Factors Influencing Indoor Air Quality in an Urban High-Rise Apartment Building

Abstract

Background: Eighty percent of North Americans reside in cities and many urban dwellers live in high-rise apartments. However, few studies have examined pollutant concentrations in North American high-rise homes. The Ottawa Apartment Study examined factors influencing pollutant concentrations in an urban high-rise apartment building in downtown Ottawa, Ontario. Methods: We recruited apartments on lower, middle, and upper levels of the building. Neighboring units were included to assess vertical and horizontal infiltration. The study measured particulate matter (PM2.5), metals, and volatile organic compounds (VOCs), as well as air exchange. Continuous and integrated measurements were collected at approximately 30 sites including apartments (indoor and balconies), hallways, stairwells and the rooftop. Perfluorocarbon tracers were deployed to provide air exchange rates between indoor micro-environments as well as the outdoor air exchange rate. Building and occupant information were obtained through baseline and daily questionnaires. Results: Metal concentrations were typically higher on balconies and in hallways, while VOC concentrations were higher in apartments. PM2.5 concentrations did not vary significantly between micro-environments. There was some evidence to suggest that ambient concentrations of some metals and VOCs were higher at street level compared with upper level balconies. Outdoor PM2.5 from the balconies and central ventilation system were the major predictors of continuous PM2.5 concentrations in the apartments, with a smaller contribution explained by neighboring units. These results were consistent with the percent contribution based on air exchange measurements. Other factors influencing indoor concentrations (e.g., occupant activities and indoor sources) were similar to those for single family homes. Conclusions: Although many North Americans live in high-rise buildings, little information is available about their residential exposures. This study provides support for identifying strategies to reduce exposure in high-rise buildings.