"Labrador lung": an unusual mixed dust pneumoconiosis

Our plain-English summary of "Labrador lung": an unusual mixed dust pneumoconiosis, by H.W. Edstrom, D.M. Rice (Canadian Medical Association Journal, 1982).

The study

• Authors: H.W. Edstrom, D.M. Rice
• Journal: Canadian Medical Association Journal
• Published: 1982;126(1):27-30
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Free full text

Abstract

Forty-eight workers involved for various periods from 1962 in mining and milling iron-containing rock in the Carol Lake area of western Labrador were found in late 1974 and early 1975 to have pneumoconiosis. Their annual chest roentgenograms demonstrated irregular nodular densities, and several revealed mild hilar lymphadenopathy or pleural thickening. All 48 workers were asymptomatic and had normal pulmonary function; their average age was 38 years. At work they had been exposed to high levels of dust containing iron, silica and anthophyllite, a type of asbestos. Lung biopsy specimens from 13 of them showed widespread focal fibrosis, large amounts of hemosiderin and silica and many ferruginous bodies; one ferruginous body was identified as having a core of anthophyllite. A granulomatous reaction was seen in two biopsy specimens and typical silicotic nodules were found in two others. The relatively brief exposure, especially in ones case (11 months), and the short latent interval before the development of the pneumoconiosis are reasons for concern for the health of iron ore workers.

In plain English

This article reported on iron ore workers in the Carol Lake area of western Labrador. Workers whose annual chest X-rays looked abnormal were referred to the authors, who examined 65 men from a work force of about 3500 at the Iron Ore Company of Canada and Scully Mines. Of the 65, 48 were found to have a mixed dust pneumoconiosis. Ten were thought to have had sarcoidosis. The 48 averaged 38 years of age. In several men the earliest X-ray changes appeared about 8 years after first exposure. One man who had worked only 11 months was diagnosed by lung biopsy 13 years later. Most had no symptoms apart from those of chronic bronchitis reported by the 27 smokers, and lung function results were generally normal. All 13 lung biopsy specimens showed widespread focal interstitial reaction with hemosiderin, silica and ferruginous bodies. One ferruginous body had a core of anthophyllite, a type of asbestos. In more than half the dust samples, levels were three to seven times above published threshold limit values. The authors concluded the disease was associated with high levels of dust containing iron, silica and anthophyllite, and said its long-term course was unknown.

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 case series: workers with abnormal routine chest X-rays were referred for history, examination, occupational questionnaire, chest X-ray, tuberculin skin test, pulmonary function and blood gas testing; some had biopsies
• Who was studied: 65 men, out of a work force of approximately 3500 at the Iron Ore Company of Canada and Scully Mines in western Labrador, who had abnormal chest X-rays; they were seen after a review that began in late 1974
• Exposure: Respirable mixed dust containing iron oxides, quartz (silica) and silicates including anthophyllite, at the concentrating mill and pellet plant of the Iron Ore Company of Canada; measured concentrations were well above American Conference of Governmental Industrial Hygienists threshold limit values, three to seven times above them in more than half the samples
• Main results:
  • Of the 65 workers examined, 48 were identified as having a mixed dust pneumoconiosis
  • Ten of the 65 workers had similar X-ray abnormalities in the past that resolved and were thought to have had sarcoidosis; the remaining seven were considered to have normal lungs
  • Chest X-rays of the 48 showed diffuse, low-density opacities about 2 mm across, more evident in the upper halves of both lungs; several men had mild hilar lymph node enlargement and several others had pleural thickening
  • The average age of the 48 workers with pneumoconiosis at diagnosis was 38 years
  • In several men, the earliest X-ray sign of pneumoconiosis appeared approximately 8 years after first exposure to the dust
  • One man who had worked for one of the companies for only 11 months had pneumoconiosis confirmed by open lung biopsy 13 years later
  • Job locations of the 48: 28 in the Iron Ore Company of Canada concentrating mill, 11 in its pellet plant, 8 in both, and 1 a driller at the Scully Mines mine
  • Most of the 48 had no symptoms at diagnosis apart from symptoms consistent with chronic bronchitis, which were reported by the 27 cigarette smokers
  • Routine pulmonary function results were generally normal; two miners had persistent basal rales (crackling sounds at the lung bases) and pleural thickening on X-ray
  • Of the 48, 11 had an open lung biopsy, 2 a transbronchial lung biopsy and 1 a lymph node biopsy
  • All 13 lung specimens showed a widespread focal interstitial reaction with collagen and fibroblasts, along with hemosiderin, silica and ferruginous bodies
  • One ferruginous body was identified by a research scientist as having a core of anthophyllite, which that scientist also found in the ore (unpublished observations)
  • Two lung biopsy specimens showed typical silicotic nodules, and two others showed a granulomatous reaction not typical of tuberculosis or sarcoidosis
  • The lymph node biopsy, from a patient with pneumoconiosis and a clinical presentation of scleroderma, showed large amounts of mixed dust with an aggressive fibrous reaction
  • Average quartz content of respirable dust samples was 18% in the concentrating mill and 3.3% in the pellet plant; iron oxides averaged 77%
• The authors' conclusion: The authors concluded that this apparently asymptomatic pneumoconiosis, which they said they were the first to describe, is associated with high workplace levels of mixed dust containing iron, silica and anthophyllite
• Limitations the authors state:
  • The authors noted the unusual tissue findings might reflect biopsy at an early stage of silicosis
  • The authors stated the long-term effects of anthophyllite exposure are unknown
  • The authors stated the long-term outlook for these workers must remain guarded until the natural history of the disease is known

Topics

Medical terms in this study, explained in our Lexicon: Pneumoconiosis, Lymphadenopathy, Pleural Thickening, Anthophyllite, Biopsy, Fibrosis, Ferruginous Bodies, Ferruginous body.

Related studies

• An unusual case of mixed-dust exposure involving a "noncommercial" asbestos — R.F. Dodson, J.L. Levin (2001)
• Dusts causing pneumoconiosis generate .OH and produce hemolysis by acting as Fenton catalysts — T.P. Kennedy, R. Dodson, et al. (1989)
• Accumulation of mixed mineral dusts in the lungs of rats during chronic inhalation exposure — C.H. McMillan, A.D. Jones, et al. (1989)
• Mixed pneumoconiosis: silicosis, asbestosis, talcosis, and berylliosis — G.J. Mark, C.B. Monroe, et al. (1979)
• Tracheal carcinoma and mixed pneumoconiosis. A causal relationship? — D. Theegarten, S. Philippou, et al. (1995)
• WHO/ILO work-related burden of disease and injury: Protocol for systematic reviews of occupational exposure to dusts and/or fibres and of the effect of occupational exposure to dusts and/or fibres on pneumoconiosis — D. Mandrioli, V. Schlünssen, et al. (2018)

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