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The first air quality review and assessment in Oldham was completed in January 2001. It was found that there was no risk that the air quality objectives in place at that time for benzene, 1,3 butadiene, lead, carbon monoxide, and sulphur dioxide would be exceeded in Oldham.
A detailed analysis of nitrogen dioxide concentrations was carried out, including dispersion modeling and monitoring of pollution concentrations. It was found that exceedances of the annual mean objective might occur in urban parts of the borough. A precautionary approach was taken to take into account possible uncertainties that may arise in predicting future pollution levels. The 1-hour objective was expected to be met.
For particulate matter it was found that the 24-hour objective might not be achieved. Any potential exceedances were restricted to within a few metres of the major roads and were included within the areas where the nitrogen dioxide objective may also be exceeded. The annual mean objective for PM10 was expected to be met.
The Government has suggested that the second round review and assessments should be carried out in two steps:
The recommended timescales for the submission of air quality review and assessment reports to Defra are set out in Table 1.4, below.
Table 1.4 – Recommended timescales for the submission of reviews and assessments relevant to Oldham Council
| LAQM Activity | Completion Date |
|---|---|
| Updating and Screening Assessment (USA) | End May 2003 |
| Detailed Assessment1 | End April 2004 |
| Progress Report | End April 2005 |
| USA | End April 2006 |
| Detailed Assessment | End April 2007 |
| Progress Report | End April 2008 |
| USA | End April 2009 |
| Detailed Assessment | End April 2010 |
1If the Updating and Screening Assessment does not identify the need for a Detailed Assessment then a Progress Report should be prepared instead.
The first Update and Screening Assessment report for Oldham Council was submitted to Defra in September 2003. This identified that a detailed assessment would be required for nitrogen dioxide and PM10. No risk of exceeding the objectives for the other 5 pollutants were identified.
The detailed review and assessment for nitrogen dioxide identified that there are likely exceedances of the annual average objective of 40 mg/m3 at many roadside locations in the borough. The previous review and assessment found widespread exceedances of the annual average objective, and may have overestimated nitrogen dioxide concentrations at background locations. Both monitored and modeled data show that likely exceedances of the annual mean air quality objective are to be found close to most of the busy roads in the borough, but that these are restricted to within a few metres of the carriageway. The assessment has identified some new areas, not previously picked up in earlier work; this includes the main thoroughfares in Shaw.
The detailed review and assessment for PM10 has shown that the current air quality objectives are likely to be achieved in all parts of the borough. Air pollution monitoring results are significantly below the 40 mg/m3 annual average, with fewer than 35 exceedances of the 50 mg/m3 24 –hour objective.
Air pollution dispersion modelling was carried out to predict ground level pollution concentrations in the borough in 2004. The results of this study have shown that the annual average objective is not likely to be exceeded at any location in the borough, as can be seen on the contour plot in the Figure below. Modelling of a variety of receptor points were also carried out, and the predicted number of days where pollution concentrations are greater than 50 mg/m3 calculated. The receptor points were chosen to represent locations at the roadside and near busy junctions. They are all in locations where exposure to the public would occur, for example, being in close proximity to housing or schools. The updating and screening assessment did not identify any significant industrial sources of PM10 so modelling to assess specific industrial locations was not carried out, although the inputs to the model did include emissions from industry. None of the receptor point locations had more than 35 days predicted to exceed 50 mg/m3 in 2004.
Figure 6.1 – Predicted nitrogen dioxide concentrations in 2005
Oldham’s first Air Quality Management Area (AQMA) was declared in 2001 for nitrogen dioxide and PM10, although exceedances of the nitrogen dioxide were much more widespread than those for PM10. The detailed review and assessment found that the current air quality objectives for PM10 are expected to be met and there was therefore a case for amending the AQMA to exclude PM10.
The Review and Assessment also considered the provisional PM10 objectives for 2010. The provisional objectives are much tighter than the current objectives and the report found that the annual average objective of 20 mg/m3 is unlikely to be met across many parts of the Borough.
An assessment of the air quality improvement required to meet the annual average objective was carried out as part of the detailed report. This has found that a reduction in NOx emissions of 55% at the location where pollution concentrations are highest will be required before the air quality objective will be met. At other locations reductions ranging from 1% to 33%, with an average reduction of 19%, would be required.