Exposure to traffic generated pollutants, especially among people living along busy roads, has been associated with increased risk of respiratory disorders among children and adults as well as with overall mortality.^1–5 Simple exposure indicators (self report, distance from pollutant sources, traffic density) and more complex and integrated models that take into account demographic factors and land use by means of geographic information system (GIS) based technology^6–8 have been employed in epidemiological studies.

As has happened in the past in occupational epidemiology, environmental epidemiologists are trying to develop more accurate methods for assessing air pollution exposure.⁹ As a result, comparing the different methods available is of great interest. In this issue, Heinrich et al have compared parental report of traffic intensity near homes (cars, trucks, buses, and mopeds on the street of residence and other nearby streets) with a combination of air pollution measures (fine particle mass, filter absorbance, and nitrogen dioxide) and GIS based modelling in two different European locations (the Netherlands and Munich, Germany).¹⁰ They found that predicted exposure estimates for air pollutants increased with self reported traffic level in Munich and in urban areas of the Netherlands. However, agreement …