Characterizing and predicting ultrafine particle counts in Canadian homes, schools, and transportation environments : an exposure modeling study with implications in environmental epidemiology

Airborne particulate matter has a negative effect on respiratory health in both children and adults, and the ultrafine fraction of particulate air pollution is of particular interest owing to its increased ability to cause oxidative stress and inflammation in the lungs. In this investigation, our objective was to characterize ultrafine particle (UFP) counts in homes, schools, and transportation environments and to develop models to predict such exposures. A number of important determinants of UFP exposures were identified including ambient temperature and wind speed for transportation environments, outdoor UFPs for classrooms, and electric oven use, cigarette smoking, indoor relative humidity, and volume for homes. In general, our findings suggest that classrooms and transportation environments may be more suitable for UFP exposure modeling than homes. However, large diesel vehicles and in-school UFP sources had a negative influence on model performance, and future studies should include factors such as traffic counts/characteristics, vehicle ventilation settings, and in-school UFP sources to improve the predictive performance of the models presented. Nevertheless, our findings are encouraging in that we demonstrate for the first time the possibility of obtaining UFP exposure estimates for homes, schools, and transportation environments using models based on ambient weather data and other readily available determinant information. As such, similar models may be useful in population-based studies interested in the potential health effects of UFP exposures