On August 9, 2013, Particle and Fibre Toxicology published a study entitled “Extrapulmonary transport of MWCNT following inhalation exposure.” The authors report that inhalation exposure studies of mice were conducted to determine if multi-walled carbon nanotubes (MWCNT) distribute to the tracheobronchial lymphatics, parietal pleura, respiratory musculature, and/or extrapulmonary organs. The study states that tracheobronchial lymph nodes were found to contain 1.08 and 7.34 percent of the lung burden at 1 day and 336 days post-exposure, respectively. On average, according to the study, there were 15,371 and 109,885 fibers per gram in liver, kidney, heart, and brain at 1 day and 336 days post-exposure, respectively. The burden of singlet MWCNT in the lymph nodes, diaphragm, chest wall, and extrapulmonary organs at 336 days post-exposure was significantly higher than at 1 day post-exposure. The abstract offers the following conclusions: “Inhaled MWCNT, which deposit in the lungs, are transported to the parietal pleura, the respiratory musculature, liver, kidney, heart and brain in a singlet form and accumulate with time following exposure. The tracheobronchial lymph nodes contain high levels of MWCNT following exposure and further accumulate over nearly a year to levels that are a significant fraction of the lung burden 1 day post-exposure.” Although the authors are affiliated with the National Institute for Occupational Safety and Health (NIOSH), the study includes a disclaimer that the findings and conclusions in the study are those of the authors and do not necessarily represent the views of NIOSH.
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