This observational study will measure the effects of daily variations in outdoor air pollution levels on asthma symptoms, lung function, markers of inflammation, and heart rate variability. Currently we are seeking volunteers with physician-diagnosed severe but well-controlled asthma who are between the ages of 18 and 75. Study participants will wear heart monitors for five 24-hour periods and will keep diaries of their activities and asthma or respiratory symptoms. Ambient air will be assessed through state operated monitoring stations. Compensation is provided.
