C 2014 American Chemical Society Instillation versus Inhalation of Multiwalled Carbon Nanotubes: Exposure-Related Health Effects, Clearance, and the Role of Particle Characteristics

ue to their extremely small size, air-borne engineered nanomaterials (ENMs) can reach the deepest por-tions of the lung when inhaled and poten-tially move into systemic circulation.1 One such ENM2 is the carbon nanotube (CNT), which is highly marketable because of its unusual tensile strength, thermal conductivity, electrical properties, and broad commercial applications. Of particular concern, CNTs have similar properties to disease-causing asbestos fibers (e.g., highaspect ratio, large surfacearea, and poor solubility). Toxicology studies using rats and mice have shown that exposure to multiwalled carbon nanotubes (MWCNTs) re-sulted in not only pulmonary inflammation * Address correspondence t