Very little data is available on the dangers of carbon nanotubes to the human body. Mostly, this is a result of vast number of variables that come into play. Structure, size ,distribution, surface area, surface charge, and purity, just to name a few, can all have an effect on the reactivity of the carbon nanotubes.
From what is available, though, it is
clear that, nanotubes can, under certain conditions, cross the
cellular membrane barriers. According to one study from the
University of Cambridge, nanotubes can accumulate inside human cells,
causing cell death. Their sharp, needle-like fibrous structure,
raises fears of complications similar to that of asbestos. A recently
publish pilot study supported these fears, showing that mice exposed
to long MWNTs developed length-dependent asbestos-like complications.