We are testing the following two hypotheses: 1) Peaks in hourly exposures to airborne particulate matter (PM) of outdoor origin will be more closely associated with acute asthmatic responses to particles than 24-hour average exposures in susceptible individuals; 2) Personal exposure to PM, and estimated particle dose to the lungs, will be more closely associated with daily asthma severity than standard outdoor particle concentrations measured as 24-hour averages at governmental monitoring sites.

We are testing the following two hypotheses: 1) Peaks in hourly exposures to airborne particulate matter (PM) of outdoor origin will be more closely associated with acute asthmatic responses to particles than 24-hour average exposures in susceptible individuals; 2) Personal exposure to PM, and estimated particle dose to the lungs, will be more closely associated with daily asthma severity than standard outdoor particle concentrations measured as 24-hour averages at governmental monitoring sites. Toxicological data for asthma exacerbations from particulate matter (PM) suggests that particle deposition in the lower respiratory tract can cause inflammatory and lung function changes suggestive of asthma pathology. There is now a scientific need to explain epidemiological findings of ambient PM effects on asthmatics at mass concentrations below what is expected (from toxicological data) to be harmful. One possibility is that study participants are encountering unmeasured short-term excursions of particle mass levels capable of inducing adverse reactions in the lung, but this effect is only captured somewhat by the regulatory standard of 24-hour averages. Our research in southern California is vital to the current controversy regarding regulatory standards given that a health-based scientific rationale for any specific PM averaging time is not established.

1) physician-diagnosed asthma, at least a 1 yr. history, including episodic symptoms of wheezing, cough and dyspnea; 2) mild to moderate severity of asthma: i) a history of at least several weeks during the warm seasons (Mar-Oct) during which the subject required regular daily use of prescribed prophylactic asthma medications; & ii) asthma exacerbations at least 2 days/week requiring as-needed bronchodilators during an extended period of 1-2 warm season months; 3) age from 9-18; 4) home, school or work addresses in Alpine, CA area; 5) no history of smoking by the subjects and no person smoking in the subject?s home.