Under part 4 of the Environment Act 1995, all Local Authorities are required to undertake reviews of air quality for specified polluting substances. These have been defined by Air Quality Standards Regulations. These are revised from time to time; the latest being issued in 2007.

The substances listed are:

How the assessments are to be done and when are defined in guidance issued by the Department for Environment, Food and Rural Affairs (Defra – a department of Government).

Timetable

Reviews are carried out on a three-year cycle, which started in 2000. Each round of reviews involves three stages:

Stage 1 of the process is to gather information about current and likely future sources of air pollution. This includes traffic on the road, industrial processes and an examination of current air pollution monitoring data for the area.

Stage 2 (“Updating and Screening Assessment”) involves the application of further screening techniques to determine both current and future levels of air pollution. If air quality in 2005 is predicted to be above the objectives then a stage 3 assessment will be required.

Stage 3 (“Detailed Assessment”) involves more complex techniques, dispersion modelling, real time monitoring and emission inventories may be required, in order to determine the nature and size of any areas where the objectives are exceeded. If at the end of stage 3 air pollutant concentrations are predicted to be above the objectives then an Air Quality Management Area must be declared followed by an Action Plan detailing how the local authority proposes to introduce measures to reduce the concentration of pollutants in line with Government objectives.

There is also a requirement to produce a Progress report in the years between the Updating and Screening Assessments. This does not apply in those years when a Detailed Assessment has been done.

The first round of the review in 2000 gave results that indicated that it was not necessary to proceed to a Detailed Assessment, as the specified pollutants were predicted to be below the Air Quality Objectives.

The report of the 2000 review is not available on-line.

During the second round, the Updating and Screening report 2004 identified that there was a possibility that, for two of the pollutants, concentrations may exceed the Objectives in specific areas.

A Detailed Assessment was carried out in 2004, examining two pollutants. Since the first round of assessment, a new housing estate had been built close to the petrol storage depot at Kingston, East Cowes. Computer modelling was therefore carried out, to predict benzene concentrations in the area. This was supplemented by diffusion tube monitoring for a short period. The results of the monitoring were reported in an Air Quality Progress Report in 2005. The modelling, together with the diffusion tube results, showed that the benzene concentration in air close to the site was very unlikely to exceed the Objective. There was therefore no need to declare an Air Quality Management Area for Benzene.

In addition, the modelling for sulphur dioxide emissions from the three cross-Solent ferry terminals also showed that there would be no exceedance of the short-term Objective for SO2.

During the third round, in 2006, it was identified that, at two of the sites (Fairlee Road and Lake Hill) there is a possibility that the Air Quality Objective for Nitrogen dioxide may be exceeded.

It was therefore decided to increase the number of diffusion tubes placed at the two sites, to monitor nitrogen oxides. Diffusion tubes are not as exact as they could be, so there was some doubt about the actual concentrations measured. Using three tubes at each site gives a more reliable result.

This was carried out using additional monitoring, using diffusion tubes. The 2007 Detailed Assessment Report concluded that there were unlikely to be exceedances of the guideline standard for Nitrogen dioxide at either of the two sites referred to above.
A Progress report was submitted in 2008.

Fourth Round Updating and Screening Assessment 2009

Before the fourth round Updating and Screening Assessment was carried out, Defra issued revised guidance.

The 2009 Updating and Screening Assessment is available.


Links

Defra air quality website http://www.defra.gov.uk/environment/quality/air/airquality/index.htm