Reduction of personal PM exposure via indoor air filtration systems in Detroit: an intervention study.

The adverse health effects of fine particulate matter (PM < 2.5 μm in diameter [PM]) air pollution are well-documented. There is a growing body of evidence that high-efficiency particulate arrestance (HEPA) filtration can reduce indoor PM concentrations and deliver some health benefits via the reduction of exposure to PM. However, few studies have tested the ability of portable air filtration systems to lower overall personal-level PM exposures. The Reducing Air Pollution in Detroit Intervention Study (RAPIDS) was designed to evaluate cardiovascular health benefits and personal PM exposure reductions via indoor portable air filtration systems among senior citizens in Detroit, Michigan. We evaluated the utility of two commercially available high-efficiency (HE: true-HEPA) and low-efficiency (LE: HEPA-type) indoor air filtration to reduce indoor PM concentrations and personal PM exposures for 40 participants in a double-blinded randomized crossover intervention. Each participant was subjected to three intervention scenarios: HE, LE, or no filter (control) of three consecutive days each, during which personal, indoor, and outdoor PM concentrations were measured daily. For mean indoor PM concentrations, we observed 60 and 52% reductions using HE and LE filters, respectively, relative to no filtration. Personal PM exposures were reduced by 53 and 31% using HE and LE filters, respectively, when compared with the control scenario. To our knowledge, this is the first indoor air filtration intervention study to examine the effectiveness of both HE and LE filters in reducing personal PM exposures.