The notorious PM2.5 (2.5 mu m diameter particulate matters) that can reach human lungs, considered as responsible for most deleterious effects of air pollution, are now unmasked. Anthropogenic carbon nanotubes and other carbon nanoparticles have been unambiguously identified as the major components of PM2.5 in alveolar macrophages of Parisian children. Soot and diesel particulate matter have recognized detrimental health effects. However, information on the health effects of anthropogenic carbon nanotubes, which are the main components of PM2.5 found within human alveolar cells, is still lacking. While nanotechnologists are focused on applications with a profit, notably in the field of nano-biomedicine, the health effects of nano-particulate pollutants attract little of their attention. In an attempt to bridge the research gaps between cutting-edge nanotechnologies, environmental studies and biomedical approaches, this opinion paper attempts to inform the nanotechnology community about critical issues related to airborne anthropogenic carbon nanotubes. The question that has to be urgently addressed is whether carbon nanotubes are the main culprit or act only as nano-vectors of carcinogenic polycyclic aromatic hydrocarbons and other toxic gaseous pollutants. (C) 2017 Elsevier Ltd. All rights reserved.