Carbon nanotubes (CNTs) can be inhaled and thus deposited in the lungs. Studies have shown that specific CNTs, namely those that are long (10-20 µm), thin (5-10nm), needle-shaped and non-soluble (biopersistent), can promote the formation of lung diseases and show behaviour similar to that of asbestos fibres. Short or long fibres that are not needle-shaped will not, however, induce inflammatory changes, no more than a single carbon particle would. Comprehensive life-cycle analyses regarding the potential environmental benefits arising from the use of CNTs (such as resource savings owing to more light-weight materials) are not available to date. At present, the production of CNTs still requires a high energy input, which offsets any potential environmental benefits. Their high reactivity and ability to transport other substances raises concerns about a possible ecotoxicity of CNTs. The data available are still restricted in scope, and the discussion of results is controversial. Given the lack of reliable data on exposure, an adequate assessment of health and/or environmental risks is not possible for the time being.
At present, specific regulations for CNTs or other nanomaterials exist neither in the laws governing chemicals nor in regulations for occupational health and safety. Hence, the relevant authorities recommend that the precautionary principle should be applied and measures taken to avoid exposure or keep it as low as possible.