Size-dependent retention of elongate mineral particles in human lungs: modeling and implications for risk assessment

Our plain-English summary of Size-dependent retention of elongate mineral particles in human lungs: modeling and implications for risk assessment, by A. Korchevskiy, R. Attanoos, A.G. Wylie (Frontiers in Public Health, 2025).

The study

• Authors: A. Korchevskiy, R. Attanoos, A.G. Wylie
• Journal: Frontiers in Public Health
• Published: 2025;13:1646016
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Introduction: Lung deposition of elongate amphibole particles is an important process impacting the risk of cancer. There is, however, a significant gap in scientific literature characterizing the role of particle size in the differences observed for deposition and clearance rate in the human respiratory system. The purpose of the paper is to explore the relationship between size distribution of elongate mineral particles in human lungs compared to corresponding distribution in the airborne exposure.

Materials And Methods: Previously published information about lung deposition for amosite and crocidolite particles in various dimensional groups, collected by the team of Pooley and Clark was reanalyzed with application of recently developed methodologies for fiber size analysis. The new metric-deposition selection ratio (DSR) is proposed; it is found by dividing the size fraction of particles in lungs to the corresponding fraction in exposure. The DSR estimations were also compared to theoretical estimations of pulmonary deposition rates of particles based on the United States Environmental Protection Agency (US EPA) Multi-Path Particle Dosimetry (MPPD) model.

Results: It was demonstrated that DSR values can be approximated by using log-log regressions with length and width of particles as independent variables. For non-asbestiform particles (cleavage fragments), the prediction of DSR from parametric and non-parametric models is demonstrated to be less than 1 (evidence of deselection in lungs). Negative correlation was found for DSR estimations and the theoretical predictions of pulmonary deposition rates by MPPD.

Discussion: The observed data for size-specific lung deposition of elongate mineral particles can be used for quantitative estimates of risk and analysis of toxicokinetic processes in human lungs. The difference between theoretical model and observed fiber deposition pattern requires further adjustments in the methods to predict lung deposition of elongate particles.

Copyright © 2025 Korchevskiy, Attanoos and Wylie.

In plain English

The authors reanalyzed fiber-size data published by Pooley and Clark in 1980 on amosite and crocidolite in lung tissue from UK mesothelioma cases and controls (assumed to be 86 cases and 56 controls). They compared these data with airborne samples from two South African mines and with a database of fiber dimensions. Using computer simulation to rebuild particle-by-particle data, they calculated a "deposition selection ratio" (DSR): each size group's share in lungs divided by its share in exposure. In regression models, DSR rose with fiber length and fell with width (combined R = 0.62, R2 = 0.38). All Pooley and Clark lung and airborne particle sets were classified as asbestiform. Applied to database amphibole particles longer than 5 μm, the model gave DSR below 0.5 for 100% of "non-criteria" particles, which the authors used as an approximation of non-asbestiform cleavage fragments. DSR correlated negatively with deposition predicted by the US EPA MPPD model (R = −0.5). The authors concluded that this difference calls for improved methods to estimate fiber transport and clearance. They noted that they lacked precise size data for specific exposure events and that cases and controls were mixed.

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: Reanalysis and statistical modeling of previously published lung-burden and airborne fiber-size data (Pooley and Clark, 1980). Particle-by-particle datasets were reconstructed by Monte Carlo simulation and compared with a dimensional database and with the US EPA MPPD deposition model.
• Who was studied: Lung tissue collected in a 1976 UK collaborative case-control analysis (Cardiff). The authors assumed it included 86 mesothelioma cases and 56 controls, pooled together. Lung data were compared with airborne samples and with a dimensional database of airborne and bulk TEM samples.
• Exposure: Amosite and crocidolite particles in lungs, compared with airborne samples from Pomfret mine (South Africa, crocidolite) and Penge mine (South Africa, amosite) and with dimensional-database data. Particles were classified into 32 length/width size categories.
• Main results:
  • Combining amosite and crocidolite, DSR increased with particle length and decreased with particle width.
  • The combined regression of DSR on length and width had R = 0.62, R2 = 0.38, p less than 0.000001.
  • Across amosite and crocidolite size groups, DSR ranged from 0 to 8.35. The highest value, 8.35, was for amosite of length 8 to 10 μm and width below 0.125 μm, compared with the dimensional database.
  • All Pooley and Clark particle populations (lung and airborne, amosite and crocidolite) were classified as asbestiform. The criteria fraction in lungs was 73 to 96%.
  • When the regression model was applied to amphibole particles longer than 5 μm in the dimensional database, 100% of non-criteria particles (approximating non-asbestiform particles) had DSR below 0.5, which the authors described as deselection. Among criteria particles, 50% had DSR above 1.
  • In a non-parametric check using crocidolite lung-to-airborne ratios applied to crocidolite and non-asbestiform riebeckite particles in the database, all non-asbestiform particles had DSR below 0.5.
  • DSR values were negatively correlated with pulmonary deposition rates predicted by the US EPA MPPD model (R = −0.5, R2 = 0.25, p less than 0.0000001).
  • A regression using average DSR and published biopersistence values for seven mineral types predicted published mesothelioma potency factors with R = 0.96, R2 = 0.93, p less than 0.004.
• The authors' conclusion: The authors concluded that the observed size distribution of particles in lungs differs significantly from the distribution the US EPA MPPD model would predict, which calls for further improvement of methods to estimate fiber transport and clearance. They also concluded that deposition probability increases with length and decreases with width, and that cleavage fragments appear to be deselected.
• Limitations the authors state:
  • The Pooley and Clark lung data represent only part of the Cardiff team's tissue archive.
  • There was no precise estimate of fiber dimensions for specific exposure events.
  • The lung data combined mesothelioma cases and controls.
  • The regression models explained only 37% to 51% of the variation.
  • Exposure characteristics could be measured only approximately.

Topics

Medical terms in this study, explained in our Lexicon: elongate mineral particles (EMPs), Deposition, Amphibole Group, Amosite, Crocidolite, Non-Asbestiform, Cleavage Fragment.

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