How to Use A Spatial–Temporal Population Exposure Model—Views of a Local Authority

Abstract

MS8 Symposium Title: Population Exposure Modeling and Urban Air Quality Management in Europe Symposium Organizers: Otto Hänninen and Matti Jantunen. MS8-01 The EXPAND model has been developed for the determination of human exposure to ambient air pollution in an urban area. The model is able to treat various environments such as homes, workplaces, and various traffic modes. The latest version includes also various population subgroups (eg, adults, elderly, and infants). The model combines the predicted hourly concentrations of pollutants and the information on people's time use at different locations. The computed results are processed and visualized using the geographic information system, which illustrates, eg, the most problematic areas and time periods. We have used this model to evaluate the population exposure to NO2 and PM2.5 in the different scenarios of a transportation system plan. From a local authority's point of view, there are some open questions that need to be addressed. Compared with dispersion models, the exposure model requires a lot of additional input data, which is difficult to get. Up-to-date time-use studies are not readily available; they do not cover all important subgroups such as infants, and they are not planned to give information on the locations where people spend their time. The evaluation of exposure is hindered due to the lack of information on indoor/outdoor ratios. At present also, the information on the exposures in different traffic modes is inadequate. The advantage of EXPAND model is that it describes the spatial and temporal variation of population exposures over the whole metropolitan area. On the other hand, the interpretation of the results for decision- and policy-makers is difficult because it does not give information on personal exposures, which is needed for the evaluation of health effects. On the other hand, the personal exposure models, in which individuals are followed for the whole day, are complex in evaluating the exposures for the whole metropolitan area, and the probabilistic models do not give the spatial and temporal variation of the exposures. Finally, the air-quality legislation is based on the limit values that are given for the concentrations of pollutants in ambient air, not for exposures. Thus, the abatement strategies tend to aim at reducing concentrations, even if it would sometimes be more cost-efficient to reduce the exposures.