This is the Third annual report of the London Air Quality Network. The report contains information on the continuous air quality monitoring data collected on behalf of thirty-three local authorities in London and two local authorities in adjacent areas by the South East Institute of Public Health during 1995, including a comprehensive graphical summary for all sites in the LAQN and a summary of the number of exceedences in tabular form.

Air Pollution Episodes

The report comments on air quality during the four quarters of 1995, drawing particular attention to the following episodes:

• 3rd - 4th January when nitrogen dioxide levels exceeded the World Health Organization guideline at a number of sites across the Network.
• 1st - 7th May where a typical summer time smog episode occurred and recorded the highest sustained ozone, nitrogen dioxide, sulphur dioxide and PM10 concentrations recorded during 1995.
• During July and August the EPAQS recommended standard for PM10 was exceeded on a number of days at several sites in the LAQN.
• In the final quarter of the year, notable PM10 episodes occurred around the time of Bonfire Night (4th-6th November) with PM10 levels reaching greater than 300 µg/m3 at several sites in the LAQN.
• A nitrogen dioxide episode occurred at the beginning of November, with elevated levels of nitrogen dioxide recorded at several sites, exceeding the World Health Organization guideline.

An initial assessment of mapping techniques has shown the suitability of mapping for the display of annual average nitrogen dioxide concentrations, with an estimated error of between 2 and 25%, as well as peak hour ozone levels to an accuracy of 10%. The provisos for such work are choice of site position/type etc.

These mapping techniques were also applied to an episode day on the 6th May 1995, and used to provide a cross-section of the London ozone plume.