Carbon nanotubes introduced into the abdominal cavity of mice show asbestos-like pathogenicity in a pilot study

Abstract

Carbon nanotubes have distinctive characteristics, but their needle-like fibre shape has been compared to asbestos, raising concerns that widespread use of carbon nanotubes may lead to mesothelioma, cancer of the lining of the lungs caused by exposure to asbestos. Here we show that exposing the mesothelial lining of the body cavity of mice, as a surrogate for the mesothelial lining of the chest cavity, to long multiwalled carbon nanotubes results in asbestos-like, length-dependent, pathogenic behaviour. This includes inflammation and the formation of lesions known as granulomas. This is of considerable importance, because research and business communities continue to invest heavily in carbon nanotubes for a wide range of products under the assumption that they are no more hazardous than graphite. Our results suggest the need for further research and great caution before introducing such products into the market if long-term harm is to be avoided.

Length-Dependent Retention of Carbon Nanotubes in the Pleural Space of Mice Initiates Sustained Inflammation and Progressive Fibrosis on the Parietal Pleura

“…injection of long CNTs, an inflammatory response with granuloma formation and fibrosis occurred, whereas there was a negligible response to short and tangled CNTs. 11 As suggested in studies by Kane et al, 12 we concluded that long fibers are retained in the peritoneal cavity as a consequence of their inability to exit through stomata in the diaphragm, through which short fibers can egress. Herein, we developed a method to deliver CNTs into the more relevant pleural space to expose both the pleural mesothelial layers and assessed the inflammatory responses and the likely mechanism by which length-dependent pathogenicity might occur at this key site.…”

“…Short CNTs did not elicit a significant inflammatory reaction at any point examined and, indeed, the results obtained from short CNT-treated mice mirrored those of the vehicle controls. These results suggest that, like asbestos, the toxicity of CNTs for the pleura adheres to the fiber pathogenicity paradigm 11 regarding the role of length in this model of direct pleural exposure.…”

“…Given the resolution of the light microscope, we assume that the visible fibers in the CNT preparation are ropes of intertwined MWCNTs. 11 After injection into the pleural space, we detected an inflammatory response to the long, but not short, CNTs. Also, in a time course with one of the long CNT samples, we found the inflammation elicited was sustained over 1 week at the level seen at 1 day.…”

“…The MWCNT panel comprised four commercially available CNTs and one sample produced in an academic research laboratory (University of Manchester, Manchester, UK) ( Table 1). The MWCNT samples were categorized as long (NTlong1 and NT long2 ), short and tangled (NT tang1 and NTtang2 ), or short and straight (NT short ), based on the manufacturer's description and physical characteristics observed using scanning electron microscopy (SEM), transmission electron microscopy, and light microscopy, as previously described by Poland et al 11 The NT long1 sample (Mitsui & Co Ltd, Tokyo, Japan) was produced by catalytic chemical vapor synthesis using the floating reaction method. The NT long2 sample was produced in an academic research laboratory (University of Manchester, Manchester, UK) using a catalytic vapor discharge method with a ferrocenetoluene feedstock to grow nanotubes from iron catalysts held on a silica plate.…”

Long‐term retention of pristine multi‐walled carbon nanotubes in rat lungs after intratracheal instillation

“…Previous studies indicated that longer fibers could not be fully phagocytosed by macrophages, and induced cytotoxicity [>15 μ m in length (Searl et al ., 1999; Poland et al ., 2008)]. However, the MWCNTs used in the present study were much shorter (average length = 2.4 μ m; 96%, < 0.5–10 μ m 96%; 2.8%, 10–15 μ m; 1.1%, > 15 μ m) than those shown to block phagocytosis.…”