10. Air pollution

10. Air pollution

indicator	policy issue	DPSIR	assessment
Multiple effects:
area with exceedance of critical loads for acidity and eutrophication	how much have we protected the environment against acid precipitation?	state	/
limit value exceedance days for atmospheric ozone	are we protecting the population effectively against exposure to photochemical substances?	state
exposure of crops and forests to atmospheric ozone	how much have we protected the environment against the effect of photochemical substances?	state
limit value exceedance days for particulate matter	are we protecting the population effectively against exposure to particulate matter?	state
Multiple pollutants:
emissions of acidifying gases	will policy targets be reached?	pressure
emissions of ozone precursors	- " -	pressure
emissions of sulphur dioxide	- " -	pressure
emissions of nitrogen oxide	- " -	pressure
emissions of ammonia	- " -	pressure
emissions of non-methane volatile organic compounds	- " -	pressure

Despite a decline in emissions of general air pollutants, the ultimate goal of avoiding all harmful effects on health, vegetation, water and soil has still to be achieved. The area where the critical load of acidifying emissions is exceeded has fallen significantly, but substantial parts of the population in EEA member countries are exposed to unacceptable concentrations of ground-level ozone and fine particles. The fifth environmental action programme emission reduction targets for 2000 will be achieved for sulphur dioxide, but are unlikely to be met for nitrogen oxides and volatile organic compounds (VOCs). The proposed EU and national 2010 targets for sulphur dioxide appear achievable, but reaching those for nitrogen oxide, ammonia and VOC emissions will require substantial further reductions and additional policies and measures in most Member States.

The main environmental problems associated with air emissions are harm to human health, the acidification and eutrophication of water and soils, and damage to natural ecosystems, cultural heritage and crops. Often these are transboundary effects, as pollutants in the air can travel a considerable distance away from their source. In addition, emissions from sources in urban areas can have a significant local impact on human health. Local and transboundary air pollution are considered as one environmental issue in this report, since the effects of air pollution are interrelated through common causes and common impacts. Policies to reduce emissions are increasingly considering various pollution problems together in a multi-pollutant, multi-effect approach (Figure 10.1).

Figure 10.1: Multi-pollutants, multi-effects

Source: EEA

10.1. Policy update

The first international treaty with strategies for reducing transboundary air pollution was the UNECE Convention on Long Range Transboundary Air Pollution (CLRTAP). Several CLRTAP Protocols are in force for its European parties, including the EU and its Member States. The substances covered and the required reductions are listed in Table 10.1. The Second Sulphur Protocol (UNECE, 1994) used the approach, for the first time, of setting emission targets to reduce the exceedance of critical deposition levels for ecosystems (‘gap closure’). This Protocol thus resulted in national emission-reduction commitments that varied according to the ecosystems’ sensitivity.

In May 1999, the European Commission presented a proposal for a Directive on national emission ceilings (NECD) (European Commission, 1999a) for the same pollutants as CLRTAP and, for the first time, for ammonia. The proposed Directive uses a similar approach as the Second Sulphur Protocol, but extends it to include reduction in exceedance of critical limit values for ozone for human health and ecosystems. These targets in the NECD proposal, which has not yet been adopted, are much stricter than currently agreed targets.

In a parallel process, on 1 December 1999 the CLRTAP agreed on national emission ceilings for many European countries (including EU Member States) in a new multi-pollutant Protocol for the same four pollutants as NECD. For a number of Member States, however, the targets are less strict than those in the proposed Directive.

Table 10.1 summarises the main current and proposed targets for the EU.

Notes: ¹ Target from the 1994 Second Sulphur Protocol. The different emission ceilings for each Member State correspond to a 62 % emission reduction for the EU.

² Targets from first NOx Protocol. These are the same for individual Member States and for the EU.
³ Targets from NMVOCs Protocol. These are the same for individual Member States and for the EU.
⁴ Targets from the multi-pollutant Protocol (1 December 1999). The emission reduction target for the EU that corresponds with different emission ceilings for each Member State is shown.
⁵ Targets from the European Commission’s 1999 proposal for a national emission ceilings directive (NECD). The emission reduction target for the EU that corresponds with different emission ceilings for each Member State is shown.

To help reach these targets, current European Community legislation aimed at reducing acidifying pollutants and ozone precursors includes a Directive on the reduction of emissions from large combustion plants and various recent Directives on vehicle emissions, the quality of petrol and diesel fuels and the sulphur content of certain liquid fuels. A Directive on the storage and distribution of petrol and the Solvents Directive on the reduction of emissions from the industrial use of organic solvents both aim to limit emissions of volatile organic compounds (VOCs). By the end of 1999, new proposals are expected from the second Auto-Oil Programme for emission limits on new cars, other technical measures and non-technical measures to encourage more environmental-friendly modes of transport. There is currently no EU legislation aimed at reducing ammonia emissions. Legislation and targets for abatement of direct emissions of fine particles are also still lacking.

In addition, measures to reduce greenhouse gas emissions (particularly carbon dioxide) could, as a side effect, reduce acidifying substances and ozone precursors. One such measure is fuel switching to natural gas.

The proposed national emission ceilings for 2010 should be regarded only as interim as they will not provide full protection to ecosystems and human health. Assuming a baseline scenario (EEA, 1999), some ecosystems in 2010 will still be receiving deposition above critical loads, and threshold values for ozone will continue to be exceeded. Future development of policies and measures in the coming years are likely be performed in parallel by UNECE/CLRTAP and the EU, following the same approach as for the recently proposed emission ceilings.

This chapter begins by using four indicators to evaluate developments in meeting critical limit values. These indicators equate approximately to the major impacts of air pollutants, i.e. acidification and eutrophication of water, soil and ecosystems; human-health effects of ground-level ozone; ecosystem effects of ozone; and human health impacts of particulate matter. This concise overview of progress in limiting multiple effects is followed by two indicators summarising the reduction in most of the pollutants involved. The distance to the various emission targets listed in Table 10.1 gives an indication of the amount of policy effort still required. The chapter concludes with a number of indicators on emissions and the gap between the target and actual reductions for the individual pollutants.

10.2. Multiple effects

10.2.1. Impact 1: Acidification and eutrophication of water, soils and ecosystems
The area where critical loads are exceeded due to emissions of sulphur and nitrogen oxides falling on water and soils (deposition) has decreased substantially since 1985 (Figure 10.2). Both sulphur and nitrogen deposition contribute to the acidification of water and soils; the lines in Figure 10.2 for the exceedance in critical loads for acidifying sulphur and acidifying nitrogen therefore run in parallel. However, the decrease in areas exposed to acidification appears to be due mainly to the decrease in sulphur oxide emissions (see Figure 10.6). Much of the deposited nitrogen accumulates in the soil or is taken up by vegetation and thus will contribute at some stage to eutrophication. The area where depositions of nitrogen exceed the critical load has remained high, reflecting insufficient reduction of nitrogen oxide and ammonia emissions (see Figures 10.10 and 10.12).

Figure 10.2: Percentage area where critical loads for acidity and eutrophication are exceeded in EEA member countries

Source: CCE for critical loads and EMEP/MSC-W for deposition estimates
Note: Figure shows area where 5th percentile critical loads for acidity and eutrophication are exceeded.

Since 1985, there has been about a 40 % reduction in the area where critical loads for acidity are exceeded.

The ecosystem area exposed to eutrophication has not changed much and is still high.

10.2.2. Impact 2: Human-health impacts due to exposure to ozone
Large numbers of people living in EEA member countries are exposed to ground-level ozone concentrations above the proposed EC threshold value (Figure 10.3).

Ozone concentrations at ground level are far higher than they would be naturally because additional ozone is formed by photochemical reactions in the atmosphere. The main substances with a role in ground-level ozone formation (i.e. ozone precursors) are nitrogen oxides, non-methane volatile organic compounds (NMVOCs), carbon monoxide and methane.

Ozone is an oxidant that can induce damage to human health (European Commission,1999b). Epidemiological and toxicological evidence indicates that exceedances of threshold values during summer smog episodes have lead to associated health problems, particularly inflammatory responses and impaired lung function. Multiannual exposure to high concentrations of ozone may lead to decrements in the lung function of young children (Frischer et al., 1999).

Insufficient data and strong year-on-year fluctuations owing to episodes of high ozone concentrations prevent clear conclusions on time trends. However, the limited monitoring data suggests that peak concentrations are decreasing.

The reduction in emissions of ozone precursors achieved in the EU (see Figure 10.7) has not yet been sufficient to make a significant difference to health risk. Increased background concentrations – caused by emissions in the whole northern hemisphere – are partially responsible for continued high concentrations in EEA member countries.

Despite projected further emission reductions, ozone concentrations are expected to exceed EC threshold values over all EEA member countries in the next decade (EMEP, 1999). By 2010, north-western European areas are expected to comply with the proposed EU target value of only 20 exceedance days per year in the long-term air quality objective (European Commission 1999b).

Figure 10.3: Population exposure in EEA member countries to ozone levels above EC targets

Source: AIRBASE
Notes: Number of days per year with 8-hour rolling average concentration greater than 120 µg/m³. Based on data from rural monitoring stations. Ozone concentrations in urban areas are often lower than rural concentrations, due to local reactions with nitrogen oxides from traffic emissions. The population exposure may therefore be somewhat overestimated.

A substantial part of the population in EEA member countries is exposed to ozone concentrations above the proposed EC target. Monitoring data suggests that ozone peak values are decreasing.

10.2.3. Impact 3: Damage of forest and crops due to exposure to ozone
Exposure to ozone can induce foliar injury in plants and thus reduce crop and forest yields. The forested area where critical ozone concentrations have been exceeded is smaller than the affected area of arable land (Figure 10.4). However, the proposed long-term critical level for forests is less stringent than the proposed EC guideline for crops. Significant fluctuations between years and lack of data for over 50 % of the relevant area prevent definitive conclusions on trends being drawn.

Despite the expected reductions in the emissions of ozone precursors following the implementation of the CLRTAP protocol and EU legislation, ozone concentrations are forecast to remain well above the critical levels for the next decade. By 2010, the gap between current concentrations and critical values is expected to have halved (EMEP, 1999).

Figure 10.4: Exposure of agricultural crops and forests in EEA member countries to atmospheric ozone

Source: EEA-ETC/AQ and EMEP/CCC
Note: Proposed EC long-term critical level is 20 mg/m³h (AOT40) for forests and 6 mg/m³h (AOT40) for agricultural crops.

A substantial proportion of forests and crops in EEA member countries are exposed to ozone levels greater than proposed EC critical levels.

10.2.4. Impact 4: Human-health problems from exposure to particulates
Recent research has shown that exposure to fine particles in the air is associated with a significant impact on human health (UNECE/WHO, 1999). The health effects attributed to fine particulates range from increased frequency and severity of respiratory problems to increased risk of premature death.

In preparation for implementing the EC Air Quality Daughter Directive, most countries have only recently introduced monitoring of particulate matter less than 10 µm in diameter (PM10), Data on PM10 concentrations is currently insufficient to draw firm conclusions about emission trends. However, concentrations of total suspended particulates (TSP) and black smoke are generally decreasing (Figure 10.5).

Particulate matter originates both from direct air emissions (primary particles) and from atmospheric reactions between sulphur and nitrogen oxides, and ammonia and organic compounds (secondary particles). Emissions of precursors of secondary particles are limited by existing environmental legislation, but there is no EU legislation directly governing primary particle emissions.

Air-pollution control techniques designed to reduce precursor emissions often reduce primary particulate emissions. However, PM10 concentrations are expected to remain well above limit values in most urban areas of EEA member countries in the coming decade. This suggests that more measures need to be taken to reduce human-health risks significantly (European Commission,1999c).

Figure 10.5: Exposure to particulate matter in urban areas of EEA member countries

Source: AIRBASE
Notes: Shows number of days when 24-hour average particulates threshold value is exceeded, averaged over all monitoring stations. The threshold value taken depends on the type of particulates measured: for PM10 (fine particulate matter) 50 µg/m³, for total suspended particulates (TSP) 120 µg/m³ and for black smoke 125 µg/m³. The implicit assumption is that an exceedance day for TSP is just as bad as an exceedance day for black smoke or PM10. Only a small proportion of the population is covered by the monitoring network.

Many people living in towns and cities in EEA member countries are exposed to higher concentrations of fine particulate matter than EC limit values.

10.3. Multiple pollutants

Emissions of gases causing acidification and eutrophication (sulphur dioxide, nitrogen oxides and ammonia) have decreased significantly in most EU Member States. Sulphur dioxide and nitrogen oxides also have health impacts. In the EU as a whole, emissions decreased by 27 % between 1990 and 1996 (Figure 10.6), despite an increase in gross domestic product (GDP).

The substantial fall in acidifying gases is mainly due to a reduction of over 60 % in sulphur dioxide emissions from industry and the energy sector since 1980 (see Figure 10.8). However, nitrogen oxide emissions decreased much less and are unlikely to meet the fifth environment action programme (5EAP) target for 2000. Ammonia emissions are stabilising (see Figures 10.12 and 10.13). The slower reduction in nitrogen oxide and ammonia emissions is reflected in a less significant reduction in deposited nitrogen and in the area in which the critical load for eutrophication is exceeded (see Figure 10.2).

Substantial further reductions of emissions of acidifying pollutants are needed to achieve the proposed NECD targets or even the less strict CLRTAP targets for 2010 agreed on 1 December 1999.

Figure 10.6: Total EU emissions of acidifying gases

Source: EEA-ETC/AE and UNECE/EMEP
Notes: Emission reduction targets are for the EU and combined for the three gases using weighting factors. Acidifying equivalents per kg used for weighting are: sulphur dioxide 31.2; nitrogen oxides 21.7; ammonia 58.8. Table 10.1 gives more information on the targets.

Emissions of acidifying gases in EU Member States have decreased significantly, showing a clear de-coupling from GDP growth. This decrease was mainly due to reductions in sulphur dioxide emissions. Further reductions in nitrogen oxide and ammonia emissions will be necessary to achieve the targets for 2010.

Emissions of gases that can lead to ground-level ozone fell in most EU Member States and by 15 % in the EU as a whole between 1990 and 1996 (Figure 10.7). These results were achieved despite an increase in gross domestic product. The reduction is mainly due to fewer VOC emissions, which fell by 13 % between 1990 and 1996 mainly due to limits on industrial emissions and measures to reduce emissions from road vehicles (see Figure 10.14). Although these reductions appear to have decreased peak concentrations of ozone, they have not been enough to limit human health and ecosystem risks significantly (see Figures 10.3 and 10.4). Further initiatives are needed to meet the 5EAP targets for 2000.

Substantial further reductions of emissions of ozone precursor pollutants are required to achieve the proposed NECD targets or even the less strict CLRTAP targets for 2010.

Figure 10.7: Total EU emissions of ozone precursors

Source: EEA-ETC/AE and UNECE/EMEP
Notes: This indicator is a first attempt at weighting total EU ozone precursor emissions, but of course it is an oversimplification. In many regions, nitrogen oxide emissions enhance ozone formation, but in urban areas, they can deplete ozone. A decrease in aggregated emissions does not therefore imply a similar decrease in ozone concentrations. Emissions are combined for four ozone precursors, but reduction targets exist only for the two main precursors (nitrogen oxides and non-methane VOCs). Weighting factors (tropospheric ozone precursor potentials) used: nitrogen oxides 1.22; non-methane VOCs 1.00; carbon monoxide 0.11, methane 0.014. Table 10.1 gives more information on the targets.

Emissions of ozone precursors in EU Member States have decreased, showing a de-coupling from GDP. However, substantial further reductions in emissions are required to achieve the targets for 2010.

10.4. Achievement of policy targets: individual substances

This section presents an overview of the development in emissions compared with the various targets for each of the four pollutants that contribute to acidification, eutrophication and ground-level ozone.

10.4.1. Sulphur dioxide
Main sources: energy (60 %), industry (25 %), transport (6 %) and household (1 %) sectors (Figure 10.8).

Development in emissions: a decrease of over 60 % from 1980 (over 40> % since 1990) in the EU. Largest reduction in the energy and industry sectors, due to a switch from coal to natural gas, construction of new power plants, use of low-sulphur coal and more flue-gas desulphurisation.

Distance to target: EC’s 5EAP target (-35 % of 1985 emissions by 2000) reached by EEA member countries in 1992. By 1996, emissions had fallen to 55 % below 1985 levels. In 1996, the EU as a whole achieved the CLRTAP Second Sulphur Protocol target (-62 % from 1980 emissions by 2000). There are important differences between Member States in approaching the proposed NECD and agreed CLRTAP targets for 2010 (Figure 10.9).

Outlook: EU baseline scenario (EEA, 1999) projection: -70 % in 2010 from 1990 levels. For some countries, additional measures will be required to achieve the proposed NECD and agreed CLRTAP Protocol targets.

Figure 10.8: Total EU sulphur dioxide emissions from major sources compared to EU and CLRTAP targets

Source: EEA-ETC/AE and UNECE/EMEP
Note: Target 2000 refers to the EC’s 5EAP target. The proposed NECD target requires a 78 % reduction below 1990 emissions by 2010 and the CLRTAP Protocol (1 December 1999) target a 75 % reduction below 1990 emissions by 2010.

Figure 10.9: Percentage change in national sulphur dioxide emissions in EU Member States, 1990-1996

Source: EEA and UNECE/EMEP
Notes: A reduction in emissions from 1990 is shown by a negative percentage.

Since 1980, EEA member countries have reduced their sulphur dioxide emissions by over 60 %. Reduction targets for 2000 have already been achieved for the EU as a whole. The targets for 2010 appear to be attainable for the EU, although additional measures will be required in some countries.

10.4.2. Nitrogen oxide
Main sources: transport (55 %) energy (19 %) and industry (14 %) sectors (Figure 10.10).

Development in emissions: a decrease of 14 % since 1990 in EU Member States, mainly due to the introduction of catalysts on new cars and improved abatement in the energy and industry sectors. Increasing road travel has partly offset reductions achieved by emission abatement. Emissions increased in some countries (Figure 10.11).

Distance to target: First CLRTAP Nitrogen Oxide Protocol target (stabilising to 1987 emissions by 1994) achieved by the EU as a whole and by most Member States. However, the fifth environment action programme target of a 30 % reduction by 2000 with respect to 1990 will not be achieved.

Outlook: EU baseline scenario (EEA, 1999) projection: -45 % in 2010 from 1990 emissions. It will be difficult to achieve the proposed NECD and agreed CLRTAP Protocol targets. Additional policies and measures will be required in various EU Member States.

Figure 10.10: Total EU nitrogen oxide emissions from major sources compared to EU and CLRTAP targets

Source: EEA and UNECE/EMEP
Note: Target 2000 refers to the EC's 5EAP target of a 30 % reduction in emissions below 1990 levels by 2000. The proposed NECD target requires a 55 % reduction below 1990 emissions by 2010 and the CLRTAP Protocol target (1 December 1999) a 50 % reduction below 1990 emissions by 2010.

Figure 10.11: Percentage change in national nitrogen oxide emissions in EU Member States, 1990-1996

Source: EEA and UNECE/EMEP
Note: A reduction in emissions from 1990 is shown by a negative percentage.

The CLRTAP target of stabilising nitrogen oxide emissions at 1987 levels was achieved by the EU as a whole. However, the EC’ 5EAP target is unlikely to be reached by 2000. The targets for 2010 will also be difficult to achieve for the EU and additional measures will be required for various countries.

10.4.3. Ammonia
Main sources: agriculture, particularly livestock (pigs, cattle, sheep and poultry) (Figure 10.12).

Distance to target: Until recently no targets existed for ammonia. The proposed NECD target is a 21 % reduction and the agreed CLRTAP Protocol a 12 % reduction below 1990 emissions by 2010.

Figure 10.12: EU total ammonia emissions from major sources compared to EU and CLRTAP targets

Source: EEA and UNECE/EMEP
Note: The proposed NECD target requires a 21 % reduction and the agreed CLRTAP Protocol target (1 December 1999) a 12 % reduction below 1990 emissions by 2010.

Figure 10.13: Percentage change in national ammonia emissions in EU Member States, 1990-1996

Source: EEA and UNECE/EMEP
Notes: A reduction in emissions from 1990 is shown by a negative percentage.

Reduction targets have been defined for the first time for ammonia emissions. The targets for 2010 will be difficult to reach for the EU and additional measures will be required for various countries.

10.4.4. Non-methane volatile organic compounds (NMVOCs)
Main sources: transport sector (Figure 10.14). The category 'other' in Figure 10.14 comprises emissions from solvent use and the storage and distribution of fossil fuels.

Development in emissions: decrease by 14 % in EU and decreases in most Member States (Figure 10.15) due to the introduction of catalytic converters in vehicle exhausts. Increasing road travel has partly offset reductions achieved by emission abatement. VOC emissions from solvent use and manufacturing processes have been reduced through best practice, substitution by water-based products and pollutant-abatement technology. These efforts are expected to increase with the implementation of the Solvents Directive.

Distance to target: The CLRTAP NMVOC Protocol target (-30 % below 1988 emissions by 1999 for EU Member States) has not been achieved. The Fifth Environmental Action Programme target (-30 % below 1990 emissions by 2000) appears unlikely to be achieved.

Outlook: EU baseline scenario (EEA, 1999) projection: - 49 % in 2010 from 1990 emissions. Current policies are not enough to reach the proposed NECD (-62 %) and the agreed CLRTAP Protocol (-59 %) targets. Additional policies and measures will be required in various EU Member States.

Figure 10.14: Non-methane volatile organic compound emissions in EU Member States from major sources compared to EU and CLRTAP targets

Source: EEA-ETC/AE and UNECE/EMEP
Note: Target 1999 refers to the EC's 5EAP target of a 30 % reduction in emissions below 1990 levels by 2000. The proposed NECD target requires a 62 % reduction and the agreed CLRTAP Protocol target (1 December 1999) a 59 % reduction below 1990 emissions by 2010.

Figure 10.15: Percentage change in national NMVOC emissions in EU Member States, 1990-1996

Source: EEA-ETC/AE and UNECE/EMEP
Note: A reduction in emissions from 1990 is shown by a negative percentage.

Total EU emissions of non-methane volatile organic compounds fell by 13 % between 1990 and 1996. However, the EC’s 5EAP target for 2000 will be difficult to achieve and reaching the targets for 2010 will require substantial further reductions in emissions. Additional measures will be required for various countries.

10.5. Indicator development

The spatial coverage requires improvement for current exposure indicators. A greater consistency between years is necessary to properly assess exposure to air pollutants and especially population exposure to particulates. A combination of modelling and monitoring data could provide a better estimate of environmental indicators in areas with unsatisfactory data coverage. Information from different indicators could be combined to produce simple indexes to monitor the state of the environment.

The main requirement for the emission indicators is improved reliability and completeness of the time series and a reduction in the uncertainty in the estimates. To achieve consistency, use of the same methodology for all years is required. There is also a need for further validation and checking within the framework of UNECE/CLRTAP, in particular by the Task Force on Emission Inventories and related EEA (ETC/AE) activities.

Separate indicators for urban emissions, including PM10 emissions, should be developed because such emissions have a major impact on urban air quality and related health effects, while trends may differ significantly from national totals.

Emission indicators for other pollutants, e.g. heavy metals and persistent organic compounds, are still missing. Future developments could also include indicators on other environmental effects (including ecosystems and material corrosion) and an indication of the cost-effectiveness of measures and policies to reduce emissions.

Indicators could also be developed to visualise the effects of policy responses to trends in air emissions and air quality. Emission reductions resulting from policy and technical measures could be presented together with the actual emissions and in relation to a ‘reference’ emission – a hypothetical emission level for the situation where no policies/measures are implemented.

Two examples from the Netherlands are presented below. The first example is for sulphur dioxide emissions from power plants (Figure 10.16). A shift in fuel from oil to natural gas produced a net downward effect on emissions until the mid-1980s, when greater use of coal reversed the trend. Flue-gas desulphurisation units began to be fitted to Dutch power plants in 1986 and, by 1996, 96 % were equipped.

Figure 10.16: Sulphur dioxide emissions from power plants in the Netherlands, 1980-1994

Source: RIVM
Note: The reference line is based on electricity produced.

The second example deals with the effectiveness of measures to reduce nitrogen oxide emissions from motor vehicles in the Netherlands (Figure 10.17). Emissions fell substantially following the introduction of catalytic converters in 1988. Until 1993, use of catalytic converters was stimulated by a lower sales tax on new cars. In 1993, new emission standards came into force that could only be met with a three-way converter. In 1994, 33 % of all passenger cars were equipped with a catalytic converter. While most of the recent decrease in nitrogen oxide emissions is due to the use of catalytic converters, the shift from petrol to diesel has also contributed (diesel cars tended until recently to have lower emissions per kilometre than petrol cars).

Figure 10.17: Nitrogen oxide emissions from traffic in the Netherlands, 1980-1994

Source: RIVM
Note: The reference line is based on the distance driven by road and for goods transport on tonne-kilometres.

10.6. References and further reading

EMEP (1999) Transboundary Photo-oxidants in Europe, EMEP Summary Report 2/99. EMEP/Meteorological Synthesising Centre-West, Oslo.

European Commission (1999a). Proposal for a Directive setting national emission ceilings for certain atmospheric pollutants and for a Daughter Directive relating to ozone in ambient air. COM (99)125. European Commission, Brussels.

European Commission (1999b). Ozone position paper. (to be published). European Commission DG Environment-D3, Brussels.

European Commission (1999c). The Auto-Oil II Programme, draft version 5.0 , November 1999. European Commission, Brussels.

European Environment Agency (1999). Environment in the European Union at the turn of the century. European Environment Agency, Copenhagen.

Frischer T., Studnicka M., Gartner C., Tauber E., Horak F., Veiter A., Spengler J., Kühr J., Urbanek R. (1999). Lung function growth and ambient ozone. A three-year population study in schoolchildren. Am. J. Respir. Crit. Care Med., 160, 390-396.

UNECE (1994). Protocol to the convention on long-range transboundary air pollution on further reduction of sulphur emissions (1994 Sulphur Protocol). UN Economic Commission on Europe, Geneva.

UNECE (1996). 1979 Convention on long-range transboundary air pollution. UN Economic Commission on Europe, Geneva.

UNECE (1999). Protocol to the 1979 convention on long-range transboundary air pollution (CLRTAP) to abate acidification, eutrophication and ground-level ozone, Gothenburg, Sweden, 1 December 1999.

UNECE/EMEP (1999). EMEP Emission data, status report 1999. Report 1/1999, EMEP/MSC-W, Oslo.

UNECE/WHO (1999). Health risk of particulate matter from long-range transboundary air pollution- preliminary assessment. Task Force on Health Aspects of Long-Range Transboundary Air Pollution, Geneva.