Inhalation of multi‐walled carbon nanotubes affects lung resistance and compliance and evokes airway hyperreactivity to methacholine in rats (660.1)

Abstract

The incorporation of carbon nanotubes into new materials has raised concerns about their potential hazards to workers exposed during manufacturing. In animals, following pharyngeal aspiration, i.t. instillation and inhalation exposures to MWCNT, airway inflammation and lung fibrosis have been reported. However, the effects of inhalation of MWCNT on pulmonary function and reactivity to inhaled methacholine (MCh), a bronchoconstrictor, have not been studied. Therefore, we investigated whether inhaled MWCNT affect lung resistance (RL) and dynamic compliance (CDyn), and/or reactivity to inhaled MCh aerosol. Male rats were exposed for 6 h to filtered air or 5 mg/m3 of aerosolized MWCNT (MWNT‐7; Hodogaya Chemical Co.; 20 ‐ 50 walls; median length, 3.86 μm; mean width, 49 nm; mass median aerodynamic diameter, 1.5 μm; particle count aerodynamic diameter mode, ~0.4 μm). Basal RL and CDyn were measured 18 h and 7 d after the end of exposure, and responses to increasing concentrations of MCh were obtained. Eighteen h after exposure basal RL was increased and basal CDyn was decreased; 7 d after exposure basal RL and CDyn were not changed. Reactivity to MCh (RL) was increased and CDyn responses were decreased at 18 h but not 7 d after exposure. The results indicate that lung function and airway reactivity changes occur acutely, but that these changes subside over time following a single MWCNT inhalation exposure.Grant Funding Source: Supported by NIOSH