Schematic of the pulmonary bacterial clearance model. We established a murine pulmonary infection model of Klebsiella pneumoniae (K.p.) to determine if pulmonary bacterial clearance is impaired by Cu nanoparticle exposure using two different exposure modes, inhalation and intratracheal instillation. Following both sub-acute inhalation (4 hr/d, 10 d; 3.5 mg/m3; 32 μg cumulative dose) and intratracheal instillation (24 hr post-exposure; 3, 35, 100 μg/mouse), mice were intratracheally challenged with K.p. bacteria at a dose of 1.4 ± 0.1 × 105 CFUs/mouse.