Angular and fibrous particles in lung in relation to silica-induced diseases

Our plain-English summary of Angular and fibrous particles in lung in relation to silica-induced diseases, by A. Dufresne, R. Bégin, C. Dion, et al (International Archives of Occupational and Environmental Health, 1998).

The study

• Authors: A. Dufresne, R. Bégin, C. Dion, J. Jagirdar, W.N. Rom, P. Loosereewanich, D.C. Muir, A.C. Ritchie, G. Perrault
• Journal: International Archives of Occupational and Environmental Health
• Published: 1998;71(4):263-9
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Introduction: The lung concentration of angular and fibrous particles was measured in cases of lung fibrosis only, in cases of lung fibrosis and lung cancer, and in cases of lung cancer only. These patients worked in different trades (mining, foundries, construction and were not a homogeneous group of exposed workers.

Material And Methods: Particles, both angular and fibrous, were extracted from lung parenchyma by a bleach digestion method, mounted on copper microscopic grids by a carbon replica technique, and analyzed by transmission electron microscopy (TEM) and energy-dispersive spectroscopy (EDS). The quartz concentration was also determined by X-ray diffraction (XRD) on a silver membrane filter after extraction from the lung parenchyma.

Results: (1) Lung cancer and lung fibrosis cases retained more metal-rich particles (P = 0.02) and more angular particles of all sorts (P = 0.009) than did lung fibrosis cases only, and the differences were statistically significant. (2) However, more quartz was retained in the lungs in lung fibrosis cases than in lung fibrosis or lung cancer cases, but the difference in the concentrations was not statistically significant. (3) More ferruginous bodies were retained in the lungs in lung cancer and lung fibrosis cases than in cases of lung fibrosis only, and the difference in the concentrations was statistically significant (P = 0.02).

Conclusion: Results obtained from lung tissue must always be interpreted cautiously. However, these results are consistent with the hypothesis that workers in some trades such as foundries were exposed not only to quartz but also to asbestos, ceramic fibers, metal-rich non fibrous particles, and other likely carcinogenic chemicals. The wide range of particle types identified in the lungs of these workers illustrates the complexity of trying to determine disease origins in these work environments. Epidemiology studies have to control for the exposure to these carcinogens as well as for smoking habits.

In plain English

This study measured mineral particles in lung tissue from 79 Quebec workers' compensation cases: 21 with fibrosis and lung cancer and 46 with fibrosis only, all likely silica-exposed in mines, foundries or construction, plus 12 trades workers with lung cancer but no fibrosis. The fibrosis-and-cancer group had more angular particles of all sorts than the fibrosis-only group (geometric mean 8.4 versus 4.89 million per mg dry lung; 95% confidence intervals 6.29 to 11.26 and 3.64 to 6.57; P = 0.009). It also had more metal-rich particles (P = 0.02) and ferruginous bodies (geometric means 4,448 versus 661 per gram; intervals 1,070 to 18,826 and 270 to 1,621; P = 0.02). Quartz was higher in the fibrosis-only group (1.35 versus 0.77 micrograms per mg; intervals 0.79 to 2.34 and 0.33 to 1.83), but not significantly. Asbestos fiber levels did not differ significantly. The authors concluded the results were consistent with the hypothesis that workers in some trades were exposed to asbestos, ceramic fibers and metal-rich non-fibrous particles as well as quartz. Smoking histories were largely unavailable, and the cases were not randomly selected.

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: Lung tissue mineral burden study comparing groups of compensation cases. Methods were electron microscopy with energy-dispersive spectroscopy, phase-contrast microscopy for ferruginous bodies, and X-ray diffraction for quartz.
• Who was studied: 79 workers seeking compensation in Quebec, with lung tissue obtained for about the last 15 years from hospitals identified in workers' compensation board (CSST) files. The groups were 21 cases of lung fibrosis and lung cancer, 46 cases of lung fibrosis only, and 12 individuals exposed in different trades (e.g., welders, tinsmiths) with lung cancer but no fibrosis, used as background references. Average age was 60.6 in the fibrosis-and-cancer group and 65.1 in the fibrosis-only group, and the authors report a statistical difference in age between these two groups.
• Exposure: Silica (quartz) exposure, likely in gold-copper-zinc mines, ferrous and nonferrous foundries and construction sites. Lung tissue was analyzed for angular (non-fibrous) particles, fibrous particles including asbestos (fiber types not specified), ferruginous bodies, and quartz and cristobalite.
• Main results:
  • Angular particles of all sorts (million particles per mg dry lung, geometric mean with 95% confidence interval) were 8.4 [6.29 to 11.26] in the fibrosis-and-lung-cancer group, 4.89 [3.64 to 6.57] in the fibrosis-only group, and 4.62 [3.21 to 6.64] in the lung-cancer-only group. The fibrosis-and-cancer versus fibrosis-only comparison gave P = 0.009.
  • Metal-rich angular particles (million per mg dry lung, geometric mean) were 0.71 in the fibrosis-and-lung-cancer group, 0.34 in the fibrosis-only group and 0.21 in the lung-cancer-only group, P = 0.02. The authors state these particles contained Al, Ni, Mn, Cd and Cr.
  • Quartz (geometric mean with 95% confidence interval) was 0.77 [0.33 to 1.83] in the fibrosis-and-lung-cancer group, 1.35 [0.79 to 2.34] in the fibrosis-only group, and 0.07 [0.04 to 0.13] in the lung-cancer-only group. A table footnote gives the units as micrograms per mg lung tissue. The difference was not statistically significant (P > 0.1).
  • Cristobalite was not found in any of the lungs.
  • Ferruginous bodies per gram (geometric mean with 95% confidence interval) were 4,448 [1,070 to 18,826] in the fibrosis-and-lung-cancer group, 661 [270 to 1,621] in the fibrosis-only group, and 372 [57 to 752] in the lung-cancer-only group, P = 0.02.
  • Asbestos fibers 5 micrometers or longer (thousand per mg dry lung, geometric mean) were 0.12 in the fibrosis-and-lung-cancer group, 0.05 in the fibrosis-only group and 0.16 in the lung-cancer-only group. The difference was not statistically significant (P > 0.1). Shorter asbestos fibers also showed P > 0.1.
  • The lung-cancer-only (trades) group retained more clay and mica-like particles. The authors said they had no explanation for this.
• The authors' conclusion: The authors concluded that results from lung tissue must be interpreted cautiously. They found the results consistent with the hypothesis that workers in some trades (not all of them) were exposed not only to quartz but also to asbestos, ceramic fibers, metal-rich non-fibrous particles and other likely carcinogenic chemicals. They said epidemiology studies need to control for these exposures and for smoking.
• Limitations the authors state:
  • There was almost no smoking history information for the cases.
  • The workers were not a random sample of silicotic individuals or of lung cancer cases among them, and they were exposed in different occupational environments.
  • There were small numbers of cases, and no information on cumulative dust exposure or domestic exposure.
  • It was not possible to determine which lobe the tissue came from, and silicosis was not graded.
  • The investigators had no control over sample selection and had to use the lung samples that were available.
  • Factors such as variation in dust exposure, breathing and clearance may have confounded the quartz results.

Topics

Medical terms in this study, explained in our Lexicon: Fibrosis, Lung Cancer, Parenchyma, Transmission Electron Microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-Ray Diffraction (XRD), Ferruginous Bodies, Carcinogenic.

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