title: Biopersistences of man-made vitreous fibers and crocidolite fibers in rat lungs following short-term exposures.
abstract: Biopersistence of commercial man-made vitreous fibers (MMVF) and crocidolite were studied in Fischer 344 rats. MMVF used were size-selected to be rat-respirable, and rats were exposed nose-only 6 h/day for 5 days to gravimetric concentrations (30 mg/m3) of two fiber glass compositions--a rockwool, and a slagwool--or to 10 mg/m3 of long-fibered crocidolite, or to filtered air. Animals were sacrificed at 1 hr, 1, 5, 31, 90, 180, 270, 365, and 545 days after exposure stopped. Fibers were recovered from digested lung tissue to determine changes in concentrations (fibers/mg dry lung) and fiber retentions (expressed as percent of day 1 retention [PR]) for selected dimension categories. One-day average concentrations of lung-retained MMVF and crocidolite fibers, of diameter > or = 0.5 micron or > 20 microns in length, were nearly equal, permitting direct comparisons between MMVF and crocidolite. At 270 days average PR for MMVF > or = 0.5 micron in diameter were from 3 to 6 +/- 2% and 27 +/- 9% for crocidolite. For fibers > 20 microns, PR were 1 to 4 +/- 4% for MMVF and 37 +/- 20% for crocidolite. At 545 days, MMVF > 20 microns in length were at background level while concentration of crocidolite fibers > 20 microns in length remained at 2000 +/- 400 f/mg DL (dry lung), or 38 +/- 9% of day-1 retention. These results suggest strongly that MMVF dissolved or fractured in vivo whereas crocidolite fibers did not change.
authors.affiliation: USG, Chicago, Illinois.
authors.forename: R P
authors.initials: RP
authors.lastname: Musselman
authors.forename: W C
authors.initials: WC
authors.lastname: Miiller
authors.forename: W
authors.initials: W
authors.lastname: Eastes
authors.forename: J G
authors.initials: JG
authors.lastname: Hadley
authors.forename: O
authors.initials: O
authors.lastname: Kamstrup
authors.forename: P
authors.initials: P
authors.lastname: Thevenaz
authors.forename: T W
authors.initials: TW
authors.lastname: Hesterberg
mesh_terms: D000280:Administration, Inhalation; D000818:Animals; D017638:Asbestos, Crocidolite; D005898:Glass; D008168:Lung / Q000378:metabolism*; D010316:Particle Size; D051381:Rats; D011916:Rats, Inbred F344; D013997:Time Factors
chemical_list: D017638:Asbestos, Crocidolite