The year 1816 was known as the 'year without summer' because of the severe climate abnormalities caused by the eruption of the Dutch East Indies Mount Tambora, which reached its climax in April 1815 and continued to emit fumes and particulate matter for about three more years. Rock erosion due to ageing and climate or, more seldom, landslides are another source of particulate matter. In most circumstances, it is man who is responsible for the formation of particularly polluting dust, and that is a rocketing increase whose entire consequences can only be a matter of speculation, since there is no experience in that matter, except for acute cases. The laboratory generation of nanoparticles, the so-called engineered nanoparticles, is completely different. In that case, the particles are produced on purpose for industrial use and, therefore, have the desired shape and composition. Cement is not a material which is particularly capable of resisting time and bad weather.