This is the fifth report of the London Air Quality Network (LAQN), which summarizes the air pollution climate of London during 1997. During 1997 the LAQN gained new sites in Greenwich, Mole Valley and Marylebone Road. The neighbouring Kent Air Quality Monitoring Network was also created, widening the perspective available on air quality in London and the south-east.

The results for nitrogen dioxide, carbon monoxide and PM10 were significantly influenced by two pollution episodes in the autumn, which are discussed in some detail in Chapter 2. During 1997 almost all sites in the LAQN exceeded the National Air Quality Strategy objectives for these pollutants. The annual average objective for nitrogen dioxide was exceeded at all Greater London sites, except Sutton 3, and the maximum hour objective was exceeded at around half of the sites. The objective for PM10 was exceeded at all LAQN sites by a large margin. The objective for carbon monoxide was exceeded at many central and roadside locations. All sites measuring sulphur dioxide in Greater London were below the objective and the only LAQN site to breach the sulphur dioxide objective was Castle Point, located on Canvey Island. The majority of ozone monitoring sites exceeded the objective.

New insights were also gained at the Marylebone Road 'Super Site' where a comprehensive suite of monitoring methods are being used. The site is an important resource, which has already permitted some interesting comparisons to be made between different monitoring methods. The site is also significant from the point of view of its location, as busy roadside locations will become increasingly important in the next few years as ambient concentrations decrease.

The Environmental Research Group made significant progress in the development of tools for the assessment of air pollution, as required by the Local Air Quality Management process. In particular, new methods have been developed for the assessment of the concentrations of nitrogen dioxide and PM10 at both background and near-road locations. A key factor in the development of these techniques has been the use of ambient monitoring data from the LAQN, which provides a unique resource in the UK. It is only because of the density and number of sites in London that these techniques can be developed specifically for the capital. Increasingly, ambient monitoring data are being used in an 'active' sense rather than being used simply as a check on whether a location exceeds objectives. The active use of these data is an important development, which would not have been possible even a few years ago. These techniques have many attractions, not least of which is their relative simplicity and transparency, which are of key importance in the air quality management process.