title: Two-week Toxicity of Multi-walled Carbon Nanotubes by Whole-body Inhalation Exposure in Rats.
abstract: To evaluate pulmonary toxicity of multi-walled carbon nanotubes (MWCNTs), F344 rats of both sexes were exposed by inhalation to 0.2, 1 or 5 mg/m(3) MWCNT aerosol for 6 h/day, 5 days/week for 2 weeks using a whole-body exposure system. At the end of the 2-week exposure period, one-half of the rats were necropsied, and at the end of an additional 4-week postexposure period, the remaining rats were necropsied. MWCNTs were deposited in the lungs of all MWCNT-exposed groups and mostly remained in the lungs throughout the 4-week postexposure period. Granulomatous changes in the lung were found in the rats exposed to 5 mg/m(3) MWCNTs, and these changes were slightly aggravated at the end of the 4-week postexposure period. In the bronchoalveolar lavage fluid (BALF), the numbers of neutrophils, percentages of bi- and multinucleated alveolar macrophages, levels of ALP activity and concentrations of total protein and albumin were elevated in the rats exposed to 1 and 5 mg/m(3) MWCNTs. At the end of the 4-week postexposure period, the values of the BALF parameters tended to remain elevated. In addition, goblet cell hyperplasias in the nasal cavity and nasopharynx were observed in the rats exposed to 1 and 5 mg/m(3) MWCNTs, but these lesions had largely regressed by the end of the postexposure period. Based on the histopathological and inflammatory changes, the no-observed-adverse-effect level (NOAEL) for inhalation of MWCNTs for 2 weeks was 0.2 mg/m(3).
authors.affiliation: Japan Bioassay Research Center, Japan Industrial Safety and Health Association, 2445 Hirasawa, Hadano, Kanagawa 257-0015, Japan.
authors.forename: Yumi
authors.initials: Y
authors.lastname: Umeda
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kasai
authors.forename: Misae
authors.initials: M
authors.lastname: Saito
authors.forename: Hitomi
authors.initials: H
authors.lastname: Kondo
authors.forename: Tadao
authors.initials: T
authors.lastname: Toya
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Aiso
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Okuda
authors.forename: Tomoshi
authors.initials: T
authors.lastname: Nishizawa
authors.forename: Shoji
authors.initials: S
authors.lastname: Fukushima
keywords: inhalation; multi-walled carbon nanotube; pulmonary toxicity; rat; whole-body exposure
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