Memorandum submitted by Dr Gary Fuller, Ben Barratt and Dr David Green, Environmental Research Group, King's College London (AQ 16)


· We have concerns about the current UK monitoring systems with respect to their ability to support effective policy interventions in order to meet EU Limit Values.

· The current UK monitoring system is designed to provide trends in regulated pollutant concentrations and is limited in its ability to explain the mechanisms behind such trends.

· A lack of understanding of air pollution sources and their linkages to ambient concentrations has been underlined in recent years by a divergence of predicted emissions reductions and measured concentrations.

· We therefore recommend that the UK monitoring system be expanded to include targeted long-term monitoring in urban centres across the UK specifically designed to further understanding of the sources and behaviour of regulated pollutants, particularly the components of particulate matter (PM) and NO2.

· Such monitoring will also be essential in order to assess the effectiveness of air quality management policies.

About us

1. The Environmental Research Group at King's College London is one of the UK's leading institutes in urban air quality assessment. Focusing mainly in London and the south east we run air quality monitoring networks on behalf of local authorities and Defra including the London Air Quality Network (see We undertake air quality modelling to support air quality policy and interventions on behalf of the Greater London Authority / Transport for London and local authorities. We are also active in research into the sources of urban air pollution and their health effects. The National Audit Office interviewed our Director, Professor Frank Kelly, on 2nd October 2009 regarding the understanding of air pollution health effects. Our comments here will therefore not address this area but focus instead on UK monitoring systems.

UK monitoring systems used by Government

2. We have concerns about the current UK monitoring systems with respect to their ability to support effective policy interventions in order to meet EU Limit Values. By submitting modelled air pollution concentrations to the EU the UK Government is only obliged to have half the standard number of monitoring sites required by the EU Air Quality Directive (EC, 2008). Whilst the use of modelling information in this way enables better spatial coverage of air pollution in the UK, the reduced number of monitoring sites may leave the UK's national monitoring networks vulnerable with respect to their ability to:

· Represent urban background and roadside concentrations in many areas of the UK.

· Provide sufficient understanding of pollution sources to direct policy and to enable changes in these pollution sources to be tracked over time.

· Determine the efficacy of air quality management interventions.

3. In London and the south east of the UK the coordination of local authority and national measurements by King's has led to a cohesive network of densely distributed monitoring sites, representing the range of pollutant exposures in the region with sites in kerbside, roadside, industrial, urban background, suburban and rural locations. Such cohesive networks are generally absent from other cities in the UK and many large urban areas do not have representative coverage of background and near road monitoring sites, for instance the UK Automatic Urban and Rural Network has only one roadside monitoring site in Greater Manchester (Bury).

4. By necessity the current design of the AURN has to ensure compliance with directive requirements. We would not advocate simply doubling the air quality monitoring sites used by Government, instead national monitoring programmes need to be targeted towards understanding sources in order to inform and track the progress of air quality management policies. More comprehensive analysis of measurement data is then required to ensure that the full value of such targeted measurement networks is realised.

5. A lack of understanding of air pollution sources and their linkages to ambient concentrations has been underlined in recent years by a divergence of predicted emissions reductions and measured concentrations. For instance, it is unclear why current polices to decrease PM10 concentrations are not yielding the desired results across Europe (Harrison et al., 2008) and, despite European and London specific measures, primary PM10 from within London increased between 1998 and 2003 (Fuller and Green, 2006). Further, progress towards reducing roadside concentrations of NO2 have been confounded by changes in the emissions of primary NO2 (Carslaw, 2005; AQEG, 2007) that were not anticipated in emissions models. These changes in emissions of primary PM10 and primary NO2 were first detected in London using the dense measurement network uniquely available in the capital. Outside London deficiencies in monitoring networks make it difficult to detect and quantify these new source trends. The UK's approach with respect to the number of monitoring sites for Directive compliance may therefore leave us vulnerable to detecting and understanding emission trends.

6. A simple network design to enable separation and quantification of pollution sources was proposed by Lenschow et al., (2001) for the understanding of PM10 sources; however this network design has applicability for other pollutants. The so-called Lenschow approach identifies monitoring sites to represent exposure at the different location types and sources can be separated by difference. For example, 'roadside minus background' concentration gives the contribution from a road or 'background minus rural' gives information about sources across an urban area and so-forth. Establishing and maintaining such site pairings allows sources to be tracked over time and augmenting the UK monitoring networks in this way may increase the source information that they are able to provide. Such separation of pollution concentrations by source is especially important for the understanding of airborne particulate matter (PM) where different pollution sources give rise to particles with different chemical and physical properties which are in turn likely to have different human health effects.

7. Only limited UK measurements are available on the composition of PM. Although Defra's networks measure particle composition in rural areas this does not have high time resolution necessary to inform Limit Value compliance, emission inventories and modelling. The UKs' measurement of urban PM composition is focused on London and is one of the few examples of the application of a Lenschow design. However the measurement of PM composition in the UK does not include sufficient chemical species to allow the mass concentration of PM to be fully accounted for using 'mass-closure' approaches. We are seeking to control a pollutant without sufficient information on its composition and sources. For instance, are increases in primary PM10 in London due to tailpipe emissions or tyre and brake wear? Issues around our control of PM10 concentrations have been bought to the fore with the recent EU Commission decision on the UK's time limit extension but there have been few systematic measurements of the complete mass of urban PM10 composition since those carried out in London and Birmingham between 2000 and 2002 (Harrison et al., 2004). Additionally, there is no national programme to measure urban PM2.5 composition despite the new EU exposure reduction obligation. Without measurements of PM2.5 composition now, in the reference years, it will be difficult to direct policy and determine changes over the ten year exposure reduction period. This approach contrasts with our near neighbours where a systematic €1m programme to measure PM2.5 and PM10 composition has just begun in Paris to expressly inform air pollution management strategies (see

8. Targeted monitoring and analysis of measurement data is also required to provide a level of accountability in air quality management policy, i.e., did a specific policy lead to identifiable improvements in air quality (and also in adverse health impacts) and was this improvement cost effective? If not, why not and how could it be improved to make it more cost effective (HEI, 2003)? Carrying out such accountability studies is a complex task given the wide range of influences on air quality independent of the effects of the policy, and requires targeted monitoring strategies. A recent example where monitoring networks were deficient was the London Congestion Charging Scheme (CCS). An accountability study to assess the effects of the CCS on air quality was very limited in success as existing monitoring was insufficient to isolate the effects of a decrease in traffic numbers and congestion from underlying trends and meteorology (Atkinson et al., 2009). In contrast, a bespoke targeted measurement programme has been funded by Transport for London to determine pollution changes arising from the London Low Emission Zone.

9. Many air quality management policies such as fleet renewal have gradual effects. Therefore, it is essential that targeted monitoring programmes or those monitoring of non-regulated pollutants (such as PM composition or O3 precursors) be carried out over the long-term. Long-term monitoring is also required to ensure that improvements are sustained over time and not eroded by unexpected changes. These targeted monitoring strategies will be essential if the UK is to meet EU Limit Values for NO2 and PM10 given the increasingly fragile reliance on vehicle emissions reductions. The cost of measurement programmes may be small compared to the cost of interventions to improve air pollution. Without a fuller understanding of the behaviour and nature of pollutants, such as NOX and PM10, effective and efficient policy decisions will be far more difficult to formulate.


10. Air Quality Expert Group (AQEG), 2007. Trends in primary nitrogen dioxide in the UK. Defra, London.

11. Atkinson R.W., Barratt B., Armstrong B., Anderson H.R., Beevers S.D., Mudway I.S., Green D., Derwent R.G., Wilkinson P., Tonne C., Kelly F.J., 2008. The impact of the Congestion Charging Scheme on pollution concentrations in London. Atmospheric Environment 43, 5493-5500

12. Carslaw, D.C., 2005. Evidence of an increasing NO2/NOX emissions ratio from road traffic emissions. Atmospheric Environment 39, 4793-4802.

13. European Commission (EC) 2008. Directive 2008/50/EC of the European Parliament and of the Council on ambient air quality and cleaner air for Europe. Commission of the European Community, Brussels.

14. Fuller, G. W. and Green D., 2006. Evidence for increasing primary PM10 in London. Atmospheric Environment 40, 6134-6145.

15. Harrison, R.M., Jones, A.M., Royston, G.L., 2004. Major component composition of PM10 and PM2.5 from roadside and urban background sites. Atmospheric Environment 38, 4531-4583.

16. Harrison, R.M., Stedman, J. and Derwent, R.D., 2008. New Directions: Why are PM10 concentrations in Europe not falling? Atmospheric Environment 42, 603-606.

17. HEI, 2003. Assessing Health Impact of Air Quality Regulations: Concepts and Methods for Accountability Research. Communication 11, September 2003. Health Effects Institute, Boston, MA 02129-4533.

18. Lenschow, P., Abraham, H.J., Kutzner, K., Lutz, M., Preuβ, J.D. and Reichenbächer W., 2001. Some ideas about the sources of PM10. Atmospheric Environment 35, S23-S33.

14 December 2009