Figure 2

Enhanced darkfield image of the transition region between terminal bronchiole and first alveolar duct bifurcation at 168 days after exposure to MWCNT. The large arrow in this micrograph indicates a cluster of MWCNTs (white fibers) in the ridge of the first alveolar duct bifurcation. Smaller arrows indicate some of the numerous singlet and small MWCNT structures distributed throughout the alveolar septa of this critical transition region between conducting airways and gas exchange regions of the lungs.