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

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 (e.g. 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 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[1] 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 (i.e. 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[2]. 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[3]. 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

[1] Trends in Primary Nitrogen Dioxide in the UK, Air Quality Expert Group, Department for Environment, Food and Rural Affairs, London, 156pp (2007).

[2] 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).

[3] Ground-level Ozone in the 21st Century: Future Trends, Impacts and Policy Implications, Science Policy Report 15/08, The Royal Society, 132p (2008).