Investigation of a minor asbestos hazard

Our plain-English summary of Investigation of a minor asbestos hazard, by M.C. Kennedy, R. Routledge (British Journal of Industrial Medicine, 1967).

The study

• Authors: M.C. Kennedy, R. Routledge
• Journal: British Journal of Industrial Medicine
• Published: 1967;24(3):232-9
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 001483).

Abstract

Twelve men who had been exposed to a minor asbestos hazard have been examined clinically, radiologically, and physiologically, and an assessment of the airborne asbestos concentration has also been made. Ten men had worked in a transformer department lagging transformer windings with asbestos paste for between 15 and 37 years. Two of these men showed minor radiological and minor physiological changes suggestive of early asbestosis. Two insulation workers had been engaged in milling and sawing asbestos sheets for five and 23 years respectively; both men showed minor radiological and abnormal physiological changes. These two men had been exposed to higher airborne concentrations of the asbestos dust than the transformer men. It is impossible to be dogmatic concerning the aetiology of these pulmonary changes, and further follow-up studies are planned. However, the findings are presented in view of the recommendation by Gilson (1966) that more evidence is required concerning possible pulmonary changes in men exposed to low concentrations of asbestos.

In plain English

This study examined 12 men exposed to a minor asbestos hazard, as the authors called it, at an English midlands electrical equipment factory using chrysotile. Ten transformer fitters had used asbestos paste on transformer windings during welding for 15 to 37 years; two insulation workers had cut and milled asbestos hardboard for five and 23 years. One insulation department sample gave less than 47, another 57, micrograms of asbestos per cubic metre; both came from the working area, not the workers' breathing zone. Transformer department breathing-zone samples showed less than 1 fibre per ml, but wire-brushing off dried paste, possibly dustier, was not observed. Five fitters had minor basal X-ray changes, and one had shadows that could possibly have been pleural plaques. The authors judged that two fitters had minor X-ray and lung-function changes suggestive of early asbestosis. Both insulation workers had abnormal lung function; the 21-year-old's chest X-ray was normal. The authors concluded asbestos dust probably caused at least some of the insulation workers' abnormal findings. They said it was difficult to be dogmatic and planned follow-up.

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: Clinical, radiological and lung-function examination of a small group of exposed workers, with workplace dust sampling; no comparison group
• Who was studied: 12 men at a large heavy electrical equipment factory in the English midlands: 10 transformer fitters aged 36 to 54 who had worked with the process for 15 to 37 years, and 2 insulation workers aged 21 (5 years' work) and 47 (23 years' work)
• Exposure: Chrysotile from Canadian or Rhodesian mines. In the insulation department, hardboard of 40% asbestos and 60% resin was cut, milled and shaped. In the transformer department, reclaimed millboard of 71 to 72% asbestos with china clay and starch was mixed with water into a paste to protect transformer windings during welding.
• Main results:
  • Insulation department: two samples were taken in the working area, not the breathing zone. The first, taken while the men were mainly sawing and filing 'ebony', gave less than 47 micrograms of asbestos per cubic metre. The second, covering one and a half hours on bakelized asbestos and one and a half hours on epoxy glass, gave 57 micrograms per cubic metre. The tentative maximum allowable concentration by this method was 100 micrograms per cubic metre.
  • Transformer department: two breathing-zone samples each showed less than 1 fibre per ml of air. The authors noted that concentrations might be greater during wire-brush removal of the dried mix, which was not seen on the day of the visit.
  • Transformer fitters: 4 of 10 had normal chest X-rays and 5 had minor basal changes, mostly a few scattered pinhead opacities
  • One transformer fitter (no. 6) had three small opacities in the left upper and mid zones that could possibly have been pleural plaques
  • No asbestos bodies were found in the sputum
  • Transformer fitters: lung volumes were within 20% of normal, except inspiratory capacity, which was abnormally small in 4 of 10 men
  • Transformer fitters: transfer factor was subnormal at rest and on exercise in two men (nos. 3 and 8), and on exercise only in two more (nos. 1 and 5). Ventilatory cost of exercise was raised in 5 of 10.
  • The authors considered that 2 of the 10 transformer fitters showed minor radiological and some physiological changes suggestive of early asbestosis. One was a non-smoker and the other a heavy cigarette smoker.
  • Insulation worker no. 11 (aged 21, 5 years' exposure) had a normal chest X-ray but the greatest physiological change of any man studied
  • Insulation worker no. 11: inspiratory capacity was 51% less than normal (the text prints this as 'SI%'; Table II gives -51%), and ventilatory capacity was 25% to 40% below predicted
  • Insulation worker no. 12 (aged 47, 23 years' exposure) had pinhead opacities at the left base and a distorted lung pattern suggestive of destructive emphysema at the right base, with low transfer factor at rest and on exercise
  • Four of the 12 men (nos. 3, 5, 11 and 12) were abnormal on four or more lung-function measures
  • Total lung capacity was not decreased in any man, which the authors took to indicate that lung fibrosis, if present, was not extensive
• The authors' conclusion: The authors concluded it was probable that inhaled asbestos dust caused at least some of the abnormal findings in the two insulation workers. They also concluded that two transformer fitters showed changes suggestive of early asbestosis, while cautioning that it was very difficult to be dogmatic.
• Limitations the authors state:
  • The authors said it was very difficult to be dogmatic about findings in men exposed to only a minor hazard
  • Transfer factor results were hard to assess because of the low exercise level used
  • The wire-brush removal of the dried mix, possibly a dustier task, was not observed or sampled
  • The insulation department samples were not breathing-zone samples
  • The cut-off for normal lung function (within 20% of predicted) was chosen arbitrarily
  • Further discussion was deferred until follow-up investigations were carried out

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Insulator.

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