Table 1 Lung histology in uninfected mouse lung tissue 72 h after intranasal instillation in viv o of either phosphate buffered saline (PBS) or ultrafine carbon black (2 × 500 μg).

Minimal diffuse alveolar microvascular congestion

Moderate to marked black particle inclusions - mainly within alveolar macrophages associated with moderate to marked secondary pneumonic reaction

Normal

Moderate sporadic black particle inclusions within bronchiolar epithelium

Minimal sporadic alveolar macrophage and neutrophil foci

Marked diffuse alveolar microvascular congestion

Marked multi-focal leucocyte infiltration of airway walls - mainly neutrophils and mononuclear cells

Marked diffuse pneumonitis with consolidated microvascular leak

Moderate multi-focal hypertrophy of transitional airway epithelium

Moderate to marked focal hypertrophy of mesothelium