Grrr people scare mongering! OP go google nanotubes! Normal carbon fibre does not have any nanotubes in it.
I develop composite and nanocomposite technology, first at Uni (phd), then as a research assistant at Uni and now my own company. I am surrounded by bullsh*t about OTT claims of nanotech and also OTT scare mongering.
Of all the particles I use, I am VERY careful with nanotubes in particular. In fact if I can avoid them I will until more studies are done on the safety – mainly their release from failed products. My speciality is on maximising the benefits of nanomaterials and not just sticking them in some resin and slapping a “nano” logo on and hiking up the price and this has benefits in the safety aspect also by modifying the interface. At the moment I won’t release a nanotube material for use by the general public, I will produce stuff for R&D for specific application but until I 100% satisfied I won’t let my products be used outside of strict controls. Asbestos is a terrifying legacy we have been left with and I won’t be a part of repeating that mistake.
But to put things into perspective:
Walking down a busy high street is one of the most dangerous things you can do. Ignoring the possibility of being mugged, run over etc you are breathing in millions of nanopartciles and other nasty substances and organic material coming from vehicle exhausts, drains and other people.