Impact of residential building regulations on reducing indoor exposures to outdoor PM2.5 in Toronto

We conducted a cost benefit analysis of residential building regulations on reducing the exposure to outdoor PM2.5 in Toronto. By combining a combined mass balanced model, a time-weighted activity exposure model, epidemiological based concentration-response, and monetary valuation method, various morbidity and mortality outcomes were estimated for different residential building scenarios. It was found that retrofitting residential buildings to comply with minimum building code regulations can save US$2.3 billion/year in health care. Citywide adoption of R2000 standard from current housing corresponds to US$3.8 billion/year. Use of mechanical HVAC systems, improved filtration (with recirculation) and tighter building envelope (lower infiltration rate) were noted as the key factors that influence PM2.5 exposure reductions and health impacts. Estimated costs of retrofitting existing homes to adopt these regulations were about 2.3-2.9 times of the health savings. Citywide use of filters with better efficiency is anticipated to lead to annual health savings significantly exceeding the capital and running costs.