On July 30, 2013, Particle and Fibre Toxicology published a study entitled “Distribution and fibrotic response following inhalation exposure to multi-walled carbon nanotubes.” In the study, the authors tested the hypothesis that inhalation exposure to multi-walled carbon nanotubes (MWCNT) produces a fibrotic response and that the response is chronically persistent. Male C57BL/6 J mice were exposed in a whole-body inhalation system to a MWCNT aerosol, and the authors examined the fibrotic response in the alveolar region at up to 336 days after termination of exposure.  The conclusion states: “Despite the relatively low fraction of the lung burden being delivered to the alveolar tissue, the average thickness of connective tissue in the alveolar region increased by 70% in the 336 days after inhalation exposure.  These results demonstrate that inhaled MWCNTs deposit and are retained within the alveolar tissue where they produce a progressive and persistent fibrotic response up to 336 days post-exposure.” While a number of the authors are affiliated with the National Institute for Occupational Safety and Health (NIOSH), the study includes a disclaimer that the findings and conclusions are those of the authors and do not necessarily represent the views of NIOSH.