Carbon nanotubes induce granulomas but not mesotheliomas.

BACKGROUND Different types of carbon nanotubes may represent toxic hazards due to their size distribution and massive surface area. They may adsorb other toxic agents that can consequently be transported into the body. Hence the aim of this study was to confirm or reject the hypothesis of carcinogenicity of two types of carbon nanotubes. MATERIALS AND METHODS Well-defined single-walled and multi-walled carbon nanotubes were studied in a specific animal model for mesothelioma induction. RESULTS Short-term pilot studies were published on the asbestos fibre-like mesothelioma-inducing effects of carbon nanotubes based on the proposed mechanistic correlation on health effects of fibres of the same size. Our results with a simple in vivo, peritoneal exposure model refute such an interpretation. The present studies with rats indicate that early granuloma formation does not lead to the development of mesotheliomas during chronic exposure of peritoneal mesothelium to either single- or multi-walled carbon nanotubes of varied size. CONCLUSION Due to the limited toxicity data on carbon nanotubes, these results may be particularly important for risk assessment purposes.