Air quality
Ambient air quality in London
One of the most enduring images of London is of a city wrapped in a blanket of 1950s smog, when pollution from burning domestic coal led to the premature death of 4,000 Londoners.
Although the peasoupers are a thing of the past, air pollution of a different form is still a major concern for
Londoners. The sulphur dioxide and black smoke from burning coal has been replaced by a number of other
pollutants, in particular those from burning petrol and diesel in cars, lorries and buses. A survey in 1998
suggested that Londoners feel that air quality is one of the most important factors influencing their health.
The Department of Health has most responsibility for air pollution and health. In 1992, it set up the Committee on the Medical Effects of Air Pollution (COMEAP). This Committee has
published several reports on the subject of air pollution and health and has contributed to policy development in
the Department for Environment, Food and Rural Affairs (DEFRA). Air quality strategies and targets are set by the DEFRA Air Quality Expert Group.
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Health aspects
Damage to health from air pollution episodes is well recognised and reported upon. An event that has received much attention is the December 1952 London smog episode, in which
smoke concentrations reached 1,600 g/m3 and sulphur dioxide (SO2) concentrations 700ppb (1,800 g/m3).
These exceptionally high concentrations affected mainly older people, with a 2.8-fold rise in deaths among people
aged 65-74 and 2.7-fold rise among those 75 and over. Deaths from bronchitis and emphysema rose 9.5-fold, pneumonia
and influenza 4.1-fold and "myocardial degeneration" 2.8-fold. Applications to the Emergency Bed Service for
hospital admissions for respiratory disease trebled and for circulatory disease doubled; applications for
sickness benefit increased by around 50%.
In December 1963, an estimated 340 deaths were attributed to a lesser episode in London. However, by the late 1960s,
acute effects of pollutants were no longer so discernible. In 1978, one study concluded, that urban air pollution in the
UK until around 1968, caused increased mortality and morbidity, with the exacerbation of pre-existing chronic respiratory
disease, but that these effects were no longer occurring, probably due to the decrease in air pollution consequent on the
Clean Air Act of 1956.
This position is no longer accepted. Just over a decade ago, another
episode of high pollution led to premature deaths and hospital admissions, although on this occasion it was no
longer sulphur dioxide that was a problem. Current ambient levels of air pollution are also associated with
raised morbidity and mortality but which pollutants affect which health outcomes, and to what extent, are still
uncertain.
Contemporary ambient levels of air pollution are also associated with
raised morbidity and mortality (Table 1). Air pollution is a particular hazard to the elderly, children, and
especially those with pre-existing disease.
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Tackling air quality
Strategies for improving external air quality in London are divided: local authority environment departments are required to produce air quality plans; traffic volumes
are under control of local authorities, GOL - Government Office for London and the Greater London Authority's Transport for London. The Environment Agency takes responsibility for air quality from industrial discharges.
The trends in air quality in London show the effects of increasing vehicle traffic. SO2 levels have been falling, while NOx levels and the traffic component of particulates are rising.
The annual mean levels have changed little in the past decade. The number and height of hourly and daily peaks vary more, reflecting changes in the weather from year to year.
Air Quality is worst in central London and in the west, where traffic is more concentrated. Air quality management and transport planning
remain different activities within local authorities, accountable to different parts of DETR, and there is no requirement to bring in public health.
Part IV of the Environment Act 1995 requires each local authority to review and assess air quality in its area. Where a local authority considers that one or more of the air
quality objectives, as prescribed in regulations, is unlikely to be met within the relevant period, it must declare an air quality management area. It must then draw up an action
plan setting out the measures it intends to take to meet the objectives and including a timetable for their implementation. Section 84(1) of the environment Act 1995 requires
authorities to undertake a further assessment of existing and likely future air quality in a designated air quality management area. Local authorities were expected to produce
a final review and assessment report by the end of December 2000, indicating whether or not the local authority proposed to designate an air quality management area and where
such an areas' boundaries should be drawn. Modelling work for the London boroughs was completed by Cambridge Environmental Research Consultants (using the ADMS Urban model) and
SEIPH (South East Institute of Public Health). It was found that, of the seven pollutants listed in the NAQS (National Air Quality Stategy), pollutants were modelled to exceed targets
that had been set: PM10 24 hour mean modelled to exceed in 2004; NO2 annual mean modelled to exceed in 2005. In February 2003, the UK Government published
an Addendum to the Air Quality Strategy, introducing tighter objectives for particles
benzene and carbon monoxide and a new objective of polycyclic aromatic hydrocarbons.
The DETR gives guidance on the four stages of review and assessment and suggests local authorities demonstrate how much of the population will be exposed to the listed pollutants,
describing how mitigating measures will reduce exceedences of pollutant levels. Air Quality Management Areas have been declared by all boroughs. The declared pollutants which will
exceed the targets in 2005 are particulates (PM10) everywhere except Greenwich and nitrogen dioxide in each borough other than Bexley: www.airquality.co.uk/archive/. Westminster City
Council included a health impact assessment (HIA) as part of its report. This HIA found that only a few deaths would result from poor air quality in the borough.
The London Planning Advisory Committee (now part of the GLA) has used air pollution measures to propose traffic reduction. To bring about significant improvements in fulfilling these
needs, it was concluded that current (1997) traffic levels across London must be reduced by between 15% and 20% on average by 2005 (LPAC, 1998). Targets for individual local authorities vary from
40% in central London to 1 0% in the periphery. These targets are based on meeting air quality measures. However, they do not take into account other public health criteria for traffic reduction.
Transport for London [formerly London Transport] are working on reducing emissions from its London bus fleet. Buses with older engines have been
retrofitted with particle traps to reduce particulate emissions and all new buses will be fitted with the
cleanest available class of engine. Euro III engines are being fitted as standard to all new buses now they are
available. Almost 50% of buses have Euro II engines. Current plans are to increase
the use of newer, cleaner technology, including reviewing the potential for trials of fuel cells and extend the
use of particle traps. (For more information see LT's Environmental Performance Report 2000 - London
Transport, Transport Strategy and Development, Windsor House, 42-50 Victoria Street, London. SW1H 0NW)
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In May 2000, a conference called 'Air pollution: London's action plan, London's air quality conference, run by the National Society
for Clean Air was organised to present work by London boroughs including present and future air quality modelling. A follow up conference,
held in July 2001, discussed where the London boroughs are in relation to air quality management plans and what work has been done towards
these goals in the future.
Details of the latest National Air Quality Strategy (consultation document published 13/1/99) are available from
the DEFRA Website, along with targets for major pollutants - benzene, 1,3 butadiene,
carbon monoxide, lead, nitrogen dioxide, ozone, particulates (PM10) and sulphur dioxide.
Within the national strategy is a separate section for London. Air quality monitoring is primarily the responsibility of local
authorities that maintain a network of roadside monitors. Data from across London are collated by the SEIPH on behalf
of the Association of London Government's Air Quality Network.
DEFRA bulletins are updated hourly on DEFRA Website, giving levels of benzene,
1,3-butadiene, ozone, nitric oxide, nitrogen dioxide, sulphur dioxide, carbon monoxide and particles (PM10). These are measured at a range
of automatic monitoring stations nationally, 108 in all of which 29 are in London.
Click here to view the DEFRA London Automatic Air Monitoring Sites
NETCEN through its National Air Quality Information Archive provides
a comprehensive website about air quality in the UK. It provides information about the daily monitoring networks, forecasts and air quality
bulletins, the National Atmospheric Emissions Inventory, and national air quality research.
The Environmental Research Group was originally part of the South East Institute of Public Health (SEIPH); during 1999 it joined the
School of Health and Life Sciences at King's College London to enable closer collaboration with other groups engaged in air pollution
research. They form the London Air Quality Networkwhich provides
data and predictions of future air quality.
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- Air pollution strategy in London. Greater London Authority
- For specific information on emissions monitoring:
Operated by The National Environmental Technology Centre.
- Modelling:
Operated by Stanger Science and Environment.
- Industrial Sources
- Pollutant Specific Guidance:
Operated by Air Quality Consultants/ University of West of England.
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- British Medical Association(1997) Road Transport and Health. London: BMA, 1997.
- Buckingham C et al (1997) London Atmospheric Emissions Inventory. London Research Centre
- GLA London Air Quality Strategy. To be published November 2001. Consultation document available sometime in early 2001.
- Stage 1, 2 and 3 NAQS review and assessment local authority papers for each borough.
- Local authority air quality action plans.
- Local authority Interim Transport Plans (resulting from GLA Act).
- Watkiss et al. Informing transport health impact assessment in London. October 2000.
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