A new study has found that carbon nanotubes—if inhaled—could be as dangerous as asbestos. This is not only problematic for a future of semiconductors that would like to exploit the technology, but the goods already on the market now that use nanotubes in composite mixtures, like baseball bats and tennis rackets.
To test the nanotubes, one lab injected the material into human-lung-like rat stomach lining and found the area inflamed after a week. So at this point we're fairly certain that inhaling nanotubes would be bad news. What we aren't certain about is whether or not nanotubes in their commercial form (like baseball bats) could ever become breathable, or even airborne in the first place.