Target Sites: Respiratory

Publisher Summary The lung is both a major pathway for toxic exposures and a vulnerable target organ in its own right. Receiving many liters of airflow per day, it has evolved a variety of host defenses and barriers to protect its structures, especially the delicate alveolar membrane. For that reason, pulmonary toxicology cannot be understood without a firm grasp of host defense mechanisms. Concepts of the respiratory tract as a target organ have changed fundamentally in the last 10 years with the discovery of ultrafine particles and their seeming ability to avoid these defense mechanisms, penetrate the vascular barrier and exert effects outside the lung. As well, the lung is a relatively limited (although not simple) structure which can respond only in a few different ways to a toxic event. The inflammatory effects of ultrafines and of synthetic nano-sized particles were initially unexpected and their study has opened new doors to the investigation of the lung and its responses. Inhalation toxicology is one of the most technically difficult fields of experimental toxicology and the study of particles presents particular challenges.