Carbon nanotubes: A new industrial revolution with implications on respiratory health?

Recently science and technology have focused on materials having smaller and smaller size, paving the way to the research on nanomaterials and to the development of nanotechnology. In this paper we initially outline the terminology concerning nanomaterials. Then we briefly describe the various types of nanobjects and the reasons behind the booming of research in the field. We subsequently analyze carbon nanoparticles with special focus on Carbon NanoTubes (CNT) and Carbon NanoFibers (CNF) as they fit the definition of 'fiber' issued by the World Health Organization (WHO): length > 5 μm, width < 3 μm, length to width ratio > 3. A fiber might be relevant in pathogenetic terms when its structure allows inhalation and is vehiculated inside human respiratory system. Fibers that are sufficiently long and biopersistent will reach lungs and can lead to local oxidative stress and inflammation. In vivo and in vitro studies have highlighted the potential toxicity of CNT and CNF fibers at a pulmonary level, as they cause damages ranging from genetic modifications to allergic reactions, bronchial remodelling, formation of fibroblastic nodules, carcinogenicity. It is hence compulsory to develop a thorough risk assessment approach dealing with all Health Safety and Environmental (HSE) aspects from all people that might be affected, from workers in production plants to consumers.