Carbon nanotubes: responsible use and meaningful risk management

The purpose of this White Paper is to give a larger audience of technologically interested people an impression of what carbon nanotubes are, what they are used for and what risks might be connected to their application. Therefore, we have collected several short contributions from our colleagues to shine flashlights onto the topic. For a scientist in basic research, carbon nanotubes are exciting objects to study fundamental phenomena in solid-sate physics, and the focus is laid on one individual tube; for engineers in materials technology carbon nanotubes belong to the family of fine powders (dust, soot, carbon black, sand, silica, nanocellulose, asbestos, fillers and additives for composites - and "asbestos" immediately rings the alarm bell for health hazards!).
As for applications, we have to distinguish between applications of a few nanotubes, as in electronics and sensing (Düsberg, Section 4), of a few grams or kilograms: actuators (Heldt, Section 5), metal matrix composites (Glanz, Section 6), heaters (Nemec, Section 7), and of tons and kilotons: composites (Moon, Section 8), Batteries (Glanz, Section 9 - Jalowy, Section10 - Jang and Börszönyi, Section 11).
If only a few nanotubes are used, as in basic research or in electronics, nanotubes are certainly dan-gerous, but usually other hazards dominate (poisonous dopants, X-rays, electron beams etc.). But even in mass applications (batteries), the specific risk of nanotubes is only one of several risks (e.g. look at the table in Jalowy’s contribution in Section 10: NMP, NMC, NCA, CNT: they are all dangerous, not only CNTs).
Compared to asbestos fibers, carbon nanotubes have the advantage of being degradable: There is chemical, biotic, enzymic and bacterial degradation of carbon nanotubes (Ata et al., Section 13). This is also an advantage when comparing nanotube batteries to classic lead batteries: Nanotubes can be removed from waste water by bleaching agents, lead cannot.
In Section 17 (Sarkas et al.) a device is described which allows to monitor the nanotube content in a general mixture of carbon dust (as often found in exhaust gases of labs, workshops, factories and production lines). Mayer-Plath et al. (Section 16) tell us what happens on a cellular level if we inhale dust particles and fibers, Münzing (Section 15) reviews the present state of registering graphene at the European Chemical Agency (ECHA), Section 12 (Fraunhofer ITEM) reports on in vitro and in vivo studies of the carcinogenic potential of carbon nanotubes (BMBF Project CarboTox), and in Section 14, Hubrich explains the safety precautions taken at Fraunhofer IPA when working with carbon nanotubes.
We hope that this White Paper will help to spread the knowledge on benefits and risks of carbon nanotube materials. Don’t hesitate to contact us, if you feel we can help you with further information.