PROJECT 7. Co-Exposure of Human Subjects to Concentrated Ambient PM and Gaseous Pollutants.

PI: T. Gordon; Co-I.: J. Fine; Consultants: L.C. Chen and J. Reibman.

Our objective is to determine whether co-exposure to ozone influences the acute cardiopulmonary effects from controlled exposures to particulate matter (PM) in human volunteers. Co-exposure of human subjects to PM and O₃ is likely to produce changes in pulmonary function and inflammation that are greater than that from exposure to PM or O₃ alone.

A pilot study, funded by the Health Effects Institute, is currently underway, examining the adverse effects of exposure to concentrated ambient PM alone in normal and asthmatic subjects. The experiments proposed here will build on these studies by enabling the controlled testing of exposure to concentrated ambient PM with and without O₃ in normal and asthmatic subjects. Normal subjects (n = 12, ages 18 to 45) will be exposed for 2 hours by face mask to filtered air, 150 µg/m³ concentrated ambient PM alone, 0.12 ppm O₃ alone, or 150 µg/m³ concentrated ambient PM and 0.12 ppm O₃ together. Biochemical and cellular parameters in sputum, coagulability indices in blood, electrocardiogram and heart rate/heart rate variability changes, and pulmonary function will be measured up to 18 hours after each exposure. Careful chemical characterization of the exposure atmospheres will insure that day-to-day variability in PM composition will be considered in the interpretation of results. Asthmatic subjects (n = 12) will be exposed to test atmospheres as described above. The same endpoints will be examined in addition to studying the TH2 cytokine profile and eosinophil-derived products in recovered sputum. Strict inclusion/exclusion criteria for study participants will ensure that the variability of asthmatics is kept to a minimum, and that medication usage is controlled during the study.

It is anticipated that concentrated ambient PM alone will not produce statistically significant adverse effects in healthy individuals. This project, however, will address the potential synergism that may occur between concentrated ambient PM and O₃. The study of human subjects with pre-existing cardiac or pulmonary disease will be an important focus. It is expected that our experiments will demonstrate that asthmatics are made more susceptible to the adverse effects of PM by co-exposure to O₃, suggesting that the health effects of very low concentrations PM on this sensitive subpopulation should be considered in the setting of PM air quality standards.