Prevalence of asbestos related lung disease among employees in non-asbestos industries

Our plain-English summary of Prevalence of asbestos related lung disease among employees in non-asbestos industries, by I. Young, S. West, J. Jackson, et al (The Medical Journal of Australia, 1981).

The study

• Authors: I. Young, S. West, J. Jackson, P. Cantrell
• Journal: The Medical Journal of Australia
• Published: 1981;1(9):464-7
• Cited by: 23 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. 000782).

Abstract

Employees from two non-asbestos industries wee examined to assess the prevalence of asbestos-related lung disease. Of the 214 employees, one suffered from a malignant mesothelioma of the pleura and in 13 (6.1%), pleural plaques were diagnosed radiologically. the plaques were symptomless and not associated with any disturbance in respiratory function. The sole source of asbestos fibre in one factory was the asbestos insulation surrounding steam and hot water pipes similar to that found throughout industry. Exposure occurred as the result of the way in which this insulation has been handled routinely in industry by people who have commonly been unaware either of their exposure or of its significance. In the second factory there was the possibility of additional exposure originating from a neighbouring industry that was a major consumer of asbestos. The results suggest that maintenance workers may be particularly at risk and that the presence of pleural plaques may be under-reported in the absence of a history of asbestos exposure to direct attention towards them. The presence of pleural plaques has important consequences for the individual and for others who have shared the work environment.

In plain English

This New South Wales survey examined workers at two factories not using asbestos in production: a rubber goods maker (factory A) and a sugar refiner (factory B). It was prompted by a malignant pleural mesothelioma in a 47-year-old factory A employee with no previous occupational asbestos exposure. Results covered 214 workers: 170 current employees and one ex-employee from factory A, and 43 from factory B. Chest X-rays showed pleural plaques in 13 (6.1%): 9 in factory A (5.3%), 4 in factory B (9.3%). They included two maintenance fitters, two fitter's assistants, a rigger, a rigger's assistant, a mechanic/driver and six rubber workers. The authors called the tradesmen's preponderance highly significant (P<0.001). No one had unequivocal asbestosis, and no pattern of disturbed lung function was linked to the plaques. The authors identified asbestos lagging on pipes and boilers as the source. It contained amosite, with small amounts of chrysotile and some crocidolite in factory A. A neighbouring asbestos user may also have contaminated factory A. The authors concluded the findings strongly suggest many people unknowingly suffered significant exposure through how insulation was handled.

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: medical and occupational history, respiratory questionnaire, chest X-ray and lung function tests of employees at two factories
• Who was studied: Employees in New South Wales (Sydney authors). Group A came from factory A, a rubber goods manufacturer: 170 current employees who had worked in the studied area for 10 or more years plus one ex-employee (30 maintenance staff, one driver, the rest rubber workers; mean age 51.6 years). From factory B, a raw sugar refiner, 88 were examined and results were reported for the 43 employed 10 or more years (39 maintenance workers, 4 boiler attendants and turbine drivers). The article gives the total group as 214 subjects. Survey dates are not given.
• Exposure: Indirect occupational exposure to asbestos lagging (insulation) on hot water and steam pipes and boilers. Factory A insulation samples contained amosite, occasionally with small amounts of chrysotile, plus a small source of crocidolite-containing insulation. Factory A dust contained roughly equal fine chrysotile and amosite, which the authors attributed partly to a neighbouring factory that was a major asbestos consumer. Factory B lagging contained only amosite and was the sole source there.
• Main results:
  • Pleural plaques were found in 13 of the 214 subjects (6.1% overall): 9 in Group A (5.3%) and 4 in Group B (9.3%).
  • Jobs of the 13 subjects with plaques: maintenance fitter 2, fitter's assistant 2, rigger 1, rigger's assistant 1, mechanic/driver 1, rubber worker 6. The authors reported the preponderance of tradesmen as highly significant (P<0.001).
  • Subjects with plaques had a mean age of 53.9 years and a mean duration of employment of 23.5 years. The authors reported that neither differed significantly from the rest of the group.
  • Only one subject with plaques initially volunteered a clear history of handling asbestos fibre; that subject had worked 17 years in floor tile manufacture before joining factory B.
  • No subject had unequivocal asbestosis. One subject with plaques had a moderately severe defect in diffusing capacity but no radiological signs of interstitial pulmonary fibrosis.
  • No pattern of disturbed lung function was specifically associated with the presence of pleural plaques on X-ray.
  • In the group analysis of lung function, duration of employment was not significant for any measure (P>0.05).
  • 54 subjects (25%) had chronic bronchitis. After adjusting for smoking and age, it had no significant association with duration of employment.
  • Asbestos fibre was identified in 11 of 15 dust samples from multiple sites in the relevant area of factory A.
  • For comparison, the authors cited mass chest X-ray surveys of adults over 40 by the New South Wales Anti-Tuberculosis Association (1977 to 1979), which reported a plaque prevalence of 0.003%, against 6.1% in the study group.
  • The authors judged talc exposure in factory A an unlikely cause of the plaques. Talc was used in a separate building about 300 metres away, none of the affected employees had worked in the talc mixing area, and no talc was found in dust samples from their work area.
• The authors' conclusion: The authors concluded that their findings strongly suggest many people have unknowingly suffered significant asbestos exposure from the way asbestos insulation has commonly been handled. They added that maintenance workers appear particularly at risk. They offered two possible explanations for the unexpectedly high plaque prevalence: more fibre may be released by handling insulation than generally recognized, and plaques may be under-recognized or under-reported when there is no exposure history.
• Limitations the authors state:
  • The New South Wales mass X-ray survey population used for comparison has serious limitations as a control group, and no information was available on the occupations of those surveyed.
  • Overseas background prevalence figures cannot be applied to an Australian population because of differences in age and sex composition, and there are no published Australian data.
  • In factory A, the contribution of exposure from the neighbouring asbestos-using industry is difficult to assess for any particular affected individual.

Topics

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Pleura, Pleural Plaques, Asbestos Exposure.

Related studies

• Asbestos-related disease in employees of a steel mill and a glass bottle-manufacturing plant — R.S. Kronenberg, J.L. Levin, et al. (1991)
• Prevalence of Asbestos-Related Disease Among Workers in Sri Lanka — B.A. Wickramatillake, M.A. Fernando, et al. (2019)
• Asbestos-related disease in public school custodians — L.C. Oliver, N.L. Sprince, et al. (1991)
• Asbestos-related disease among sheet-metal workers. Preliminary results of the National Sheet Metal Worker Asbestos Disease Screening Program — L.S. Welch, D. Michaels, et al. (1991)
• Asbestos related diseases from environmental exposure to crocidolite in Da-yao, China. I. Review of exposure and epidemiological data — S. Luo, X. Liu, et al. (2003)
• Asbestos-related diseases in construction carpenters — M. García-Closas, D.C. Christiani (1995)

Browse more research in The Medical Journal of Australia, or return to medical research.