Micrographs of illustrating distribution of MWCNTs in the lungs 1 day after termination of inhalation exposure. Examples of MWCNTs (arrows) in the three highest initial sites of deposition, alveolar macrophage, alveolar interstitium and bronchiole, are illustrated by the light micrograph of A. A MWCNT (white fibers)-loaded macrophage is shown in the enhanced darkfield image of B. The FESEM of C shows a section through a MWCNT-loaded alveolar macrophage. The enhanced darkfield image of D shows a MWCNT penetration of the visceral pleura (arrow) and other MWCNTs in the alveolar interstitium (tailless arrows). MWCNT in an alveolar macrophage indicated by smaller arrow.