Scientists' Contributions  
   

AIR POLLUTION: LONDON'S ACTION PLAN

London Air Quality Consultation Conference, 26 May 2000

Roy Colvile
Imperial College T H Huxley School of Environment, Earth Sciences and Engineering, Prince Consort Road, London SW7 2BP, UK

Introduction

An audience of about two hundred from local and national government, governmental and non-governmental organisations, environmental consultants, universities, fleet operators and representatives of industry gathered in London on 26 May for the official unveiling of the results of the statutory Review & Assessment of air quality that has been in progress in the UK Capital over the past year. The conference was one of several initiatives being taken to ensure that the process of air quality management is carried out with full consultation of all interested parties and ownership by the population and business community of London as a whole. EURASAP Treasurer, Roy Colvile, has been working with some of the local authorities in London on various aspects of this process, and writes the following summary of the conference for comparison with parallel developments in the home cities and towns of other EURASAP members.

Background

The background to the current Review & Assessment of air quality was introduced by means of a video1 by the 33 London boroughs that constituted the only local government in London until the establishment of the office of Mayor of London in May this year. At first, the fragmented city government structure coupled with the complexity of the local air pollution climate had caused London to lag behind the rest of the UK in implementing the new air quality legislation, but much progress has been made, according to the chairman of the National Society for Clean Air and Environmental Protection, Richard Mills. Now, in many ways, London is leading not only in the UK but also in Europe in its application of operational air quality modelling to determine what action is required to improve air quality over the next five years.

The introductory video explained how road traffic has become the dominant local source of air pollution in London since the demise of the famous smogs of the 1950s, although other sources were mentioned, including sulphur dioxide from oil-fired power stations to the east of London. Fine particles were cited as the worst current air pollutants for health effects, with vehicle exhaust currently responsible for two thirds of these plus 90% of oxides of nitrogen and carbon monoxide at roadside locations. Much was made of the popular perception of London, by locals and tourists alike, as a dirty, congested city where air quality is getting worse (regardless of whether or not this perception is entirely realistic). London's extensive air quality monitoring network of over seventy stations indicates that the new air quality standards are regularly not met. Computer modelling indicates that, on current trends, some areas will still exceed standards in 2005. The various policies that could be used locally to control emissions were introduced (see below). The video ended with a warning from a medical doctor about what will happen if we fail to meet air quality standards, given that general practitioners regularly see patients in their surgeries whose symptoms are made worse by air pollution, and yet increasing activities such as walking and cycling that can reduce our use of polluting motor cars can have a most beneficial effect on our health.

The regulatory framework behind the current Review & Assessment of Air Quality is the UK National Air Quality Strategy2, which arises from the UK Environment Act, 1995. This defines eight pollutants (benzene, 1,3,butadiene, lead, carbon monoxide, nitrogen dioxide, fine particles (PM10), sulphur dioxide and ozone), for the first seven of which local government throughout England and Wales is legally required to review the "current" (1996/7) urban air pollution climate and assess whether or not standards will be met in future. The future projection uses a "business as usual" scenario taking into account the expected impact of national and Europe-wide application of emissions abatement technology. Guidance from Central Government3 recommends this review and assessment is carried out by means of a three-stage process, each stage resulting in moving on to the next unless it can be demonstrated that air quality standards will be met without taking any local action to control emissions. The first stage is a desk-based study of approximate calculations based on road traffic flows etc. The second takes a more detailed look at available monitoring data and emissions inventories. The third stage requires accurate calculations usually using atmospheric dispersion modelling. It was the results of this third stage review & assessment that were the subject of the London Air Quality Consultation Conference.

Health-based air quality standards in the UK are based on recommendations of a national Expert Panel on Air Quality Standards4 (EPAQS), or the World Health Organisation where EPAQS have not yet made a national assessment. Objectives to be attained allow a certain number of hours or days per year when the standards are allowed to be breached and define the year after which this air quality should be delivered every year. This is similar to the way the European Directives are written, though some of the national objectives have earlier attainment dates (mostly 2005 and 2004) to ensure compliance with European law allowing for a few years' margin for error. The UK objective for PM10 was initially set at 50µg m-3 99th percentile of hourly running 24-hour averages to be achieved by 31 December 2005, but was relaxed to the less stringent 90th percentile of daily averages in line with the European Directive, to be achieved in the UK by 31 December 2004. This revision, introduced following a complete review of the National Air Quality Strategy when the current Labour government took over from the previous Conservative one at the last General Election, with the slogan "delivering cleaner air more quickly", was finally approved mid-way through the process of review and assessment of local air quality, resulting in some frustration and delay to the process.

At any location where the review & assessment indicates the "business as usual" scenario is likely to result in a failure to meet the air quality objectives, local government is required to declare an Air Quality Management Area with an Air Quality Action Plan to implement local measures to reduce emissions beyond what will be achieved by national and Europe-wide measures. Air quality in these areas will then be subject to further monitoring, refinement of model predictions (for example use of more accurate traffic flow data, currently a major source of uncertainty locally), co-ordination of air quality management policies with all parties involved and full consultation on the content of the Action Plan. The themes of partnership, consultation and wide ownership of the whole process recur frequently. This kind of approach can perhaps be traced back to 1992 Rio Earth Summit and Agenda 21 ("think globally, act locally" to prevent climate change), despite the fact that any reduction in emissions of greenhouse gases resulting from the National Air Quality Strategy will be coincidental, these being beyond the scope of the strategy.

Results

Across London there was some variation in following the guidelines for review & assessment of air quality, as it was found not to be necessary or efficient to complete all three stages in some areas, especially where it rapidly became clear that air quality objectives would not be met in this the most polluted large urban area in the UK. Each of the 33 local authorities was responsible for its own local air quality review & assessment, though many acted in close collaboration or as a consortium with neighbours. Two main methods were used for third stage reviews & assessments: A consortium of eight central London authorities, plus four of the outer London boroughs, employed Cambridge Environmental Research Consultants (CERC) to apply the ADMS-Urban air quality management system5 based on a second-generation Gaussian Plume Model and the Danish Operational Street Canyon Plume Model6. The rest of London was mapped by the South East Institute for Public Health (SEIPH), taking advantage of the city's dense monitoring network that they oversee, using an empirical method which is a local application of the national-scale modelling of the UK Atmospheric Particles Expert Group7 and incorporating the Dutch CAR-International roadside air pollution model8.

London is the same as the rest of the UK in that objectives for benzene, 1,3,butadiene, carbon monoxide and lead will be met by national policies alone, especially the banning of leaded petrol (gasoline) accompanying the introduction of vehicle exhaust catalysts. In most local authority areas, this became clear before proceeding to stage three of the review & assessment. Furthermore, the UK Environment Agency, who are responsible for large point sources of air pollution, have indicated that they will require each individual source to apply emissions abatement technology sufficient to ensure that it is not responsible for failure to meet the objective for sulphur dioxide. This leaves nitrogen dioxide and PM10 as the two pollutants that require additional emissions abatement policies to be applied by local government in London.

At the conference, emphasis was made of the good accuracy of the two quite different modelling or air quality mapping approaches that were used, and the comparability of the two sets of results. Local validation, using monitoring results from 1996 and 1997, indicates that precision as good as about (10% can be achieved for the annual average concentration of nitrogen dioxide at most individual monitoring sites with just a few per cent bias in any year across the monitoring network on average as a whole. Accuracy for PM10 is a little less good, and difficult to quantify because of the smaller number of monitoring sites for this pollutant. Nevertheless, the variability in future projected air quality is sufficiently low for these small margins of error to present some difficulty where the results of different modelling techniques meet at local government boundaries.

The area of exceedence of the 21 ppb annual average nitrogen dioxide air quality standard in London has the shape of an elliptical blob in the centre with strips following main roads radiating away from this and along orbital routes, especially the orbital motorway. There is a very significant additional area of exceedence in the vicinity of Heathrow Airport, and some small areas in busy suburban satellite town centres such as Croydon to the south.

According to CERC's calculations, the radius of the central ellipse 21 ppb annual average nitrogen dioxide contour is about 2km; according to SEIPH, it is three to four km. This apparently rather large discrepancy occurs because the spatial variability of nitrogen dioxide concentration across the whole conurbation in 2005 is projected to be from about 10 ppb on the outskirts to 30 ppb at central roadside location, this variability occurring over an area some 50 km across. A 10% bias in one model relative to the other is thus sufficient to result in a significant difference in the predicted size of the air quality management area that will need to be declared based on its results. The area of exceedence of the PM10 air quality objective is more difficult to quantify than the annual average nitrogen dioxide, but most local authorities appear to be reaching the conclusion that air quality management areas for these two pollutants should be the same. What is most important though - and this was stressed at the conference by Quentin Given of the London Borough of Camden - is that air quality action plans will be made, and we should not be distracted into arguing over the exact location of the air quality management area boundary on the map of London.

Future action

The greater part of the London Air Quality Consultation Conference was taken up with presentations of the complete range of issues to be considered in drawing up and implementing air quality action plans in London.

Some parties have been pessimistic that air quality management areas will suffer a fall in property values and other symptoms of environmental blight similar to what is already experienced associated with the identification of contaminated land, siting of incinerators, nuclear and chemical installations and the like. There is also some fear that the boundaries of the areas will be difficult to defend in court if subjected to legal challenge. Henry Derwent from the UK Department of the Environment Transport and the Regions, however, was of the opinion that the pessimism will prove to have been unfounded as there will be wide acceptance in London of the need to improve air quality. A clear audit trail for the decision of where to declare an air quality management area (which is not an exact science but includes political considerations alongside scientific ones) will allow the decisions to be defended if they are reasonable and based on good evidence.

Darren Johnson, Green Party candidate in the election for Mayor of London and now appointed as Environmental Advisor to the Mayor's office, outlined some of the opportunities that the new Mayor has in carrying out his duty to draw up an Air Quality Strategy for London, which must be interlinked with seven other strategies including noise and waste management to achieve sustainable development and health equality. If congestion charging for car drivers is introduced, the revenue from this might be invested in London's famous buses (still mostly red, but increasingly no longer the traditional open-backed double-decker variety that have rather high particulate emissions) which already carry more passengers than air travel does globally and represent the one part of London's transport sector where capacity for growth remains without requiring very great capital investment. 15% traffic reduction was cited as a target that should be achievable by policies including transport mode shift such as from car to bus.

These two keynote presentations by national and London-wide government representatives respectively were followed by a number of shorter presentations by local government officers and other closely involved in London's air quality management process:

Conclusions

London's long-standing reputation for poor air quality may not be justified any more when compared with other world cities such as Athens, Los Angeles and Delhi, but air pollution remains high on the list of concerns of residents, workers and visitors. The Review & Assessment of air quality has enabled quantification of what local action must achieve in supplementing national and Europe-wide policies to reduce emissions. While some of these policies are likely to be unpopular as individual freedom to travel by car is restricted, some could also deliver health and quality of life benefits far in excess of the small impact of marginally improved air quality (given that the most significant air pollution emissions abatement will be achieved by the national measures). London therefore now finds itself at the second turning point in air pollution emissions since the problem of the 1950s smogs was solved, as the whole population is being invited to mobilise itself and alter its attitudes and behaviour to achieve a better urban environment in which good air quality is a major indicator of sustainable development.

We would welcome a discussion in the pages of the EURASAP Newsletter comparing London's approach with what is happening in other cities, from the Mediterranean through to Scandinavia, Eastern Europe and the former Soviet Union, and the extent to which differences in approach are appropriate for the different source characteristics and air pollution climatologies, or is the mechanism for attaining European air quality standards determined more by politics than by the science of air pollution?

Acknowledgements

EURASAP is grateful to the UK National Society for Clean Air & Environmental Protection and The Association of London Environmental Health Managers for organising the conference, and for the additional support of the UK Environment Agency, the Government Office for London and the London Local Authorities, including free charities' admission to the conference which encouraged this article to be written.

References

  1. Air Quality: London's Action Plan. Delivering cleaner air for London, a video by the 33 London boroughs, supported by The Association of London Environmental Health Managers, Crest Video and Multimedia Services +44 20 8651 1801, http://www.crestvideo.co.uk
     
  2. The Air Quality Strategy for England, Scotland, Wales and Northern Ireland. Working together for clean air. UK Department of the Environment, Transport and the Regions in partnership with the Scottish Executive, the National Assembly for Wales and the Department of the Environment in Northern Ireland. Cm 4548 SE 2000/3 NIA 7, January 2000. London: The Stationery Office, ISBN 0-10-145482-1. http://www.environment.detr.gov.uk/airquality/index.htm
     
  3. Framework for Review and Assessment of Air Quality. Part IV The Environment Act 1995 Local Air Quality Management LAQM.G1(00) March 2000, Department of the Environment, Transport and the Regions: London, National Assembly for Wales. ISBN 1-85112-3695. (http://www.environment.detr.gov.uk/airq/laqm/g100/pdf/g100.pdf)
     
  4. For example, Particles, November 1995. London: The Stationery Office. ISBN 011 753199 5. See http://www.environment.detr.gov.uk/airq/aqs/index.htm
     
  5. C A McHugh, D J Carruthers, H A Edmunds, ADMS-Urban: an air quality management system for traffic, domestic and industrial pollution, Int.J.Env. and Poll. 8, 666-674, 1997.
     
  6. R Berkowicz, O Hertel, N N Sorensen, J A Micelsen, Modelling air pollution from traffic in urban areas. In: R J Perkins, S E Belcher (Eds.) Flow and dispersion through groups of obstacles Proceedings of conference on flow and dispersion through groups of obstacles, Institute of Mathematics and its Applications, University of Cambridge, March 1994. Oxford: Clarendon Press, 1997.
     
  7. Source Apportionment of Airborne Particulate Matter in the United Kingdom, prepared on behalf of the UK Department of the Environment, Transport and the Regions, the Welsh Office, the Scottish Office and the Department of the Environment (Northern Ireland). Report of the Airborne Particles Expert Group, January 1999. ISBN 0-7058-1771-7. (see http://www.environment.detr.gov.uk/airq/airbornepm/ap05.pdf)
     
  8. J den Boeft, H C Eerens, W A M den Tonkelaar, P Y J Zandfeld. CAR International: A simple model to determine city street air quality. Sci.Tot.Env. 190, 321-326, 1996.
       
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