9 Acknowledgements

This work was funded by the UK Department of the Environment, Transport and the Regions as part of their Air Quality Research Programme.
Monitoring data for London Air Quality Network site at Croydon 2 was provided by the South East Institute of Public Health. The authors would like to thank David Carslaw and Sean Beavers of the South East Institute of Public Health for helpful discussions on the methods for predicting NO2 from NOx concentrations.