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2.0 NATIONAL AIR QUALITY STRATEGY

The Department of the Environment published the original National Air Quality Strategy (NAQS) in 1997. This set out a framework of standards and objectives for eight ambient air pollutants that have the potential to cause harm to human health, i.e. benzene, 1,3 butadiene, carbon monoxide, lead, nitrogen dioxide, particulates (PM₁₀), sulphur dioxide and tropospheric ozone. All these pollutants are associated with local air quality problems, except ozone, which is a regional pollutant.

The aim of the strategy was to reduce the impact on human health of these pollutants by reducing airborne concentrations. The NAQS identified air quality standards for these pollutants based on the recommendations of the Expert Panel on Air Quality Standards (EPAQS) or World Health Organisation (WHO) guidance (where no EPAQS recommendation existed). The NAQS set out specific target dates by which time these standards should be achieved.

The NAQS together with these standards and objectives have been the subject of periodic review, and consultation documents were published in 1998 and 1999 by the Department of the Environment, Transport and the Regions (DETR). The NAQS has now evolved into the Air Quality Strategy for England, Scotland, Wales and Northern Ireland (AQS). The goals of this strategy are the same as for the NAQS and incorporate European Directives and the impact of devolution.

The Air Quality Regulations 2000 set standards and objectives for seven pollutants that are associated with local air quality (see Appendix 1). The objectives are aimed at reducing the health effects of the pollutants to negligible levels.

2.1 The role of local authorities

2.2 Methodology

2.2.1 Phased approach

2.1 The role of local authorities

Local authorities in the UK have a duty, under the Environment Act 1995, Part IV, to review and assess air quality in their areas. The Air Quality Regulations 1997 define a phased approach to the review and assessment on the basis of guidance provided by the DETR.

2.2 Methodology

In undertaking the review and assessment process, local authorities are required to have regard to locations where individuals are likely to be exposed over the averaging time of the relevant National Air Quality Objective. For objectives with short averaging periods (i.e. sulphur dioxide and nitrogen dioxide) the review and assessment process should be focused on any non-occupational, near-ground level outdoor location given that exposures over such short-term averaging times are potentially likely. For objectives with longer averaging times (i.e. benzene, 1,3 butadiene, carbon monoxide, lead, nitrogen dioxide and particulates) the review and assessment process should be focussed on the following near-ground level outdoor locations:

Background locations;
Roadside locations; and
Other areas of elevated pollutant concentrations where a person might reasonably be expected to be exposed (e.g. in the vicinity of housing, schools or hospitals etc.) over the relevant averaging time of the objective.

2.2.1 Phased approach

Clearly some local authorities have far fewer sources of air pollution than other authorities. Therefore in order that the complexity and detail of review and assessment process was consistent with degree of air pollution problems within individual local authorities, the Government required local authorities to adopt a phased approach to their review and assessment of air quality:

First stage the First Stage of the review and assessment process required that all local authorities:

a. Identify any potentially significant sources^* in their districts of the seven pollutants to be considered; and

b. Consider whether any of these pollutant sources were likely to affect any person (a receptor) such that they would experience pollution levels in excess of the National Air Quality Standards over the relevant time period (i.e. a relevant location); and

c. Consider whether there were any proposed future developments which could result in the emission of any significant quantities of the pollutants; and

d. Consider whether there were any sources of these pollutants outside the local authoritys boundaries that were likely to have a significant impact on air quality.

(* Includes road traffic and industrial processes)

The First Stage therefore primarily involved the collection of existing data on air quality measurements and emission sources for the seven pollutants of interest in the Air Quality Strategy for England, Scotland, Wales and Northern Ireland. Using DETR guidance, these data were then used to define whether there was likely to be an air quality problem in a specific future year, which varied according to the pollutant.

If having undertaken the First Stage the local authority concluded that they did not have any potentially significant sources of the pollutants in question they would not have to proceed to the Second Stage of the process.

Second Stage the aim of the Second Stage was to provide further screening of pollutant concentrations in local authority areas to identify hotspots of pollution. The guidance suggested that each local authority should select a number of locations in their area, where the highest likely concentrations would occur of the pollutants identified in the First Stage review and assessment as having the potential to exceed the National Air Quality Objectives. The authority should then consider pollution levels in these locations in more detail using one or both of two alternative approaches, i.e.:

a. A projection of current monitoring data; or

b. The use of a screening model, e.g. the Design Manual for Roads and Bridges.

If the Second Stage review and assessment predicted that levels of any pollutant would exceed the relevant National Air Quality Objective the local authority was required to undertake a more detailed Third Stage study.

NB. The DETR indicated that it was acceptable for a local authority to move directly to from a first stage study to a third stage study without undertaking the second stage process.

Third stage In proceeding to the Third Stage of the review and assessment process a local authority should undertake an accurate and detailed review and assessment of current and future air quality within their districts to predict whether any exceedances of the National Air Quality Objectives were likely. This would involve more sophisticated modelling or monitoring techniques, although less sophisticated techniques could also play an important role. The local authority should then estimate the magnitude and geographical extent of any such pollutant exceedances.

Air Quality Management Areas (AQMA)

An AQMA should only be declared if a Third Stage study has indicated that such an area is necessary. An AQMA is a designated geographical area in which the local authority predicts that any pollutant will exceed the relevant National Air Quality Objective at the relevant target date. In declaring such an area the local authority would be required to undertake to:

a. Assess existing and future air quality within the AQMA;

b. Prepare a report on this assessment within 12 months following the designation of the AQMA (and make the report available for public consultation);

c. Devise and implement written proposals (i.e. an Action Plan) for improving air quality within the AQMA so as to achieve the National Air Quality Objectives with timescales in which the local authority propose to implement the provisions of the plan.