A considerable number of these particles are deposited in the respiratory tract, depending on their size, density, shape, electric charge and surface properties. The breathing pattern and the health state of the lungs of the individual are also of great influence on the phenomenon. Most particles entering the respiratory tract are expelled through expiration. The entrapment can also occur in the upper respiratory tract where a pathology may originate. A correlation between what had been inhaled and lung cancer was already made, and it is easy to find inside the cancer an important concentration of all the particulate matter inhaled and captured during the patient's life, including urban, industrial and occupational pollution. The massive introduction of sub-micron- and nanosized particles in the environment, in food and in drugs increases the exposure of everyone to these stimuli which can interest the whole body.