Pulmonary function in long-term asbestos workers in China

Our plain-English summary of Pulmonary function in long-term asbestos workers in China, by X.R. Wang, E. Yano, M. Wang, et al (Journal of Occupational and Environmental Medicine, 2001).

The study

• Authors: X.R. Wang, E. Yano, M. Wang, Z. Wang, D.C. Christiani
• Journal: Journal of Occupational and Environmental Medicine
• Published: 2001;43(7):623-9
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The relationship of pulmonary function to exposure to asbestos and radiographic abnormalities has been controversial, especially when smoking is present as a confounder. The aim of the study was to provide further understanding on the radiographic-physiologic associations in nonsmoking and smoking asbestos workers. Radiographic asbestosis, pleural lesion, and pulmonary function were studied in 269 Chinese asbestos workers, with average exposure years of 23 for male workers and 18 for female workers. Their functional data were compared with those of 274 controls without exposure to dust. Although most of the male workers were smokers, none of the female workers smoked. In comparison with controls, asbestos workers had significantly lower lung volume and diffusing capacity, irrespective of gender. Female workers and smoking male workers had lower measurements of forced expiratory volume in 1 second and instantaneous forced expiratory flow at 50% and 25% of forced vital capacity. After adjustment for relevant covariates, asbestos exposure, asbestosis, and pleural abnormalities were associated with decreased parameters of pulmonary function, including lung volume, diffusing capacity, and airway flow. These data indicate that asbestos-related functional defects manifested by lung restriction and mild airway obstruction correlate with exposure to asbestos and with parenchymal and pleural abnormalities, independent of smoking.

In plain English

This study, done in 1994, compared lung function in 142 men and 127 women from an asbestos-product factory in Chongqing, China, where chrysotile was used to make textiles and shingles, with 274 workers from a nearby factory who had no exposure to industrial dust. Exposed men averaged 23 years of exposure and women 18. Most men smoked; no women did. X-rays showed asbestosis in 50 exposed men and 21 exposed women. After adjusting for age, height, weight and (in men) smoking, exposed workers of both sexes had significantly lower total lung capacity, diffusing capacity and some airflow measures than controls. Among men, lower FEV1 and airflow results were significant in smokers but not in the 18 exposed nonsmokers. In regression analyses, exposure, asbestosis and, in men, pleural abnormalities were associated with poorer lung function. The authors concluded the defect was mainly restrictive with milder airway obstruction, independent of smoking. They also called smoking a major contributor to airway obstruction. They noted the workers were heavily exposed, exposure was measured only as duration, and the way workers were selected may have left out healthier ones.

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: Comparison of lung function in asbestos-exposed factory workers versus unexposed control workers, with chest X-ray assessment and regression analysis; examinations in 1994
• Who was studied: 142 male and 127 female asbestos workers (active and retired, at least 3 years of direct exposure) from an asbestos-product factory in Chongqing, China, mostly those living near the factory plus nearly all workers diagnosed with asbestosis. Controls were 176 male and 98 female workers with no industrial dust exposure from another factory in the same area. Examined in 1994.
• Exposure: Chrysotile asbestos used to produce asbestos textiles and asbestos shingles since the 1950s. Total dust always exceeded 3 mg/m3 and asbestos levels exceeded 1.5 fibers/cm3, with no effective personal protection. Average exposure duration was 22.8 years for men and 18.1 years for women.
• Main results:
  • Asbestosis (category I or higher) was diagnosed in 50 of 142 exposed men (35.2%) and 21 of 127 exposed women (16.5%), and in none of the controls.
  • Nearly all lung function values were lower in exposed workers than in unexposed workers, in both men and women. The differences were statistically significant for total lung capacity, RV/TLC, forced vital capacity, FEV1, diffusing capacity, alveolar volume, and airflow at 50% and 25% of FVC.
  • Average total lung capacity was 5.36 L in unexposed men versus 4.78 L in exposed men, and 4.07 L in unexposed women versus 3.76 L in exposed women (p less than 0.01 in both sexes).
  • Among men compared by smoking status, exposed ever-smokers (124) had significantly lower FEV1 and airflow at 50% and 25% of FVC than unexposed smokers. Exposed nonsmokers (18) did not differ significantly from unexposed nonsmokers on these measures.
  • Among exposed workers, only total lung capacity was significantly lower in those with asbestosis than in those without, for both sexes.
  • In regression analyses, asbestos exposure was associated with reduced airflow at 50% and 25% of FVC in both sexes, as well as with lower lung volume and diffusing capacity.
  • Exposure duration was associated with reduced FVC, FEV1, PEF and airflow at 75% of FVC in men (P less than 0.01). No such association was seen in women.
  • In men, asbestosis was significantly associated with decreased total lung capacity and diffusing capacity.
  • In men, pleural abnormalities were associated with reduced TLC, RV/TLC, FVC, FEV1 and airflow at 75% of FVC. Of the 35 men with pleural abnormalities, 32 (91%) also had asbestosis.
  • In women, asbestosis was significantly associated with decreased TLC, RV/TLC, FEV1/FVC, PEF, airflow at 75% of FVC, and diffusing capacity. Pleural abnormality could not be entered into the women's regression models.
  • The FEV1/FVC ratio did not decrease in exposed workers. In exposed men it was slightly higher than in unexposed men, a difference that was not statistically significant.
• The authors' conclusion: The authors concluded that in these heavily exposed workers the lung function defect was predominantly restrictive, accompanied by milder airway obstruction. They found this defect correlated with asbestos exposure and with parenchymal and pleural abnormalities, independent of smoking. They also stated that smoking was a major contributor to airway obstruction in asbestos workers.
• Limitations the authors state:
  • The workers were heavily and chronically exposed, so the results may not apply to other groups and reflect only impairment linked to heavy, long-term exposure.
  • There was no detailed individual exposure information. Exposure duration was used as a stand-in for exposure level and did not reflect actual exposure levels.
  • Subject selection: workers without asbestosis were chosen by residence near the factory. Those not included were likely younger, with shorter exposure, and healthier.
  • The readers who assessed pleural abnormalities could not be blinded to signs of asbestosis on the same X-rays. This may partly explain the high rate of pleural abnormality found in workers with asbestosis.
  • Some workers, especially those with respiratory symptoms, may not have breathed out fully during testing, so FVC in asbestos workers might be underestimated.

Topics

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

Medical terms in this study, explained in our Lexicon: Diffusing Capacity (DLCO), Asbestos Exposure.

Related studies

• Pulmonary function of nonsmoking female asbestos workers without radiographic signs of asbestosis — X.R. Wang, E. Yano, et al. (1998)
• Decreased lung function in long-term asbestos cement workers: a cross-sectional study — C.G. Ohlson, T. Rydman, et al. (1984)
• Pulmonary function in asbestosis: serial tests in a long-term prospective study — M.E. Bader, R.A. Bader, et al. (1965)
• Longitudinal changes in pulmonary function of asbestos workers — X. Wang, M. Wang, et al. (2010)
• Oxidative effects of lungs in Wistar rats caused by long-term exposure to four kinds of China representative chrysotile — Y. Cui, Y. Zha, et al. (2019)
• Long-term instillation to four natural representative chrysotile of China induce the inactivation of P53 and P16 and the activation of C-JUN and C-FOS in the lung tissues of Wistar rats — Y. Luo, J. Deng, et al. (2020)

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