Toxicology of Industrial Compounds

8
Pulmonary Toxicity Studies with Man-made
Organic Fibres: Preparation and Comparisons of
Size-separated Para-aramid with Chrysotile
Asbestos Fibres
DAVID B.WARHEIT, 1 MARK A.HARTSKY, 1 CHARLES
J.BUTTERICK 2 and STEVEN R.FRAME 1
1 DuPont Haskell Laboratory, Newark, DE, 2 Texas Tech
Health Sciences Center Lubbock, TX
Introduction
This study was designed to compare the pulmonary toxic effects of
inhaled, size-separated preparations of chrysotile asbestos fibres with paraaramid
fibrils at similar aerosol fibre concentrations. Chrysotile samples
are known to have an abundance of short fibres, with mean lengths
generally in the range of 2 µm. This is important to note because one of the
critical factors influencing the pathogenesis of fibre-related lung disease is
fibre dimension (Davis et al., 1986). As a consequence, attempts were made
to selectively enhance the mean lengths of chrysotile asbestos fibres used in
this inhalation toxicity study, in order to make reasonable comparisons
between the two fibre-types.
Methods
General experimental design
Groups of male Crl: CDBR rats (7–8 weeks old, Charles River Breeding
Laboratories, Kingston, New York) were used to assess the pulmonary
effects of 2-week inhalation exposures to size-separated preparations of
Kevlar ® para-aramid fibrils or chrysotile asbestos fibres. Animals were
exposed 6 hr day −1 , 5 days week −1 for 2 weeks. For this study, Kevlar ® was
utilized as a representative para-aramid fibril. The two commercial types of
para-aramid fibres are Twaron ® , made by Akzo, and Kevlar ® , made by
DuPont. Following exposure, the lungs of p-aramid or chrysotile-exposed
animals and age-matched sham controls were subsequently evaluated by
bronchoalveolar lavage fluid analysis at 0 h, 5 days, 1 and 3 months
postexposure. The lungs of additional animals were evaluated for
biodurability, pulmonary clearance, pulmonary histopathologic lesions and