The role of particulate matter in exacerbation of atopic asthma

Increasing evidence shows that elevated levels of particulate matter (PM) c an exacerbate existing asthma, while evidence that PM can promote the induc tion of asthma is limited. PM in ambient air has been associated with incre ased emergency room visits and medication use by asthmatics. Controlled hum an exposure studies of acid aerosols suggest increased responses among adol escent asthmatics. Increased ambient and indoor levels of bioaerosols (e.g. , house dust mite, fungal spores, endotoxin) have been associated with exac erbation of asthma. Environmental Protection Agency (EPA) studies focus on the effects of exposing humans and animal models to a combination of variou s PM samples (e.g., diesel exhaust particles, oil fly ash) and allergens (e .g., house dust mite, ovalbumin). These research efforts to understand the mechanisms by which PM exposure can promote allergic sensitization and exac erbate existing asthma concentrate on the role of transition metals. Expo s ure of animal models to combined PM and allergen promotes allergic sensitiz ation and increases allergic inflammation and airway hyperresponsiveness. E xposure of healthy human volunteers to emission source PM samples promotes inflammation and increased indices of oxidant formation correlating with th e quantity of transition metals in the samples. Results of these studies su ggest that transition metals in ambient PM promote the formation of reactiv e oxygen species and subsequent lung injury, inflammation, and airway hyper responsiveness leading to airflow limitation and symptoms of asthma. Copyri ght (C) 2001 S. Karger AG,Basel.