Performance of Portable Air Cleaners During a Randomized Crossover Trial in Three Multi-Unit Residential Buildings
ALEXANDER MENDELL, Seungjae Lee, Jeffrey Siegel, University of Toronto
Abstract Number: 298
Working Group: Reducing Aerosol Exposure with Control Technologies and Interventions
Abstract
Portable air cleaners (PACs) can be used to reduce indoor concentrations of fine particulate matter (PM2.5). Reducing PM2.5 concentrations in the home, where most exposure occurs, can potentially improve health outcomes. This study evaluated PACs in 60 apartments in three neighbouring multi-unit buildings in downtown Toronto, Canada using a three-arm randomized crossover design. Participants’ homes were monitored for a total period of three weeks, during which they experienced three experimental conditions: Placebo (noise generated without filtration), Constant (PAC always operating), and Auto (PAC operating when concentrations were measured above 10 μg·m-3). PM2.5 concentrations were continuously monitored, as was PAC operation. Weekly surveys were used to estimate how frequently participants engaged in activities that could affect PM2.5 measurements. Mean concentrations during the Placebo arm ranged from 2 to 527 μg·m-3. Mean concentrations were reduced in 56 homes during the Constant arm, with absolute reductions between –10 and 251 μg·m-3 and relative reductions between –64% and 98%. During the Auto arm, mean concentrations were reduced in 50 homes accompanied by a substantial reduction in PAC runtimes relative to the Constant arm. After adjusting for measured factors and unmeasured differences between homes, the average reduction in mean concentration was found to be 66% (95% CI: 59% – 72%) during the Constant arm and 40% (95% CI: 27% – 50%) during the Auto arm. Much of the variation in weekly concentrations was attributable to behaviours evaluated by the surveys (e.g., smoking, cleaning, and balcony door opening), which also contributed to the large difference in concentrations between homes. This variation is reflected in the wide range of absolute and relative reductions measured across the study population. Interventions targeting air pollutant concentrations should measure and adjust for behaviours and other environmental factors when analyzing and reporting their results.