Pulmonary response to impaired lung clearance in rats following excessive TiO/sub 2/ dust deposition
Rats were exposed to TiO/sub 2/ by the inhalation route at concentrations of 0, 10, 50, or 250 mg/m/sup 3/ for 6 hr/day, 5 days/week for 2 years. Lung weights of rats at 10 mg/m/sup 2/ were within normal limits after 2 years exposure. Lung weights increased significantly after 6 months at 50 mg/m/sup 3/ and after 3 months at 250 mg/m/sup 3/. After 2 years exposure, TiO/sub 2/ retention in dried lung was 3.1% at 10 mg/m/sup 3/, 16.9% at 50 mg/m/sup 3/, 28% at 250 mg/m/sup 3/. Lung clearance mechanisms appeared to be overloaded at 250 mg/m/sup 3/. Dust particles were retained in the lung in a dose-related fashion, but there was no significant difference in lung clearance rate between 10 and 50 mg/m/sup 3/. Lung response at 10 mg/m/sup 3/ satisfied the biological criteria for a nuisance dust, while adverse effects resulting from gradually accumulated particles (8.1%, 67.7 mg per lung) were found after 1 year of exposure to 50 mg/m/sup 3/. Cholesterol granulomas were developed with degenerative foamy dust cells at 50 and 250 mg/m/sup 3/ after 1 year or exposure. After 2 years exposure at 250 mg/m/sup 3/, bronchioloalveolar adenomas occurred in the alveoli showing type II pneumocyte hyperplasia, while cystic keratinizing squamous carcinomas were developed from squamous metaplasia of alveoli showing bronchiolarization in the alveolar duct region.
- Research Organization:
- E.I. du Pont de Nemours and Co., Inc., Newark, DE
- OSTI ID:
- 5144010
- Journal Information:
- Environ. Res.; (United States), Vol. 41:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
TITANIUM OXIDES
CARCINOGENESIS
LUNG CLEARANCE
RETENTION
TOXICITY
ADENOMAS
CARCINOMAS
CHRONIC EXPOSURE
DEPOSITION
DOSE-RESPONSE RELATIONSHIPS
DUSTS
EXPERIMENTAL NEOPLASMS
LUNGS
MACROPHAGES
PARTICULATES
RATS
SIZE
ANIMAL CELLS
ANIMALS
BODY
CHALCOGENIDES
CLEARANCE
CONNECTIVE TISSUE CELLS
DISEASES
EXCRETION
MAMMALS
NEOPLASMS
ORGANS
OXIDES
OXYGEN COMPOUNDS
PARTICLES
PATHOGENESIS
PHAGOCYTES
RESPIRATORY SYSTEM
RODENTS
SOMATIC CELLS
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
VERTEBRATES
560305* - Chemicals Metabolism & Toxicology- Vertebrates- (-1987)