European Commission DG Environment. National Emission Ceilings Directive Review. Task 2 Feasibility of an Emission Ceiling for Particulate Matter

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1 European Commission DG Environment National Emission Ceilings Directive Review Task 2 Feasibility of an Emission Ceiling for Particulate Matter Final Report Entec UK Limited

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3 Report for Michel Sponar DG ENV-C.1 European Commission Avenue de Beaulieu 5 6/103B-1160 Brussels Belgium Main Contributors Helen ApSimon (Imperial College) Katherine Wilson Alistair Ritchie Alun McIntyre Mark Watson Issued by Katherine Wilson European Commission DG Environment National Emission Ceilings Directive Review Task 2 Feasibility of an Emission Ceiling for Particulate Matter Final Report Approved by Alistair Ritchie Entec UK Limited Entec UK Limited Windsor House Gadbrook Business Centre Gadbrook Road Northwich Cheshire CW9 7TN England Tel: +44 (0) Fax: +44 (0) h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task Certificate No. EMS Certificate No. FS In accordance with an environmentally responsible approach, this document is printed on recycled paper produced from 100% post-consumer waste, or on ECF (elemental chlorine free) paper

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5 i Executive Summary This Report Entec UK has undertaken a project for the European Commission (Contract No /2004/383810/MAR/C1) to support the review of Directive 2001/81/EC, referred to as the National Emission Ceilings Directive (NECD). This report relates to Task 2 of the project: Analysis of the feasibility of an emission ceiling for particulate matter (PM) and related reporting requirements. In addressing this task, Entec has employed Helen ApSimon as an associate to undertake a large proportion of the work. Helen is Professor of Air Pollution at Imperial College London, and has worked extensively for Task Forces under the Convention on Long-Range Transboundary Air Pollution of the UN ECE. She is also a member of the Air Quality Expert Group (AQEG) for the Department for Environment, Food and Rural Affairs (Defra) in the UK. The setting of emission ceilings has been considered in the context of the wider objectives of reducing overall concentrations of particulate matter and associated health effects arising from human exposure. The report is structured around answers to the six questions below. What are the limitations of current EU policy approaches to reducing exposure to particulate matter? How much do secondary and primary components of anthropogenic origin contribute to concentrations, and how is this likely to change with current legislation? What are the appropriate geographical scales for control, i.e. to what extent is primary anthropogenic particulate matter a transboundary/local problem? How much do different anthropogenic sources contribute to primary emissions; how significant are they in health terms and how well can they be quantified for reliable emission inventories and estimation of abatement potential? What are the characteristics of these source components in terms of: source type (e.g. point, elevated or ground level, diffuse, area, fugitive sources); particle size distribution; particle composition/ chemical speciation; relative health impact; and uncertainty? How can emission ceilings be decided and for what components? Can integrated assessment or gap closure methods be extended to primary particulate matter, or are there other ways of selecting what emission ceilings are appropriate? Are emissions ceilings measurable and efficient in terms of effects? What are the issues for implementation and compliance assessment and how do these compare with other approaches for (a) reporting emissions and measurements; and (b) modelling? What are the pros and cons of the various options for introducing emission ceilings for particulate matter? The key recommendations from our analysis are summarised below. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

6 ii Recommendations General recommendations relating to the feasibility of an emission ceiling for PM 1. The Commission should consider additional policy measures to reduce population exposure to PM. Rationale Air quality limit values currently set for PM 10 and under consideration for PM 2.5, can result in focussing on reducing concentrations in hot spots, when reductions elsewhere may be more cost-effective in terms of benefiting the wider population (particularly given that there is no identified threshold of effects). Additionally, controlling ambient concentrations has proven to be difficult for Member States, when there are significant contributions from natural or transboundary sources. The concept of gap closure on ambient concentrations has been suggested as a means of achieving relative reductions in population exposure. However, such a measure may not be possible for implementation in the short-term, as it may require at least three years of PM 2.5 monitoring data, in order to establish a baseline. The setting of an emission ceiling for primary PM could complement other legislation to control particulate matter. Furthermore, the setting of an emission ceiling specifically for PM 2.5 would focus more emphasis on the finer fraction PM 2.5, considered to be most important for health effects. In order to focus action more directly on reducing human exposure and associated health impacts, there can be significant advantages in introducing ancillary requirements to also achieve prescribed reductions in population exposure (e.g. spatially disaggregated emission inventories as described below). Related recommendations It is recommended that the Commission keep under review developments in evidence of the relative health effects of PM 10, PM 2.5 and coarse PM, to inform the identification of the targeted PM size fraction(s) in any future EU policy development on PM. Whilst PM 2.5 is the priority size fraction to be concerned about for health effects, PM 10 and coarse PM should also be taken into account. The absence of an identifiable threshold of effects on health should be a major consideration in future policy development and the setting of long-term objectives. Given this no threshold situation, the Commission should consider setting relative emissions ceilings, rather than absolute targets. This may also increase the feasibility of an emission ceiling for PM, by avoiding problems when recalculating baselines, for example, following revisions of emission factors. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

7 iii Substantial effort needs to be allocated to the improvement of emission inventories for particulate matter, concentrating on emissions of PM 2.5 and sources correlated with urban areas. Further work is also needed to assess and reduce uncertainties. It is further recommended that development of emission inventories for PM 2.5 is linked to development of corresponding inventories for chemical components that may be related to toxicity of particles (such as PAHs, metals and elemental/organic carbon). This would enable rapid adaptation in response to new evidence on which components are responsible for adverse health effects 1. Truly national emission ceilings structured in the same manner as current NECD pollutants 2. National emission ceilings for primary anthropogenic PM, structured in a similar manner as current NECD pollutants, could be a short-term means of achieving some reductions in primary emissions. Rationale The policy would be simple to introduce with relatively straightforward reporting requirements. Whilst emission reductions might not target the sources that contribute most to population exposure, they could be a means of addressing the transboundary contribution made by primary particulates, as highlighted in the EMEP research. However, it is noted that current modelling methods may overstate such transboundary contributions, and that local benefits of emission reduction in the home country will often be considerably greater. Related recommendations It is recommended that further investigation is undertaken of the EMEP modelling of transboundary contributions, including border grid-square effects, to increase understanding of the PM 2.5 concentrations in areas close to national borders, and apportionment between national and transboundary contributions. Dual targets for reducing both emissions and population exposure: a first level approach, using spatially disaggregated emission inventories 3. Whilst a truly national emission ceiling for PM could potentially lead to reductions in transboundary contributions, a first level approach, using spatially disaggregated emissions inventories with population data, could provide a means of enhancing NECs for PM to target emission reductions in areas where population exposure is thought to be highest. This could be achieved with little additional data requirements. This option is strongly recommended as a first step. 1 However if new evidence indicated the ultrafine particles are responsible for health effects, these particles contribute very little by mass to PM 2.5, and legislation based on controlling particle mass would not be appropriate for their control. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

8 iv Rationale Evidence has been presented indicating that low level sources in urban agglomerations give high contributions to population exposure, and that reduction of exposure to primary PM 2.5 is a far more national/local problem and less a transboundary problem than secondary inorganic aerosol 2. Careful attention is therefore needed as to where emission reductions are made within a country. Existing population data (for example that due to be published by Eurostat later this year 3 ) could be combined with spatially disaggregated emission inventories, which would have to be developed by Member States prior to the implementation of the legislation. This information could be used to develop a weighted index that would better reflect the relative contribution per ton to population exposure. The reduction of the overall index weighted sum of emissions would be an approximate indicator of the targeting of reductions to the important emissions for population exposure. It should achieve the percentage reduction relative to the base year prescribed as an ancillary requirement to the emission ceiling for each Member State. Related recommendations If this policy was to be implemented, all Member States would need to develop spatially disaggregated emission inventories. Dual targets for reducing both emissions and population exposure: a second level approach, using integrated assessment modelling 4. A longer term recommendation is to develop a second level approach, using integrated assessment modelling with population data, to give more detailed estimates of population exposure attributable to different sources. Rationale A more sophisticated level two approach could rely on more detailed national modelling, combining population data with modelling of concentrations to give more detailed estimates of population exposure attributable to different sources. It would require gridded emissions data and population data. It would then be possible to explore the response of the population exposure index to different abatement options, taking spatial considerations into account, developing curves of exposure index against cost. Emission ceilings could then be guided by specified reductions in exposure index. 2 It should be noted that in modelling sulphate concentrations EMEP currently assume that 5% of the sulphur is directly emitted as primary sulphate aerosol, equivalent to 650 kt of primary particulate matter in the PM 2.5 size range emitted from EU and New Member States in This percentage may be an overestimate with implications for the sulphate contribution in the major source areas. It is not included in the primary PM emission inventories as this would be double counting with the SO 2 inventories, but would clearly be very significant if it was considered as a contribution to primary PM This dataset will be at a 100 m by 100 m scale (EC, 2004) h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

9 v Implementation of the second level approach described above could eventually be combined with the method suggested by Laxen and Moorcroft (2005) to reduce population exposure based on monitoring of the enhancement of concentrations in urban agglomerations. The combination of the two approaches would mean that the percentage reduction in ambient concentrations under gap closure could be linked to the emission reductions that are required to achieve them. This would allow regulatory authorities to target those emissions thought to be most important for population exposure, whilst at the same time, providing a means of measuring the impact of these emission reductions on ambient concentrations to which the population is exposed. The concentration method suggested by Laxen and Moorcroft (2005) requires at least three years of baseline monitoring data. As such, if implemented for PM 2.5, there would be a time delay before compliance could be monitored. Related recommendations A model similar to that being developed by IIASA for enhanced concentrations in urban areas should be used to relate emissions and concentrations at a fine resolution (5 x 5 km). Member States should be encouraged to develop their own more detailed assessment models, using their knowledge of particular situations in their own countries for reporting compliance. The simple approach developed by IIASA could then serve as a default method. Careful consideration is required on the basis for selecting emission ceilings and setting targets. One option is to select emission reductions that achieve the greatest decrease in population exposure (and on the basis of a proportional relationship the greatest health benefit) whilst still being relatively cost-effective, irrespective of where the reductions are made and who receives the maximum benefit. The alternative is to set gap closure targets for reducing either concentrations or population weighted concentrations by a set percentage, to spread benefit proportionally across Europe. These alternatives could lead to quite different emission ceilings from optimisation calculations with RAINS or other integrated assessment models. The links between gap closure on ambient concentrations and the second level emissions approach should be further investigated, in order that short term policy measures, such as the first-level approach, can be implemented in a manner that allows for the progression to longer-term approaches. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

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11 vii Contents 1. Introduction This Report Background Task 2 scope and report structure Limitations of Current EU Approaches Policies to reduce the impacts of particulate matter on health What are the limitations of current EU policy approaches in reducing exposure to particulate matter? Policy framework Current European legislation applicable to particulate matter Policies relating to particulate matter implemented outside the EU Summary How much do primary and secondary components of anthropogenic origin contribute to concentrations, and how is this likely to change with current legislation? Spatial variability and source apportionment Modelled concentrations of primary and secondary concentrations across Europe current and projected Summary Geographical Scales for Control The behaviour of primary and secondary emissions Impacts on population exposure Sectoral effects Source apportionment by the EMEP model National contributions to population exposure Summary Source Characteristics Introduction 38 h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

12 viii 4.2 Sectoral analysis Approach to sectoral analysis Total Annual PM Emissions, EU PM emissions by sector PM emissions by source PM emissions by fuel type Emissions, exposure and health impacts Summary tables for characteristics of PM source components within the EU Uncertainty Summary Potential Role for Emission Ceilings Target setting Extension of integrated assessment modelling to primary PM Using the current RAINS approach Modelling the abatement of different source types Are there alternative ways of setting emission ceilings for PM? Towards long-term objectives: relative as opposed to absolute emission ceilings Truly National Emission Ceilings Sector/source specific ceilings or ceilings on urban emissions Ceilings to take account of population exposure Alternative methods Summary Implementation and compliance Reporting requirements Emissions Modelling requirements Measurements Comparison with other approaches Summary Pros and Cons of Emission Ceilings Summary 70 h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

13 ix The potential need for an emission ceiling in addition to limit values for PM 10 and PM Characteristics of exposure to primary particulates Emission ceilings on PM 2.5 as opposed to PM Relative ceilings or absolute ceilings General advantages and problems in setting emission ceilings Different options for setting emissions ceilings and their relative merits Advantages and disadvantages of setting emission ceilings as compared with gap closure on ambient concentrations Legislation on PM 2.5 emission standards for specific sources Recommendations References 78 Table 1 EU limit values under the 1st Air Quality Directive 15 Table 2 Summary of legislation in place, advantages and limitations 17 Table 3 Annually averaged primary and secondary inorganic concentrations of PM 2.5 averaged over the Netherlands by anthropogenic source. Calculated for the year 1995, based on emissions for the Netherlands and the CEPMEIP inventory for European countries (RIVM, 2002) 22 Table 4 Emission projections (kt) for the baseline scenarios with climate measures (August 04) for EU-25, Switzerland and Norway 23 Table 5 Transboundary contributions of primary and secondary particulates to PM 2.5 concentrations in Member States for 2002 (EMEP, 2004c) 33 Table 6 Relative contribution of PM 2.5 to PM 10 for the EU-25 (IIASA, 2004b August 04 Baseline Table 7 with climate measures ) 39 Characteristics of PM source components within the EU-25, arranged by the sectors presented by Amann et al. (2004a) in Figure Table 8 Parameters that affect uncertainty in the context of emissions inventories 50 Table 9 Options for setting emissions ceilings 64 Table 10 Advantages in setting emission ceilings for primary PM Table 11 Some difficulties in setting national emission ceilings 72 Table 12 Pros and cons of alternative approaches to setting emission ceilings 73 Table 13 Comparison of emission ceilings approach and gap closure approach to reducing enhanced concentrations in urban areas to decrease population exposure to PM Figure 1 Interaction of different forms of legislation applying to particles. The associated advantages and limitations are considered in more detail below. 14 Figure 2 Schematic illustration of relative contributions to PM concentrations in g/m 3 for road side sites in an east-west row of grid squares (right to left) across London (based on estimates for1996) (Mediavilla-Sahagun and ApSimon, 2003) 20 Figure 3 Estimated contribution to PM 10 at a busy traffic site from all sources for Berlin in 2002 (also accounting for secondary sources of PM) (Sadler and Lutz 2004) NB # based on values recorded at the top of a radio tower, 324 m above ground 21 Figure 4 Source attribution for PM 10 in Augsburg Königsplatz (g/m³) (Strauss 2004) 21 Figure 5 Modelled contributions of secondary inorganic aerosol (SIA) and primary PM 2.5 concentrations in 2000 with projected % reductions by 2010 (data from EMEP model) 25 Figure 6 Modelled contributions of anthropogenic PM 2.5 (primary and secondary inorganic aerosols) with projected changes by 2010 and Rural concentrations, annual mean h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

14 x [µg/m3] from known anthropogenic sources. Average of calculations for 1997, 1999, 2000 & 2003 meteorologies (Amann et al., 2004b) 26 Figure 7 Typical dependence on distance of contributions from primary and secondary emissions, assuming a uniform spatial density of emissions 29 Figure 8 Illustration of relative contributions to population exposure in different distance bands due to sources of equivalent magnitude located in an urban agglomeration 30 Figure 9 Comparison of the relative contributions of different sectors to UK emissions of primary PM 10, and to exposure of the UK population, based on the UKIAM model. 31 Figure 10 EMEP assessment of relative response to emission reductions from different countries in the EU-25, North Sea and Baltic (for 2010 CLE scenario). The whole of a pie chart (100%) corresponds to the total reductions added for all EU25 plus N Sea and Baltic 33 Figure 11 Footprint of Luxembourg PM emissions from EMEP model 35 Figure 12 Projected PM emissions across EU-25 (IIASA, 2004b August 04 Baseline with climate measures ) 40 Figure 13 Chemical components (g/m 3 ) at roadside sites coarse fraction (AQEG, 2004) 42 Figure 14 Chemical components (g/m 3 ) at background coarse fraction (AQEG, 2004) 42 Figure 15 Chemical components (g/m 3 ) at roadside fine fraction (AQEG, 2004) 43 Figure 16 Chemical components (g/m3) at background fine fraction (AQEG, 2004) 43 Figure 17 Sources of primary PM 2.5 emissions (Amman et al., 2004a) 44 Figure 18 Proportions of PM 10 emissions by fuel type between 2000 and 2020 (IIASA, 2004b August 04 Baseline with climate measures ) 45 Figure 19 Proportions of PM 2.5 emissions by fuel type between 2000 and 2020 (IIASA, 2004b August 04 Baseline with climate measures ) 45 Figure 20 Comparison of national emission inventories for PM10 with the RAINS estimates (for the year 2000) (Amann et al., 2004c) 48 Figure 21 Comparison of national emission inventories for PM2.5 with the RAINS estimates (for the year 2000) (Amann et al., 2004c) 49 Figure 22 Comparison of national emission inventories for existing NECD pollutants with the RAINS estimates (for the year 2000) (Amann et al., 2004c) 50 Figure 23 Components of integrated assessment modelling applied to NECs 54 Figure 24 Population-exposure distribution (NSCA, 2004). Area A represents the effects of policies targeted at reducing exposure only to those exposed above the Limit Value; Area B represents the effects of policies aimed at reducing exposure in the general population. Area B is much greater than Area A, and therefore, in simplified terms Policy B is more cost effective than Policy A. However, the greater level of exposure to each person in Area A will clearly need to be factored into the consideration of priority. 58 Figure 25 Example of curve indicating reduction in population exposure as a function of cumulative cost (based on national scale integrated assessment model, UKIAM Oxley et al., 2004). 61 Appendix A Simple model to illustrate comparison of the atmospheric transport of primary and secondary PM over different distance ranges h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

15 11 1. Introduction 1.1 This Report Entec UK has undertaken a project for the European Commission (Contract No /2004/383810/MAR/C1) to support the review of Directive 2001/81/EC, referred to as the National Emission Ceilings Directive (NECD). This report relates to Task 2 of the project: Analysis of the feasibility of an emission ceiling for particulate matter (PM) and related reporting requirements. In addressing this task, Entec has employed Helen ApSimon as an associate to undertake a large proportion of the work. Helen is Professor of Air Pollution at Imperial College London, and has worked extensively for Task Forces under the Convention on Long-Range Transboundary Air Pollution of the UN ECE. She is also a member of the Air Quality Expert Group (AQEG) for the Department for Environment, Food and Rural Affairs (Defra) in the UK. 1.2 Background Epidemiological evidence linking exposure to fine particulate matter and health effects has led to concerted action across the EU to reduce ambient concentrations. Hitherto, in the absence of clear identification of particular associated chemical components or size fractions that are responsible for adverse impacts on human health, legislation has mainly been directed towards ambient air quality limits on the concentrations of total PM 10, particles of aerodynamic diameter less than 10 microns able to penetrate to the lung. However it is likely that the finer fraction below 2.5 microns, which can penetrate deeper into the lungs, poses a greater risk (WHO, 2004a). There is no apparent threshold of concentration for such effects. The aim of this work is to consider the benefits and limitations of complementary legislation setting emission ceilings as part of a strategy to reduce health risks associated with human exposure to fine particulates. Particulate matter in the air is partly due to primary emissions, and partly the result of secondary formation from gaseous precursors. EU Air Quality Limit Values set for will be exceeded in many Member States, particularly in urban areas close to major roads (WGPM, 2004). Such patterns of exceedence tend to result in a focus on localised measures to eliminate hot-spots, particularly on primary emissions from traffic, and may have little effect on overall concentrations affecting exposure of the general population. Thus it is timely to consider how other legislative limits such as emission ceilings could help to reduce concentrations and population exposure more broadly, while also assisting in the attainment of air quality limit values. Under the National Emissions Ceilings Directive (NECD) the precedent has already been set for controlling precursor emissions of secondary particulates, namely SO 2, NO X and NH 3. This report will therefore focus on the feasibility of ceilings for primary particle emissions. 4 PM limit values have been set under the First Daughter Directive (1999/30/EC) of the Air Quality Framework Directive (96/62/EC). h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

16 12 Furthermore, the focus is on emissions of anthropogenic origin only. It will consider alternative ways in which such emission ceilings could be set and the additional benefits they could bring. This leads on to the challenges and problems of deriving such ceilings in a robust and meaningful manner, and in their introduction and implementation under corresponding EC Directives. It will be necessary to consider the adequacy of basic data on emissions and national emission inventories and the range of measures available to reduce them and their effectiveness and reliability. It is also important to recognise the shorter distance scales important in atmospheric transport of primary emissions, and the consequences for source apportionment and patterns of population exposure. 1.3 Task 2 scope and report structure The setting of emission ceilings has been considered in the context of the wider objectives of reducing overall concentrations of particulate matter and associated health effects arising from human exposure. The lay-out of the report is structured around answers to the six questions detailed below. Section 2. Section 3. Section 4. Section 5. Section 6. Section 7. What are the limitations of current EU policy approaches to reducing exposure to particulate matter? How much do secondary and primary components of anthropogenic origin contribute to concentrations, and how is this likely to change with current legislation? What are the appropriate geographical scales for control, i.e. to what extent is primary anthropogenic particulate matter a transboundary/local problem? How much do different anthropogenic sources contribute to primary emissions; how significant are they in health terms and how well can they be quantified for reliable emission inventories and estimation of abatement potential? What are the characteristics of these source components in terms of: source type (e.g. point, elevated or ground level, diffuse, area, fugitive sources); particle size distribution; particle composition/ chemical speciation; relative health impact; and uncertainty. How can emission ceilings be decided and for what components? Can integrated assessment or gap closure methods be extended to primary particulate matter, or are there other ways of selecting what emission ceilings are appropriate? Are emissions ceilings measurable and efficient in terms of effects? What are the issues for implementation and compliance assessment and how do these compare with other approaches for (a) reporting emissions and measurements; and (b) modelling? What are the pros and cons of the various options for introducing emission ceilings for particulate matter? h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

17 13 2. Limitations of Current EU Approaches 2.1 Policies to reduce the impacts of particulate matter on health Current EU legislation is targeted at achieving reductions in total PM 10, or even total suspended particulate, TSP. However, in reviewing links between exposure to particulate matter and health effects, the WHO (WHO, 2000; WHO, 2003) indicates that recent studies in which the PM 10 size fractions and/or constituents have been measured suggest that the observed effects of PM 10 are in fact largely associated with fine particles, strong aerosol acidity or sulphates (which may serve as a proxy for the other two) and not with the coarse (PM 10 PM 2.5 fraction). Although there may still be some adverse health effects from the coarse fraction, this indicates that legislation should move towards achieving reductions in the emissions and concentrations of finer particles. The WHO (2004a) highlights the lack of data available to establish whether certain sources or certain particle compositions give rise to special concern with regard to health impact. It states that toxicological studies have pointed to primary combustion-derived particles as having a higher toxic potential. Combustion particles are often rich in transition metals and organic compounds, and also have a relatively high surface area. By contrast, the WHO (2004a) states that several other single components of the PM mixture (e.g. ammonium salts, chlorides, sulfates, nitrates and wind-blown dust such as silicate clays) have been shown to have a lower toxicity in laboratory conditions. However, the WHO (2004a) stresses that despite these differences found under laboratory conditions, it is not currently possible to quantify the contributions from different sources and different PM components to the health effects caused by exposure to ambient PM. In the meantime WHO has provided dose-response functions in the form of relative risk estimates for the effects of long-term exposure to particulate matter on the morbidity and mortality associated with a 10 µg/m 3 increase in the concentration of PM 2.5 or PM 10. There is no established threshold below which such effects can be discounted. In the absence of clearer information on which types of particle are most harmful, aiming to control particulate concentrations by overall mass (e.g. µg/m 3 of PM 10 or PM 2.5 ) in order to reduce population exposure as much as possible (ALARA 5 ) is the best precautionary approach. It is against this background that current and future legislation needs to be considered. In addition it should be recognised that fine particles also play a role in climate change, with black carbon particles contributing to warming, and other particles to cooling, together with indirect effects related to particle effects on cloud properties and reflectance. Fine particles also affect visibility, although this seems to have been of less concern in Europe than in the United States. 5 As Low As Reasonably Achievable h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

18 What are the limitations of current EU policy approaches in reducing exposure to particulate matter? Policy framework Environmental legislation relating to air quality can be targeted at different parts of the pathway from source to exposure, and their impacts are inter-related (Figure 1). Thus, setting of limits on annual average concentrations, as under the First Air Quality Directive, sets limits on individual risk from exposure at the most polluted locations. Other legislation targets emissions from particular sources, e.g. the Large Combustion Plant Directive (LCPD) sets limits on emissions from major point sources, and other standards target products from industry such as fuels or vehicle emissions. The setting of national emission ceilings provides an overall limit on the emissions contributing to concentrations, but leaves flexibility for individual countries in the steps taken to achieve them, reflecting the diverse sources of particulate emissions in each Member State. Sources/Emissions Concentrations Exposure/Risk LCPD EURO standards etc National Emission Ceilings Directive 1st Air Quality Directive WHO estimates of risk coefficients for health effects Figure 1 Interaction of different forms of legislation applying to particles. The associated advantages and limitations are considered in more detail below Current European legislation applicable to particulate matter EU First Air Quality Directive (99/30/EC) The First Air Quality Directive sets upper limits on ambient concentrations for fine particles, and hence on maximum levels of individual risk from outdoor sources. It currently applies only to total PM 10, setting limits both on annual concentrations and on the number of days in excess of 50µg/m 3 (Table 1). Thus, it addresses short-term episodes of peak concentrations as well as longer-term average concentrations and exposure. However, additional limit values have been discussed for the finer fraction, PM 2.5, in future, somewhere in the region 12 to 20 µg/m 3 (WGPM, 2004). h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

19 15 Table 1 EU limit values under the 1st Air Quality Directive 24 hour limits Annual Achieve by Stage 1 limit value 50 µg/m 3 with up to 35 exceedences per year 40 µg/m 3 (less binding than 24 hr limit) 1 January 2005 Stage 2 limit value 50 µg/m 3 with up to 7 exceedences per year 20 µg/m 3 1 January 2010 There is likely to be widespread local exceedence of 2005 objectives and provisional limit values for 2010 (WGPM, 2004; AQEG, 2004; Sadler and Lutz, 2004), especially in urban areas close to busy roads. Hence, attention has been focused on reducing hot-spots of high concentrations, bringing in local government and an additional associated range of nontechnical measures affecting traffic activity levels as well as the technological options. However, such measures to eliminate hot-spots of high concentration may not be as effective in reducing overall population exposure (e.g. Mediavilla and ApSimon, 2003; Schneider, 2004). A further consideration is that exceedence depends on overall concentrations that include a large imported contribution from long-range transboundary transport of PM not subject to local/national control 6. There are also considerable difficulties in assessment of compliance with respect to concentrations, with heavy reliance on monitoring and associated uncertainties, and large inter-annual variability (AQEG, 2004). These are discussed later in Section 6. Limits on specific sources Other legislation targets specific sources. Thus the LCPD sets limits on particulates emitted in flue gases from stacks from major combustion sources, and also sets limits on their emissions of SO 2 and NO X as precursor emissions of secondary PM. The emission limits applicable to particulate matter relate to Total Suspended Particulate, TSP, rather than the finer fractions, but steps taken to control such emissions are generally also effective in achieving reductions in PM 10 and PM 2.5 (WGPM, 2004). Other examples of policies limiting particulate emissions in the industrial sector include the IPPC Directive and the Waste Incineration Directive. For the road transport sector there are the EURO standards for vehicle exhaust emissions, governing mobile sources marketed internationally and crossing international borders. Although the emission limits are framed in terms of PM 10, such emissions are effectively PM 2.5 or even finer (IIASA, 2004b). Successive stages of the EURO standards introduce progressive reductions but PM 10 is a relatively recent addition to the pollutants covered and this legislation does not cover older vehicles or induce retrofitting. Other legislation contributing to reduction of PM from transport, and also other combustion, covers cleaner fuels with lower sulphur content. Although such fuel standards can be introduced in Member States, it is more difficult to negotiate tighter fuel standards for transport emissions 6 Emissions from natural sources also contribute to total concentrations to which individuals are exposed. However, where Member States can demonstrate that limit values will be exceeded as a result of natural events, Article 5(4) of the First Daughter Directive (99/30/EC) enables Member States only to implement action plans where limit values are exceeded owing to causes other than natural events. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

20 16 such as those from international shipping, which are becoming increasingly important relative to land-based emissions 7. Future EU policy for energy efficiency in buildings could also have an impact on PM emissions. In December 2003, the Commission submitted a proposal for a directive on energy efficiency and energy services, which aims to set new rules designed to ensure that all Member States save at least 1% more energy per year, leading to around 6% annual energy savings in The Energy Efficiency Directive will be discussed in Parliament, with a common position expected to be reached by June 2005 (Euractiv, 2005). It is important to note that small scale combustion installations, not widely regulated at an EU level, will become a major source of PM 2.5 in the future (See Section 4.2). National emission ceilings The current National Emission Ceilings Directive, NECD, imposes ceilings on national emissions of SO 2, NO X, NH 3 and VOCs. The NECD drew on the development of the previous Gothenburg protocol under the Convention on Long-Range Transboundary Air Pollution, which was focused not primarily on particulate matter, but on combating transboundary effects of acidification, eutrophication and excess tropospheric ozone. However because it limits precursor emissions of secondary inorganic aerosol (SIA) it is also leads to reduction of PM. An advantage of an emission ceiling is that it provides Member States with flexibility in the way in which the ceiling is achieved, allowing them to maximise environmental benefits nationally and link to other policies and objectives. Thus they may not rely on the mainly add-on or endof-pipe technological measures incorporated in the RAINS model, but use alternatives such as fuel switching in conjunction with energy policies Policies relating to particulate matter implemented outside the EU Ambient air quality limits for PM 2.5 The US has recently introduced new ambient air quality standards for PM 2.5. These are: 65 g/m³ as the 98 th percentile of a 24 hour average; and 15 g/m³ as an annual average, determined by the average of three consecutive annual average values (Harnett, 2004). Emission permits and permit trading Another approach, used in the United States for example, is the issuing of emission permits that can be traded. Thus the emissions are limited by the volume of permits issued, but individual companies or organisations can choose to buy or sell permits and adjust their emission limits accordingly. This also introduces flexibility with economic advantages. A limitation is that there is no geographical control within the trading scheme itself on where the emission reductions are achieved. This type of cap and trade measure has not yet been applied to PM emissions, but rather NO X and SO 2 from industrial sources. A NO X trading scheme is developing in the Netherlands (see Tasks 1 and 3 of this study). A more detailed discussion of emissions trading is 7 In July 2004, the EC submitted a proposal to amend Directive 1999/32/EC as regards the sulphur content of marine fuels h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

21 17 given in a separate report for the EC on the Review of the LCPD, which is currently work in progress Summary Table 2 summarises the advantages and limitations of current European legislation relating to particulate matter. Table 2 Summary of legislation in place, advantages and limitations Legislation Focus Advantages and limitations Other comments 1 st AQ Directive PM 10 in hot-spots-> e.g. traffic in urban areas Brings in local government/action with local measures. Much of the PM not subject to national/local control. Difficulties in assessing compliance and most Member States will have areas of exceedence Sets limits on levels of individual risk. May not reduce concentrations where already below limit value Proposal to set limits for PM 2.5 too. Addresses episodes as well as longer term Since there is no established threshold for health effects, the long-term objective should be to reduce exposure of population everywhere as much as possible LCPD TSP, SO 2 and NO X from major combustion sources Covers a substantial proportion of emissions, with more reliable estimation. Emissions of PM from tall stacks will have less effect on exposure per ton than low level emissions. Measures to reduce TSP will generally reduce PM 10 and PM 2.5 as well IPPC Directive All key pollutants Takes into account site specific consideration, and has a broad sectoral coverage of industry Difficult to assess its specific impact on PM emissions EURO standards PM 10 and NO X from transport sector Provides control on vehicles transported between Member States Controls exhaust emissions and new vehicles only. Since exhaust particles are very small, applies in effect to PM 2.5 or even PM 1. Fuel standards Sulphur content Covers fuels marketed in EC (but more difficult to negotiate for non-ec emissions, e.g. international shipping). Includes transport and fuels used in urban areas National Emissions Ceiling Directive, NECD SO 2, NO X, NH 3 and VOCs Limits precursor emission of secondary PM, and hence the transboundary component of PM. Can in principle be extended to other pollutants, specifically primary PM emissions Originally directed at other transboundary effects, not directly at PM h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

22 18 The table above summarises the legislation in place, and the emissions targeted, but it is evident that only some sources and sectors are directly affected. Current legislation addresses PM 10 (or even TSP) rather than PM 2.5, although in many cases associated action will affect both. New legislation in the form of a National Emission Ceiling for particles could extend current coverage of secondary particle precursor emissions, and embrace primary sources of PM 2.5 not targeted under existing legislation but which contribute to population exposure and associated health risks. There are proposals to introduce air quality limit values for PM 2.5 in future legislation. Furthermore, suggestions have been made to move towards a gap closure approach in order to reduce enhanced PM concentrations in urban agglomerations. The advantages and disadvantages of an emission ceiling relative to such other approaches are considered in Sections 6.2 and How much do primary and secondary components of anthropogenic origin contribute to concentrations, and how is this likely to change with current legislation? Spatial variability and source apportionment European monitoring data for PM 10 (including both primary and secondary components) indicate a relatively smooth rural background concentration distribution, with enhanced levels in urban areas and in the surroundings of some specific industrial sites. Superimposed on this distribution are localised ribbons of peak concentration along major roads, merging into the background within a few tens of metres from the road. In the UK, for example, roadside concentrations are on average 7 to 8 µg/m 3 higher (based on 1.3 x TEOM measurements) than urban background stations, which in turn are a few µg/m 3 higher than rural concentrations (AQEG, 2004). Whereas PM 10 annual means at rural stations in Europe are generally below 30 µg/m 3, and below 20 µg/m 3 at many (~50%) sites, they approach or even exceed the annual limit of 40 µg/m 3 in the Czech Republic and in Poland in Silesia (WGPM, 2004). Higher rural levels are also observed in parts of the densely populated Netherlands and Belgium. Higher concentrations also occur in southern Europe, for example in Spain, where natural particles from soil and Saharan Dust are significant. There is insufficient European monitoring data available on PM 2.5 to deduce spatial differences in concentration properly. However there is a similar pattern with urban background site levels (12-22 µg/m 3 cited by WGPM, 2004) generally less than those close to busy roads (around µg/m 3 ). It is shown below that the more spatially uniform SIA can account for a large proportion of the background concentrations, with primary emissions producing a far more spatially varying superimposed contribution, especially in urban areas. Before proceeding to the separate consideration of primary emissions and precursor emissions of secondary particulates it is useful to consider their relative contributions by source apportionment at different types of location. As an illustration to put the different source contributions into perspective in a populated city area, Figure 2 gives the pattern of exposure based on modelling and assessment of the situation in London in 1996 (before air quality limits were introduced). This gives a breakdown of annual average particulate contributions to PM 10 exposure at busy road-side locations in a row of 1x1 km grid squares forming an east-west transect across Greater London. The top dark blue section on each column represents the highly localised enhancement at the road-side due to the traffic on the road. Below this is the h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

23 19 contribution from other primary emissions in London, as represented in the London atmospheric emissions inventory (GLA, 2003), distinguishing the contributions from central, inner and outer London. Note the limited influence of emissions from inner and outer London on the central area, pointing to the relative importance of local emissions and short distance scales. The broad pink band represents the substantial contribution of secondary particles, formed mainly during longer range transport from outside the area and hence rather uniform across the city. This portion will vary across Europe, with higher concentrations across the centre of Europe and lower concentrations in more remote areas such as Scandinavia. It will already be reduced significantly by emission reductions of SO 2, NO X and NH 3 introduced in accordance with the Gothenburg protocol, NECD, LCPD, etc., but could be reduced further, including emissions not covered by this legislation such as shipping. Finally there is a substantial extra residual contribution (background) that is not well understood, or represented in an emission inventory, but is thought to be largely coarser primary material in the 2.5 to 10 micron range from such sources as suspension of road dusts and other intermittent natural as well as man-made sources. Setting limits on PM 2.5 emissions rather than PM 10 emissions would avoid many of the uncertainties concerning the origins of this residual contribution, and of episodes of high dust concentration due to natural causes more prevalent over drier areas of southern Europe. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

24 20 Urban Scale Integrated Assessment Model (USIAM) Blame Matrix for Central London Trajectory Including Coarse and Secondary Particulate Contributions (1996), (Imperial College, 60 Background Secondary Area LEZ Area Inner Area Outer Area M25 Area Not in London 1996 Local Street Canyon ! "!# $ ) % % ) # '! () ( #% & 40 * Figure 2 Schematic illustration of relative contributions to PM concentrations in g/m 3 for road side sites in an east-west row of grid squares (right to left) across London (based on estimates for1996) (Mediavilla-Sahagun and ApSimon, 2003) Another example of source apportionment for PM 10 is shown in Figure 3 for a busy traffic site in Berlin (Sadler and Lutz, 2004). Again the local traffic contribution is superimposed on an urban background, mainly due to traffic and domestic emissions. But nearly 50% of ambient concentration is attributed to the regional background from outside the city, with distant sources providing a very substantial contribution of secondary particulate matter. Of the local and urban background contributions from traffic a large proportion is non-exhaust emissions such as resuspended road dust, and mainly in the coarse fraction which does not travel far (hence its lower significance in the regional background). This implies that for PM 2.5, with this coarser fraction removed, the regional background and secondary component account for an even larger proportion of the total. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

25 21 Figure 3 Estimated contribution to PM 10 at a busy traffic site from all sources for Berlin in 2002 (also accounting for secondary sources of PM) (Sadler and Lutz 2004) NB # based on values recorded at the top of a radio tower, 324 m above ground Figure 4 Source attribution for PM 10 in Augsburg Königsplatz (g/m³) (Strauss 2004) A similar picture is given for Augsburg in Germany in Figure 4 (Strauss 2004), with the regional background accounting for 45% of the total concentration. An even higher proportion of 54% is cited for an industrialised area in Duisburg in Germany (Wurzler 2004). Other cities show a similar pattern with long-range contributions accounting for around a third to one half of the overall PM 10 concentrations, and secondary particulate accounting for a large proportion of the long-range contribution. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

26 22 An example of source apportionment for the finer fraction PM 2.5 is given below in Table 3 for average values over the Netherlands based on modelling. The primary fraction contributes about one third, and the secondary contribution the remaining two thirds. Of the primary about half is attributed to Dutch sources, and half imported, with the transport sector the largest contributor especially for the Dutch contribution. By comparison only one quarter of the secondary is attributed to Dutch sources, indicative of its longer range nature 8 : 9.9 g/m³ out of a total of 13.8 g/m³ is transboundary, of which 2.3 g/m³ is primary particulate. Table 3 Annually averaged primary and secondary inorganic concentrations of PM 2.5 averaged over the Netherlands by anthropogenic source. Calculated for the year 1995, based on emissions for the Netherlands and the CEPMEIP inventory for European countries (RIVM, 2002) Dutch sources Primary PM 2.5 (g/m³) NH X (g/m³) NO Y (g/m³) SO X (g/m³) Summed concentration (g/m³) Industry Energy Transport (Note 1) Agriculture Others SUM Other countries Industry Energy Transport (Note 1) Agriculture Others SUM All sources SUM Notes: 1) Including international shipping 8 Equivalent figures are given for modelled anthropogenic contributions to PM 10, with a slightly larger total of 16.5µg/m 3 instead of 13.8 µg/m 3, and 6 µg/m 3 of primary PM 10 as compared with 4.5 µg/m 3 of primary PM 2.5. However there is an estimated additional non-modelled contribution of 18 µg/m 3 thought to be sea salt, crustal and biogenous material, and the northern hemisphere background. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

27 23 The overall picture that emerges is that there is a relatively smoothly varying annual background concentration of PM 2.5 across broad regions, of which the major part is secondary inorganic particulate- see maps in next section. Contributions from urban and other sources are superimposed on this background to give localised areas of enhanced concentrations (typically an extra 2 to 6 µg/m 3 in urban agglomerations except close to busy roads) due to primary particulate emissions Modelled concentrations of primary and secondary concentrations across Europe current and projected Emission reductions Within the CAFE program, baseline scenarios have been derived up to the year 2020 reflecting the impact of current legislation on future emissions (IIASA, 2004b). These scenarios are based on the RAINS model coupled to energy scenarios from the PRIMES model, with modification to reflect changes in response to climate change. Table 4 gives the projected changes in emissions of primary PM 10 and PM 2.5 and precursor emissions of SO 2, NO X, NH 3, PM 10 and PM 2.5 for 2010 and 2020 according to the CAFE scenarios. These are compared with the emissions in Table 4 Emission projections (kt) for the baseline scenarios with climate measures (August 04) for EU-25, Switzerland and Norway SO NO X (as NO 2) NH PM PM Impacts on concentrations Estimates by IIASA for the baseline projections indicate reductions in primary PM 2.5 emissions between 2000 and 2010 of approximately 30% with an additional 20% between 2010 and 2020, based on the with climate measures scenario. Reductions in primary PM 2.5 concentrations due to anthropogenic primary emissions from these countries will on average be of similar 9 In addition to the land-based emissions covered by the NEC there are estimated emissions from shipping in European seas and the N-E Atlantic of 2829 kt of SO 2, and 3991 kt of NO X (as NO 2 ), for which future projections will depend on ongoing negotiations (EMEP 2004b). 10 It is important to note that in the modelling by EMEP described below, 5% of the sulphur dioxide is assumed to be emitted as primary sulphate aerosol, equivalent to 650 kilotons of primary particulate aerosol in the PM 2.5 size range emitted from the EU and New Member States in This percentage may be an overestimate, with implications for the sulphate contribution in the major source areas (see Section 3). It is not included in primary PM emission inventories, but would clearly be very significant if it was to be included. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

28 24 magnitudes, but there will be large variations from country to country and place to place. As indicated later in Section 3, estimating the effects on population exposure requires detailed assessment focused on populated urban agglomerations, and will be dependent on how and where the emission reductions occur. The Eulerian model of EMEP has been used to model concentrations of primary anthropogenic PM 10 and PM 2.5, and also the secondary inorganic aerosol, SIA. The results compare favourably with other European scale modelling (EURO DELTA project; EMEP, 2004a). It has not yet been possible to make reliable model estimates of secondary organic aerosol due to inadequate knowledge and measurements for comparison. Maps of the total concentration of SIA and primary PM 2.5 concentrations are illustrated in Figure 5 for the year , together with estimated changes according to the projected baseline scenario of IIASA that is described in Table 4. Figure 6 presents the total anthropogenic contributions to concentrations of PM 2.5 in 2000, 2010 and It is clear from Figure 5 that the SIA component is responsible for a large proportion of the background PM concentrations, especially for PM The maps indicate SIA concentrations of between 5 and 9 µg/m 3 over most of Europe, with higher concentrations between 10 and 15 µg/m 3 over the Benelux countries and parts of Germany, northern Italy and the New Member States. The concentrations of anthropogenic primary PM are generally lower; that is, below 3 µg/m 3 across most of the EU25, with occasional areas up to 5 µg/m 3. However this does not account for spatial variation within the 50 x 50 km EMEP grid squares, and locally higher concentrations in urban agglomerations (Section 3). The plot of changes in modelled contributions of SIA from 2000 to 2010 (Figure 5) indicates significant reductions made as a result of current legislation to control the precursor emissions. Reductions in contributions of primary PM 2.5 appear to be greatest in Central Europe. As the contribution of SIA reduces, the contribution of primary PM 2.5 emissions may become relatively more important in some areas. Given these projected changes, it is interesting to consider the potential forms of Figure 2 and Figure 3 in 2010 and Figure 6 clearly shows that the absolute contribution of long-range transboundary particulates will reduce significantly by 2010 and 2020 under current legislation. The relative proportions of primary and secondary particles that contribute to this long-range element will change, depending on the relative reductions made in primary and secondary contributions by 2010 and 2020 in different geographical areas. 11 The combination of the above modelled primary and SIA concentrations does not account for the total observed PM 2.5 concentrations. In addition to the secondary organic components, there are other important contributions, particularly water that may account for around 20 to 35% of the modelled concentrations (EMEP, 2004b). 12 Whereas most of the SIA is in the finer PM 2.5 fraction, some of the nitrate is in the coarser mode contributing only to PM 10 (EMEP, 2003). h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

29 Primary PM2.5 Secondary Inorganic Aerosol Figure 5 Modelled contributions of secondary inorganic aerosol (SIA) and primary PM 2.5 concentrations in 2000 with projected % reductions by 2010 (data from EMEP model) h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

30 Figure 6 Modelled contributions of anthropogenic PM 2.5 (primary and secondary inorganic aerosols) with projected changes by 2010 and Rural concentrations, annual mean [µg/m3] from known anthropogenic sources. Average of calculations for 1997, 1999, 2000 & 2003 meteorologies (Amann et al., 2004b) 2.4 Summary The key points raised in this section are listed below. The WHO has identified no threshold of health effects for PM, and has identified fine particles (PM 2.5 ) as being more likely to cause damage to health. However it is not yet clear which chemical components are more harmful. Air quality limit values are currently set for PM 10 and are under consideration for PM 2.5. However, the legislation in its current form can result in focussing on reducing concentrations in hot spots, when reductions elsewhere may be more cost-effective in terms of benefiting the wider population (particularly given that there is no identified threshold of effects). The setting of an emission ceiling for PM would complement other legislation to control particulate matter. Secondary inorganic particulate resulting from long-range transport is a major component of PM 2.5, and varies smoothly across Europe with little change in populated urban areas. The primary contribution to regional background concentrations is much smaller, but varies more spatially with significant enhancement in urban areas. Anthropogenic contributions (both primary and secondary) to PM 2.5 concentrations are projected to decrease significantly by 2010 and further by 2020 as a result of current EU legislation to reduce secondary precursors (LCPD, NECD, etc.) and primary PM 2.5 emissions. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

31 27 3. Geographical Scales for Control 3.1 The behaviour of primary and secondary emissions The atmospheric dispersion of primary and secondary particulate matter leads to quite different characteristic ranges of influence, that is the distance range beyond which emissions have little effect on particulate concentrations at a receptor. Secondary particles take time to form in the atmosphere and hence contribute negligibly to concentrations close to the source. Concentrations rise with distance from the source, until eventually dilution and depletion by dry and wet deposition reduce them to negligible levels. For primary particles the situation is quite different, and local contributions depend greatly on immediate dispersion. Contributions to concentrations can be very large near the point of emission for low level sources. For higher level sources in most atmospheric conditions, concentrations will reach a maximum at a certain distance from the source, typically within a few kilometres for a tall stack release. For the larger particles, nearer 10 microns in size, the effective range will be reduced through gravitational settling. Figure 7 provides an illustration of the typical variation of the relative contributions of primary and secondary sources to ambient concentrations at distances from 0.1 km (100 metres) to 3000 km from the source. It is based on simple modelling described in Appendix A, combining a simple Gaussian plume model close to the source with a Langrangian box model at longer distances simulating columns of air moving radially outwards from the source. Assuming an equal rate of emission at the centre from different types of primary and secondary sources, the graphs indicate the average contribution to concentrations on circles of different radial distance from the source, integrated round the circle perimeter. Thus, if there was a uniform distribution of people everywhere, this would be an indication of the relative contribution to population exposure for different radial distances. The scale is logarithmic, covering several orders of magnitude. The dark blue line (Primary Low) corresponds to a near ground level release of primary PM 2.5, whereas the lighter blue (Primary High) represents an elevated source (~100 metres), the two converging after a few kilometres once the elevated emission has dispersed down to ground level. Both are subsequently depleted at the same rate during longer range transport. The pink and yellow lines give the corresponding dependence on distance for secondary particles. The pink line (Secondary N) corresponds to gradual conversion of primary precursor emissions to secondary PM at a few percent per hour, but with little depletion of the primary emissions by other processes, typical of the behaviour of NO X. The contribution to particulate concentrations is very small up to distances of 100 km or more because of the time needed to form the particles, but eventually becomes similar to that for primary emissions as conversion becomes more complete and the resulting particulate matter is depleted, mainly by wet deposition, at a similar rate. The yellow line (Secondary S) corresponds to a situation with a lower conversion rate to secondary particulate (~1% per hour) but additional depletion of the primary component by other processes. This is more like the case of emission of gaseous SO 2 h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

32 28 subject to dry deposition. In both cases the contribution of secondary particulates is greatest a few hundred kilometres away. Relative effect of primary and secondary emissions Log10 Concentration = Log10 Distance distance (km) (km) PrimaryLow SecondaryN SecondaryS PrimaryHigh Figure 7 Typical dependence on distance of contributions from primary and secondary emissions, assuming a uniform spatial density of emissions 3.2 Impacts on population exposure We can take the illustration in Figure 7 one stage further to consider the relative effect of sources for different population distributions. Consider the situation where the emission is an urban agglomeration. As an example, consider a city of 1 million people with a diameter of 20 km (a population density of 2500 per square kilometre). In general this urban area will be embedded in a larger region between 10 and 300 km from the source with a lower population density (assumed to be 250 people per km 2, an order of magnitude less than the city density, which is fairly typical for several countries in Europe). Beyond this, between 300 and 1000 km, we will assume that there are more remote regions, with lower overall population density assumed to be 50 people per km 2. Figure 8 illustrates the relative contributions to population dose for this example, for the low level primary source, the secondary N and the secondary S, all sources having the same magnitude of emission. It is clear how the primary contribution to population exposure is now much greater, and the population exposure is concentrated mainly close to the source, with only a relatively small contribution beyond 300 km, in contrast to the other pollutants. A higher level primary source in the city would give a lower contribution to the exposure of the local urban population, somewhere within the range of the arrow on the red column depending on the height and location relative to the centre of the city. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

33 29 A low level source in a rural area outside the city, for example from agriculture, would have a lesser effect on population exposure (as represented by the base of the arrow on the red column in Figure 8); giving a greater ratio of regional to local exposure Exposure White arrow indicates the potential range of contribution to the exposure of the local urban population, of a high level primary source depending on the height and location of the source relative to the centre of the city Primary (low level) 1 2 Secondary (NO 3) 3 Secondary (SO 4) 10kmx x x x km 50 people per km x km 250 people per km 10kmx km 2500 people per km 2 Figure 8 Illustration of relative contributions to population exposure in different distance bands due to sources of equivalent magnitude located in an urban agglomeration 13 The conclusion from this illustration is that the population exposure due to a primary low level source will be much greater for a source in an urban agglomeration than for an equivalent source in a rural area. However, the impact of a primary high level source on exposure for a local population will be somewhat reduced, compared to that of a low level source in the same location. It matters therefore where sources are located relative to population centres and urban agglomerations, indicating more emphasis on reduction of sources in such areas, especially low level ones. The benefit of reducing low level primary emissions in urban areas will be greatest for the local population, and will be relatively small beyond 100 to 300 kilometres. Thus the benefits will generally be mainly felt within the country making the reduction and in bordering areas of neighbouring countries. The latter benefits may be greater where there are cities close to boundaries as discussed below. This is in contrast to the behaviour of the secondary particulates which give little contribution close to the source, and a larger proportion of their population exposure at distance ranges beyond one to three hundred kilometres i.e. on a transboundary scale. 13 NB Does not allow for increased mass due to oxidation (ratio of NO 3 /NO 2 and SO 4 /SO 2 ) which would increase the NO 3 row by ~30% and the SO 4 by ~50%; or for a fraction of the NO 3 as gaseous HNO 3 h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

34 30 Taking the integrated concentrations between 10 and 1000 km for the secondary N and S and primary components in the simple model above, and weighting them appropriately in proportion to the equivalent emissions of SO 2, NO X and NH 3 and primary PM for the year 2000 (Table 4) implies that the secondary inorganic aerosol would be on average at least twice as large as the primary contribution (even if most of it behaved more like the secondary case S). It is interesting to compare these results with data and maps in the previous section which indicate that primary long-range transboundary particulate matter is a far lesser contributor to ambient PM 2.5 concentrations. However, it is important to note that this does not take account of particle composition. Primary long-range contributions may be a small proportion of the overall pollution burden, but if composed of relatively more harmful substances, it could account for a greater proportion of the effect. Section 4 will consider these issues further. 3.3 Sectoral effects As indicated in Section 3, different sources of primary particulate emissions can have different impacts, depending on their source characteristics (e.g. the comparison between low level and high level sources). Since different sectors have different source characteristics (e.g. agricultural sources in rural areas, major and point sources often emitting from tall stacks), it would be expected that the total contribution to population exposure per ton emitted would differ between sectors. This is illustrated in Figure 9 below, based on analysis with the UK scale integrated assessment model UKIAM, which is analogous to the RAINS model and simulates dispersion of primary PM at a national scale (Oxley and ApSimon 2004). The pie charts compare the proportion of emissions from different sectors with the corresponding proportional contribution to exposure of the UK population. It can be seen how this places more emphasis on the transport sector, and less on the agricultural and major point sources. With this in mind, the following sections will consider the sectoral breakdown across the EU25. Figure 9 Comparison of the relative contributions of different sectors to UK emissions of primary PM 10, and to exposure of the UK population, based on the UKIAM model. 3.4 Source apportionment by the EMEP model The analysis above, and source apportionment data in Section 2, can be compared with source apportionment derived from the EMEP Eulerian model. Four examples are shown in Figure 10 h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

35 31 for a sample of Member States Luxembourg, the Netherlands, the UK and the Czech Republic considering the contributions from the EU25 and the relevant sea areas (the North Sea and the Baltic). These figures clearly indicate that the proportion of primary particulate matter attributed to the home country itself is much greater than the home contribution to SIA, reflecting the contrasting characteristics of primary and secondary PM discussed above. It is also apparent that most of the imported primary particulate matter is attributed to neighbouring countries, where special consideration is needed 14. Main contributors to primary PM 2.5 concentrations (%) Main contributors to SIA concentrations (%) Netherlands Luxembourg 14 This is consistent with earlier modelling (ApSimon et al., 2001; Gonzalez del Campo, 2003) during the development of the Gothenburg protocol to investigate the role of primary particulate matter in transboundary pollution, but based on the coarser 150x 150 km grid then used by EMEP and the preliminary PM inventories of TNO. By omitting the contribution of emissions to concentration within the same 15x150 km grid square in which they originated, it was shown that this contribution led to doubling of concentrations over the more polluted emitting regions of Europe. Over the cleaner remote areas of Europe long-range transport contributed a larger proportion, but here total concentrations of anthropogenic primary PM 2.5 overall are already fairly low (<2 µg/m 3 according to Figure 5). h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

36 32 Main contributors to primary PM 2.5 concentrations (%) Main contributors to SIA concentrations (%) Czech Republic UK Figure 10 Main contributors to primary PM 2.5 and SIA concentrations in selected EU Member States (%) (EMEP, 2004c) Table 5 presents the transboundary contributions of primary and secondary particulates to ambient PM 2.5 concentrations in Member States calculated from the pie charts as show in Figure 10 (after EMEP, 2004c). The table shows the significant variation in contributions made by transboundary primary and secondary particulates across Europe 15. However, the relative primary transboundary contribution is lower than the corresponding secondary transboundary contribution in the majority of Member States A useful further analysis would have been to compare the relative contributions of total (national and transboundary) primary PM 2.5 and SIA to total PM 2.5 concentrations in each country. However, the method used by EMEP to derive these estimates did not automatically produce this information (EMEP, 2005). As such, this comparison is not included within this report. However, in September 2005, EMEP are due to release new data for different meteorological conditions and emission scenarios, which will include total PM 2.5, primary PM 2.5 and SIA. This will allow for more effective evaluation and comparison of the transboundary contributions from other Member States. 16 It must, however, be recognised, that the chemical composition of primary and secondary PM is very different, and whilst primary PM may be a smaller proportion of the total contribution to concentrations, their effects may be proportionally greater as a result of toxic components. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

37 33 Table 5 Transboundary contributions of primary and secondary particulates to PM 2.5 concentrations in Member States for 2002 (EMEP, 2004c) Member State % contribution of transboundary primary particulates to PM 2.5 concentrations % contribution of transboundary SIA to PM 2.5 concentrations Austria Belgium Cyprus Czech Republic Denmark Estonia Finland France Germany Greece Hungary Ireland Italy Latvia Lithuania Luxembourg Malta (Note 1) (Note 1) Netherlands Poland Portugal Slovakia Slovenia Spain Sweden UK Minimum Maximum (Note 2) Notes: 1. There is no EMEP report for Malta 2. Not including the 100% figure for Luxembourg However, especially for small Member States, the EMEP model may underestimate the home country contribution and overestimate the imported contribution of primary particulate matter from neighbouring countries, due to its relatively coarse grid and treatment of grid squares overlying the country borders. This can be illustrated by the example of Luxembourg. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

38 34 Figure 11 shows the effect of reducing primary emission in Luxembourg across its own territory and neighbouring countries. It can be seen how the grid square size spreads out the footprint of emission within Luxembourg across the whole of 50x50 km squares in the EMEP grid spanning the boundary. There is a reciprocal effect from emissions outside Luxembourg in border crossing squares on estimated concentrations inside Luxembourg. This artificial border effect is likely to enhance the estimated contributions to primary PM 2.5 between neighbouring countries in the EMEP assessment. However, it is important to note that the significance of this effect will be relative to the size of the country, with greater overestimations in Luxembourg than in larger Member States. Figure 11 Footprint of Luxembourg PM emissions from EMEP model Another point to note is that the effect of reducing emissions in a neighbouring country close to the common border will have a greater effect than the same emission reduction some hundreds of kilometres away. The simple analysis earlier in this section suggests that contributions to concentration from a primary source fall off on average rather faster up to 10 km from the source and then more slowly with increasing distance. So, for example, cutting primary emissions from a source in country Y 30 km away across a boundary from a large town in country X, could make ten times as much difference to the concentrations affecting the town s population as the same reduction 300 kilometres further away elsewhere in that neighbouring country Y. Since setting a national ceiling does not dictate where emission reductions would be made in a neighbouring country, this emphasizes the need for special consideration where there are large cities and/or sources close to borders. This should be borne in mind when considering how the RAINS integrated assessment model assumes a uniform spatial scaling of emissions across a h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

39 35 country in conjunction with an EMEP national footprint, analogous to that illustrated for Luxembourg, to estimate the benefit of reducing primary emissions in a country. This is discussed in Section 5 of this report. It is also noted that there is an independent study commissioned by the EC under the Clean Air For Europe programme concerned with optimal areas for control of acidification, eutrophication and ground-level ozone. This may provide further investigation of similar situations arising in relation to ammonia and nitrogen deposition, where local scale transport and spatial emission patterns are again important. 3.5 National contributions to population exposure The discussion of source apportionment above refers only to concentrations. That is, the pie charts in Figure 10 refer to the contribution of emitting countries to average concentrations across the country under consideration, rather than the population exposure. When considering population exposure the correlation between urban populations and enhanced concentrations of primary PM 2.5 due to local emissions increases the importance in health terms of the relative contribution of the home country. Thus as an example consider a country with 50 million people, of which 10 million live in urban agglomerations with an average local enhancement in PM 2.5 concentration of 3 µg/m 3, and the remaining 40 million people exposed to the average background concentration of 0.5µg/m 3 attributable to the country s own emissions. The total population exposure from emission in the home country is 55 person g/m 3, of which 30 comes from the additional exposure of the urban population to higher concentrations 17. Thus, in this example, allowance for urban agglomerations doubles the national contribution to population exposure as compared with exposing the whole population to the average concentration attributable to the country s own emissions In recognition of the importance for population exposure of locally enhanced concentrations in urban areas due to primary emissions, and the lack of spatial resolution of such areas by the EMEP 50x50 km grid, IIASA have drawn on the CITY DELTA project comparing different models applied to European cities to develop a simple scheme for representing concentrations in cities. This reflects correlation between the higher emission densities in cities and concentrations with a finer grid resolution (~5x5 km grid), with some adjustment for average local winds and dispersion. The aim is to incorporate this in the RAINS model as discussed in Section Summary The key points raised in this section are listed below. Exposure to primary particulate matter is far more dependent on local sources and less dependent on transboundary sources than exposure to secondary inorganic aerosol. 17 Person g/m³ is a measure of exposure whereby the ambient concentration is multiplied by the number of people exposed. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

40 36 Population exposure due to a primary low level source will be much greater for a source in an urban agglomeration than for an equivalent source in a rural area. However there will be some reduction for an elevated source compared to a low level source. It matters therefore where sources are located relative to population centres and urban agglomerations, indicating more emphasis on reduction of sources in such areas, especially low level ones. Furthermore, that primary combustion-derived particles have been described by the WHO (2004a: 10-11) as having a higher toxic potential adds weight to arguments for further emissions reductions of primary PM in populated areas. Contributions from neighbouring countries will depend on emissions close to mutual borders. It may therefore be important where a neighbouring country makes reductions towards attainment of an emission ceiling for neighbouring countries as well as for its own population. The modelling by EMEP of border areas needs further consideration. Some of these issues will be incorporated within the EC s ongoing optimal areas study. Further investigation is also required to establish source apportionment of responsibility for population exposure as opposed to concentrations, and how this enhances the ratio of responsibility from national emissions and imported fluxes. The pattern of emissions reduction in a country will be important as well as the overall national reduction in emissions. This indicates that straight ceilings on the total emission of primary PM 2.5 from each country would not be sufficiently geographically targeted to necessarily maximise benefits for population exposure. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

41 37 4. Source Characteristics 4.1 Introduction Building on the key findings developed in Sections 2 and 3, this section presents a commentary on the characteristics of PM emissions from different sources to: - develop an understanding of the relative contribution from different anthropogenic sources to primary emissions of PM 10 and PM 2.5 size fractions; - investigate the potential significance of emissions in relative health terms; - determine how well the emissions can be quantified; and - estimate the uncertainty associated with potential abatement measures relevant to the source. This has been addressed by undertaking a sector-by-sector analysis to distinguish the characteristics of emissions, including: source type; particle size distribution; particle composition/ chemical speciation; relative health impact; and, uncertainty in emissions. Section 4.2 includes relevant background material to provide additional context to the sectoral analysis. Section 4.3 details the sectoral analysis of PM emissions within EU Sectoral analysis Approach to sectoral analysis For the purposes of this study, the approach taken for undertaking a detailed analysis of sectors has been devised to achieve optimum transparency in order to allow robust sectoral comparisons. This logical approach will allow the sectors that are dominant contributors to both PM 10 and PM 2.5 to be readily identified. The starting point is the total annual emissions of PM 10 and PM 2.5 across the EU-25 taken from the RAINS database. These emissions can be analysed to break down the total into contributions from each key sector. This in turn allows further analysis in terms of emissions by source and fuel, which reveals those sources that may be considered to dominate the contribution to the total (i.e. those sources that contribute >1% of the total emissions). One of the outcomes of such an analysis is effective source characterisation. Furthermore, since the h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

42 38 PM 10 emissions inventory implicitly includes all PM 2.5 emissions a comparison between the inventories for PM 10 and PM 2.5 provides an indication of the relative particle size distribution Total Annual PM Emissions, EU-25 Analysis of EU-25 emissions data for particulate matter provides a high level indication of the relative contribution of PM 2.5 to PM 10 based on historical emission inventory data (year 2000) and projected emissions (2010 and 2020). This is summarised in Table 6. Table 6 Relative contribution of PM 2.5 to PM 10 for the EU-25 (IIASA, 2004b August 04 Baseline with climate measures ) Pollutant Total Emissions, kt PM 10 2,445 1,726 1,485 PM 2.5 1,749 1, % PM 2.5 to PM 10 (Note 1) 72% 68% 65% Notes: 1. The ratios described here may overestimate the proportion of PM 2.5 to PM 10, owing to missing sources suspected to be present within the PM 10 fraction, such as resuspended dust. The reductions in particulate emissions indicated by the projected emissions data can also be presented graphically, and are included in Figure 12, supporting data presented in Section They indicate that emissions of PM 2.5 will fall in line with reductions in PM 10, with PM 2.5 emissions accounting for a slightly lower proportion of the total PM 10 emissions by 2020 (Table 6). h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

43 39 Figure 12 Projected PM emissions across EU-25 (IIASA, 2004b August 04 Baseline with climate measures ) PM emissions by sector The RAINS database defines economic activities relevant for air emissions that are divided into the four categories: Energy, Process, Agriculture, and Mobile. These key sectoral categories will be discussed briefly below: Energy production Combustion processes are the dominant contributor to particulate emissions from the energy sector. As described in Section 2.1, the WHO (2004a) cites studies suggesting that combustion sources are particularly important with regard to health impacts, owing to the fact that they are often rich in transition metals and organics and have a relatively high surface area. Less volatile elements tend to condense onto the surface of smaller particles in the flue gas stream. Therefore, enrichment in the finest particle fractions is observed. The content of heavy metals in coal is normally several orders of magnitude higher than in oil (except occasionally for Ni and V in heavy fuel oil) and in natural gas (EEA, 2004). Agriculture Analysis of the sources detailed in the RAINS database indicates that these may include activities such as ploughing, tilling and harvesting, and also livestock, and fertiliser use. Within the RAINS model, the dominant sources of emissions of particulate matter within this sector are from livestock. However, this may reflect the limited data availability from other sources within this sector. There are also likely to be large temporal and spatial variations in emissions. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

44 40 Agricultural sources may emit particles directly. Both their size (particle diameter and shape) and the composition (element and species composition, active biological material such as bacteria) are interesting properties that are currently the subject of research. Consequently, speciation and consideration of relative health impacts is currently unfeasible. Process The numbers of sources that contribute to particulate emissions from the Process sector are extremely diverse, and emissions typically are not derived from fuel use. Information on particle composition is not currently collected for emission inventories, so little data on the chemical composition of particles emitted can be provided. In general, however, it would be expected that emissions from small and inefficient combustion processes would largely consist of carbon while emissions from large combustion processes would contain some carbon but would predominantly consist of inorganic matter deriving from the mineral content of the fuel. This may include metals in the fly ash. Particulate matter emissions from most industrial processes (e.g. cement manufacture); quarrying and construction would be inorganic matter, often chemically similar to the raw materials or products of the processes. These will usually contain a high proportion of alkaline earth metal compounds. (AQEG, 2004) Mobile Particulate emissions from mobile sources include both road vehicles and off-road machinery, as well as other forms of non-road transport. Emissions may arise due to: exhaust emissions; brake wear; tyre wear; abrasion. Figure 13 to Figure 16 illustrate the typical chemical composition of airborne particles at roadside and background sites for coarse and fine particles. The sources above are likely to be the main contributors, in addition to prevailing background concentrations from other activity. For the coarse particles (2.5 m to 10 m), the main difference is the higher proportion of ironrich dust at the roadside. This is much less significant in the fine fraction (<2.5 m), in which elemental carbon and organic compounds account for almost two thirds of total particulates 18. Similar results have been found in a recent study by Hueglin et al. (2005), which indicate that organic matter and elemental carbon are the main contributors at kerbside locations. The respective proportional contributions reduce successively as measurements are compared with urban background, near-city and rural sites. The authors conclude that the results implicate road traffic emissions as the contributing source. 18 It is important to note that these figures are based on Tapered Element Oscillating Microbalance (TEOM) measurements, which lose water, nitrate and other volatile components from the composition analysis. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

45 41 Figure 13 Chemical components (g/m 3 ) at roadside sites coarse fraction (AQEG, 2004) Figure 14 Chemical components (g/m 3 ) at background coarse fraction (AQEG, 2004) h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

46 42 Figure 15 Chemical components (g/m 3 ) at roadside fine fraction (AQEG, 2004) Figure 16 Chemical components (g/m3) at background fine fraction (AQEG, 2004) The progressive uptake of abatement measures targeted at controlling emissions of particulate matter from vehicle exhausts (i.e. particulate traps) to comply with tightening emission standards has inevitably resulted in the proportional contribution from other sources associated with mobile activity (such as abrasion or brake and tyre wear) increasing. Emissions from off-road transport have traditionally been targeted by legislation to a lesser extent than road transport. However, as road transport emissions decrease, these sources will become increasingly more significant. Diesel off-road machinery can contain high proportions of PM 2.5. Railways may also contribute significantly to PM emissions, as a result of emissions from diesel driven engines, as well as abrasion from brake and track wear PM emissions by source An analysis of the four key sectoral activities outlined in Section reveals the dominant contributors within each sectoral category for both PM 10 and PM 2.5. The progressive uptake, typically of the most cost-effective measures, reduces total emissions, whilst resulting in a steady increase in the significance of sectors not targeted to the same extent h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

47 43 historically (Figure 17). This trend is evidenced by the increase in significance of agriculture between 2000 and 2020, and a decrease in the significance of energy (public power) and diesel emissions across the same period for example. Wood burning for domestic heating is clearly an important source now and even more so in the future as emissions from other sectors are reduced. Within emission inventories, there are currently large uncertainties about the quantities of wood burned as well as future trends. Research is currently being undertaken in Sweden, which will increase understanding in this area (Illerup et al., 2004). Figure 17 Sources of primary PM 2.5 emissions (Amman et al., 2004a) PM emissions by fuel type Analysis of the proportions of particulate emissions by fuel type between 2000 and 2020 as depicted in the CAFE August 04 baseline, indicates that the relative contribution from fuel sources such as medium distillate, brown coal, and hard coal will decrease whilst the relative contribution from process sources (no fuel use) will significantly increase. This is illustrated in both Figure 18 and Figure 19 below for PM 10 and PM 2.5 respectively and is potentially important with regard to health impacts, given the suggestion that combustion-derived particles may be relatively more toxic. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

48 44 No fuel use Gasoline Diesel Heavy fuel oil Other solid fuels (biomass, wood, etc) Hard coal Brown coal / lignite Figure 18 Proportions of PM 10 emissions by fuel type between 2000 and 2020 (IIASA, 2004b August 04 Baseline with climate measures ) No fuel use Gasoline Diesel Heavy fuel oil Other solid fuels (biomass, wood, etc) Hard coal Brown coal / lignite Figure 19 Proportions of PM 2.5 emissions by fuel type between 2000 and 2020 (IIASA, 2004b August 04 Baseline with climate measures ) Emissions, exposure and health impacts The conclusions to be drawn from the preceding sections are that the most important sources in the future with regard to total emissions will be domestic combustion and industrial processes. However, referring back to Figure 9, these sources may not be the most important in relation to exposure. The relatively low proportion of emissions from road transport may mask the importance of this source with regard to population exposure and health impacts. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

49 Summary tables for characteristics of PM source components within the EU-25 Table 7 summarises PM source components within the EU-25, arranged according to the sectors presented by Amann et al. (2004a) in Figure 17. The components include: Source type; Particle size distribution; Particle composition/ chemical speciation; Relative health impact; Uncertainty in emissions; and, Uncertainty of abatement measures. The sub-sectors and fuel types within each category are identified within the emissions section on the IIASA RAINS website 19. Table 7 Characteristics of PM source components within the EU-25, arranged by the sectors presented by Amann et al. (2004a) in Figure 17 Sector 1 Fuel type Particle size distribution (% PM 2.5 of PM 10) in Particle size distribution (% PM 2.5 of PM 10) in Source type 7 Particle composition /chemical speciation /relative health impacts 10 3, 4, 5, 6, 8, 9, Uncertainty associated with emissions 3, 11 Agriculture No fuel use 20% 20% Fugitive Relative health impact low - presence of microbial flora in the dust etc 8 (increases health risk); but noncombustion emissions; relatively low proportion of PM 2.5; and emissions away from centres of population (reduces health risk) Emissions in the RAINS model appear to be dominated by dust from animal housing, but there may be many missing sources. High uncertainty Off-road Mainly diesel, some gasoline 94% 94% Low level line source Relative health impact high due to combustion emissions and relatively high proportion of PM 2.5. Emission factor depends upon vehicle class and driving condition Nonexhaust (vehicles) Around 60% diesel, and 40% gasoline 41% 41% Diffuse area Relative health impact medium due to relatively low proportion of PM 2.5 (reduces health risk), Emission factor depends upon vehicle class and driving condition 19 h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

50 46 Sector 1 Fuel type Particle size distribution (% PM 2.5 of PM 10) in Particle size distribution (% PM 2.5 of PM 10) in Source type 7 Particle composition /chemical speciation /relative health impacts 10 3, 4, 5, 6, 8, 9, Uncertainty associated with emissions 3, 11 but potential heavy metals and organic compounds from brake wear and tyre wear (increases health risk) Diesel exhaust, HDV Diesel 98% 98% Low level line source Relative health impact high due to combustion emissions and relatively high proportion of PM 2.5. Emission factor depends upon vehicle class and driving condition Diesel exhaust, cars Diesel 96% 96% Low level line source Relative health impact high due to combustion emissions and relatively high proportion of PM 2.5. Emission factor depends upon vehicle class and driving condition Domestic wood stoves Wood 97% 97% Point Relative health impact high due to combustion emissions and relatively high proportion of PM 2.5. This sector is also a key source of PAH emissions. Very high Industrial processes No fuel use 68% 69% Various Relative health impact medium due to non-combustion emissions (reduces health risk), but slightly higher proportion of PM 2.5 and potential for heavy metal components (increases health risk) Medium to high Industrial combustion Hard coal and brown coal 52% 66% Point Relative health impact high due to average proportion of PM 2.5. and combustion emissions Low Power generation Hard coal and brown coal 60% 65% Point Relative health impact high due to average proportion of PM 2.5. and combustion emissions Low 1. IIASA baseline (2004b) 2. Excluding contributions from sectoral sources of < 1% of total EU-25 emissions, but including emissions representing >75% of the total h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

51 47 3. AQEG (2004) 4. CAFE position paper (WGPM, 2004) 5. WHO report (2003) 6. WHO report (2004a) 7. A line source is considered to be a point source at low or no elevation 8. Thomson Martin, W et al (2004) 9. Toxicological studies have highlighted primary, combustion-derived particles having a high toxic potency. Several other components of the PM mix including sulphates and nitrates are lower in toxic potency; but it is currently not possible to precisely quantify the contributions from different sources and different PM components to health effects from exposure to ambient PM (AEAT, 2004) 10. Not including consideration of other pollutants 11. AEAT (2004) 4.3 Uncertainty A key question regarding the feasibility of an emission ceiling relates to the how well the sources of emission are known and can be quantified by Member States. The level of uncertainty within current emission inventories can be demonstrated by the comparison of the CAFE August 04 baseline (formulated from the IIASA RAINS model) with national emissions inventories (Figure 20 and Figure 21). Many of the discrepancies have been attributed to the inclusions and omissions of certain source groups. These figures may be compared with those presented for other pollutants (Figure 22), demonstrating the additional uncertainty and lack of national estimates for both PM 10 and PM 2.5, compared with existing NECD pollutants. Figure 20 Comparison of national emission inventories for PM10 with the RAINS estimates (for the year 2000) (Amann et al., 2004c) h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

52 48 Figure 21 Comparison of national emission inventories for PM2.5 with the RAINS estimates (for the year 2000) (Amann et al., 2004c) h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

53 49 SO 2 NO X VOCs NH 3 Figure 22 Comparison of national emission inventories for existing NECD pollutants with the RAINS estimates (for the year 2000) (Amann et al., 2004c) Uncertainty can arise from a number of key parameters when considering emission inventories. These key parameters are summarised in Table 8. Table 8 Parameters that affect uncertainty in the context of emissions inventories Key Parameter Description Emissions of pollutant from source Emissions associated with a specific sectoral activity may be determined in a number of different ways: Pollution inventory data from regulated industrial sectors; Emission factors; Empirical calculation; Research studies. The uncertainty associated with this parameter is therefore dependent upon the underlying methodology employed to determine the emissions, e.g. measurement or estimation. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

54 50 Key Parameter Description Technical abatement efficiency Missing sources This parameter may have the lowest associated uncertainty for measures controlling stack emissions such as ESPs, fabric filters, etc., since the performance of these measures is typically based on proven, well-documented technological performance. However, for measures controlling fugitive emissions (e.g. dust suppression with sprays, improving road surfaces, etc.) uncertainties can be very high. The incompleteness of current PM inventories has been mentioned above, e.g. within the agricultural sector where animals appear to be the greatest source because they are one of the few sources that are quantified. The inclusion or omission of various sources across the EU introduces a further element of uncertainty when comparing emissions inventories compiled by different parties. The database of emission factors compiled by TNO (2004) reveals the large uncertainties in emission factors for a wide variety of sources. For power stations for example, uncertainties in activity data are dominated by uncertainties in the energy projections, whereas for domestic wood burning there are large uncertainties about the current quantities of wood burned as well as future trends. For sources such as exhaust emissions there is a firm basis for defining emission factors in the EURO standards, whereas, for fugitive emissions from many industrial processes, emission factors are far more uncertain and based on very limited data. It is interesting to note that often, the best defined sectors could be those that have the most important health impacts, e.g. power generation, industrial combustion, road transport. However, the change in contributions to total emissions by 2020 (illustrated in Figure 17) shows how the more uncertain sources (including agriculture, domestic wood stoves and industrial process emissions) will become increasingly more important in relative terms as emissions from other sectors are controlled by current legislation, both with regards to total mass and population exposure. In view of the preceding section indicating the importance of the location of sources with respect to urban agglomerations, the spatial disaggregation of PM inventories will be especially important. Inevitably some abatement measures will be sector-wide across a country, for example for transport, but in other cases they could be restricted to specific areas, such as specific cities, and industrial areas and wood burning areas 20. The situation is analogous to that for VOCs, which are also emitted from a wide variety of sources and sectors, and for which early inventories were very incomplete and uncertain, and needed much improvement to become sufficiently reliable for use under the NECD. Work is in progress to improve emission estimates for particulate matter in important sectors, such as studies in Scandinavia on emission from different types of wood-burning stove. But much more work is needed in many other areas too, in parallel with development of reliable guidelines for compilation of national PM inventories in Europe. Fortunately the focus on emissions of PM 2.5, and on sources in urban agglomerations, leads to less dependence on sectors with greater uncertainty such as agriculture, or sources such as coarser fugitive and resuspended dusts highlighted in the CAFE Working Group report (WGPM, 2004). It is important to note that whilst emission inventories are improved and new sources are added, overall national totals are likely to be revised over time. As such, there would be significant 20 This will also be considered under the EC s ongoing optimal areas study. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

55 51 advantages in setting emission ceilings as relative percentage reductions rather than as absolute ceilings. This would enable countries to work towards a set target, in spite of potential adjustments to sectoral and national baselines. Furthermore, although the evidence on which components of PM are responsible for health effects is still unclear, it is suggested that parallel work on emission inventories for such components is directly linked to size differentiated PM inventories, for example inventories for elemental and organic carbon, metals, and PAHs. By bringing together such inventory work, it would be more straightforward to see how possibly harmful components might be reduced, as well as the overall mass emissions. 4.4 Summary The key points raised in this section are listed below. Different sources will generate particles with different chemical characteristics and size distributions. At present, there is insufficient understanding of how such characteristics influence health impacts for the WHO (2004a) to recommend that legislation on PM should move beyond consideration of particle size fractions to target specific sources. However, the limited research that has been undertaken suggests that combustion sources are particularly important for health, describing primary combustionderived particles as having a higher toxic potential (WHO, 2004a: 10-11). According to IIASA projections under the CAFE baseline scenarios, both PM 10 and PM 2.5 emissions will reduce from 2000 to 2020, with the proportion of PM 2.5 particles dropping slightly from 72% to 65%. By 2020, current legislation will limit emissions from a number of sectors, notably diesel exhausts and power generation. Consequently, the proportional sector contributions to total emissions will change, with agriculture, domestic wood stoves and industrial processes becoming more significant with regards to emissions. By 2020, the proportional fuel contributions to total emissions will also change, with no fuel use becoming more important. This could be important for health impacts, given the reduced importance of these non-combustion emissions in health terms, as suggested by the WHO (2004a). Emissions from the sectors contributing proportionately higher PM emissions in 2020 (agriculture, domestic wood stoves and industrial processes) are currently more uncertain than other sectors, such as public power and road transport. However spatial distributions and atmospheric dispersion patterns also affect their relative contributions to population exposure (Figure 9). There are currently large uncertainties within emission inventories for PM, which are revealed in a comparison between the RAINS baseline and national inventories. As such, the improvement of emission inventories would be an important task if emission ceilings are to be implemented. This work could be incorporated with ongoing research into inventories for components of PM (e.g. elemental and organic carbon, metals, and PAHs), enabling concurrent analysis of how different PM components may be affected under different policy scenarios. Additionally, relative emissions ceilings, set in terms of percentage reductions, could be considered as a means of providing Member States with fixed targets, when improvements in emission inventories are likely to lead to changes in national baselines. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

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57 53 5. Potential Role for Emission Ceilings 5.1 Target setting In setting emission ceilings, the aim is to achieve a cost effective improvement in environmental protection, in the case of PM with respect to reduced health risks. Since there is no established threshold of concentration for such risks it is not possible to achieve complete protection, and hence the setting of interim targets needs to be considered, having regard to issues of equity between improvement in severely polluted areas and in the broader community, and other legislation already in place such as air quality limit values. For the existing NECs, integrated assessment modelling has been used to guide the selection of emission ceilings for different Member States. This has been shown to provide a more cost effective improvement than setting a uniform percentage emission reduction across all countries (as in the early protocols under CLRTAP). Thus, integrated assessment models such as RAINS (and also other European models such as ASAM- ApSimon et al., 1994 and MERLIN- Freidrich, 2004) bring together information on projected baseline emissions, atmospheric transport (reflected in relationships between emissions from each country and their contributions to deposition or atmospheric concentration at receptor locations), criteria for environmental protection and data on potential abatement measures and costs (Figure 23). PROJECTED EMISSIONS ATMOSPHERIC TRANSPORT CONCENTRATION & EXPOSURE COST EFFECTIVE OPTIMISATION ABATEMENT OPTIONS COSTS & EXCEEDENCE OF TARGET LEVELS FOR PROTECTION Figure 23 Components of integrated assessment modelling applied to NECs These data are used to derive least-cost solutions to achieving target levels of deposition and concentration. Since it is often not possible to eliminate exceedence of the environmental criteria completely, these targets are often based on closing the gap between current levels of h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

58 54 deposition or concentration and the critical loads or levels defining the criteria for protectionthe so-called gap closure approach. The cost-effective scenarios derived are evaluated by complementary cost-benefit analysis, comparing the implied costs of emission reduction across all the countries, and the environmental benefits (Holland, 2004; Holland et al., 1999; ApSimon et al., 1997). For the current NECs this analysis indicated that the benefits from reduced emissions of SO 2, NO X, and NH 3 in reducing particulate concentrations and associated health risks outweighed other benefits. It was also shown that the strategies and emission ceilings originally derived by RAINS with respect to acidification, eutrophication and excess tropospheric ozone were also cost-effective in reducing such exposure to secondary inorganic aerosol (Warren and ApSimon, 1998; Warren and ApSimon, 2000). IIASA have since included both secondary inorganic aerosol and primary particulate matter within the RAINS model, using a linear relationship from WHO between PM concentrations and enhanced risk of mortality as an indicator of health effects. Their analysis indicates an average shortening of life by between 3 and 9 months in most countries attributable to these contributions to current PM concentrations (IIASA, 2004a). 5.2 Extension of integrated assessment modelling to primary PM Using the current RAINS approach Ideally, the setting of emission ceilings for primary PM should be consistent with the methods used for deriving secondary precursor emissions, i.e. using integrated assessment modelling for guidance. However, there are some differences. In general, a country can benefit more itself from reducing primary PM 2.5 emissions affecting its urban areas than other countries will benefit from these reductions. That is, primary PM is more a national problem as compared with the more transboundary nature of secondary particulates. However, there may be situations where a country can reduce exposure overall more cost-effectively by reducing its primary PM emissions than by reducing precursor emissions of SIA both within and outside the country. Hence there is an advantage in considering both primary and secondary PM 2.5 together. The situation is analogous to that for reduced and oxidised nitrogen with respect to acidification and eutrophication, where ammonia emissions lead to far greater localised nitrogen deposition closer to the source, but oxidised nitrogen is a truly longer range pollutant. In this case, a precedent has been set and the RAINS model has been applied to establish emission ceilings for ammonia, a pollutant for which there were also great uncertainties in emissions from agriculture as the dominant sector, and for which many countries did not include any emissions from nonagricultural sources at the time of the Gothenburg protocol However, the highly variable patterns of spatial deposition, correlated with local ammonia sources, were smoothed out within EMEP grid squares, and the resulting total (oxidised plus reduced) nitrogen deposition compared with critical loads for sensitive ecosystems. One result of this was an underestimate of ecosystems exceeded (SERI, 2004), as would be the result for population exposure to primary PM if juxtaposition of populated urban agglomerations and higher emissions and concentrations was not addressed. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

59 55 To represent a balance between different types of primary PM source, a way has to be found in which the greater impact of primary PM sources in urban agglomerations (as presented in Section 3) can be reflected in integrated assessment modelling. At a national scale, integrated assessment modelling can resolve such issues with a finer grid resolution and more detailed modelling (e.g. UKIAM Oxley et al., 2004). At a European scale IIASA is developing a methodology for modelling enhanced concentrations of primary PM 2.5 in cities, drawing on results of the CITY DELTA project. This is being incorporated in RAINS together with urban population data, and is a major step forward towards embedding finer grid scale modelling coupled to the EMEP model to give more accurate representation of population exposure to PM 2.5. A related consideration is that of setting targets for reduction of PM concentration on which to base the emission reductions required. As explained above, in the past RAINS has used a gap closure approach, aiming to reduce exceedence of the critical load or level set for protection in each grid square by at least a specified percentage. In the absence of a threshold for PM, the critical level is zero and gap closure is equivalent to setting targets of reducing the concentrations by a specified percentage. This could only apply to the concentrations attributable to anthropogenic emissions included in the modelling, and not to total PM concentrations including natural contributions and water content which are not well defined, or sources not represented in the inventories. When such targets are adopted, the emission ceilings derived by RAINS for their attainment tend to be driven by particular binding grid cells where it is particularly difficult to attain the target. There are particular conflicts here if a country finds itself incurring a large effort and expenditure to achieve the binding target in another country (e.g. by reducing SIA precursor emissions), when the same investment could achieve a much greater reduction in population exposure terms for its own population (e.g. by control of primary emissions). Similarly the application of non-technical measures, or measures not included in RAINS, targeted within the binding square, might do more to reduce population exposure in that square for less cost than controlling the imported fluxes 22. There are also questions of equity. Should the aim be the same percentage reduction in a remote and sparsely populated grid cell where PM concentrations are already low, as in a highly populated and polluted grid-cell? Attaining the required percentage reduction in the former could depend far more highly on the reduction of secondary PM, and, if difficult, could make the cell a binding cell. There are alternative ways of setting targets, and alternative ways of deriving optimised solutions to the particular approach adopted in RAINS, which might be more satisfactory. For example those measures could in theory be selected that give the greatest overall reduction in population exposure for least costs, irrespective of the geographical distribution of the benefits. Other limitations of integrated assessment modelling also apply to PM, such as the dependence on cost-curves and largely end-of-pipe measures, whereas a wider range of options is often available. This is where the flexibility within a country in meeting its ceiling is an advantage. 22 A similar situation arises with ammonia when exceedence depends crucially on the detailed spatial relationship between emissions and valued sensitive ecosystems within a grid-square, and the application of local measures (e.g. ApSimon and Oxley, report for TFIAM on local measures in the form of buffer zones.) h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

60 56 However there is also another difficulty arising from the problem of scale for primary emissions especially, in that where a country makes reductions will affect how much it benefits itself as well as how much it helps neighbouring countries, in particular in populated border areas and towns Modelling the abatement of different source types It is apparent from Section 3 that where an emission reduction of primary PM is made within a country can have a large effect on its effectiveness in reducing population exposure. In some sectors, emissions will be correlated with population; for example, traffic emissions. But in others, the emissions may be remote or within an urban area. There is also the distinction between low and high level sources, with the latter having a lesser effect on localised population. The RAINS model currently does not include any spatial differentiation as to where reductions are made within a country, but estimates effects and benefits of abatement on the assumption that emissions are scaled in the same proportion across the whole country. This is on the basis that current national ceilings do not prescribe where emission reductions are to be made within a country any more specifically. It is clear from Section 3 that such an approach would not distinguish between different types of source and associated population exposure and setting an emission ceiling based on such assumptions would not necessarily maximise health benefits. A specific reduction in a country s emissions can have very variable benefits for a country s own population, and to some extent in bordering areas of neighbouring countries, depending on how and where reductions are made within it. A solution to this problem might be helped by the development of curves of reduction of population exposure versus cost in place of the current cost curves of emission reduction against cost for each country. This is discussed in Section 5.3 below. 5.3 Are there alternative ways of setting emission ceilings for PM? Towards long-term objectives: relative as opposed to absolute emission ceilings Before addressing issues for implementation and compliance it is necessary to consider some alternative options for defining emission ceilings and targets for emission reduction. Emission ceilings for current NECD pollutants have been set as an upper limit on the total anthropogenic emissions of a specified pollutant from each Member State, to be met by a specified date. These ceilings have been established with consideration for environmental objectives that set absolute targets for reducing the impact of acidification, eutrophication and ground level-ozone over the long term. Impacts on acidification and eutrophication and the impacts of ground-level ozone on vegetation are measured against critical loads and critical levels, below which significant adverse effects on the environment do not occur according to present knowledge. However, as stated above, with regard to health impacts the WHO (2004) has recently reported that no such threshold is evident for PM and ozone. In these circumstances, reducing exposure to a certain target level or absolute objective would not be as beneficial as relative, year on year reductions in exposure h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task

61 57 across the entire population (Figure 24). This should be taken into account during the development of long-term objectives for reducing the impacts on health. Figure 24 Population-exposure distribution (NSCA, 2004). Area A represents the effects of policies targeted at reducing exposure only to those exposed above the Limit Value; Area B represents the effects of policies aimed at reducing exposure in the general population. Area B is much greater than Area A, and therefore, in simplified terms Policy B is more cost effective than Policy A. However, the greater level of exposure to each person in Area A will clearly need to be factored into the consideration of priority. As an alternative to absolute targets, an emission ceiling could be specified as a percentage reduction in emissions relative to a base year, as in commitments under the Climate Change Convention, rather than as absolute tonnage values. This approach would also help to ensure countries deliver on the level of ambition they originally agreed and make agreements more robust to technical developments in inventories (Rea, 2004). As identified under Task 1 of this study, Member States have expressed difficulties in that the current NECD contains absolute ceilings and as such, does not account for adjustments to compensate for changes in methods used to compile emission inventories. For example, the NO X emission factor used to estimate emissions from heavy duty vehicles has increased since the negotiations for the NECD. Member States baseline emissions have increased accordingly, but the NECs have remained constant. This means that Member States need to make greater absolute reductions than they originally agreed to. This may be particularly relevant to particulate emissions, given the problems discussed in Section 4.3 concerning the completeness of and uncertainties in current emission inventories. As there is significant scope for improvements in the emission inventories for particulate matter in the future, this suggests that relative emission ceilings may be more beneficial for this pollutant, compared to current NECD pollutants, where emission inventories have been developed over a longer period of time. Three different options for emission ceilings are considered below. h:\projects\em-260\13000 projects\ ec necd review\reports sent to ec\05 amended final report (20th may 05)\task 2\ amended final report - task