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EC number: 235-120-4
CAS number: 12070-08-5
Table1: Lung and final body weights of rats exposed to TiO2at
0, 10, 50, or 250 mg/m³.
Final body weights
Lung/body weight ratio
0 mg/m³ (Control)
*Significantly different (p < 0.05) from control group by Dunnett`s test.
Table2: Incidence of main nonneoplastic lesions in the
nasal cavity and trachea
Sq. metaplasia, anterior
Sq. metaplasia, posterior
( ) the number of rats examined is in parentheses
Table3: Incidence of main nonneoplastic lesions in the
nasal cavity and trachea
Aggregates, foamy alveolar
Alveolar cell hyperplasia,
Anaplastic carcinoma, large cell
Squamous cell carcinoma
( ) In parentheses is the number of rats examined
In a combined repeated dose and carcinogenicity study
Titanium dioxide was administered to 400 male and female Crj:
CD(SD) rats by inhalation at nominal concentrations of 0, 10, 50,
and 250 mg/m³ 6 hours a day, 5 days a week for 24 month.
There were no abnormal clinical signs, body weight changes,
or excess mortality in any exposed group. Exposed groups showed
slight increases in the incidence of pneumonia, tracheitis, and
rhinitis with squamous metaplasia in the anterior nasal cavity.
The lung reaction was characterized by dust-laden macrophage (dust
cell) infiltration in the alveolar ducts and adjoining alveoli
with hyperülasia of type II pneumocytes. Exposure to 50 and 250
mg/m³ resulted in dose dependent dust cell accumulation, a foamy
macrophage response, type II pneumocyte hyperplasia, alveolar
proteinosis, alveolar brochiolarization, cholesterol granulomas,
focal pleurisy, and dust deposition in the tracheobronchial lymph
nodes. The pulmonary lesions with massive dust accumulation
appeared to be the result of an overwhelmed lung clearance
mechanism at 250 mg/m³ exposure., Bronchioloalveolar adenomas and
cystic keratinizing squamous cell carcinomas occurred at 250 mg/m³
Based on the findings at the low dose (alveolar cell
hyperplasia, broncho/bronchiolar pneumonia) the concentration of
10 mg/m³ is considered as NOEC for non-neoplastic changes in this
Bronchioloalveolar adenomas and cystic keratinizing squamous cell
carcinoma occurred at 250 mg/m³ TiO2 exposure (the tumours
produced were ultimately characterized as primarily benign
pulmonary keratin cysts (Warheit and Frame,2006)), while no
compound-related lung tumors were found in rats exposed either to
10 or 50 mg/m³. Thus, the concentration of 50 mg/m³ represents the
NOEC for carcinogenicity in rats.
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