Contents 1. Introduction
To date, researchers have identified over 500 different compounds contained in human breath, some of which are present at parts per billion (ppb) or even parts per trillion (ppt) concentration levels [1]. These molecules have both endogenous and exogenous origins and provide information about physiological processes occurring in the body as well as environment related ingestion or absorption of contaminants [2]. The sources of endogenous molecules are normal and abnormal physiological processes, whereas the sources of exogenous molecules are: inspiratory air, ingested food and beverages, or any exogenous molecule that has entered the body [2]. While the presence and concentration of many of these molecules are poorly understood, many “biomarker” molecules have been correlated to specific diseases and metabolic processes. Such correlations can result in noninvasive methods of health screening for a wide variety of medical conditions.
