"Earlier today, at the annual meeting of the Society of Toxicology, NIOSH researchers reported preliminary findings from a new laboratory study in which mice were exposed by inhalation to multi-walled carbon nanotubes (MWCNT). The study was designed to investigate whether these tiny particles have potential to initiate or promote cancer.
By “initiate,” we mean the ability of a substance to cause mutations in DNA that can lead to tumors. By “promote,” we mean the ability of a substance to cause cells that have already sustained such DNA mutations to then become tumors. "
See the NIOSH Science Blog