LAQN Pollution Episodes

Pollution Notification released on 14/12/2007

On Tuesday 11th December, weather conditions became increasingly cold and calm, with very light winds resulting in a widespread primary pollution episode. Initial analysis suggests that this is the most significant nitrogen dioxide incident for 10 years.

Nitrogen dioxide was elevated across the region, particularly on Wednesday 12th with ‘moderate’ levels recorded at 18 sites, including the background sites Ealing 1, Kensington & Chelsea 1, and Tower Hamlets 1.

The EU limit value concentration of 200 mgm-3 (hourly mean) for nitrogen dioxide was exceeded at 72 sites including several background sites. The hourly mean Air Quality Strategy Objective for nitrogen dioxide of not more than 18 hours per year above 200 mg m-3 was breached at 9 sites, and equalled at 2 sites, on the basis of measurements during this episode alone. The background sites at Tower Hamlets 1 recorded 17 hours above 200 mgm-3 and Barnet 2 14 hours. Initial analysis suggests that this is the most significant nitrogen dioxide incident for 10 years, with west - central London seeing the most widespread and elevated levels; hourly mean concentrations at the background sites Ealing 1 and Kensington & Chelsea 1 exceeded 400mg m-3.

AQS Objectives

Continued on next page.