A large amount of epidemiological and experimental studies indicate that particulate matter (PM), including, ultrafine particles, have close association with many respiratory and cardiovascular diseases. PM is a complex mixture of organic and inorganic airborne substance, generally composed of a core of ash or carbon, which is coated with organic molecules and transition metals of a broad size range. Between all the transition metals in PM composition, iron is almost always the most abundant in urban and rural areas. As a transition metal, iron is capable of generating reactive oxygen species (ROS) and contributing to oxidative stress, especially in the alveolar epithelium. Oxidative damage and cell death in the alveolar epithelium are the principal mechanisms attributed to PM and asbestos-induced lung injury. We hypothesize that iron content increases the expression of ferritin in alveolar epithelial cells (AEC), which in turn activates p53- dependent cell death pathway.