Pulmonary dust foci as rat pneumoconiosis lesion induced by titanium dioxide nanoparticles in 13-week inhalation study

Table 1 Incidence and grade of the histopathological findings of the lung and mediastinal lymph nodes after inhalation exposure to TiO2 NP

Exposure concentration (mg/m³) No. of Animals Examined	Male					Female
	0	6.3	12.5	25	50	0	6.3	12.5	25	50
	10	10	10	10	10	10	10	10	10	10
Histopathological findings
Mediastinal lymph node
Deposition of particles	0	3	6**	9***	10***	0	6**	7**	9***	10***
		< 1 >	< 1 >	< 1 >	< 1.5 >		< 1 >	< 1 >	< 1 >	< 1.5 >
Lung
Deposition of particles: air space	0	10***	10***	10***	10***	0	10***	10***	10***	10***
		< 1 >	< 1 >	< 1 >	< 2 >		< 1 >	< 1 >	< 1 >	< 2 >
Deposition of particles: BALT	0	6**	9***	9***	10***	0	9***	9***	8***	10***
		< 1 >	< 1 >	< 1 >	< 1 >		< 1 >	< 1 >	< 1 >	< 2 >
Alveolar multifocal lesion
Agglomeration of particle-laden macrophages: air space	0	0	7**	10***	10***	0	4*	9***	10***	10***
			< 1 >	< 1 >	< 2 >		< 1 >	< 1 >	< 1 >	< 2 >
Destruction of particle-laden macrophages	0	0	0	0	10***	0	0	0	0	9***
					< 1 >					< 1 >
Reactive AEC2 hyperplasia	0	0	1	5**	10***	0	2	4*	9***	10***
			< 1 >	< 1 >	< 2 >		< 1 >	< 1 >	< 1 >	< 2 >
Fibrosis, interstitial	0	0	0	0	0	0	0	0	0	0
Hyperplasia, bronchiolo-alveolar	0	0	0	0	0	0	0	0	0	0

Values indicate number of animals bearing lesions
The values in angle brackets indicate the average severity grade index of the lesion. The average severity grade is calculated with the following equation:
(grade X number of animals with grade)/number of affected animals
Grade: 1, slight; 2, moderate; 3, marked; 4, severe
BALT: Bronchus-associated lymphoid tissue
Significant difference: *, p < 0.05; **, p < 0.01; ***, p < 0.001 by Chi square test compared with the respective controls

ISSN: 1743-8977