Combined Use of an Electrostatic Precipitator and a HEPA Filter in Building Ventilation Systems: Effects on Cardiorespiratory Health Indicators in Healthy Adults

HEPA filtration in combination with an electrostatic precipitator (ESP) can be a cost-effective approach to reducing indoor particulate exposure, but ESPs produce ozone. The health effect of combined ESP-HEPA filtration has not been examined. We conducted an intervention study in 89 volunteers. At baseline, the air handling units of offices and residences for all subjects were comprised of coarse, ESP, and HEPA filtration. During the 5-week long intervention, the subjects were split into two groups, one with just the ESP removed and the other with both the ESP and HEPA removed. Each subject was measured for cardiopulmonary risk indicators once at baseline, twice during the intervention, and once two weeks after baseline conditions were restored. Measured indoor and outdoor PM 2.5 and ozone concentrations, coupled with time-activity data, were used to calculate exposures. Removal of HEPA filters increased 24-hour mean PM 2.5 exposure by 38 (95% CI: 31, 45) µg/m 3 . Removal of ESPs decreased 24-hour mean ozone exposure by 2.2 (2.0, 2.5) ppb. No biomarkers were significantly associated with HEPA filter removal. In contrast, ESP removal was associated with a −16.1% (−21.5%, −10.4%) change in plasma soluble P-selectin and a −3.0% (−5.1%, −0.8%) change in systolic blood pressure, suggesting reduced cardiovascular risks.