This significantly updated and expanded new edition presents the scientific foundations of inhalation research essential to the design and conduct of toxicologic studies. It incorporates the major advances that have been made in the field, including recent advances in biology and the rapidly increasing global concerns and studies on particulate air pollution. The Second Edition was motivated by: new developments in the ultrafine particle health effects and concentrated aerosol research advances in understanding postnatal lung growth and the deposition and clearance of inhaled particles new techniques in toxicity testing the explosion of knowledge in the genetic and molecular realms the introduction of a large number of transgenic animal models updated ethical guidelines for animal testing the emergence of aerosol medicine the growing threat of aerosol-related terrorism increased appreciation of nonpulmonary effects of inhaled substances use of medical scanning techniques to study respiratory tract structure the introduction of new inhalation exposure systems the emergence of aerosol concentrators for use in air pollution studies