A dynamical model of the transport of asbestos fibres in the human body

Our plain-English summary of A dynamical model of the transport of asbestos fibres in the human body, by A. DeStefano, C.F. Martin, D.I. Wallace (Journal of Biological Dynamics, 2017).

The study

• Authors: A. DeStefano, C.F. Martin, D.I. Wallace
• Journal: Journal of Biological Dynamics
• Published: 2017;11(1):365-377
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

We present a model for the transport of a single type of asbestos fibre through the human body. The model captures the transport modes that pertain particularly to the lungs and the mesothelium. Numerical solutions of the system follow observed movement in the body. We compare the accumulation of fibres in the lungs versus the mesothelium, and then we give analysis and results for various cases of exposure level and exposure time. Models, such as the one developed here, can give clues as to how asbestos fibres impact the body, and where to look for major impact.

In plain English

This article is a mathematical modelling study, not a study of people or animals. The authors built a compartment model, a set of equations, describing how a single type of inhaled asbestos fibre, all of one length and diameter, might move after entering the lungs. In the model, fibres are removed by macrophages (scavenger cells), pass into the lymphatic system, blood and pleural cavity, or become lodged in tissue or embedded in cells of the lungs, mesothelium or soft tissue. Parameter values were set by relative size rather than measured. The defaults were meant to describe short, thin fibres under normal (undiseased) conditions. In computer runs, the model predicted more fibres embedded and lodged in the lungs than in the mesothelium. When exposure stopped, free fibres cleared but embedded and lodged fibres remained. Under prolonged high exposure, embedded and lodged fibres kept rising linearly. In a numerical experiment varying exposure level and duration, long low-level exposure left fewer fibres embedded in mesothelial cells than short high-level exposure. The authors concluded the model illustrates qualitative aspects of fibre movement. They said good parameter estimates are needed for quantitative results.

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: Theoretical mathematical compartment model (differential equations) with computer simulations run in MATLAB; no human or animal data were collected
• Who was studied: No people or animals were studied. The model represents the human body, starting from fibres that have already entered the lungs.
• Exposure: Inhaled fibres of a single, unnamed asbestos type, all of one fixed length and diameter, with default parameters describing short, thin fibres. Simulated exposure level (input I) was varied from 0.25 to 1.25 and duration from 100 to 500 model time units.
• Main results:
  • Under 'normal' parameter settings, the model predicted more fibres embedded in cells and lodged in tissue in the lungs than in the mesothelium.
  • When exposure ended, the modelled system cleared of free fibres, leaving only fibres embedded in cells or lodged in tissue.
  • Under prolonged high exposure, the numbers of lodged and embedded fibres in the model grew linearly over time.
  • In the model's subsystem of free fibres and macrophages in the lungs, the lungs eventually cleared of free fibres once input stopped.
  • Across the exposure-level and duration scenarios, modelled fibre amounts in the mesothelium ranged from 0.0196 to 6.9821 (model units).
  • Under 'normal' settings, low exposure for a long time resulted in fewer fibres embedded in mesothelial cells than high exposure for a relatively short time.
• The authors' conclusion: The authors concluded that the model illustrates some qualitative aspects of how asbestos fibres move in the body. They said better parameter information may allow more precise, quantitative predictions.
• Limitations the authors state:
  • Parameters were set by relative size, not measured. The authors state that quantitatively accurate results need good estimates of all parameters.
  • The model makes a number of simplifying assumptions.
  • All fibres were assumed to be the same length and diameter, although real asbestos fibres vary.
  • Only exposure from the air was modelled. Gastrointestinal exposure was not included.
  • Accumulation of asbestos in the kidneys or gastrointestinal tract was not modelled.
  • The transition of cells to cancer and the immune response in the lymph system were left out of this model.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelium.

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• Asbestos exposure increases paracellular transport of fibrin degradation products across human airway epithelium — T.J. Gross, S.M. Cobb, et al. (1994)
• Transport of inhaled dust to extrapulmonary sites — P.F. Holt (1981)
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