Memorandum submitted by the Natural Environment
Research Council (AQ10)
1. The Natural Environment Research Council
is one of the UK's seven Research Councils. It funds and carries
out impartial scientific research in the sciences of the environment.
NERC trains the next generation of independent environmental scientists.
2. Details of NERC's Research and Collaborative
Centres and Major programmes are available at www.nerc.ac.uk.
3. NERC's comments are based on input from
Professor Roy Harrison, Professor of Environmental Health at the
University of Birmingham and NERC Theme Leader for Environment,
Pollution and Human Health, and Swindon Office staff.
4. Summary:
— The current regime of air quality
management has failed to deliver anticipated improvements in air
quality, especially in the case of nitrogen dioxide, particulate
matter and ground-level ozone.
— There have been failures to anticipate
the factors which have led to a stalling in air quality improvement
with respect to nitrogen dioxide and particulate matter. In the
case of ground-level ozone, international action across continents
is required.
— Probably the weakest link in delivering
better air quality has been local government, which lacks the
expertise, resources and in some cases the political will and
powers needed to take decisive action.
— There are fundamental weaknesses
in basic knowledge in some areas which need to be remedied by
further strategic research.
WRITTEN EVIDENCE
The monitoring and modelling systems used by the
Government and whether these provide an adequate measure of air
quality;
5. The United Kingdom has a number of advanced
automatic and manual monitoring networks for different pollutant
groups. Although in a number of cases the monitoring commenced
prior to EU Directive requirements, the measurement techniques
and spatial density of the network are nowadays largely prescribed
by EU Directives. Contracts for network management are awarded
by competitive tender and generally speaking the quality and cost-effectiveness
of UK networks is very high. EU Directives allow a lower network
density if numerical modelling is carried out to provide information
on zones which are not directly monitored, and the UK follows
this option. As a general statement, the monitoring systems used
by government provide an adequate measure of current air quality.
Some pollutants (because of EU Directives) are monitored at far
higher density than is necessary for the protection of public
health (for example, carbon monoxide) whereas in the case of other
pollutants (eg dioxins) greater reassurance could be given to
the public over the level of exposures if a greater number of
monitoring sites were operational.
6. The quality of modelling work is variable
in relation to current pollutant levels and there are serious
questions over the ability of government-sponsored modelling work
to predict future air quality on timescales both of days and years.
As an example, the failure of abatement policies to reduce airborne
particle (PM10) concentrations since 2000 was not foreseen by
modelling. The Defra evidence budget for air quality has changed
little in real terms over the past 20 years, but during this time
there has been a steady shift of funds away from research, including
modelling, into monitoring, to the detriment of the better knowledge
and understanding of air quality processes which underpin model
development.
The extent to which the Government fully understands
and has identified the health and environmental risks caused by
poor air quality
7. While the responsibility for managing
air quality lies with Defra, expertise in understanding the health
impacts of poor air quality lies within the Health Protection
Agency, key personnel having transferred a few years ago to the
HPA from the Department of Health. Since 1993, the Department
of Health has been advised by the Committee on the Medical Effects
of Air Pollutants (COMEAP) and until recently by the Expert Panel
on Air Quality Standards (EPAQS), a Defra committee with a joint
Defra/HPA Secretariat. Recently, EPAQS has become the Sub-Committee
on Standards of COMEAP. Through these expert committees, the Government
has access to extremely high quality advice from UK experts, and
the UK has been a world leader in interpreting the evidence base
on air quality and health and in quantifying the public health
impacts of poor air quality. It is notable that in international
fora such as expert meetings organised by the European Union or
World Health Organisation, it is typical for UK medical and environmental
scientists to play a very major role. Regarding the environmental
risk caused by poor air quality, Defra sponsors research in the
area of pollutant effects on the environment which has influenced
EU policy on critical loads.
8. Many uncertainties remain in relation
to the impacts of air pollutants upon human health and the environment.
For example, the WHO air quality guidelines for nitrogen dioxide
which form the basis of the EU Directive Limit Values for this
pollutant are poorly supported by evidence from research. There
are also many unanswered questions relating to the health effects
of airborne particles. In particular, Limit Values do not discriminate
between particles of different chemical composition and from different
sources. Were it to be demonstrated that specific types of particles
were of higher toxicity than other types, policy could target
the more toxic particles thereby allowing more cost-effective
air quality improvements. Regrettably, UK government funding of
research in air quality and health has been at a very low level
in recent years and the topic has not been a high strategic priority
for the Medical Research Council. Excellent work was done with
European Union funding up to FP5 but the more recent Framework
Programmes have not supported significant work in this research
area. NERC is funding a new research programme jointly with MRC
and ESRC on Pollutant Exposures and Human Health which may include
work on air pollutants.
The extent to which the delivery chain for air
quality is coherent, integrated, co-ordinated and effective and
whether the bodies with responsibility for managing air quality
have appropriate incentives, understand their role and responsibilities,
and are adequately resourced.
9. The management of air quality in the
UK depends upon a complex inter-linkage of responsibilities. The
general policy framework is set by Defra but increasingly over
recent years has been dictated by the requirements of European
Union Directives. When the UK National Air Quality Strategy was
established in 1997, the majority of objectives were set on the
basis of advice from the government's Expert Panel on Air Quality
Standards, or WHO guidelines. Nowadays, by far the majority of
objectives are determined by European Union Limit Values set in
Brussels. Many of the measures which are influential in controlling
air quality are also set from Brussels. These include legislation
such as the Large Combustion Plant Directive, the National Emissions
Ceilings Directive and Directives dealing with the quality of
fuels and the exhaust emissions from road vehicles. The requirements
of the Directives are translated into UK law and practice by Defra,
the Environment Agency and the Department for Transport. Overall,
although complex, this establishes a coherent framework.
10. The regulation of atmospheric emissions
from major industries is the responsibility of the Environment
Agency. This activity takes place within the framework provided
by the Integrated Pollution Prevention and Control (IPPC) regulations
established by the EU and Directives such as the Large Combustion
Plant Directive. The Environment Agency is in most instances an
effective regulator and the UK has some of the best control of
industrial emissions in the world.
11. Most major industrial installations
are sited outside of urban areas, but it is within major urban
areas that the poorest air quality is encountered. The pollutants
causing the most major compliance problems are nitrogen dioxide
and particulate matter (measured as PM10). Responsibility for
local air quality management lies with local government and this
has proved to be by far the weakest link in the delivery chain
for good air quality.
12. The largest number of air quality management
areas have been declared due to exceedence of the annual average
Limit Value for nitrogen dioxide. The air quality situation with
regard to this pollutant was until recently expected to improve
dramatically as a result of reduced oxide of nitrogen emissions
from road vehicles, but this improvement has not materialised.
Nitrogen dioxide in the atmosphere arises from two sources. The
first is direct emissions, which historically comprised only a
small proportion of the total oxides of nitrogen emitted from
combustion sources such as traffic. The second is the atmospheric
oxidative conversion of nitric oxide (which comprises the major
nitrogen oxide emission from traffic) to nitrogen dioxide by reaction
with atmospheric ozone. Projections of improvements in nitrogen
dioxide concentrations have been largely confounded by increased
direct emissions of nitrogen dioxide, such[5]
that while total oxides of nitrogen emissions have been falling,
the percentage of nitrogen dioxide in those emissions has been
increasing. This was looked at in depth by Defra's Air Quality
Expert Group who concluded that this arose mainly from two factors.
The first was the retro-fitting of particular types of particle
traps on buses which enhance the emissions of nitrogen dioxide;
the second being that more recent diesel engine technologies lead
to a higher proportion of nitrogen dioxide in the emissions. Whilst
the former effect was clearly foreseeable, the latter appears
to have been overlooked until it showed up in the air quality
data. This is very much a weakness of the framing of emissions
regulations and of foresight within responsible agencies. As a
result of these problems, current trends in nitrogen dioxide at
the majority of monitoring sites are relatively flat (ie concentrations
are changing little year by year) whilst some sites have shown
marked increases in nitrogen dioxide. As tighter and better framed
emissions regulations for vehicles will take considerable time
to deliver benefits, the only way of achieving rapid improvements
in air quality is through reductions in traffic volumes.
13. The situation with regard to airborne
particulate matter (PM10) has also proved problematic. Central
urban concentrations were declining at a significant rate up to
2000. Since that year, however, the decline has ceased and concentrations
have been almost constant.[6]
This is contrary to expectations based on the projections of emissions.
A large proportion of PM10 particles at UK sites comprises secondary
sulphates and nitrates which are formed within the atmosphere
from the oxidation of sulphur dioxide and oxides of nitrogen.
While the emissions of sulphur dioxide have been falling dramatically
and those of oxides of nitrogen declining slowly, there has been
no perceptible change in the concentrations of nitrate and sulphate
particles during this period. The causes of this effect (referred
to as non-linearity) are not fully known and further research
is strongly justified. Shipping will soon become the dominant
source of sulphur dioxide emissions in Europe, and abatement measures
in this sector have lagged far behind those in other sectors.
14. The second most important contributor
to airborne particles in polluted urban areas is road traffic.
The continued tightening of EU Directive Limits on exhaust emissions
should have led to a substantial reduction in airborne particle
concentrations from traffic, which does not appear to be the case
as judged from the air quality data. The most likely reasons for
this are twofold. Firstly, motor engine manufacturers design their
engines to meet emissions standards on specific test cycles. If
such test cycles do not well represent the modes of the engine
during urban driving, on-road emissions can be appreciably higher
than those evaluated in the standard test cycle. Secondly, only
rather recently has it been recognised that a substantial proportion
of the PM10 emitted by road traffic does not come from the exhaust
pipe. Rather, it comes from abrasion sources such as the wear
of brakes, tyres and road surface, and by the turbulent suspension
of particles from the road surface into the air. The factors determining
the non-exhaust particle sources are not particularly well understood
but it is likely that this source has remained constant or even
increased over the past decade due to changes in traffic fleet
volumes, speeds and the general increase in vehicle weights.
15. A further source of airborne particles
for which we have very poor UK data is wood smoke. There is concern
that with continuing increases in the cost of fossil fuels and
electricity, more home-owners will turn to wood burning for home
heating. Across mainland Europe, this is a major source of PM10
within urban areas and there must be a real prospect that this
will increase in the UK with a substantial associated detriment
to the achievement of air quality targets for PM10 and PM2.5.
16. Responsibility for compliance with air
quality strategy objectives lies with local government authorities.
Unfortunately, such authorities have proved highly ineffective
at improving air quality. In many cases, they lack the knowledge
and expertise to make the necessary judgements of the measures
necessary and in some cases lack the political will or powers
to bring about the necessary improvements. If local authorities
are going to remain the main agent for ensuring compliance of
local air quality with the objectives of the National Air Quality
Strategy, there needs to be a considerable enhancement in their
knowledge base and a strengthening of the political will to make
hard decisions which will lead to genuine air quality improvements.
17. A further pollutant which is more of
a problem in rural than urban areas and which lies outside of
local air quality management regulations is ground-level ozone
(not to be confused with stratospheric ozone which plays an important
role in filtering harmful ultraviolet light). Ground-level ozone
is harmful both to human health and to growing crops, and there
is serious concern that despite action in Europe to limit the
emissions of the pollutants responsible for its formation in the
atmosphere (oxides of nitrogen and volatile organic compounds),
the lack of effective action outside of Europe will lead to a
substantial global increase in ground-level ozone concentrations.[7]
European policy has been rather effective in reducing peak summer-time
concentrations of ground-level ozone, but the hemispheric background
which is heavily influenced by precursor emissions in Asia and
North American continues to increase.
The steps that need to be taken to ensure that
air quality targets will be met in the future.
18. There are a number of measures which
would be highly beneficial in the long-term improvement of the
air quality situation in the UK. These include the following:
(a) There should be a requirement for the measurement
of the nitrogen dioxide content of the emissions from all combustion
sources, including road vehicles. Limits should be set on emissions
of nitrogen dioxide, whereas the current emission limits apply
only to NOx (which is the sum of nitrogen dioxide and nitric oxide).
(b) There needs to be intensive research on the
emissions of non-exhaust particles from road vehicles culminating
in the establishment of regulatory limits on the emissions of
non-exhaust particles under standard test conditions.
(c) A far greater implementation of traffic management
measures is required in order to reduce exceedences of air quality
objectives for nitrogen dioxide and PM10.
(d) There needs to be strong enforcement of regulations
against wood burning within urban areas.
(e) Firm international action is required to
ensure continued reductions of sulphur dioxide, oxides of nitrogen
and volatile organic compounds which are the precursors of secondary
particle formation in the atmosphere. In particular, the regulation
of sources such as shipping and aircraft, which to date have been
little affected by emissions regulations, needs to be a high priority.
Action on the emissions of precursors of ground-level ozone needs
to be taken worldwide in order to generate benefits with respect
to this pollutant.
(f) There needs to be a considerable strengthening
of the local air quality management regime in terms of both raising
the performance level of local government officers and also strengthening
the regulations requiring local air quality management.
(g) The capability of Defra to predict future
air pollutant concentration trends has been very poor in some
areas. This reflects fundamental weaknesses in the understanding
of basic air pollution processes which can only be remedied by
an increase in strategic research in the field.
11 December 2009
5 Trends in Primary Nitrogen Dioxide in the UK, Air
Quality Expert Group, Department for Environment, Food and Rural
Affairs, London, 156pp (2007). Back
6
Why are PM10 Concentrations in Europe not Falling?, R.M. Harrison,
J. Stedman and D. Derwent, New Directions, Atmospheric Science
Perspectives Special Series, Atmos. Environ., 42, 603¸606
(2008). Back
7
Ground-level Ozone in the 21st Century: Future Trends, Impacts
and Policy Implications, Science Policy Report 15/08, The Royal
Society, 132p (2008). Back
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