Relationship between chest X-ray findings and pulmonary function tests in dust workers

Our plain-English summary of Relationship between chest X-ray findings and pulmonary function tests in dust workers, by Y. Tonori, M. Niitsuya, T. Sato, et al (Industrial Health, 2005).

The study

• Authors: Y. Tonori, M. Niitsuya, T. Sato, Y. Sugiura, H. Miyake, Y. Aizawa
• Journal: Industrial Health
• Published: 2005;43(1):256-66
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Occupational injuries are decreasing due to the improvement in occupational management in the workplace in recent years. However, pneumoconiosis and its complications remain important occupational diseases. Based on the report 'survey on classification for supervision of pneumoconiosis in Japan' performed in 1994, this study compared age, number of years at the job and pulmonary function tests among work types, and examined the characteristics of cases in which pulmonary function results were worse than expected from the chest X-ray findings. In the comparison among work types, mean age was higher and %VC was lower among workers exposed to silica or asbestos, and FEV1.0% appeared to be lower among silica-exposed workers. Multiple regression analysis showed that silica or asbestos-exposed work environments strongly affected %VC. Some cases showed dissociation between the X-ray findings and pulmonary function tests, which appeared to be caused by certain types of work environments. In this study, all the subjects had findings of pneumoconiosis in their chest X-ray. It is necessary to perform a longitudinal survey on pneumoconiosis-free subjects to clarify the precise association of lung function tests with chest X-ray.

In plain English

This cross-sectional study analyzed 20,809 health examination certificates of Japanese dust workers who applied for classification for supervision of pneumoconiosis between April 1994 and March 1995. All had pneumoconiosis findings on chest X-ray. Jobs were grouped as silica work (12,392 workers), work with neither silica nor asbestos (8,018), or asbestos work (399). The authors compared two breathing test results, %VC and FEV1.0%, across these groups within X-ray categories PR1 to PR4; PR4 had no asbestos workers. Asbestos workers had lower mean %VC than workers exposed to neither dust in PR1 to PR3 (p less than 0.01). Asbestos workers' FEV1.0% varied by category: it was low in PR1 (p less than 0.01), but higher than in workers exposed to neither dust in PR2 and PR3 (p less than 0.05). The authors nonetheless stated that asbestos exposure did not reduce FEV1.0% in this study, while age and silica work did. The authors concluded that silica and asbestos exposure reduces pulmonary function. They noted that smoking was not recorded, that only workers with X-ray findings were included, and that the multiple correlation coefficients were low.

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 study of pneumoconiosis health examination certificates
• Who was studied: 20,809 dust workers in Japan, all with pneumoconiosis findings on chest X-ray, who applied for classification for supervision of pneumoconiosis to one of the 47 Prefectural Offices for Labor Standards between April 1, 1994 and March 31, 1995. Of 24,548 certificates received, 3,739 were excluded: 683 female, 1,560 PR0, 702 with complications, and 794 clearly mistaken or unreasonable records. In category PR4, the 896 workers were 751 silica workers and 145 workers without silica exposure; there were no asbestos workers.
• Exposure: Type of dust work, taken as the job held longest. The groups were silica-handling work (12,392; 59.6%); work handling neither silica nor asbestos, namely carbon, refining, welding and aluminum (8,018; 38.6%); and asbestos-handling work (399; 1.9%). The article does not name an asbestos fiber type.
• Main results:
  • In category PR4, the 896 workers comprised 751 silica workers and 145 others. PR4 contained no asbestos workers, so there is no asbestos comparison for PR4.
  • Mean %VC was lower in asbestos workers than in workers not exposed to silica or asbestos in X-ray categories PR1, PR2 and PR3 (p<0.01).
  • In PR1, silica workers had lower mean %VC than workers not exposed to silica or asbestos, after adjusting for years at the job (p<0.01).
  • In PR1, PR2 and PR3, asbestos workers had the highest proportion of the three work types in the reduced %VC group, defined as below the mean minus 1 SD (p<0.01).
  • In multiple regression, with workers exposed to neither silica nor asbestos as the reference group, the asbestos regression coefficients for %VC were negative: -7.892 (PR1), -13.784 (PR2) and -24.547 (PR3), each p<0.01. The silica coefficients ranged from -0.621 to -2.534.
  • In PR1, mean FEV1.0% was lower in silica workers than in workers not exposed to silica or asbestos (p<0.01).
  • FEV1.0% results for asbestos workers differed by category. Mean FEV1.0% was higher in asbestos workers than in workers not exposed to silica or asbestos in PR2 and PR3 (p<0.05). Among asbestos workers in PR1, mean FEV1.0% was low (p<0.01).
  • In multiple regression for FEV1.0%, the asbestos coefficients were -1.087 (PR1, marked with an asterisk), 3.112 (PR2) and 8.753 (PR3). The authors stated that asbestos exposure did not reduce FEV1.0% in this study.
  • In the FEV1.0% comparison, mean age was higher in the reduced group than in the corresponding group in all PR categories (p<0.01).
• The authors' conclusion: The authors concluded that silica and asbestos exposure reduces pulmonary function. They also concluded that asbestos work reduced %VC more than work without silica or asbestos, while silica work and age reduced FEV1.0%.
• Limitations the authors state:
  • Only persons diagnosed with pneumoconiosis by X-ray were included. Workers with lung dysfunction but no X-ray diagnosis were not studied.
  • Smoking was not analyzed because it was not part of the pneumoconiosis health examination.
  • X-ray findings of silicosis differ from those of asbestosis within the same PR category, which may affect comparisons of lung function within a category.
  • The multiple correlation coefficients of the regression models were low.
  • Age may confound years at the job. The authors suggested age-matched analyses for each work type and longitudinal follow-up studies.

Topics

Medical terms in this study, explained in our Lexicon: Chest X-Ray, Pulmonary Function Test (PFT), Pneumoconiosis, Occupational Disease, FEV1.

Related studies

• Findings from high resolution computed tomography of the lung and pleura of symptom free workers exposed to amosite who had normal chest radiographs and pulmonary function tests — S. Neri, A. Antonelli, et al. (1994)
• Decline in annual lung function in workers exposed to asbestos with and without pre-existing fibrotic changes on chest radiography — T. Nakadate (1995)
• 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)
• Effect of tale dust inhalation on lung function — M. Kleinfeld, J. Messite, et al. (1965)
• Pulmonary ventilatory function in talcosis of lung — M. Kleinfeld, J. Messite, et al. (1964)
• The relation among pulmonary function, chest roentgenographic abnormalities, and smoking status in an asbestos-exposed cohort — L. Rosenstock, S. Barnhart, et al. (1988)

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