The prevalence of pleural plaques and/or pulmonary changes among construction workers in Okayama, Japan

Our plain-English summary of The prevalence of pleural plaques and/or pulmonary changes among construction workers in Okayama, Japan, by T. Kishimoto, K. Morinaga, S. Kira (American Journal of Industrial Medicine, 2000).

The study

• Authors: T. Kishimoto, K. Morinaga, S. Kira
• Journal: American Journal of Industrial Medicine
• Published: 2000;37(3):291-5
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Since asbestos has been widely used in Japanese building materials since 1960s, a large number of Japanese construction workers may be exposed to asbestos occupationally.

Methods: Among 2951 construction workers in Okayama, Japan, the prevalence of asbestos-induced pleural or pulmonary changes was examined by screening chest x-rays; these findings were confirmed by computed tomography (CT) scanning of the chest.

Results: Among 2951 construction workers, 168 (5.7%) were found to have significant findings for pleural plaque or pulmonary changes on chest x-ray. Seventy-four had both pleural plaque and asbestosis, 85 pleural plaques alone, and 9 asbestosis alone. In 11 subjects, pleural plaques were suggested by chest x-ray, but neither pleural plaque nor asbestosis was demonstrated by chest CT. Honeycombing as one of the characteristic findings of asbestosis was found in 29 subjects. Others showed subpleural spots or curvilinear shadow, which suggested the early stage of asbestosis. The occupations of these workers were carpenters (64), plasterers (27), and concrete board cutters (14). About 30% of the workers with these findings were aware that they were handling asbestos in activities such as installation of asbestos boards, and/or asbestos spraying.

Conclusions: As the incidence of malignant mesothelioma and primary lung cancer associated with asbestos exposure are high, screening by chest CT is necessary for detecting asbestos-induced pulmonary and/or pleural lesions. Education for protection such as telling about the presence of asbestos in building materials is also necessary.

Copyright 2000 Wiley-Liss, Inc.

In plain English

First, the authors cut building boards and corrugated slates for 5 minutes and measured airborne asbestos. The fiber type was not named. Counts averaged 0.153 fibers per cubic centimetre for boards and 0.103 for slates. The authors reported this as within the Japanese legal standard but far above a WHO standard. Second, specialists read chest x-rays of 2,951 male union construction workers in Okayama, Japan, and workers with findings had chest CT. CT showed pleural plaques and/or asbestosis in 168 workers (5.7%): 74 had both, 85 had plaques alone and 9 had asbestosis alone. Honeycombing was seen in 29. Findings were present in 17.4% of workers aged 61 or older versus 6.1% of those aged 51 to 60. Of the 168, 150 were classed as heavy smokers. The authors concluded that chest CT screening and education about asbestos in building materials are necessary. They noted that lung scarring from other causes, including smoking, could not be fully excluded, and that only workers with x-ray findings had CT.

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 screening study (chest x-ray, with chest CT for those with findings), plus a cutting experiment measuring airborne asbestos fibers
• Who was studied: 2,951 construction workers, all male, aged 32 to 73 (mean 53), members of a Construction Workers' Union in Okayama Prefecture, Japan; year of screening not stated
• Exposure: Work with building materials, mainly building boards and corrugated slates. Jobs included carpenters (1,717 of the workers), plasterers (547), concrete shaving, installation of asbestos boards and asbestos spraying. The fiber type was not specified.
• Main results:
  • Cutting experiment: asbestos fiber counts averaged 0.153 fibers/cm3 for building boards and 0.103 fibers/cm3 for corrugated slates (Table I site means 0.111 to 0.190 for boards and 0.074 to 0.124 for slates). Dust concentration was 12.4 mg/m3.
  • The authors reported the fiber level as within the Japanese Labor Safety and Sanitation Law standard but far exceeding the WHO's standard (printed as 500 fibers/m3)
  • Chest x-ray showed pleural plaques or fibrous lung changes in 179 of the 2,951 workers (6.1%)
  • Chest CT showed pleural plaques in 159 workers (5.4%) and pulmonary asbestosis in 83 (2.8%)
  • Of the workers with CT findings, 74 had both pleural plaques and pulmonary asbestosis, 85 had pleural plaques alone and 9 had pulmonary asbestosis alone (168 workers, 5.7%)
  • In 11 workers, the x-ray suggested pleural plaques but CT showed neither pleural plaques nor pulmonary asbestosis
  • Honeycombing was seen on CT in 29 workers. Nine of them showed only PR0/1 on x-ray.
  • The percentage of workers with findings was 17.4% among those aged 61 or older (75 of 440), 2.9 times the 6.1% among those aged 51 to 60 (64 of 1,044). It was 0.7% in the youngest group, aged 40 or younger.
  • Among the 168 workers with findings, 131 (78%) had worked in their occupation for 31 years or more
  • Among the 168 workers with findings, 64 were carpenters, 27 were plasterers and 14 were concrete board cutters
  • Of the 168 workers with findings, 150 (89%) had a smoking index the authors classed as heavy smoking
• The authors' conclusion: The authors concluded that, because asbestos-related mesothelioma and lung cancer rates are high, chest CT screening is necessary to detect asbestos-induced lung and pleural lesions, and that education documenting asbestos in building materials is also necessary
• Limitations the authors state:
  • No bronchoalveolar lavage or lung biopsy was done, so lung fibrosis from other causes, including smoking, could not be completely excluded
  • CT was not performed in workers without plaques at x-ray screening, so the true prevalence of pleural plaques could not be measured accurately
  • CT findings are not always correct; plaques not seen on HRCT are sometimes found at autopsy

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Pleural Plaques, Chest X-Ray, Honeycombing, Asbestos Millboard, Malignant Mesothelioma, Lung Cancer, Asbestos Exposure.

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