Biological activity of respirable industrial fibres treated to mimic residence in the lung

Our plain-English summary of Biological activity of respirable industrial fibres treated to mimic residence in the lung, by K. Donaldson (Toxicology Letters, 1994).

The study

• Author: K. Donaldson
• Journal: Toxicology Letters
• Published: 1994;72(1-3):299-305
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The durability of fibres in the lung environment after deposition could be a key factor in determining whether they accumulate to a sufficient tissue dose to cause pathological change. There is a shortage of information on the relative durabilities of respirable industrial fibres of various types. We describe a strategy for assessing the ability of different fibre types to persist in the lung milieu and to retain their biological activity. This is particularly important for the development of mesothelioma, where the long latent time that characterises this disease would be expected to exclude, from culpability, fibres that are not durable. We have combined a pre-treatment step in pH 5.0 or 7.0 with an assay that relies on the ability of fibres to damage the mesothelium. The long-term aim is to assess the impact that treatment in various pH solutions has on (a) fibre size/number, (b) loss of key elements, (c) the ability to damage the mesothelium. Such information should enable us to better predict the potential of fibres to cause mesothelioma.

In plain English

This laboratory study described a method for testing whether industrial fibres keep their biological activity after being soaked in solutions meant to mimic conditions in the lung. Fibres were first soaked in strong acid or, for 1 month, in buffer at pH 5.0 or pH 7.0. They were then injected into the abdominal (peritoneal) cavity of groups of 3 or 4 mice, and inflammation was measured 4 days later. At equal mass, fibres (erionite, long fibre amosite, UICC chrysotile, Kevlar) caused far more inflammation than non-fibrous dusts such as quartz and coal mine dust. Strong acid reduced the activity of a glass fibre but did not alter amosite asbestos. After 1 week in strong acid, rock wool (MMVF 21) lost 92% of its silicon and a refractory ceramic fibre (RCF 1) lost 12%. After 1 month in buffer, rock wool lost activity while RCF 1 changed much less. The results section names pH 7.0 for this and the discussion names pH 5.0. The author predicted that RCF 1 would be more likely than MMVF 21 to cause mesothelioma, and stated that the assay needs more validation.

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: Laboratory animal experiment: fibres were pre-treated in acid or buffer solutions to mimic some dissolution in the lung, then injected into the mouse peritoneal cavity, and the inflammatory response was measured as a marker of biological activity.
• Who was studied: Groups of 3 or 4 C57 B16 mice aged over 6 weeks. The total number of mice is not given.
• Exposure: Assay sensitivity test: 0.5 mg injected into the peritoneal cavity of either compact dusts (fly-ash, coal mine air dust, DQ 12 quartz, rutile titanium dioxide) or fibrous dusts (fibrous erionite, long fibre amosite, UICC chrysotile, Kevlar). Dissolution studies used a Johns Manville special purpose glass microfiber, long fibre amosite asbestos, MMVF 21 (rock wool) and RCF 1 (a titanium-containing refractory ceramic fibre). These were treated in oxalic acid (14 days), 1 M HCl (7 days), or acetate buffer at pH 5.0 or 7.0 (1 month).
• Main results:
  • When fibrous and non-fibrous particles were injected at equal mass (0.5 mg), the inflammatory response to the fibres greatly exceeded that to the non-fibrous particles. Results are shown only in a figure; no numbers are printed in the text.
  • Strong acid treatment reduced the biological activity of the vitreous (glass) fibre but did not alter the activity of amosite asbestos.
  • After 1 week of strong acid treatment, RCF 1 lost 12% of its silicon and MMVF 21 (rock wool) lost 92%.
  • After 1 month in buffer, the results section reports reduced biological activity for MMVF 21 at pH 7.0 and much less reduction for RCF 1.
  • The discussion instead states that only pH 5.0 treatment reduced the activity of MMVF 21, and that it had no effect on RCF 1.
• The authors' conclusion: The author concluded that the assay may be able to tell high-durability fibres from low-durability fibres. Based on this assay, the author predicted that RCF 1, compared to MMVF 21, would be more likely to keep its biological activity on reaching the pleura and so more likely to cause mesothelioma.
• Limitations the authors state:
  • The author called the strong acid treatment extreme.
  • At the time of writing, there were no data on silicon loss or fibre number after pH 5.0 treatment. The author said these data are needed to separate the effects of chemical change from changes in fibre length and diameter.
  • The author stated that more validation of the assay is required.

Topics

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

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

Related studies

• Inflammation generating potential of long and short fibre amosite asbestos samples — K. Donaldson, G.M. Brown, et al. (1989)
• Renal, vascular and cardiac fibrosis in rats exposed to passive smoking and industrial dust fibre amosite — P. Boor, S. Casper, et al. (2009)
• Bromo-deoxyuridine (BRDU) uptake in the lungs of rats inhaling amosite asbestos or vitreous fibres at equal airborne fibre concentrations — K. Donaldson, D.M. Brown, et al. (1995)
• Superoxide anion release by alveolar macrophages exposed to respirable industrial fibres: modifying effect of fibre opsonisation — K. Donaldson, I.M. Hill, et al. (1995)
• The in vivo biological activity of ceramic fibres — R.C. Brown, J.A. Hoskins, et al. (1995)
• Detection of surface free radical activity of respirable industrial fibres using supercoiled phi X174 RF1 plasmid DNA — P.S. Gilmour, P.H. Beswick, et al. (1995)

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