Mineral particles, mineral fibers, and lung cancer

Our plain-English summary of Mineral particles, mineral fibers, and lung cancer, by A. Churg, B. Wiggs (Environmental Research, 1985).

The study

• Authors: A. Churg, B. Wiggs
• Journal: Environmental Research
• Published: 1985;37(2):364-72
• Cited by: 32 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. 001240).

Abstract

The total fibrous and nonfibrous mineral content of the lung has been analyzed in a series of 14 men with lung cancer but no history of occupational dust exposure, and in a series of 14 control men matched for age, smoking history, and general occupational class. The lung cancer patients had an average of 525 +/- 369 X 10(6) exogenous mineral particles and 17.4 +/- 19.6 X 10(6) exogenous mineral fibers/g dry lung, while the controls had averages of 261 +/- 175 mineral particles and 4.7 +/- 3.2 X 10(6) mineral fibers/g dry lung. These differences are statistically significant for both particles and fibers. Kaolinite, talc, mica, feldspars, and crystalline silica comprised the majority of particles of both groups. Approximately 90% of the particles were smaller than 2 micron in diameter and approximately 60% smaller than 1 micron; the mean particle size in the cancer group was 1.1 +/- 0.2 micron and in the control group 1.3 +/- 0.2 micron. In both groups, patients who had smoked more than 35 pack years had greater numbers of particles than patients who had smoked less than 35 pack years. It is concluded that, in this study, lungs from patients with lung cancer had statistically greater numbers of mineral particles and fibers than lungs from controls, and that smoking influences total long-term retention of particles from all sources.

In plain English

This study compared minerals in autopsy lungs of 14 Vancouver men with lung cancer and, according to relatives, no occupational dust exposure, and 14 men without lung cancer. The groups were matched for age, sex, smoking history and blue- or white-collar work. Using electron microscopy, the authors counted mineral particles and fibers. The cancer group averaged 525 ± 369 million exogenous mineral particles and 17.4 ± 19.6 million exogenous mineral fibers per gram of dry lung. The controls averaged 261 ± 175 million exogenous particles and 4.7 ± 3.2 million exogenous fibers per gram of dry lung. Both differences were statistically significant. Asbestos made up about 6% of fibers in the cancer group and about 17% in controls. Most particles were kaolinite, talc, mica, feldspars or crystalline silica. In both groups, men who had smoked more than 35 pack years had more particles, but this was not statistically significant in either group. The authors concluded that, in this study, cancer patients' lungs held more particles and fibers, and that smoking influences long-term particle retention. They said the smoking finding needs checking with more cases and nonsmokers.

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: Matched comparison of mineral particle and fiber content in autopsy lung tissue from cases and controls, using electron microscopy, electron diffraction and energy dispersive X-ray spectroscopy
• Who was studied: Autopsy lungs came from the University of British Columbia Health Sciences Centre Hospital and Vancouver General Hospital. The cases were 14 men with pathologically confirmed lung cancer and no history of occupational or other mineral dust exposure, based on relatives' answers to a standardized questionnaire. The controls were 14 men without lung cancer or a history of dust exposure. They were matched to the cases by age (within 10 years), sex, smoking history (within 10 pack years) and occupational category. Each group had 11 blue-collar and 3 white-collar workers. The article does not give the dates of the autopsies.
• Exposure: The study measured the lung burden of exogenous (from outside the body) mineral particles and fibers in upper-lobe tissue. Only particles and fibers measuring 0.5 micrometers or more were counted. Fibers included asbestos (chrysotile; tremolite, actinolite and anthophyllite; amosite and crocidolite) and non-asbestos minerals such as talc, kaolinite, mullite, silica and feldspars. Smoking history in pack years was also examined. Apatite and iron-containing particles were treated as likely endogenous (formed in the body) and were excluded.
• Main results:
  • The lung cancer group averaged 525 ± 369 million exogenous mineral particles and 17.4 ± 19.6 million exogenous mineral fibers per gram of dry lung. The control group averaged 261 ± 175 million particles and 4.7 ± 3.2 million fibers per gram of dry lung.
  • Both differences were statistically significant: P less than 0.01 for particles and P less than 0.025 for fibers.
  • In 10 of the 14 matched pairs, the cancer patient had a higher total particle number than the matched control.
  • Asbestos fibers made up about 6% of all fibers in the cancer group and about 17% in the control group.
  • Kaolinite, talc, mica, feldspars and crystalline silica made up about 75 to 85% of all particles.
  • Mean particle size was 1.1 ± 0.2 micrometers in the cancer group and 1.3 ± 0.2 micrometers in the control group. The authors described the size distributions of the two groups as roughly similar.
  • In both groups, men who had smoked more than 35 pack years had more particles than those who had smoked less. The difference was not statistically significant in either group. It approached significance when the two groups were combined, and became highly significant (P less than 0.01) when one anomalous patient was excluded.
• The authors' conclusion: The authors concluded that, in this study, lungs from lung cancer patients had statistically greater numbers of mineral particles and fibers than lungs from controls, and that smoking influences total long-term retention of particles from all sources. They suggested that, whatever the mechanism, lung cancer is related to the total number of particles in lung tissue.
• Limitations the authors state:
  • The authors attributed the non-significant smoking result to the small sample size and the variability of particle burden.
  • The smoking observation needs to be checked with more cases and with nonsmokers.
  • The authors considered that occupational exposures might have been missed in the cancer group. They judged this possible in the odd case but not a full explanation.
  • The cancer patients may have smoked differently (for example, down to the butt), which would increase their actual dose.
  • Iron-containing particles and apatite were excluded as likely endogenous, although some of them could have come from outside the body.

Topics

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

Medical terms in this study, explained in our Lexicon: Mineral Fiber, Lung Cancer, Talc, Mica, Crystalline.

Related studies

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• Effects of cigarette smoke on epithelial uptake of non-asbestos mineral particles in tracheal organ culture — B. Keeling, J. Hobson, et al. (1993)
• A comparison of asbestos fiber potency and elongate mineral particle (EMP) potency for mesothelioma in humans — D.H. Garabrant, S.T. Pastula (2018)
• Physicochemical characterization of cryogenically ground, size separated, fibrogenic particles — P.S. Thorne, E.N. Lightfoot, et al. (1985)
• Dimensions of elongated mineral particles: a study of more than 570 fibers from more than 90 cases with implications for pathogenicity and classification as asbestiform vs. cleavage fragments — V.L. Roggli, C.L. Green (2019)
• Iron from a geochemical viewpoint. Understanding toxicity/pathogenicity mechanisms in iron-bearing minerals with a special attention to mineral fibers — A.F. Gualtieri, G.B. Andreozzi, et al. (2019)

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