Evaluation of the fate and pathological response in the lung and pleura of brake dust alone and in combination with added chrysotile compared to crocidolite asbestos following short-term inhalation exposure

https://doi.org/10.1016/j.taap.2014.12.012Get rights and content
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Highlights

  • Evaluated brake dust w/wo added chrysotile in comparison to crocidolite asbestos.

  • Persistence, translocation, pathological response in the lung and pleural cavity.

  • Chrysotile cleared rapidly from the lung while the crocidolite asbestos persisted.

  • No significant pathology in lung or pleural cavity observed at any time point in the brake-dust groups.

  • Crocidolite quickly produced pathological response in the lung and pleural cavity.

Abstract

This study was designed to provide an understanding of the biokinetics and potential toxicology in the lung and pleura following inhalation of brake dust following short term exposure in rats. The deposition, translocation and pathological response of brake-dust derived from brake pads manufactured with chrysotile were evaluated in comparison to the amphibole, crocidolite asbestos. Rats were exposed by inhalation 6 h/day for 5 days to either brake-dust obtained by sanding of brake-drums manufactured with chrysotile, a mixture of chrysotile and the brake-dust or crocidolite asbestos. The chrysotile fibers were relatively biosoluble whereas the crocidolite asbestos fibers persisted through the life-time of the animal. This was reflected in the lung and the pleura where no significant pathological response was observed at any time point in the brake dust or chrysotile/brake dust exposure groups through 365 days post exposure. In contrast, crocidolite asbestos produced a rapid inflammatory response in the lung parenchyma and the pleura, inducing a significant increase in fibrotic response in both of these compartments. Crocidolite fibers were observed embedded in the diaphragm with activated mesothelial cells immediately after cessation of exposure. While no chrysotile fibers were found in the mediastinal lymph nodes, crocidolite fibers of up to 35 μm were observed. These results provide support that brake-dust derived from chrysotile containing brake drums would not initiate a pathological response in the lung or the pleural cavity following short term inhalation.

Abbreviations

Crl: Wi(Han)
Wistar rats, Specific Pathogen Free from Charles River Deutschland
SEM
scanning electron microscope
WHO
World Health Organization
MMMF
man made mineral fibers
VDI
Verein Deutscher Ingenieure (English, Association of German Engineers)
GMD
Geometric mean diameter
GML
Geometric mean length
GSD
Geometric standard deviation
MMAD
Mass median aerodynamic diameter
%CT/FOV
percentage of the elastin and collagen per area of lung tissue
CM
Confocal microscopy
TGF-ß
Transforming growth factor (TGF)-β
bFGF
Basic fibroblast growth factor
PDGF
Platelet-derived growth factor
CTGF
connective tissue growth factor

Keywords

Brake dust
Chrysotile
Crocdiolite asbestos
Fiber inhalation toxicology
Lung
Pleura

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Deceased.