The purpose of this report is to review air quality in London during the 1st quarter of 2002 and to report detailed measurement results for the year ending 31st March 2002.

Two new monitoring sites joined the LAQN during the quarter.

Widespread ‘moderate’ ozone was measured during March for the first time by the LAQN.

Measurements during the 12 months ending 31st March 2002 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. This objective was also exceeded at background locations in inner London and at the outer London sites Barnet 2, Hillingdon, Hounslow 2, Heathrow and Waltham Forest 1.
• The incident based NO2 objective was exceeded at the kerbside sites Marylebone Road and Redbridge 2, 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 Barnet 1, Marylebone Road and Redbridge 3, and the roadside sites Bexley 4, Brent 2, Enfield 4, Lambeth 1 and Redbridge 4.
• The annual mean PM10 objective was exceeded at Bexley 4 and Enfield 4.