The purpose of this report is to review air quality in London during the second quarter of 2001 and to report detailed measurement results for the year ending 30th June 2001.

The Brent 2 and Richmond 2 sites joined the network during the quarter.

Air pollution during the quarter was dominated by a photochemical pollution incident at the end of June which caused ‘high’ O3 and some ‘moderate’ SO2 and PM10. Lesser photochemical incidents were measured during May.

Measurements during the 12 months ending 30th June 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. The annual mean NO2 objective was also exceeded at background and suburban locations in inner and west London.
• The incident based NO2 objective was exceeded at the kerbside sites Marylebone Road and Redbridge 2, and at the roadside site Kensington & Chelsea 3.
• Exceedences of the O3 objective were measured in the outer suburbs and at sites outside London.
• The incident based PM10 objective was exceeded at the kerbside sites Marylebone Road and Rebridge 3, and the roadside sites Bexley 4, Enfield 2, Hounslow 3 and Redbridge 4.
• The annual mean PM10 objective was exceeded at Marylebone Road only.
• The SO2 objective was not exceeded at any site.