ABSTRACT
It is difficult to imagine a material that, when inhaled in a liquid or solid aerosol form, does not have the potential for producing lung disease. Thus, most commonly encountered substances are now associated with air contamination criteria for protecting people from overexposure. Most air contamination criteria relate to the total airborne mass per unit volume of air. Unfortunately, the accurate measurement of such a total airborne mass concentration is usually impractical but, even if successful, it would be inadequate for predicting the pathological effects of inhaling most aerosols. The reason for this is that the human respiratory tract does not uniformly sample airborne particles of various sizes. The application of information on how the aerodynamic size of aerosols determines the inhalability (the fraction of airborne mass that actually enters the nose or mouth during inhalation) and the regional deposition of particles within the respiratory tract can lead to acquiring size-selective samples that more closely relate to aerosol inhalation hazards. Size-selective aerosol samples may be defined as reliably collected aerosol fractions which are expected to be available for deposition in the various subregions of the respiratory tract.
