Thickening of pulmonary interlobar fissures: exposure-response relationship in crocidolite and amosite miners

Our plain-English summary of Thickening of pulmonary interlobar fissures: exposure-response relationship in crocidolite and amosite miners, by A. Solomon, L.M. Irwig, G.K. Sluis-Cremer, et al (British Journal of Industrial Medicine, 1979).

The study

• Authors: A. Solomon, L.M. Irwig, G.K. Sluis-Cremer, R.G. Thomas, R.S. Du Toit
• Journal: British Journal of Industrial Medicine
• Published: 1979;36(3):195-8
• Cited by: 15 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. 001056).

Abstract

ABSTRACT In a cross-sectional study of all white and mixed-race men employed at South African crocidolite and amosite mines, data on duration of asbestos exposure and radiological findings were available for 162 men, 94% of the total population. Postero-anterior radiographs were read by three experienced readers. Abnormality was regarded as present if reported by at least two of them. The reading included an assessment of whether interlobar fissures were not visible, were visible but not thickened, or were thickened according to criteria shown in a reference radiograph. Fissures which were visible but not thickened were seen in almost half the men and were not more common in men with longer asbestos exposure. On the other hand, thickened fissures increased in prevalence from about 2% in those who had worked with asbestos for 7 years or less, to 25% in those with more than 15 years' asbestos exposure. Some other asbestos-associated pleural or parenchymal abnormality occurred in 69% of men with thickened fissures. The prevalence of thickened fissures as an isolated abnormality was also related to the duration of asbestos exposure. Because its prevalence is related to duration of exposure, and its recognition is not subject to excessive inter-observer variation, we suggest that thickening of the fissures is a valuable sign in the radiological assessment of workers exposed to asbestos.

In plain English

This cross-sectional study examined chest X-rays of 1692 white and mixed-race men (94% of 1801) employed at South African crocidolite and amosite mines and mills between 1970 and 1975. Three readers, blind to age and mining history, read each X-ray independently. An abnormality counted only if at least two readers reported it. For the minor (horizontal) fissure, readers recorded not visible, visible but not thickened, or thickened. Major (oblique) fissures were recorded as thickened in the few cases seen. Visible but not thickened fissures (793 men, 46.9%) showed no clear relationship to exposure. Thickened fissures (86 men, 5.1%) rose in prevalence from about 2% in men with 7 years or less of asbestos work to 24.7% in men with more than 15 years. This link remained significant after allowing for age, and held for the 27 men whose only abnormality was thickened fissures. Readers disagreed no more on thickened fissures than on chest-wall pleural thickening. The authors concluded this supported the hypothesis that asbestos was the cause, and suggested recording the sign in asbestos studies and the ILO classification.

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 study of chest X-rays read independently by three readers, analysed by duration of asbestos exposure
• Who was studied: 1692 of 1801 (94%) white and mixed-race men employed at South African crocidolite and amosite mines and mills at some time between 1970 and 1975
• Exposure: Work in crocidolite and amosite mines and mills, measured as years of work in asbestos mines and mills
• Main results:
  • The three categories (not visible, visible but not thickened, thickened) were applied to the minor (horizontal) fissure. Major (oblique) fissures were recorded as thickened in the few cases in which they were seen
  • In the whole group, visible but not thickened fissures were found in 793 men (46.9%) and thickened fissures in 86 men (5.1%)
  • Visible but not thickened fissures showed no clear relationship to asbestos exposure
  • Prevalence of thickened fissures rose from about 2% in men with 7 years or less of asbestos work to 24.7% in men with more than 15 years (36 of 146 men in the over-15-year group)
  • Thickened fissures were also related to age, but the effect of duration of asbestos exposure remained significant after taking age into account
  • Only 27 of the 86 men had thickened fissures as an isolated abnormality. In these men, prevalence was still significantly related to duration of exposure, rising from 1.2% (7 of 569) with 1 year or less to 6.2% (9 of 146) with more than 15 years
  • Inter-observer agreement: of 197 men in whom at least one reader reported thickened fissures, 36 (18.3%) were agreed by one other reader and 50 (25.4%) by two other readers. For pleural thickening of the chest wall, at least one reader reported it in 180 men, of whom 42 (23.3%) were agreed by one other reader and 34 (18.9%) by both other readers
• The authors' conclusion: The authors concluded that the strong relationship between thickened fissures and duration of exposure supported the hypothesis that asbestos was the cause. They found that reading thickened fissures was subject to no more inter-observer error than reading pleural thickening of the chest wall. They suggested including this sign in studies of asbestos exposure and in future amendments to the ILO U/C classification

Topics

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

Medical terms in this study, explained in our Lexicon: Crocidolite, Amosite, Asbestos Exposure.

Related studies

• Risk of asbestosis in crocidolite and amosite mines in South Africa — L.M. Irwig, R.S. du Toit, et al. (1979)
• Prevalence of radiographic asbestosis in crocidolite miners and millers at Wittenoom, Western Australia — W.O. Cookson, N.H. De Klerk, et al. (1986)
• Visceral pleural thickening in asbestos exposure: the occurrence and implications of thickened interlobar fissures — S.D. Rockoff, E. Kagan, et al. (1987)
• Factors influencing the reading of small irregular opacities in a radiological survey of asbestos miners in South Africa — G.K. Sluis-Cremer, P.A. Hessel, et al. (1989)
• Nodular thickening of interlobar fissures: an early manifestation of malignant mesothelioma: a case report — S. Bandoh, J. Fujita, et al. (2001)
• Progression of irregular opacities in asbestos miners — G.K. Sluis-Cremer, E. Hnizdo (1989)

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