Housing, indoor air quality, and pediatric asthma in a low income multifamily housing site in Boston - a systems science approach

摘要

Aim. Asthma is a complex disease affecting over 20 million children in the United States, with a disproportionate impact on low income urban populations. The causes of asthma exacerbations are multifactorial, and include exposure to residential indoor environmental contaminants such as allergens and combustion pollutants. Housing characteristics and building interventions (e.g. energy-saving retrofits) impact asthma outcomes by modifying exposures to these indoor environmental contaminants, but quantifying the impact of these changes is challenging given complex airflows, variable pollution source characteristics, and unknown resident behavior. Methods. Using a systems science approach, we applied a pediatric asthma discrete event simulation model (DEM) to evaluate the health impacts of energy-saving building retrofits in a low-income multi-family housing complex in Boston, MA. Indoor environmental conditions and pollutant concentrations (NO2 and PM2.5) were modeled using CONTAM, a multi-zone airflow and contaminant transport analysis program. The resulting air exchange rates and pollutant concentrations were used in conjunction with allergen data to parameterize the DEM for a large simulated population of asthmatic children. Simulations were run for 100,000 children in pre and post retrofit scenarios, with outputs such as pollutant concentrations and pediatric asthma outcomes evaluated over 10 years. Results. Across all simulated households, retrofits led to a 2% increase in PM2.5 concentrations from environmental tobacco smoke, and a 46% and 22% decrease from cooking activities and outdoor infiltration, respectively. NO2 concentrations post retrofit also decreased by 45% and 8% for cooking and outdoor infiltration respectively. Cockroach allergen was reduced 82% post retrofit. These differences are due to a combination of factors, including post retrofit changes in air exchange rates, exhaust fan installation and use, and filter efficiency improvements in the mechanical ventilation system. Post retrofit, we estimated that there were on average 6% fewer days with asthma symptoms, and a 16-19% reduction in serious asthma events including clinic visits, emergency room visits, and hospitalizations. In addition, there were significant reductions in the percentage of children progressing to a more severe asthma classification over the simulation period (from 21% to 8%). Conclusion. Our simulation models indicated that building retrofits targeting energy savings resulted in a decrease in asthma outcomes, although with variable impacts as a function of resident behaviors such as smoking and exhaust fan use. Our study illustrates the utility of a systems science approach to evaluate the complex tradeoffs between building retrofits, indoor air quality and pediatric asthma outcomes.