Development of the DIDEM model: comparative evaluation of CALPUFF and SPRAY dispersion models.

In the last years, research efforts have been addressed on the effects of single and multiple pollutants on human health, in particular in densely populated areas. Modelling tools, integrating atmospheric science with the latest evidence available from air pollution epidemiology and exposure science, represent a valuable support to health impact assessment. This article considers the latest developments of the DIATI Dispersion and Externalities Model (DIDEM). To extend DIDEM’s scope of analysis, the inte- gration with different pollutant dispersion models was recently implemented. Particularly, in this arti- cle, a comparative evaluation between CALPUFF (California Puff) Lagrangian puff model and SPRAY Lagrangian particle model is presented. To help reaching this objective, the case study of Turin’s district heating system, presented in previous publications, was re-considered and deepened. CALPUFF and SPRAY models were compared on the same emission scenario. NOx and total PM concentrations result- ing from the simulations were of the same magnitude, with some difference in the spatial distribution. Total health damage costs differed between 8.5% and 9.7%, with lower values corresponding to SPRAY simulations. This difference mostly corresponds to the different spatial distribution of pollutant con- centrations which, in turn, correspond to different exposure levels. The possibility of selecting different modelling tools extends the usability of DIDEM to a larger set of applications, including a wider scope of application and a larger range of users. The results provide important information in the view of the characterization of the overall uncertainty of the impact pathway approach methodology.