title: Patterns of histopathological change determined by the point counting method and its application for the hazard assessment of respirable dust.
abstract: We evaluate the morphometric point counting method (PCM) for qualitatively analyzing pulmonary inflammation and collagen deposits (i.e., fibrosis) in the assessment of the biological hazards of inhaled respirable particles at a realistic dose comparable to that of exposure in the work environment. Rats were exposed by intratracheal instillation to a 2-mg dose, which is close to the estimated overdose at which macrophage clearance is impared, of each of 3 kinds of particulate matter: crystalline silica, crocidolite asbestos, and titanium dioxide. The lung tissue was evaluated at 3 days, 1 wk, and 1, 3, and 6 mo after exposure. Digital images taken of the lung tissue after processing and staining of the lung sections were examined by the PCM under light microscopy. Evidence of inflammation along with progressive inflammatory changes occurred with crystalline silica and crocidolite, which are well-known hazardous particle types. In contrast, lung tissue from rats exposed to titanium dioxide particles demonstrated a decreasing pattern of histopathological change with increasing retention time. Differences in repair patterns of TiO(2) versus crocidolite and silica following the 2-mg dose exposure suggest that the PCM scoring system may be a useful and sensitive tool for qualitatively evaluating the biological hazards of new particle types, for which no toxicological information exists for low-dose exposure, by using the results from assessment of fibrogenic particle types (such as crocidolite and crystalline silica) as well as particle types with low toxicity (such as TiO(2)) as reference points.
authors.affiliation: Department of Environmental Health Engineering, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan. gamisan@med.uoeh-u.ac.jp
authors.forename: Akira
authors.initials: A
authors.lastname: Ogami
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Morimoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamato
authors.forename: Takako
authors.initials: T
authors.lastname: Oyabu
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Kajiwara
authors.forename: Isamu
authors.initials: I
authors.lastname: Tanaka
mesh_terms: D000393:Air Pollutants / Q000633:toxicity*; D000818:Animals; D017638:Asbestos, Crocidolite / Q000633:toxicity; D003094:Collagen / Q000378:metabolism; D003584:Cytological Techniques; D004305:Dose-Response Relationship, Drug; D004391:Dust; D007091:Image Processing, Computer-Assisted; D007442:Intubation, Intratracheal; D008168:Lung / Q000473:pathology*; D008297:Male; D011014:Pneumonia / Q000139:chemically induced / Q000473:pathology; D011658:Pulmonary Fibrosis / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D017751:Safety Management; D012822:Silicon Dioxide / Q000633:toxicity; D016707:Tissue Fixation; D014025:Titanium / Q000633:toxicity
chemical_list: D000393:Air Pollutants; D004391:Dust; D017638:Asbestos, Crocidolite; C009495:titanium dioxide; D012822:Silicon Dioxide; D003094:Collagen; D014025:Titanium