Studying the potential release of carbon nanotubes throughout the application life cycle

Carbon nanotubes (CNT) are expected to be applied in a wide range of industrial applications and consumer products. As a consequence of widespread usage and their supposed persistence against degradation, human and environmental exposure to CNT is likely to increase. There are still many open questions regarding the effects of human or ecological exposure. However, the results of toxicological studies suggest that nanotubes may affect human health. Here we study possible sources of CNT-release on the basis of two case studies. In order to investigate whether and under which conditions CNT may be released from applications, we track the CNT throughout their life cycle as part of two types of consumer products: lithium-ion secondary batteries and synthetic textiles. The findings of the case studies suggest that a release of nanotubes can occur not only in the production phase, but also in the usage and disposal phases of nanotube applications. The likelihood and form of release is determined by the way CNT are incorporated into the material. A considerable part of all CNT used may finally be dispersed somewhere in the technosphere or the environment, e.g. by cross-product contamination during recycling. As long as potential adverse effects of CNT cannot be ruled out, we recommend implementing precautionary measures along the value chain (including the end-of-life treatment) in order to reduce the release and possible negative environmental or human health effects of CNT. (c) 2007 Elsevier Ltd. All rights reserved.