Lung function and chest radiograph abnormalities among construction insulators

Our plain-English summary of Lung function and chest radiograph abnormalities among construction insulators, by S.M. Kennedy, S. Vedal, N. Müller, et al (American Journal of Industrial Medicine, 1991).

The study

• Authors: S.M. Kennedy, S. Vedal, N. Müller, A. Kassam, M. Chan-Yeung
• Journal: American Journal of Industrial Medicine
• Published: 1991;20(5):673-84
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 004857).

Abstract

We carried out a prevalence survey of pulmonary health parameters among current and retired construction insulators (50 years old and older) from all areas of British Columbia, Canada. The study population included 59 active workers (81 percent participation in this group) and 29 workers who were retired or inactive due to illness (69% participation). Radiograph results were compared to those from actively working bus mechanics from the same age group, and retired grain and civic workers, who were all tested in the same manner. Chest radiographs were read independently by two readers and were graded according to the ILO classification system. Pleural abnormalities alone were found in 34% (20) of active workers (5% in comparison group) and 45% (13) of non-active workers (14% in comparison group). Rates for parenchymal abnormalities for these same groups (ILO grade 1/0 or higher) were 17% (5%) and 20% (5%), respectively. Airflow obstruction was present in 35% (31) of the insulators and was associated with age and the presence of diffuse pleural thickening, and 5 or more years of employment in pulp mills. Restrictive lung function was present in 22% (19) of the insulator population and was associated with age and radiographic evidence of parenchymal fibrosis. The results indicate that construction insulators, a group at high risk for asbestos-related lung disease, also have a high prevalence of airflow obstruction. This was associated not only with smoking, but also with diffuse pleural thickening and a history of pulp-mill employment, suggesting that airflow obstruction in this population is also partly work related.

In plain English

In 1988 the authors surveyed British Columbia heat and frost insulators' union members aged 50 or older. Of those invited, 59 of 73 active and 29 of 42 retired workers took part. Of the 88 insulators, 39 had normal chest X-rays, 33 had pleural fibrosis alone and 16 had parenchymal fibrosis. Pleural abnormalities alone appeared in 34% of active insulators versus 5% of bus mechanics, and 45% of retired insulators versus 14% of retired grain and civic workers. Airflow obstruction was found in 35% (31) of insulators and restrictive lung function in 22% (19). After adjusting for age, years since first exposure and smoking, diffuse pleural abnormality remained significantly associated with airflow obstruction. Five or more years in pulp mills had an odds ratio of 2.6 (95% CI 0.9 to 7.7) for obstruction, just short of statistical significance. A follow-up of 17 cases and 17 controls found no difference in handling polyurethane foam insulation. The authors suggested that airflow obstruction in this population may be partly work related. They noted that exposure histories were self-reported and retrospective.

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 prevalence survey (1988), with a small nested case-control follow-up on polyurethane foam (isocyanate) exposure
• Who was studied: Active and retired members of Local 118 (British Columbia) of the International Association of Heat and Frost Insulators and Asbestos Workers, aged 50 or older on January 1, 1988: 59 of 73 active workers and 29 of 42 retired workers. The comparison groups were 66 employed bus mechanics aged 50 and older (88% participation) and 83 retired grain elevator and civic workers (65% participation).
• Exposure: Work as construction insulators handling insulation products, including sprayed-on asbestos, asbestos block and asbestos board. Specific fiber types are not named. The study also looked at other industrial exposures, such as 5 or more years in pulp mills, oil refineries and mining, and at polyurethane (isocyanate) foam insulation.
• Main results:
  • Among the 88 insulators, 39 had a normal chest radiograph. Pleural fibrosis alone was seen in 33 (23 discrete, 10 diffuse) and parenchymal fibrosis in 16.
  • Pleural abnormalities alone were found in 34% (20) of active insulators versus 5% of the comparison group (bus mechanics), and in 45% (13) of non-active insulators versus 14% of the comparison group (retired grain and civic workers).
  • Controlling for smoking, insulators were three to four times more likely to have parenchymal abnormalities and three to six times more likely to have pleural abnormalities than the comparison groups (p less than 0.01 in each case).
  • Airflow obstruction was present in 35% (31) of the insulators.
  • Restrictive lung function was present in 22% (19) of the insulators.
  • Insulators with pleural fibrosis alone showed evidence of airflow obstruction but not restriction, compared with those with normal radiographs.
  • After adjusting for age, latency (years since first asbestos exposure) and cigarette consumption, diffuse pleural abnormality remained significantly associated with reduced lung function measures and with airflow obstruction.
  • Five or more years of work in pulp mills was the only work exposure that approached statistical significance for airflow obstruction (odds ratio 2.6, 95% CI 0.9 to 7.7).
  • More frequent handling of asbestos-block insulation showed a dose-response trend with both pleural and parenchymal fibrosis (72%, 85% and 94% handled it in the normal, pleural-only and parenchymal groups).
  • In the follow-up comparing 17 insulators with both airflow obstruction and isolated pleural abnormality to 17 matched insulators with normal results, there were no differences in handling of polyurethane foam insulation products.
• The authors' conclusion: The authors concluded that construction insulators also have a high prevalence of airflow obstruction, associated not only with smoking but also with diffuse pleural thickening and a history of pulp-mill work. They suggested this obstruction is partly work related.
• Limitations the authors state:
  • Work and exposure histories were collected subjectively and retrospectively, without objective confirmation, which the authors call a potential source of error.
  • The small study population made it unlikely that relationships with other work exposures could be identified with strong statistical confidence.
  • The radiographs may have been overinterpreted because the readers knew the workers' occupation.
  • Not all participants could be recontacted for the polyurethane foam follow-up because several had died.
  • Because most insulators reported handling asbestos block, the authors found it difficult to draw firm conclusions from the asbestos-block trend.

Topics

Medical terms in this study, explained in our Lexicon: Chest X-Ray, Insulator, ILO Classification, Obstructive Lung Disease, Diffuse Pleural Thickening, Restrictive Lung Disease, Parenchymal Fibrosis.

Related studies

• Risk and significance of chest radiograph and pulmonary function abnormalities in an elderly cohort of former nuclear weapons workers — M.A. Mikulski, P.G. Hartley, et al. (2011)
• Spirometric impairments in long-term insulators. Relationships to duration of exposure, smoking, and radiographic abnormalities — A. Miller, R. Lilis, et al. (1994)
• Comparative quantitative evaluation of pleural fibrosis and its effects on pulmonary function in two large asbestos-exposed occupational groups--insulators and sheet metal workers — R. Lilis, A. Miller, et al. (1992)
• Chest radiographs in subjects with asbestos-related abnormalities: comparison between ILO categorizations and clinical reading — B. Hilt, A. Borgerson, et al. (1992)
• Correlation between respiratory symptoms and pulmonary function in asbestos-exposed workers — C.A. Brodkin, S. Barnhart, et al. (1993)
• Pulmonary function and pleural fibrosis: quantitative relationships with an integrative index of pleural abnormalities — R. Lilis, A. Miller, et al. (1991)

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