Chronic Inhalation Studies of Diesel Exhaust Gas Morphological Changes Observed in Intra-and Extra-Pulmonary Organs
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Chronic inhalation of diesel exhaust gas (particulate, 4.9±1.6 mg/m<SUP>3</SUP>) to Fisher 344 strain SPF rats, were carried out up to 2 years, and histopathological findings were studied at 1, 3, 6, 12 and 24 months after the start of exposure and after further 6 months observation without exposure.<BR>The prominent change observed in the lungs of whole-exhaust exposed rat was deposition of the inhaled particulates in the alveolar spaces being taken by alveolar macrophages, associated with proliferation of type II alveolar epitheliums on the alveolar wall and of respiratory bronchiolar epitheliums, which extended towards alveolar ducts and neighboring alveoli.<BR>These proliferative foci of the both kinds of epitheliums appeared in the lungs of 6 months exposed rats, increased their extent in accordance with exposure duration and/or age.<BR>Neoplastic change was found in the lungs of 2 year, whole-exhaust exposed rats in 8 of 19 (42.1%), some of which showed malignancy in 5 of 19 (26.3%).<BR>Two types of lung cancer, adenocarcinoma and adenosquamous/squamous carcinoma were seen, probably representing the two different original cells, type II alveolar epithelium and bronchiolar one.<BR>Malignant lymphoma of the spleen with or without leukemia was the major cause of death after 1 year exposure, and significantly higher rate of this pathological condition was observed in the whole-exhaust exposed and filtered-exhaust exposed groups than in the control group. Histologically, two types of the change were noted, lymph folicle replacing type and red-pulp infiltrating one. The latter developed more to leukemia than the former.<BR>Mammary gland adenoma and subcutaneous fibroma developed more in both of the exposed groups than control one and sarcoma was detected only in the whole-exhaust exposed groups. Multi-tumor bearing rats were found in the two exposed groups but not in the control one.<BR>Further studies under various exposure conditions are required in future.
- 社団法人 大気環境学会の論文
社団法人 大気環境学会 | 論文
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