Types, numbers, sizes, and distribution of mineral particles in the lungs of urban male cigarette smokers

Our plain-English summary of Types, numbers, sizes, and distribution of mineral particles in the lungs of urban male cigarette smokers, by A. Churg, B. Wiggs (Environmental Research, 1987).

The study

• Authors: A. Churg, B. Wiggs
• Journal: Environmental Research
• Published: 1987;42(1):121-9
• Cited by: 35 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. 000951).

Abstract

We analyzed the exogenous mineral particle concentration, size, type, and distribution for particles larger than 0.1 micron in the left lungs of 10 long-term male cigarette smokers. The mean number of particles found was 465 +/- 295 X 10(6)/g dry lung, of which 80% were kaolinite, micas, feldspars, free silica, and talc. Lead particles were extremely rare, despite their ubiquity in urban air. Overall there were no differences in particle concentration in upper vs lower lobes or central vs peripheral sampling sites. However, a significant correlation was found for upper lobe (r = 0.68), but not lower lobe (r = 0.08), particle concentration and amount of cigarette smoking. Overall, the geometric mean particle size was 0.6 +/- 2.1 microns; 56% of the particles in the upper lobes were larger than 0.75 micron in diameter, compared to 17% in the lower lobes, and the mean upper lobe particle size was greater than the mean lower lobe particle size for all individual mineral types. There was a remarkable homogeneity of mean particle size from patient to patient (mean intercase arithmetic particle size +/- SD of 0.8 +/- 0.1 micron). Particle size was not affected by the amount of smoking. We conclude that contrary to some published acute deposition data, there are no long-term differences in upper vs lower lobe particle concentration; total upper lobe particle retention is influenced by the amount of smoking as measured by pack-years, whereas total lower lobe particle retention appears to be independent by the amount of smoking; particles retained in the upper lobe are somewhat larger than those retained in the lower lobe, but the amount of smoking does not appear to influence retained particle size; the size of long-term retained particles most likely reflects largely atmospheric particle burden; and in the absence of overwhelming dust loads, the lung is able to regulate retained particle concentration and size in a fairly narrow range.

In plain English

This study examined mineral particles in autopsy lung tissue from 10 men over 50 in the Vancouver area. All were current cigarette smokers with no lung disease other than chronic airflow obstruction. A questionnaire given to relatives found no occupational dust exposure. Men with lung cancer were excluded. The authors dissolved samples from four sites in the left lung and identified particles larger than 0.1 micrometre by electron microscopy. The mean count was 465 plus or minus 295 million particles per gram of dry lung. About 80% were kaolinite, silica, micas, feldspars and talc, and lead particles were rare. Asbestos was not among the mineral types reported. Counts did not differ between upper and lower lobes or between central and peripheral sites. Upper lobe counts correlated with pack-years smoked (r = 0.68); lower lobe counts did not (r = 0.08). Upper lobe particles were larger: 56% exceeded 0.75 micrometre, versus 17% in the lower lobes. Mean particle size varied little between men. The authors concluded that, without heavy dust exposure, the lung appears to keep retained particle number and size within a fairly narrow range.

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: autopsy study of lung tissue (mineral particle analysis by electron microscopy) in a small series of cases
• Who was studied: 10 men over 50 years old, current cigarette smokers, examined at autopsy. All had lived in the Vancouver area for at least 10 years. None had lung disease other than chronic airflow obstruction. Lung cancer cases were excluded. Occupational dust exposure was ruled out by a questionnaire given to relatives. Study dates are not given.
• Exposure: Cigarette smoking (15 to 100 pack-years, mean 45 plus or minus 24) and non-occupational mineral particles, presumed by the authors to come from urban air. Asbestos fibers were not among the mineral types reported.
• Main results:
  • Across all 10 men, the mean particle concentration was 465 plus or minus 295 million particles per gram of dry lung.
  • About 80% of particles were five minerals: talc, kaolinite, micas, feldspars and crystalline silica. Kaolinite was the most common mineral at all sites except the peripheral lower lobe.
  • Only rare lead particles were found, although the authors note lead is common in urban air.
  • Particle concentration did not differ significantly between sampling sites, between upper and lower lobes, or between central and peripheral sites.
  • Pack-years smoked correlated with upper lobe particle concentration (r = 0.68, P < 0.03) but not with lower lobe concentration (r = 0.08).
  • In the upper lobes, 56% of particles were larger than 0.75 micrometre, compared with 17% in the lower lobes. The upper and lower lobe size distributions differed statistically (Chi square = 677, P = 0.0001).
  • The larger particle size in the upper lobes did not correlate with the amount of smoking.
  • Mean particle size varied little from man to man: the average of the 10 case means was 0.8 plus or minus 0.1 micrometre, and case means ranged from 0.6 to 1.0 micrometre.
  • Total particle concentration varied only about fivefold from the highest to the lowest of the 10 men.
• The authors' conclusion: The authors concluded that, in the absence of massive (occupational) dust exposure, the lung may be able to regulate retained particle burden within a fairly narrow range of size and number. They also concluded that the sizes of retained particles probably reflect the particles present in the air.
• Limitations the authors state:
  • Particles that analyzed as pure iron, iron plus phosphorus, or calcium plus phosphorus were left out, because the authors could not tell whether they came from inside the body or from outside.
  • Particles smaller than 0.1 micrometre were not counted. The authors also note that size data on airborne particles, measured and identified in the same way, are hard to obtain for comparison.

Topics

Medical terms in this study, explained in our Lexicon: Mica, Talc, Deposition.

Related studies

• Effects of cigarette smoke on epithelial uptake of non-asbestos mineral particles in tracheal organ culture — B. Keeling, J. Hobson, et al. (1993)
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• Mineral particles of varying composition induce differential chemokine release from epithelial lung cells: importance of physico-chemical characteristics — J. Ovrevik, T. Myran, et al. (2005)
• Inhalation toxicity of mineral particles: critical appraisal of endpoints and study design — H. Muhle, I. Mangelsdorf (2003)
• Physicochemical characterization of cryogenically ground, size separated, fibrogenic particles — P.S. Thorne, E.N. Lightfoot, et al. (1985)
• Fiber size and number in workers exposed to processed chrysotile asbestos, chrysotile miners, and the general population — A. Churg, B. Wiggs (1986)

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