1 Supplemental methods

The Danish AirGIS modelling system: input data and application. Input data for the AirGIS system were obtained from various sources and were integrated into the model. A GIS-based road network, including construction year and traffic during the period 1960 onwards, was developed, and a database on emission factors for the Danish car fleet, with data on light- and heavy-duty vehicles back to 1960, was built and entered into the emission module of the street pollution model. The national topographic GIS database of buildings was supplemented by the construction year and building height from the national Building and Dwelling Register, which provided the correct street and building geometry for a given year at a given address. The geocode of an address reflects the location of the front door, usually within 5 m. Air pollution is calculated for 2 m height at the façade of the address building. The dispersion modelling system has been used in several large epidemiological studies in Denmark [1-6], and the street pollution model, OSPM, which is a core part of AirGIS, has been used in many other countries [7]. The AirGIS modelling system cannot provide reliable estimates of past particulate matter concentrations because the necessary data on previous urban background concentrations an