to symptoms. The authors concluded that fibrosis on X-ray and its progression were significantly responsible for lung impairment and symptoms. They noted 18% to 30% of invited workers did not take part.

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 respiratory health survey (questionnaire, lung function tests, chest X-rays) in three industries, done in 1989
• Who was studied: Male current and retired workers exposed to dust for at least 2 years, in a city in southwest China: 220 silica workers, 277 asbestos workers and 511 coal workers
• Exposure: Silica sand containing 70% to 80% quartz (refractory brick plant); predominantly chrysotile asbestos used to make asbestos textiles and shingles (asbestos product plant); coal mine dust (underground coal mine)
• Main results:
  • 85 of the asbestos workers had asbestosis (compared with 112 silica workers with silicosis and 223 coal workers with coal workers' pneumoconiosis)
  • No asbestos worker was classified as having stage III asbestosis
  • Compared with asbestos workers without asbestosis, workers with asbestosis had significantly lower vital capacity and DLco (p less than 0.05) but similar FEV1 and FEV1/FVC
  • In all three dust groups, chronic cough and dyspnea were significantly more common in workers with pneumoconiosis than in those without (p less than 0.01)
  • In asbestos workers, DLco decreased significantly as radiographic stage increased (p less than 0.01)
  • After adjustment for smoking and cumulative exposure, more severe asbestosis was significantly associated with lower DLco and higher FEV1/FVC
  • In asbestos workers, cumulative years of dust exposure were associated with reduced DLco
  • In asbestos workers, each one-stage increase in radiographic stage (stage entered as an ordinal variable 0 to 3) was associated with chronic cough (odds ratio 2.0, 95% CI 1.67 to 3.36) and dyspnea (odds ratio 2.9, 95% CI 1.35 to 6.30)
  • The odds ratios linking radiographic stage to symptoms were greatest in silica workers, followed by asbestos workers
  • At equivalent radiographic stages, lung function was generally lower in silica workers than in coal or asbestos workers, particularly at stages II and III
  • In each group, current or ex-smoking was a significant contributor to respiratory symptoms
• The authors' conclusion: The authors concluded that, although changes varied by dust type, the presence and progression of fibrosis seen on chest X-ray were significantly responsible for reduced lung function and respiratory symptoms
• Limitations the authors state:
  • 18% to 30% of invited workers did not participate
  • Retired non-participants were generally older and less fit than participants, which likely led to an underestimate of respiratory impairment
  • Some workers with pneumoconiosis who were required to attend did not participate, including 2 with asbestosis, mostly because they were too old or too ill
  • The sample size at stage III was too small to draw a valid conclusion about differences at that stage
  • Smokers and nonsmokers were not analyzed separately by stage because of limited numbers at stages II and III
  • The number of ex-smokers among asbestos workers was small

Topics

Medical terms in this study, explained in our Lexicon: Pulmonary Function Test (PFT), Chest X-Ray, Parenchymal Fibrosis, Dyspnea, Pneumoconiosis, Silicosis, Diffusing Capacity (DLCO), Fibrogenic.

Related studies

• Respiratory impairments due to dust exposure: a comparative study among workers exposed to silica, asbestos, and coalmine dust — X. Wang, E. Yano, et al. (1997)
• Diesel exhaust and coal mine dust: lung cancer risk in occupational settings — B. Hoffmann, K.H. Jöckel (2006)
• Investigative techniques in the laboratory study of coal workers' pneumoconiosis: recent advances at the cellular level — J.S. Harington (1972)
• Vapor, dust, and smoke exposure in relation to adult-onset asthma and chronic respiratory symptoms: the Singapore Chinese Health Study — T.D. LeVan, W.P. Koh, et al. (2006)
• Mortality from lung cancer and respiratory disease among pottery workers exposed to silica and talc — T.L. Thomas, P.A. Stewart (1987)
• Plasma lipid peroxides among workers exposed to silica or asbestos dusts — A.A. Kamal, A. Gomaa, et al. (1989)

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