Urban scale integrated assessment of options to reduce PM10 in London towards attainment of air quality objectives

Epidemiological studies have indicated that the fine fraction of airborne particulate matter (PM10) is harmful to human health. In order to explore what can be done to attain air quality objectives (AQO) in the London metropolitan area it is necessary to analyse and compare a range of options for reducing emissions from different environmental and economic perspectives. The dominant sources of PM10 in the urban environment today are from traffic; hence abatement strategies must include reduction of traffic emissions. The USIAM model has been developed and used to examine and rank a large number of different kinds of road source emission reduction strategies, and explore their resulting projected concentrations for 2005. Such analysis can aid in deciding which strategy is most cost efficient from both the perspective of attaining present and future AQOs, and of reducing population exposure to harmful PM10 concentrations. The model base case scenario for 1996 has been compared with measured PM10 concentrations in locations throughout the area of study, resulting in error estimates well within the typical ±10% to 50% error often quoted for this kind of air dispersion modelling. This work indicates that the most cost effective strategies from both perspectives analysed are those involving the use of alternative fuels, particularly switching diesel vehicles to LPG and/or CNG. The model also implies that measures involving road user charging appear to be less effective.