The nexus of energy and health : a systems analysis of costs and benefits of ozone control by activated carbon filtration in buildings
Americans spend nearly 90% of their lifetimes indoors, where they receive 50-70% of their exposure to ozone. The US EPA has designated ozone as a hazardous air pollutant and ozone exposure has been linked to respiratory mortality, hospital admissions, restricted activity days, and school loss days. In addition, the most susceptible populations to ozone exposure are children and the elderly, especially if they suffer from an existing respiratory health condition. One possible solution to reduce indoor ozone exposure is to use activated carbon filtration in a building's heating, ventilation, and air conditioning (HVAC) system. In many cases, using commercially available activated carbon filters will have minimal additional capital and energy costs in comparison to standard particle filters. A complex systems model for evaluating the potential costs and benefits of ozone control by activated carbon filtration in buildings was developed as part of this dissertation. The modeling effort included the prediction of indoor ozone concentrations and exposure with and without activated carbon filtration. As example applications, the model was used to predict benefit-to-cost ratios for commercial office buildings, long-term healthcare facilities, K-12 schools, and single-family homes in 12 American cities in five different climate zones. Health outcomes due to reduced indoor ozone exposure were determined using the USEPA methodology for outdoor ozone exposure, which includes city-specific age demographics and disease prevalence. Health benefits were evaluated using disability-adjusted life-years, which were then converted to a monetary value to compare with activated carbon filtration costs. Modeling results indicate that activated carbon filtration during the summer ozone season should be beneficial and economically feasible in commercial office buildings, long-term healthcare facilities, and K-12 schools. The benefits of activated carbon filtration in single-family homes are predicted to be marginal, except for sensitive populations or in cities with high seasonal ozone and high air conditioning usage. Field experiments of activated carbon filters in an operational university laboratory resulted in an average ozone single-pass removal efficiency of 70%. An additional benefit-cost analysis of activated carbon filtration in the laboratory showed that ozone-related health costs were reduced by 62% and fan energy costs were reduced by 21% compared to a baseline condition. Finally, the field study demonstrated that activated carbon filtration for ozone removal could be economically beneficial in buildings with very high ventilation due to reductions in health, energy, and filter replacement and installation costs.