The respiratory system, as illustrated inFigure 1, continually exchanges gases, taking inoxygen from the environment and replacing itwith carbon dioxide, but as most environmentsare impure, pollutants, too, enter the body by wayof the mouth and nose. The lung parenchyma(main tissue) and respiratory passages contain nofiltering system, and once breathed in, pollutantsof various sizes pass into different parts of therespiratory system. In general, larger particlesland, by way of direct interception and impaction,along the upper airway passages, including inthe nose, mouth, and pharynx, which Figure 1shows. Asbestos fibers are an example ofrespirable particulates that become lodged inthe upper airway