Bike-workshop staffers who have been blithely trimming carbon fibre steerer tubes may wish to take precautions in the future. Researchers now believe that certain carbon nanotubes could pose the same cancer risk as asbestos. The Medical Research Council's toxicology unit found that both long CNTs and long asbestos fibres induced mesothelioma in the pleural cavity of mice.
According to a study published in Current Biology "carbon nanotubes are similar to asbestos in terms of their fibrous shape and biopersistent properties and thus may pose an asbestos-like inhalation hazard.”
However, the toxicology unit's director Professor Anne Willis, speaking to European Pharmaceutical Review, stated that not all CNTs pose an asbestos-like risk: “The immune system does a good job of recognising shorter, thicker or tangled up nanotubes. Special cells break down these types of fibre and clear them out of the body, so not all nanofibres pose a hazard.”
Road.cc says "this begs the question of what kinds of nanotubes are likely to be found in bike parts."
Benedict Pfender told Road.cc: “There’s still a lot of issues with large scale production of CNTs and controlling them for production. In terms of CNT use, it seems the only real application is as a toughener/strengthener for the matrix material in carbon composites – however it’s not super clear how widespread this is in the industry.
“However, we must also consider the safety of working with carbon fibre itself. Obviously cutting a steerer generates some dust – though I would be inclined to say that it’s not likely to be of an amount that will be of particular concern.
“All of these health hazards are about exposure and increasing risk with increasing exposure. Sawdust (wood) can be hazardous if you breathe in enough of it. Cutting a steerer is not really going to generate much debris – just do it in a well ventilated environment.”