Respiratory health of workers exposed to metal dusts and foundry fumes in a copper refinery

Our plain-English summary of Respiratory health of workers exposed to metal dusts and foundry fumes in a copper refinery, by G. Ostiguy, C. Vaillancourt, R. Bégin (Occupational and Environmental Medicine, 1995).

The study

• Authors: G. Ostiguy, C. Vaillancourt, R. Bégin
• Journal: Occupational and Environmental Medicine
• Published: 1995;52(3):204-10
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: To assess airflow limitation in workers exposed long term to metal dust, the prevalence of pleural plaques in those workers exposed in the past to asbestos, the influence of pleural plaques on lung function, and the possible association with airway disease caused by asbestos.

Methods: A cross sectional and longitudinal (seven year) survey of 494 long term (mean (SEM) 21(1) years) workers in a copper refinery was carried out from medical questionnaires, chest radiographs, and forced spirometry.

Results: The prevalence of lifetime non-smokers was 19%, current smokers 39%, and ex-smokers 42%. The prevalence of chronic obstructive pulmonary diseases (COPD) (forced expiratory volume in one second (FEV1) < 80% predicted) was 5%, small airway dysfunction (SAD) (maximal mid-expiratory flow (MMEF) < 60% predicted) was 7%, and this did not differ from the control population. The COPD and SAD were associated with cumulative smoking index but not with the cumulative work years at the plant or with any type of work at the plant. The mean (SEM) reduction of FEV1 was 20(7) ml in non-smokers, 26(4) ml in smokers, and 26(5) ml in ex-smokers (P > 0.05). In the smokers and ex-smokers with COPD, the loss of FEV1 was 53(10) (P < 0.02). The prevalence of pleural plaques was 11% (P < 0.0001); pleural plaques were found in older workers with known exposure to asbestos. The pleural plaques were circumscribed and associated with a non-significant 196 ml reduction in forced vital capacity (FVC) and non-significant reduction of FVC over time. The pleural plaques were not associated with COPD or SAD. The cumulative smoking index obtained by a technician did not differ from that by a chest physician.

Conclusions: Despite exposures to asbestos that produced pleural plaques and exposures to metal dusts and foundry fumes the long term workers of this plant did not have excessive prevalence of COPD or SAD. The data suggest that low level long term exposure to metal dusts, gases, and foundry fumes do not necessarily cause respiratory dysfunction, circumscribed pleural plaques with low grades of width and extent do not reduce FVC significantly, and exposure to asbestos dust that produced pleural plaques does not necessarily produce airway dysfunction.

In plain English

In 1991 the authors surveyed all 494 workers at a Montreal copper refinery. The workers were exposed to metal dusts, acid mists and foundry fumes, and asbestos had been used there to insulate foundry furnaces. Breathing tests for 396 of them were compared with tests going back to 1983-4, and chest X-rays were read using the ILO system. Chronic obstructive pulmonary disease (COPD) was found in 5.26% of workers: 2% of never-smokers, 4.9% of ex-smokers and 7.2% of current smokers. Airflow problems were linked to smoking history, not to years worked at the plant. Pleural plaques, all circumscribed and low grade, were seen in 54 of 494 workers (11%) and in 44 of 208 workers aged 50 or over (21%). Workers with plaques had a forced vital capacity 196 ml lower than controls. This difference was not statistically significant, and plaques were not significantly associated with COPD or small airway dysfunction. The authors concluded that despite asbestos exposure that produced plaques, and exposure to metal dusts and foundry fumes, these long-term workers did not have an excessive prevalence of COPD or small airway dysfunction.

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 and longitudinal (seven-year) respiratory survey of a whole workforce, with case-control analyses within the study population
• Who was studied: All 494 employees (all but one men) of a Montreal copper refinery at the 1991 survey. 396 (80%) of them were also tested in 1983-4. 208 workers aged 50 and over were analysed as a separate group. Mean time at the plant was 20.6 years.
• Exposure: Metal dusts (copper, silver, selenium, lead, arsenic and other trace metals), mild acid mists and foundry fumes. Asbestos (fiber type not stated) had been used to insulate foundry furnaces and related equipment, and was gradually removed over the past 10 years. Air sampling reportedly showed exposures within threshold limit values.
• Main results:
  • Among all 494 workers, COPD prevalence was 5.26%: 2% in non-smokers, 4.9% in ex-smokers and 7.2% in current smokers. It reached 13% in current smokers aged over 50.
  • COPD prevalence in smokers and ex-smokers compared with non-smokers: relative risk 5.8 (0.8-44), P = 0.05
  • Small airway dysfunction (SAD) prevalence in the workers was significantly lower than in a Michigan general-population reference
  • People with COPD or SAD had significantly higher smoking indices than those without. Years worked at the plant were not significantly associated with airflow dysfunction, and no work site contributed consistently.
  • Annual loss of FEV1 was significantly higher in people with COPD. Table 3 prints 70 (SEM 11) for COPD cases versus 46 (SEM 3) for controls, P 0.037; the table does not state units.
  • Pleural plaques were found in 11% of all 494 workers (54 cases) and in 21% of the group aged 50 and over (44 of 208). They were found mainly in older workers.
  • All plaques were circumscribed and of low grade; 9% of cases had calcified plaques
  • Workers with plaques had a forced vital capacity (FVC) 196 ml (2.4% of predicted) lower than controls without plaques. This difference was not statistically significant.
  • Between the 1983-4 and 1991 surveys, workers with plaques lost FVC at 31 (SEM 12) ml per year, compared with 15 (SEM 6) ml per year in those without. The difference was not significant.
  • No significant association was found between pleural plaques and COPD or SAD
• The authors' conclusion: The authors concluded that, despite asbestos exposure that produced pleural plaques and exposure to metal dusts and foundry fumes, the long-term workers of this plant did not have an excessive prevalence of COPD or small airway dysfunction
• Limitations the authors state:
  • Only active workers were included, so the low prevalence of small airway dysfunction is most likely a healthy worker effect
  • Analysis of work history did not confirm the link between plaques and past asbestos exposure at the plant
  • Some cases and controls were missing from one of the two surveys used for the lung-function decline analysis

Topics

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

Medical terms in this study, explained in our Lexicon: Pleural Plaques, Chest X-Ray, Spirometry, COPD, FEV1.

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