Low exposure to asbestos. Gas exchange in ship pipe coverers and controls

Our plain-English summary of Low exposure to asbestos. Gas exchange in ship pipe coverers and controls, by R.L. Murphy, E.A. Gaensler, R.A. Redding, et al (Archives of Environmental Health, 1972).

The study

• Authors: R.L. Murphy, E.A. Gaensler, R.A. Redding, R. Belleau, P.J. Keelan, A.A. Smith, A.M. Goff, B.G. Ferris
• Journal: Archives of Environmental Health
• Published: 1972;25(4):253-64
• Cited by: 39 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. 001341).

In plain English

This was the second of three surveys of pipe coverers at a New England shipyard. Their asbestos dust exposure had been monitored and was at or near the then-recommended limit of 5 million particles per cubic foot. The study compared 84 pipe coverers with 70 controls, who were shipfitters and pipe fitters without known asbestos exposure, matched for age and length of employment. Smoking was similar in both groups. Pipe coverers had significantly lower vital capacity and total lung capacity. They also had lower single-breath and exercise diffusing capacity, a measure of how well gas passes from the lungs into the blood. Obstructive airway disease was about equally common in both groups. All workers meeting the clinical definition of asbestosis had markedly reduced gas transfer. Eight pipe coverers had reduced gas transfer but no clinical abnormalities and a normal vital capacity. Among 32 pipe coverers re-examined in 1970, mean single-breath diffusing capacity fell 12.6% and mean vital capacity fell 4.5%. The authors concluded that the tests gave corroborative evidence that some pipe coverers had asbestosis despite low exposure. They said the meaning of isolated reductions in diffusing capacity needs further study.

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 comparison of asbestos-exposed workers with matched controls (the second of three shipyard surveys), with a later re-examination of a subset of pipe coverers
• Who was studied: Pipe coverers at a New England shipyard (101 in the first survey, 84 in this second survey) and controls selected from shipfitters and pipe fitters without known asbestos exposure, matched for duration of employment and age (94 in the first survey, 70 in this one). 66.4% of the pipe coverers and 68.1% of the controls were current smokers.
• Exposure: Asbestos dust exposure as shipyard pipe coverers for 1 to 30 years. The exposure had been under surveillance for 20 years and was at or near the then-recommended threshold limit value of 5 million particles per cubic foot (mppcf). No fiber type is named.
• Main results:
  • Compared with controls, pipe coverers had significantly lower FVC (vital capacity), FEV1 and total lung capacity (P less than .01).
  • Obstructive airways disease was not more common in pipe coverers. Nine pipe coverers (10.7%) and five controls (7.1%) had an FEV1% more than 2 standard deviations below the predicted mean, which the authors called an insignificant difference.
  • Among the gas exchange tests, the largest differences between pipe coverers and controls were in single-breath diffusing capacity (DLSB) and exercise steady-state diffusing capacity (DLSS-Ex) (P less than .01).
  • All workers with clinical asbestosis also had severely reduced diffusing capacity and fraction of carbon monoxide removed.
  • Eight pipe coverers had impaired diffusing capacity and fraction of carbon monoxide removed, but had no clinical abnormalities and a normal FVC.
  • In the 1970 follow-up of 32 pipe coverers, mean FVC fell from 3.70 to 3.53 liters, or 4.5% (P less than .01).
  • In the same 32 pipe coverers, mean DLSB fell from 26.9 to 23.5 ml/min/mm Hg, or 12.6%. This was 0.96 ml per year, compared with a predicted decrease of 0.26 ml per year.
  • Over the same interval, the number of these workers with a reduced FVC rose from 12 to 14, and the number with a reduced DLSB rose from 12 to 19.
• The authors' conclusion: The authors concluded that tests of respiratory gas exchange gave corroborative evidence that some pipe coverers had asbestosis despite the low level of their exposure. They noted that in their longitudinal studies DLSB deteriorated more rapidly than vital capacity, suggesting this measurement may prove more sensitive.
• Limitations the authors state:
  • The authors stated that the significance of an isolated reduction in diffusing capacity requires further study, and that only follow-up examinations will show whether it detects early asbestosis.
  • Neglecting carbon monoxide back pressure may have led to underestimating diffusing capacity by up to 4% in some cases.
  • The authors' end-tidal CO2 method gave slightly lower steady-state diffusing capacity values and tended to accentuate differences between normal subjects and those with lung disease.

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.

Related studies

• Prevalence of chronic respiratory disease. Asbestosis in ship repair workers — B.G. Ferris, M.V. Panadive, et al. (1971)
• Asbestosis following brief exposure in cigarette filter manufacture — A.M. Goff, E.A. Gaensler (1972)
• Early effects of asbestos exposure on lung function — G. Jodoin, G.W. Gibbs, et al. (1971)
• Early Diagnosis of Respiratory Abnormalities in Asbestos-Exposed Workers by the Forced Oscillation Technique — P.M. de Sá, H.A. Castro, et al. (2016)
• Ethnic differences in lung function: evidence for proportional differences — C.E. Rossiter, H. Weill (1974)
• Thin-section CT abnormalities and pulmonary gas exchange impairment in workers exposed to asbestos — A. Sette, J.A. Neder, et al. (2004)

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