Lung function studies of asbestos workers

Our plain-English summary of Lung function studies of asbestos workers, by M.L. Wang, P.L. Lu (Scandinavian Journal of Work, Environment & Health, 1985).

The study

• Authors: M.L. Wang, P.L. Lu
• Journal: Scandinavian Journal of Work, Environment & Health
• Published: 1985;11 Suppl 4:34-42
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 001260).

Abstract

Pulmonary function tests have been conducted on 155 asbestos workers and 130 referents. It was found that the lung function impairment in asbestos workers is predominantly a restrictive ventilatory defect appearing even when radiographic changes are not detectable. There was, however, no evidence of airway obstruction. As the disease progressed, all the pulmonary function indices, including vital capacity (VC), forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1.0), maximal ventilation volume (MVV), total lung capacity (TLC), and pulmonary diffusing capacity (DLCO), were reduced dramatically, with the exception of FEV1.0/FVC(%). It is suggested that both radiographic examination and pulmonary function tests should be used as early detection measures of asbestos-induced lung disorders. VC, FVC, and FEV1.0 are the simplest, most reproducible, and most valid indices for the health surveillance of asbestos workers, while the FVC test is the most valuable for epidemiologic study. With stepwise regression analysis a quantitative relationship between dust exposure and pulmonary function was demonstrated. There was no significant difference in the small airway function of the exposed workers and the referents. Further study is needed to investigate the possibility of asbestos-induced small airway obstruction and to estimate the roles played by cigarette smoking and air pollution.

In plain English

This was a lung function survey at an asbestos-products factory in Shanghai, China. The authors tested 155 randomly sampled asbestos workers. By chest X-ray, 50 were certified as having asbestosis, 51 had suspected asbestosis and 54 had no definite signs. They were compared with 130 workers from a Shanghai machine manufacturing plant. The article does not name the asbestos fiber type. Compared with these referents, the asbestos workers had lower VC, MVV, FVC, FEV1.0 and TLC, with greater declines in more advanced X-ray categories. FEV1.0/FVC showed no significant difference. Even workers without definite X-ray signs had statistically significant declines in FVC, VC, TLC and MVV. In a subgroup of 49 workers, diffusing capacity was also lower. In regression analysis adjusted for age, sex, height and weight, dust exposure was the main factor influencing lung function. The authors concluded that the impairment is mainly a restrictive defect, that it can appear in workers without radiographic changes, and that X-rays and lung function tests should be used together. They noted that smoking and air pollution were not fully considered.

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 lung function survey comparing asbestos workers (grouped by chest X-ray category) with a reference group, plus regression analysis of dust exposure and lung function
• Who was studied: 155 asbestos workers, a category-stratified random sample from 750 workers with over 13 years' tenure, aged 30 to 65, at a Shanghai asbestos-products factory: 50 with asbestosis categories I and II (25 men, 25 women), 54 with exposure but no definite radiographic signs (A0), and 51 with suspected asbestosis (A0-1). The comparison group was 130 workers (72 men and 58 women) from a machine manufacturing plant in Shanghai. Diffusing capacity and closing volume tests were done on a subsample of 49 asbestos workers and 35 referents.
• Exposure: Asbestos dust in an asbestos-products factory. The fiber type is not named. Cumulative dust exposure was calculated as average yearly workplace dust concentration (mg/m3) times working tenure, in mg-years. The authors cite past average levels of 12 mg/m3 in the spinning area, 26.3 mg/m3 in the opening area, and 52.6 mg/m3 before 1958 in a small textile plant.
• Main results:
  • Compared with the referents, the asbestos workers had decreased VC, MVV, FVC, FEV1.0 and TLC. The decline increased across radiographic categories from A0 to A0-1 to A I, II.
  • FEV1.0/FVC % showed no significant difference between the asbestos workers and the referents.
  • Even in the A0 group (no definite radiographic signs), the decline in FVC, VC, TLC and MVV was statistically significant compared with the referents.
  • In the subsample of 49 asbestos workers compared with 35 referents, DLco, Kco and CV/VC % were reported as declined (p less than 0.001, 0.01 and 0.01, respectively). Differences were statistically significant for all these indices except V50 and V25.
  • Pleural and parenchymal changes on X-ray had independent effects on the decline of VC, FVC and TLC.
  • The conformity rate between the Chinese radiographic categories and the ILO classification grades was 65%.
  • In stepwise regression on all 285 subjects, after adjustment for age, sex, height and weight, the main factor influencing lung function was dust exposure. FEV1.0/FVC % was related only to age and cigarette smoking.
  • Using the regression equation for 170-cm male workers, the projected annual FVC decline was 30 ml with no exposure. At 2, 12, 26.3 and 52.6 mg/m3 it was 52, 59, 68 and 84 ml.
  • For the same model, continuous exposure at 2, 12, 26.3 and 52.6 mg/m3 was projected to allow 35, 27, 20 and 14 years of work before FVC fell below 80% of the value predicted for unexposed workers.
  • For FEV1.0 in 170-cm males, the projected annual declines were 33 ml with no smoking and no exposure, 41 ml with smoking only, 54 ml with exposure only, and 62 ml with both. For FEV1.0, only duration of exposure, not cumulative exposure, was significant in the regression.
• The authors' conclusion: The authors concluded that lung function impairment appears even without radiographic changes. They found its severity parallels the category of asbestosis, and its basic character is a restrictive ventilatory defect with little evidence of airway obstruction. They judged FVC best suited for epidemiologic surveys, and recommended using chest radiography and lung function tests together in diagnosis and health surveillance of asbestos workers.
• Limitations the authors state:
  • Smoking and air pollution were not fully considered, so the authors said it was too early to give a conclusive view on small airway impairment as an early index of asbestosis.
  • The projection equations would be less likely to give good estimates for older or undersized workers.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Pulmonary Function Test (PFT), FEV1, Total Lung Capacity (TLC), Diffusing Capacity (DLCO).

Related studies

• The acute effects of chrysotile asbestos exposure on lung function — K.W. Harless, S. Watanabe, et al. (1978)
• Lung function in relation to radiographic changes in asbestos workers — S. Zedda, G. Aresini, et al. (1973)
• Pulmonary function of nonsmoking female asbestos workers without radiographic signs of asbestosis — X.R. Wang, E. Yano, et al. (1998)
• An 11-year longitudinal study of the occupational dust exposure and lung function of polyvinyl chloride, cement and asbestos cement factory workers — A. Siracusa, A. Forcina, et al. (1988)
• Radiographic changes and lung function in relation to activity of the glutathione transferases theta and mu among asbestos cement workers — K. Jakobsson, A. Rannug, et al. (1995)
• Regional lung function in asbestos workers: observations and speculations — R.H. Secker-Walker, J.E. Ho (1982)

Browse more research in Scandinavian Journal of Work, Environment & Health, or return to medical research.