NIOSH Sub-acute Inhalation Studies with Multi-walled Carbon Nanotubes (MWCNTs) by Vincent Castranova


Title: NIOSH Sub-acute Inhalation Studies with Multi-walled Carbon Nanotubes (MWCNTs)

Speaker: Dr. Vincent Castranova 

Chief, Pathology and Physiology Research Branch, NIOSH, 

CDC Distinguished Consultant, 

Professor, Basic Pharmaceutical Sciences, West Virginia University

Professor, Environmental and Occupational Health, University of Pittsburgh

Date: June 24, 2013
Time: 1:30-2:30pm
Place: 665 Huntington Ave, Building 1, Room 1302, Boston, MA 02115

Abstract:Mice were exposed by inhalation to 5 mg/m3 of MWCNT, 5 hours/day, for up to 15 days. Pulmonary responses, MWCNT translocation from the lung, and lung tumor formation were monitored up to 17 months post-exposure. Initial lung burden was approximately 30 ug/lung. MWCNT, deposited in the conducting airways, were cleared within days. However, MWCNT in the respiratory zone exhibited very slow clearance with a half time in the range of 500 days. Inhalation of MWCNT resulted in a rapid inflammatory response which slowly returned toward control over 168 days post-exposure. In addition, collagen within alveolar walls increased with time post-exposure, progressing to a persistent level significantly above control from 84-168 days post-exposure. At 1 days post-exposure, single MWCNT fibers were found in the tracheobronchial lymphatics, the chest wall, diaphragm, and systemic organs. This translocation continued slowly, increasing the number of extra-pulmonary fibers over the 332 day post-exposure period. Tumor formation was evaluated 17 months after inhalation of MWCNT, using an initiation/promotion model. Although MWCNT alone did not induce significant tumors, inhalation of MWCNT substantially increased tumor formation, size, and carcinogenicity after administration of a DNA damaging chemical, methylcholanthrene, indicating that MWCNT act as a potent promoter.  These results will be discussed in relation to the recent NIOSH REL for carbon nanotubes.