Table Of ContentUrban Air
Quality
in the
United
Kingdom
January 1993
First Report of the
Quality of Urban Air Review Group
Prepared at the request of the
Department of the Environment
22501843244
Urban Air
Quality
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Kingdom
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January 1993
First Report of the
Quality of Urban Air Review Group
Prepared at the request of the
Department of the Environment
© Quality of Urban Air Review Group 1993
ISBN 0 9520771 16
Further copies available from: “8
Department of the Environment
PO Box 135 ;
Bradford ti
West Yorkshire =O)
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The Quality of Urban Air Review Group
Chairman
Prof R M Harrison
The Queen Elizabeth II Birmingham Centenary
Professor of Environmental Health
University of Birmingham
S M Bland
Department of the Environment
Dr P Brimblecombe
University of East Anglia
Dr R G Derwent
Her Majesty’s Inspectorate of Pollution
Dr G J Dollard
Harwell Laboratory
Prof R S Hamilton
Middlesex University
A J Hickman
Transport Research Laboratory
Dr C Holman
Independent Consultant
Dr DP H Laxen
Rendel Science & Environment
Dr P Mallaburn
Department of the Environment
Dr R L Maynard
Department of Health
Dr T A McMullen
Department of the Environment
Prof M J Pilling
University of Leeds
Dr F B Smith
Centre for Environmental Technology, Imperial College
Dr ML Williams
Warren Spring Laboratory
Secretary
R Barrowcliffe
Environmental Resources Limited
The authors accept responsibility for the contents of this report but the
views are their own and not necessarily those of the organisations to
which they belong or the Department of the Environment
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Executive Summary and Recommendations
Executive Summary and
Principal Recommendations
OVERVIEW
Forty years ago, smoke and sulphur dioxide pollution from domestic coal burning caused an air
pollution episode that led to the premature deaths of 4,000 Londoners. These so-called smogs
have been all but eliminated by a combination of measures of which the most important were the
Clean Air Acts of 1956 and 1968, the move away from domestic coal burning for home heating
and the centralisation of electricity generation in large power stations away from towns and
cities.
Largely because of pollution emissions from motor traffic, urban air quality is once more causing
public concern. Because of this concern, and to increase public awareness of air quality issues
generally, the Government has established a public information system through which daily
bulletins of air quality are issued via the media. These bulletins include health advice for the
benefit of those whose health may be affected by high concentrations of air pollutants. Although
the current situation is markedly less serious than the smogs of the 1950s, pollution concentrations
regularly exceed international health guidelines in UK towns and cities, and on December 13th
1991 London experienced the most severe nitrogen dioxide pollution since regular monitoring
began in 1971.
The UK Government and the European Community are responding to this problem with a range
of pollution abatement measures designed to cut emissions from motor traffic, of which the
three-way catalytic converter is the best known. This will cut emissions dramatically from each
new petrol car and should result in marked improvements in air quality. Local authorities and
non-Government organisations are also advancing abatement strategies such as traffic
management and the promotion of public transport as well as developing local pollution alert
systems.
However, the experience of other countries, most notably the United States of America, is that the
growth of motor vehicle traffic will offset many of the air quality benefits accruing from better
emission controls. For example, although three-way catalysts have been mandatory on cars in
the US since 1983, the National Ambient Air Quality Standards are still regularly exceeded. In
the UK, motor traffic is estimated to double by 2025 and there is real concern that even with the
substantial financial investment in exhaust emission controls, the US experience will be repeated
here.
The Government’s Environment White Paper “This Common Inheritance’ marks a shift in
Government thinking by signalling that effective pollution abatement must be shown to deliver
acceptable air quality. The White Paper outlines an iterative strategy for achieving this goal, via:
¢ improved urban air quality monitoring plus public information;
¢ the development of UK air quality standards;
¢ the integration of air quality standards and pollution control.
Quality of Urban Air Review Group i
Urban Air Quality in the UK
As part of the scientific evaluation of this strategy, the Quality of Urban Air Review Group
(QUARG) was invited by the Government to review the present state of urban air quality in the
UK and to prepare scientific advice on the impact on our air quality of more stringent pollution
control measures, such as the introduction of catalytic converters. This is the first report of the
Group and outlines what we know about urban air quality and where further research is needed.
The terms of reference and membership of the Review Group appear in AnnexA of the Report.
The principal recommendations of the report are summarised in this Executive Summary. These
should be read in conjunction with the detailed recommendations at the end of each of the
chapters.
MAIN URBAN AIR QUALITY ISSUES
The current expansion of UK urban pollution monitoring (the Enhanced Urban Network) has
resulted in data being available for more pollutants at more sites. Real-time readings are now
available for the following pollutants:
— benzene, 1,3-butadiene and other volatile organic compounds;
— airborne fine dust (PM 9);
— carbon monoxide;
— ozone;
— sulphur dioxide;
— nitrogen dioxide.
Motor traffic has played an ever increasing role in urban air pollution as the pollutants, such as
smoke and sulphur dioxide, traditionally associated with coal combustion have declined to
near-rural concentrations. Urban concentrations of nitrogen dioxide and carbon monoxide
exceed international health guidelines in many heavily trafficked areas.
Urban ozone concentrations occasionally exceed international health guidelines during
summer pollution episodes. Whilst urban concentrations of ozone are usually lower than
those in surrounding rural areas, the available monitoring data are few, and give no indication
of spatial variations across our cities. However, average urban ozone concentrations are likely
to increase as a result of the introduction of three-way catalytic converters.
Whilst long-term average concentrations of sulphur dioxide have diminished greatly,
concentrations can still exceed the World Health Organization 1-hour guideline in some urban
areas.
Executive Summary and Recommendations
¢ Certain weather conditions can lead to extreme concentrations of pollution generated by road
traffic and other low level sources. For example, during the London pollution episode of
December 1991 concentrations of nitrogen dioxide and benzene were unprecedented.
¢ There are few data to indicate long-term trends across the country, but those that are available
suggest a general increase in nitrogen dioxide concentration over the last decade. However,
recent data for a limited number of traffic-saturated inner-city sites have shown little change in
concentrations. The expansion of urban monitoring via the Enhanced Urban Network, and
national diffusion tube surveys will give a greatly improved view of future urban pollution
trends.
¢ It is inevitable that over the next few decades, the beneficial impact on urban air quality of
control measures such as the three-way catalyst will be considerably offset by the predicted
growth in road traffic. It is however, not possible to quantify this impact precisely at present.
MONITORING RECOMMENDATIONS
e Although there is a growing UK urban air quality database, there remains a clear need for the
expansion of air quality monitoring. The Group recognises the importance of the
Government’s Enhanced Urban Network in beginning this process and recommends that for
adequate national coverage of the UK, the network be developed to monitor in at least 24 of
the UK’s major towns and cities.
e Aninterim list of 24 priority towns and cities, compiled by the Department of the Environment,
is given in Annex B of the Report. The Group is currently reviewing the basis for selection of
monitoring sites in the light of air quality survey data and developments in international
legislation.
e The Group is concerned that to serve common policy and scientific objectives the
Department’s total urban monitoring effort is now in urgent need of rationalisation and
review, subject to the requirements of international legislation.
¢ The Group recognises that in addition to the national networks, there is a considerable amount
of monitoring being carried out at a local level by local authorities and other organisations.
The Group considers that proper central scientific co-ordination of this effort will result in
valuable additional information being collected and will make the best use of both local and
national resources. The Group therefore recommends that the Government establishes such a
co-ordination framework.
Quality of Urban Air Review Group iii
Urban Air Quality in the UK
The Group considers that the location of the Enhanced Urban Network stations within each
urban area is adequate to reflect broadly the exposure of the general public. However, more
research is needed involving monitoring, in conjunction with dispersion modelling, in order to
quantify better the exposure of individuals to air pollutants. This should include measurements
in different locations, such as inside cars and alongside busy roads.
Urban monitoring at a more limited number of sites should also seek to measure concentrations
and trends in other substances of health significance, most notably the following:
— acid aerosol;
— toxic organic micropollutants such as polynuclear aromatic hydrocarbons
and their derivatives, dioxins and dibenzofurans;
— toxic metals such as mercury.
Current air quality monitoring in the UK is designed to provide information upon both central
urban background and rural concentrations. However, there is a strong case for enhancement
of monitoring at both roadside and suburban locations, which currently have very sparse
coverage.
RESEARCH RECOMMENDATIONS
The Group considers that it is not possible with current knowledge to establish a quantitative link
between changes in national pollutant emissions and changes in urban air quality. The Group
recommends the establishment of a substantial programme of research aimed at understanding
urban pollution emissions, chemistry and dispersion. This need is most acute in relation to
nitrogen dioxide.
This programme should consider the following as priority research areas.
Atmospheric Chemistry and Dispersion Modelling
The behaviour and fate of pollutants in urban areas is poorly understood. Considerable effort
needs to be devoted to this issue if the link between emissions abatement and improvements in
air quality is to be fully quantified. It is particularly important to understand the relationship
between emissions and measured concentrations of pollutants in urban areas.
New theoretical and experimental studies are required to understand the structure of the lower
atmosphere in urban areas, how this is influenced by the character and distribution of
buildings and open spaces, and how this structure influences the spatial and temporal
distribution of pollution concentrations.
