Nicky Woodfield, Air Quality Management Resource Centre, University of West of England, on 11 March 2003

This Resource Centre is the only facility in England for research into the measurement and management of air quality; Nicky Woodfield is the Coordinator of the Centre.

There are numerous regulations, directives and Acts of Parliament concerning air quality, especially with regard to road transport. The basis of all of them is the effect on human health of the seven currently listed pollutants – nitrogen oxides (NOx), sulphur dioxide (SO2), particulates (PM10), benzene (Bz), carbon monoxide (CO), 1.3 butadiene, lead (Pb).

Each of these affects people according to the length of exposure and the concentration encountered, so measuring and assessing their importance in a particular situation is complicated. There are a wide range of permissible conditions set for each pollutant by different bodies, such as the UK Department of the Environment, Transport and the Regions (DETR), the Expert Panel on Air Quality Standards, the European Community (EU), the World Health Organisation (WHO) and the United Nations Economic Commission for Europe (UN).

Local Authorities are responsible for measuring and managing air quality. The procedure used differs in different countries in the EU and the results are not always comparable. In the UK, each Local Authority (LA) can select from a number of commercial measuring methods for each pollutant but must validate the performance of the one selected. Only a few LA have continuously operating monitors recording test results; Bath has one that is moved around to various sites. The alternative is to use diffusion tubes for spot checks at intervals.

The regulations call for the reporting of the concentration averaged over different periods according to its effect on the human body. The current UK Government standards set figures for the running annual mean for Bz and 1.3 butadine; both the annual and the 1-hour mean for NO2; 15-minute, 1-hour and 24-hour means for SO2; running 24-hour and annual means for PM10; annual mean for Pb. For transport (road traffic) situations only NO2 and PM10 are critical; the other pollutants are of importance in industrial locations.

LA have been measuring and monitoring in their areas over the years since the 1995 Environment Act to determine where pollution is worst (the ‘hot spots’). For any area that exceeds the limits set down they have to declare an Air Quality Management Area (AQMA) and then prepare an Air Quality Action Plan (AQAP) to improve the quality in it. The AQMA may cover just one part of one street (as has been done for London Road) or a whole Borough, as has been done in parts of London, or a series of roads (especially if they are ‘canyons’– narrow roads lined by high buildings) or just ‘hot spots’ such as road junctions.

95% of LA have annual NO2 levels exceeding the limit; 30% have NO2 and PM10 exceeding the 24-hour limit. Traffic is the main cause in 86% of LA.

The intention is to incorporate air quality as a section of Local Plans, Local Transport Plans, Local Agenda 21 and Community Plans so that money is made available to improve the localities where it is bad. This requires closer co-operation between departments within LA than occurs generally at present. Policy in Local Plans must be written with air quality considered and Planning Applications include assessments of the effect of developments on air quality. Transport planners are the key people. They need to provide better information on vehicle splits, counts and speeds.

Annual reports to Government are required until 2010 but the limits are being reduced for some pollutants over this period by many of the bodies setting them.


An extensive discussion followed during which the following points were noted:

A suggestion that controlling exhaust fumes from diesel engines by after-burners would be more cost effective than AQPA. Alternatively, that automatic monitors could switch all traffic lights to red when the limit was exceeded.

Railways do not produce PM10 in spite of the appearance of diesel exhaust fumes from engines. Only SO2 is a problem and enclosed stations being ‘buildings’ are exempt from air quality control.

The location of monitors should measure concentrations where people will be present for at least 8 hours – hence first floor levels in ‘canyons’ rather than at ‘push chair’ level.

Action Plans have to balance their effect on surrounding areas with that within the area.

Air traffic deposits fuel droplets but only affects air quality in the region of airports by road traffic and aircraft ground movements.

It is possible that particulates smaller than PM10 , such as PM 2.5 or even PM1, may be more important since they penetrate further into the respiratory system.

B&NES have published their Air Quality Report 2001/2002 which contains considerable information on standards and results of measurements in Bath.

See for local air quality data & for national data

Donald Lovell