The purpose of this report is to review air quality in London during the 4th quarter of 2001 and to report detailed measurement results for the year ending 31st December 2001.

Five new monitoring sites joined the London Air Quality Network (LAQN) during the quarter;

• Brent 3
• City of London 1
• Lambeth 2
• Lambeth 3
• Mole Valley 3

The most notable air pollution event of the 4th quarter of 2001 was the PM10 associated with Guy Fawkes Night.

Measurements during the 12 months ending 31st December 2001 have been compared to the Air Quality Strategy (AQS) Objectives:

• The Redbridge 2 kerbside site exceeded the CO objective.
• The annual mean NO2 objective was exceeded at all kerbside and roadside measurement sites except Havering 1. This objective was also exceeded at background locations in inner London and at the outer London sites Heathrow and Waltham Forest 1.
• The incident based NO2 objective was exceeded at the kerbside sites Marylebone Road, Redbridge 2 and Redbridge 3, and at the roadside sites Brent 2 and Kensington & Chelsea 3.
• Widespread exceedences of the O3 objective were measured in outer London and at sites in the Home Counties.
• The incident based PM10 objective was exceeded at the kerbside sites Marylebone Road and Rebridge 3, and at the roadside sites Bexley 4, Camden 3, Enfield 2, Enfield 4, Hounslow 3, Lambeth 1, and Redbridge 4.
• The annual mean PM10 objective was exceeded at Marylebone Road and Enfield 4.