In 1996 the EU introduced a new concept for evaluating and managing air quality by adopting a framework directive to be implemented by daughter directives. To date directives have been adopted for the atmospheric content of sulphur dioxide, nitrogen oxides, particles, lead, benzene, carbon monoxide and ozone. A directive on the atmospheric content of arsenic, cadmium, nickel and PAH is being drawn up. Limit values and the Danish levels are mentioned in the following sections.

Danish energy policy

The major cause of emissions of air pollutants in Denmark is the use of fossils fuels - i.e. of coal, oil and gas products. Therefore the emissions are closely related to the national energy policy that has been implemented in a series of action plans.

From coal to oil and back to coal

Traditionally coal has been the dominating source of energy in Denmark, but in the years after the second world war oil played an increasing role and contributed in the beginning of the 1970's about 90%. With the energy crisis in 1973 and the dramatically increasing oil prices it became evident that Denmark must be made less vulnerable to changes in supply security and energy prices. In the first energy plan from 1976 (Energy Policy 1976) the main objective was to reduce our dependence on oil, to direct the supply towards natural gas and nuclear power, but also to use coal and renewable energy. The immediate result was a change to coal in the electricity production and application of natural gas and renewable resources. The introduction of nuclear power was postponed. At the same time the increase in energy consumption was slowed down by means of energy saving campaigns and economic instruments.

Environmental issues played a modest role, and an investigation in 1980 concluded that even with an increase in coal consumption by a factor of five from 1975 to 1989 the problems could be handled. The question of climate changes was not addressed at all.

Danish gas and oil

An energy plan in 1981 was based on domestic production of gas and oil and continued efforts to save energy, i.a. for space heating, including an extension of district heating based on combined power-heat production. Still, however, the main objectives were supply security and economic efficiency.

Efficient energy production and energy savings are essential elements in the abatement of air pollution. The transport sector is a critical area in Danish environment and energy policy. Attempts to limit car traffic by increasing use of public means of transport and bicycles have so far had modest success.

In 1985, after years of discussion, the Danish Parliament definitively decided to remove nuclear power from Danish energy policy. In the same year an international conference on greenhouse effect, climate change and ecosystems created a political understanding that emissions of carbon dioxide could be the overwhelming problem of the future.

The Brundtland Report and what followed

On April 27th 1987, the Brundtland Commission published its report Our Common Future. Earlier technological development was seen as a threat to the environment and had been discussed in terms of limits to growth. Now development was seen as a necessary prerequisite in the fight against poverty and environmental degradation. It should, however, be sustainable. As a preliminary goal it was proposed that energy consumption per capita in the industrialised countries should be halved within 40 years (i.e. before 2027), thus enabling a 30% increase in the developing countries.

The environment in focus

As a direct consequence of the Brundtland Report the Energy 2000 Action Plan for Sustainable Development was published in 1990. Now the environment was seriously set in focus. The energy consumption, as it was in 1988, should be reduced by nearly 15% before 2005, and emissions of carbon dioxide, sulphur dioxide and nitrogen oxide by 20, 60 and 50% respectively. Energy 2000, however, did not address the transport sector, as it was recognised that the sector was facing a necessary and unavoidable development, and, therefore, a specific action plan was drawn up: the government's transport plan of action for environment and development. The energy consumption and emissions of carbon dioxide should only be stabilised before 2005 and then reduced by 25% before 2030. As appeared later, even this target has not been easy to reach. Emissions of nitrogen oxide and hydrocarbon should be reduced by 40% before 2000, by 60% before 2010 and further up to 2030. Emissions of particles should be halved before 2010 and be further reduced up to 2030.

Energy consumption and economic growth
From the end of 1950's and up to 1970 the Danish gross energy consumption more than doubled. since then it has by and large been stabilised, although the mix of energy sources has changed drastically. Since 1980 the production of renewable energy has more than tripled. The largest increase has been for wind power.
        

The gross domestic product has increased much more than the energy consumption. The reason is partly a change towards less energy consuming activities, but also more efficient production of electricity and district heating, with strongly increased use of combined power and heat production (about a doubling since 1980). In addition, energy is used more efficiently by insulation of buildings, more effective domestic appliances etc.
By and large we have managed to decouple economic growth and the ensuing welfare from the increase in energy production and the related pollution.

(Source: Danish Energy Agency)

The threat of climate changes

The most recent official energy plan, Energy 21 from 1996, focuses on emissions of carbon dioxide and maintains the goal of a 20% reduction in 2005. At the same time the concept ecological footprint was introduced in the debate, and a stabilisation of the atmospheric concentration of carbon dioxide of 450 ppm was recommended. By this it was recognised that much more extensive reductions of carbon dioxide would be necessary. A decrease in the total energy consumption of about 17% up to 2030 is assumed. At the same time an almost complete phase-out of coal, a nearly unchanged use of oil and gas and a large increase in renewable energy sources were assumed. More than half of the electricity and district heat production shall be based on renewable energy in 2030.

The environmental target for the development in the energy sector is dominated by the national climate commitments under the Kyoto Protocol. The declared goal therefore focuses on reduction of emissions of carbon dioxide. It is obvious, however, that by and large any reduction in the use of fossil fuels will result in a reduction of emissions of a series of other more direct air pollutants - notably sulphur dioxide, nitrogen oxide and hydrocarbons.

Sulphur and acidification

Sulphur dioxide is together with soot the classical urban pollution, which causes respiratory trouble, soiling and material disintegration. Sulphur pollution arises mainly because organic materials, comprising both fossil fuels and bio fuels, contain sulphur. During combustion the sulphur is oxidised to sulphur dioxide (SO₂). In the atmosphere it is further transformed to sulphate (SO4 ^-2) that is deposited either as salts or as sulphuric acid and is a significant reason why precipitation polluted with sulphur becomes acid.

Until the early 1970's it was the general political assumption that sulphur pollution was a local problem and could be solved by cleaner fuels in residential furnaces and high stacks dispersing the pollution from power plants. It was, however, a short-sighted solution. In June 1981 Statens Naturvådsverk (Swedish Environmental Protection Agency) published a report where the problem was spelled out as shown in the box.

At that time 18,000 of Sweden's 85,000 large lakes were acidified and half of them to a degree that seriously harmed fish life. The Swedish area where the critical load for acidification is exceeded is now more than halved, from above 80% to below 40%.

Emissions of sulphur dioxide
Danish emissions of sulphur dioxide peaked around 1970 and have since been reduced to around 1/10. The pattern is by and large the same as for Europe as a whole.

Concentrations of sulphur dioxide
The reduction of emissions of sulphur has been a contributing factor for the heavy decrease of concentrations in Danish cities. Around 1970 the yearly average in Copenhagen was about 80 µg/m³. Today it is below 5 µg/m³. For comparison, the EU limit value is 20 µg/m³.

Danish emissions

In Denmark the sulphur content in oil has been regulated since 1972 and SO₂ emissions from power plants and combined power-heating plants since 1984. The rules have been tightened several times, and taxes on sulphur were introduced in 1998. By use of cleaner fuels and desulphurisation of flue gas in power plants it has been possible to reduce Danish emissions of sulphur dioxide from nearly 600,000 tons per year to below 50,000 tons. Thus the target set for 2010 in the ECE and EU agreements (55,000 tons) is already achieved.

To this must, however, be added a significant, but not yet regulated contribution from shipping in the Danish waters. In 1990 to 2000 it was 133,000 tons per year and thus more than twice the contribution from landbased Danish sources. This contribution, however, is of minor importance for the air quality in urban areas, since ferries use cleaner fuel in harbours.

Sulphur dioxide in Danish cities

Efforts to reduce airborne sulphur pollution have contributed significantly to a reduction in local levels. It does not exclude, however, that under special meteorological conditions high peak values can appear. In the 19th century the average concentration of sulphur dioxide in the centre of Copenhagen must have been nearly 100 µg/m³ during the winter. When measurements proper were initiated in the beginning of the 1960's it was about 80 µg/m³. The impacts can still be seen in the form of deteriorated sandstone monuments and corroded statues. Today the levels of sulphur dioxide are less than 5 µg/m³ and thus significantly below both current and planned limit values.

A corresponding development has been seen in other cities in Denmark and abroad, caused by several conditions: less sulphur in fuel oil and coal, regulation of emissions from power plants, and increased use of natural gas that does not contain sulphur. A contributing factor is increasing use of district heating often based on combined power and heat production in large plants with high stacks and flue gas desulphurization.

Extensive damages to ecological systems focus attention on transboundary sulphur pollution. The phenomenon, however, is complicated, and with decreasing emissions of sulphur the largest acidifying contribution today comes from nitrogen. Also pollution with ozone can be important. The recent years' growing occurrence of the "red" Norway Spruce in Denmark may be related to climate change.

Nitrogen and eutrophication

Air pollution with nitrogen compounds is more complicated than sulphur pollution. Like sulphur dioxide (SO₂), nitrogen dioxide (NO₂) immediately irritates the respiratory system and harms vegetation. Furthermore, NO₂ can be oxidised and contribute to acidification. However, NO₂ can under the influence of sunlight react with hydrocarbons and form photochemical oxidants, of which ozone (described in the following section) is the most important.

Finally, nitrogen has a fertilising effect. Air pollution with nitrogen compounds therefore contributes to the eutrophication that puts pressure on sensitive nature. Also the deposition of nitrogen to inner Danish waters is a contributing cause of oxygen deficiency.

Through chemical processes in the soil ammonia can liberate hydrogen ions and, thus, contribute to acidification.

Formation and emissions of nitrogen oxides

As was the case with sulphur dioxide, pollution with nitrogen dioxide is mainly due to combustion - partly because the fuels contain nitrogen compounds. But also nitrogen in the combustion air is oxidised - first into nitrogen monoxide (NO) and later in the atmosphere into NO₂, which is the actual harmful compound.

Danish emissions of nitrogen oxide expressed as NO₂ increased to about 300,000 tons per year in the middle of the 1980's. It then remained nearly constant until the middle of the 1990's, but is now reduced to about 200,000 tons per year. The reason has mainly been installation of low-NOx burners and de-NOx equipment in power plants and district heating plants. Increasing use of catalytic converters in cars has at the same time more than counteracted the increase in traffic. Emissions today, however, are still larger than the EU and ECE targets for 2010 of 127,000 tons a year.

Air pollution with nitrogen compounds contributes to eutrophication of the aquatic environment. This can result in extensive oxygen deficiency and fish deaths. For the total inner waters around Denmark about 1/4 of the bio-available nitrogen comes via the air. Also for natural ecosystems, where the species are adjusted to a nutrient-poor environment, pollution with nitrogen compounds may change the composition of the species and reduce their number.

Nitrogen dioxide in Danish cities

In the last decade, the yearly average of nitrogen dioxide in Danish cities has also fallen, although not as fast as the emissions. In Copenhagen, thus, from about 50 to 40 µg/m³. This corresponds to the present EU limit value, whereas the level envisaged is 30 µg/m³. The reason why the decrease has not yet been larger is, partly, that the NO₂ level depends upon the occurrence of ozone in the air.

Ammonia

Nitrogen is also present in the form of ammonia (NH₃) - a gas that is i.a. formed in bacterial decomposition of organic material. Earlier ammonia was only discussed in connection with odour problems, although in fact it is not the ammonia, but a series of degradation products that cause the greatest nuisances. In Denmark emissions of ammonia are almost exclusively due to agriculture - in particular evaporation in connection with application of nitrogen fertilisers (including manure). Only 2% are due to traffic.

In agriculture nitrogen in different forms of fertilisers and atmospheric deposition is added to the soil. In return, nitrogen is removed with crops and animal products. The nitrogen surplus constitutes the environmental problem proper. This includes the loss of nitrogen in the form of emissions of ammonia to the atmosphere, now in the order of 100,000 tons per year. It has been reduced by about 30% since 1985 i.a. by application of other foodstuffs, by sealing manure containers and by using dragging tubes in the distribution of the manure.

Further, in 2000-2001 a new ammonia action plan to limit the evaporation was adopted. It is expected that Denmark will be able to reach the EU and ECE target for emissions of ammonia in 2010 (39,000 tons) as a result of i.a. the Action Plan for the Aquatic Environment II.

Exceedance of critical loads

In Denmark the total area where the critical load is exceeded is only very modest, but it includes agricultural land, cities etc. Of the natural area proper, which constitutes 15- 20%, still about half is loaded above the critical limit of eutrophication load. In recent years a minor reduction seems to have occurred, but more exact inventories have not been drawn up.

Emissions of nitrogen oxides and ammonia
Danish emissions of nitrogen oxide peaked in the late 1980's, and have now fallen by about 30%. According to recent inventories emissions of ammonia have fallen by about 30% since 1985.

(Sources: Risø and NERI)
      

NO₂ in urban and rural air
The concentration of NO₂ in Danish air has also been reduced, but not as fast as emissions.

(Source: NERI)
       

Total acidifying emissions
Sulphur dioxide, nitrogen oxide and ammonia all have an acidifying effect. The emissions can be expressed with a common unit: acid equivalents. The sum has fallen in Denmark by about 40% in the recent decade, and ammonia is now dominating. This, however, does not give a direct impression of the actual load, which is strongly influenced by transboundary pollution with a significant contribution from sulphur.

(Source: NERI)

Organic compounds
– and photochemical smog

Volatile hydrocarbons (Volatile Organic Compounds, VOC) are organic compounds which are of great significance to the impacts on health and the environment caused by air pollution. They can contribute to the formation of photochemical air pollution, give rise to odour nuisances or simply be hazardous. Usually a distinction is made between methane (CH₄) and the other volatile hydrocarbons (NMVOC, nonmethane VOC). Methane is a greenhouse gas, but is chemically not particularly active. It therefore plays a minor role as direct pollution. Non-volatile hydrocarbons can, however, also affect health, as particles or adsorbed to the surface of particles.

Formation and emissions of hydrocarbons

VOC`s have many sources: evaporation of fuels, incomplete combustion, releases in industrial processes, use of organic solvents etc. Danish emissions have been largely constant at well over 200,000 tons per year from 1985 to 1990. It was then reduced to less than 15,000 tons per year in 2000, mainly because of the introduction of 3-way catalytic converters in petrol cars and reduced use of organic solvents. Both the EU's and the EEC's emission ceiling for 2010 is 85,000 tons per year, which - in view of the development - should be possible to achieve.

Ozone

Ozone (O₃) is a reactive form of oxygen (O₂), in which the molecules have three atoms instead of two. In relation to the environment, ozone plays two different roles: In the stratosphere it forms the so-called ozone layer that shields against short wave UVradiation. At low altitude, on the other hand, it is a contaminant that attacks respiratory systems, certain materials and vegetation.

Due to its reactivity ozone can influence the mucous membranes in the eye and in the respiratory system. Especially persons with respiratory diseases are sensitive and will at elevated levels experience an aggravated health condition.

Ozone load measured at forest stations
Ozone load on vegetation is measured as AOT (Accumulated exposure over a Threshold) which is a product of the time in which the levels exceed a critical level, e.g. 40 ppb, and this exceedance. The diagram shows AOT40 values measured at Ulborg and Frederiksborg forest stations. It appears that Ulborg situated to the west is generally exposed to the largest load, that it is frequently above the 10,000 ppb x hours a year, which is considered a critical level. For many years this situation has remained fairly stable. (ppb is parts per billion)

(Source: NERI)

Emissions of hydrocarbons
Danish emissions of hydrocarbons have been reduced by about 25% since 1985.

(Source: NERI)

As an air pollutant ozone is not a compound that is emitted, but a so-called secondary pollution - something that is formed from other, primary pollutants. The primary pollutants are nitrogen oxides and hydrocarbons that under the influence of sunlight react and form of series of so-called photochemical oxidants. Ozone is the most important.

In Southern Europe photochemical air pollution (photochemical smog) is often an urban phenomenon generated by car traffic. In the cities in Northern Europe, however, decomposition of ozone dominates as a consequence of emissions of NO from cars, and the levels are generally lower than in the countryside. Here the highest concentrations appear in the summer and at south easterly wind. The reason is that during highpressure episodes in Eastern and Central Europe high ozone concentrations build up and are transported to Denmark.

Consequently, it is not possible for Denmark to control ozone levels by national reductions of emissions. Ironically, the levels in Copenhagen are generally lowest on weekdays, when the traffic is most dense, and pollutants (especially nitrous oxide) consume ozone.

Volatile organic compounds can under the influence of sunlight react with nitrogen oxide and form ozone, the most important element of the so-called photochemical air pollution. Ozone is harmful for the respiratory system and for vegetation. In Danish cities the concentration is generally low, but in rural areas elevated concentrations result in loss of crop yield.

Economic evaluations of damage

In Denmark no detailed calculations have been made of the negative economic impact of ozone on the agricultural sector in the form of reduced crop yield. But an estimate of damages on wheat, grass and production forest is DKK 0.5 to 2 billion (Euro 65- 260 million) per year. This is in agreement with similar Swedish estimates. Such figures must, however, be considered with caution in a world with overproduction and economically subsidised agriculture. It has never been attempted to evaluate the economic impact on natural vegetation and health in Denmark.

Other hazardous compounds

A series of organic compounds are hazardous in themselves. By measurements and calculations of emissions, the permissible load of these compounds in the atmospheric environment is regulated when plants are approved. In recent years a few compounds have, however, attracted special interest.

Dioxins

The so-called dioxins comprise 210 closely related polychlorinated dibenzodioxines (PCDD) and furanes (PCDF). Their transport in the environment is complicated. The main source is combustion, typically incineration of material containing chlorine, but dioxin is also formed in e.g. straw and wood stoves.

Primarily, dioxin is an air pollutant, but it is not direct inhalation, that is crucial for the impact on health. Dioxins, which are very stable, are deposited on the soil and water surfaces. As they are fat-soluble they move easily from the soil and water to the food chains and are then absorbed through the food. This also means that it can be dispersed in various ways.

Dioxins are some of the most toxic compounds known. They are carcinogenic, they may have endocrine-disrupting effects, and inflict damages to the unborn child. Special attention has been given to the content of dioxin in mother's milk.

In 1998 WHO (World Health Organisation) established a tolerable daily intake (including the related PCB) at between 1 and 4 pg/kg bodyweight, while at EU level the tolerable daily intake has been fixed at 2 pg/kg. At the same time it is estimated that the load in Europe is an average of 2-6 pg/kg. The Danish Veterinary and Food Administration has on the basis of data from other countries conservatively estimated that the Danish intake is about 5 pg/kg. Although the content of dioxin in food and mother's milk is falling, there is every reason to continue efforts to reduce the load. The Minister for the Environment has in collaboration with the Minister for Food, Agriculture and Fisheries prepared a dioxin action plan to reduce dioxin emissions and provide new knowledge on sources and pollution of food and environment.

Further, the Minister for the Environment has issued a statutory order under which the incineration plants must observe a limit value of 1.1 nanogram dioxin per cubic meter flue gas by the end of 2004. So far it appears that this is possible at about 90% of all utilities. Industry is faced with similar requirements.

Many organic compounds are hazardous. Even if they start as air pollution, they may go a long way through dispersion in the atmosphere and the food chains before the impacts appear. This may make it difficult to trace the sources and reduce emissions. Dioxin in mother's milk is a typical example.

The EU has further established limit values for a series of animal foodstuffs in particular. The objective is to reduce the total human exposure to dioxin by at least 25% in 2006.

Polycyclic organic material

Combustion of material - typically wood and oil products with cyclic hydrocarbons - generates a series of mutagenic and carcinogenic compounds. The polycyclic aromatic hydrocarbons (PAH) are the most important.

Environmental concern for these compounds dates back to the 19th century, when many incidences of skin cancer were observed in workers in the tar industry. The first carcinogenic compound, benzo(a)pyrene was identified in tar in 1933, but it was not before the 1970's that the relation with air pollution became evident. Volatile PAH is in the gaseous phase, but the heavier and carcinogenic PAH has a tendency to attach to particles. Inhalation of such particles in the working environment has been shown to cause lung cancer.

In Denmark measurements were carried out at the Copenhagen Airport in 1988-89, and concentrations of about 2 ng/mg³ were found. At the busy street H.C. Andersens Boulevard in central Copenhagen up to 10 ng/m³ were measured.

As part of the report to UNECE, emission inventories have been prepared for four compounds: Benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene and indeno (1,2,3-cd)pyrene. Total emissions in 2000 were about 11,000 kg. There are minor contributions from traffic and mobile sources, but nearly 3/4 come from increasing combustion of wood in private fireplaces.

Benzene

As described earlier lead is now completely removed as an additive to petrol in Denmark, and, thus, lead in the air has practically disappeared. But it has not been without side-effects, because it was necessary to control the octane number of the petrol buy changing its composition.

Some years ago it appeared that urban air contained the carcinogenic hydrocarbon benzene. A closer investigation indicated that benzene solely arises from unburned components in petrol. The refineries were therefore interested in introducing quickly a new technology for production of petrol with a low content of benzene. The reduction of the content of benzene in motor fuel has been documented by analysis of samples from Statoil at Kalundborg and Shell at Fredericia. In both cases the content was reduced from 3.5% to 1% during the summer of 1998. At the same time it was shown that the content of benzene in the air at the very busy street Jagtvej in Copenhagen has within a few years been reduced from about 10 µg/m³ to 3.4 µg/m³. The EU limit value for 2005 is 5 µg/m³. The problem with benzene is therefore largely under control.

Emissions of PAH
Danish emissions of PAH (Poly Aromatic Hydrocarbons) have increased in recent decades, when the emissions have been measured. The main source is small firing units - i.a. open fireplaces and wood burning stoves.

(Source: NERI)
    

Concentration of benzene
On the very busy street Jagtvej in Copenhagen the concentration of benzene has fallen drastically since the middle of the 1990's when a reduction of the content of benzene in petrol was introduced.

(Source: NERI)

Lead and other metals

Many metals are poisonous, and WHO has proposed limit values for a series of them. The new EU directives for air quality will - beside lead - apply to cadmium, arsenic, nickel, and possibly mercury.

Lead

For many years lead was added to motor vehicle petrol in order to increase the octane number for motors with higher compression, and, thus, improve efficiency. Apart from the surroundings of certain industrial installations, these lead additives were the absolutely dominating source of lead in the air in Danish cities.

Denmark has, like the other EU countries, introduced limits for the content of lead in petrol. Measures were first taken in 1978, the rules were tightened during the 1980's, and since 1984 there has been no lead in the petrol - and not in the EU since 2000. The result has been almost complete disappearance of lead from the urban air, the present level in Copenhagen is approx. 15 µg/m3 or only 3% of the EU's planned limit value for 2010 (0.5 µg per m3).

This does not mean, however, that the human lead load has fallen correspondingly, because lead, like other heavy metals, can also be taken up with food. In this connection it is important to note that the concentration of lead in Danish rural areas has always been significantly lower than in the cities and to a large extent is influenced by longrange transport. Therefore, in relative terms, the lead load is not equally reduced. Since 1990 lead concentrations have fallen to about one third (from 25 to 8 µg/m3), and the deposition of lead has fallen correspondingly. The concentrations in the soil will, however, remain fairly constant, since the lead does not disappear, but remains in the soil.

Lead in petrol and lead emissions
Lead additives in motor vehicle petrol used to be the dominating source of air pollution with lead in Danish urban areas and along busy roads. Starting in 1978 the permitted lead content has gradually been reduced to zero. The result has been a corresponding decrease of total lead emissions in Denmark.
          

Lead in urban air and in rural areas
In the same period the lead concentration in urban air has fallen to about 1/100. The concentration in rural areas (approx. 1/10 of that in urban areas) - and thus of the lead deposition - has not been equally reduced measured in relative terms. The reason is a significant contribution from longrange transport.

(Source: NERI and City of Copenhagen)

Elevated levels of lead in the blood can reduce intelligence. Some scientists have even dared the hypothesis that extensive lead poisoning contributed to the fall of the Roman Empire. Air pollution with lead has largely disappeared in Denmark, but it is not the only source of lead in humans.

Other metals in the air

Emission inventories for other heavy metals than lead - for example cadmium, mercury, nickel and zinc - show less distinct, but in most cases significant reductions in recent years, due to purification of emissions from power plants, incineration plants and industrial plants. Also concentrations of a series of heavy metals in urban air have fallen, but as there appears to be many different sources it is difficult to point to one single reason.

Heavy metals in soil

In 1996 it was concluded that the present deposition of heavy metals is generally very small compared to the natural content in the soil. It is therefore not expected to be an acute problem. As deposition can take place directly on the eatable parts if the plants, there is still reason to follow closely the development for especially lead, cadmium and mercury.

Lead deposition in Danish rural areas
During the last decade lead deposition in rural areas (average of measurements at Tange and Keldsnor) has been more than halved. Similar, but smaller reductions have been observed for i.a. zink and copper.

(Source: NERI)

Large and small particles

Pollution with particles results in increasing illness, deterioration of general wellbeing and shorter lifetime of persons who are particularly exposed to respiratory diseases.

In contrast to gaseous air pollutants, particles are not a well-defined compound. They occur in varying sizes, shapes and chemical composition. Often the compounds attached to the surface of the particles are important - and not the particles themselves. In addition their size is determining for how long they stay in the atmosphere, and how easy they are deposited in e.g. human lungs.

Roughly, particles are divided into three size groups: coarse (larger then 2.5 µm), fine (smaller than 2.5 µm) and ultrafine (smaller than 1 µm). It appears that the fine and ultrafine particles are most hazardous.

Health impacts

Foreign estimates suggest that the average lifetime is reduced by about half a year per 10 µg/m³ PM10. If this estimate is applied to larger Danish cities, the reduction of the average level by 1/3 will reduce mortality by about 400 per year of 1 mio. inhabitants.

If the smallest particles are the most dangerous, it is because larger particles predominantly consist of worn road surface or compounds from natural sources that are not especially dangerous. Further, a given weight contains a much larger number of particles   if they are small than if they are large. And their total surface is larger.

Most countries have established limit values for the mass of particles. Regulation on this basis may therefore be less efficient, because it is not the dangerous part that is directly regulated.

Particles in the air

Particles in the form of soot was, together with sulphur dioxide, the main component in the "classical" urban air pollution, and it was measured by blackening of filter paper. Soot has now largely disappeared from Danish open air due to cleaner fuels and better combustion systems possibly equipped with smoke filters.

Today the main part of the particles in the air is due to traffic - especially diesel cars - and other mobile sources. The rest can be industrial emissions e.g. from cement production or arise from natural sources as soil, vulcanos, forest fires or seaspray.

The total amount of dust (total suspended particulate matter) is measured by weighting filters, and halving of the yearly averages since the beginning of the 1980's has been observed. The amount of particles below 10 µm (PM10) has only been measured for a couple of years, and so far no trend has been observed.

Particles in Danish urban air
Emissions of soot and larger particles have been strongly reduced by the use of cleaner fuels and improved combustion and purification technology, and their concentrations in urban air have fallen correspondingly. Very small particles have been measured for too short a period to show any trend. Soot is measured in the very busy street Stormgade in Copenhagen, TSP (Total Suspended Particulate Matter) is measured i.a. in the city of Aalborg. PM10 (the weight of particles below 10 µm) is measured on the busy street Jagtvej in Copenhagen.

(Sources: HLU and NERI)
        

Particulate pollution was earlier soot from heating units. It could i.a. make it impossible to dry clothes in the open air, and it may also be the reason why umbrellas were originally black. Today small particles especially from traffic are most important. They are invisible to the naked eye, but they can be inhaled. The particles may have serious effects on human health, and may aggravate the condition of sensitive persons suffering from respiratory and heart diseases. Compounds on the particles can also have a number of impacts, e.g. be carcinogenic.

Danish research

Danish scientists are in the front of the development. Knowledge is still insufficient, but in recent years the basis for decisions has been improved. In the appropriation act funds have been allocated until 2004 to a special research programme on air pollution, especially on particles in the air.

The institutions under the Ministry of the Environment collaborate with a number of other Danish experts. It is expected that the programme will give the Ministry a much better understanding of the health consequences of particles in the air, and where the particles come from - and thus indicate the regulatory measures with the largest reduction potential.

From the Geneva Convention
– to the Gothenburg Protocol and the NEC directive

In 1976 the Nordic environment ministers proposed a European convention on transboundary air pollution, especially with sulphur compounds. After negotiations in ECE, 34 countries and the EC Commission signed the Geneva Convention in 1979. The convention came into force in 1983, and has now been ratified by 47 countries on the European continent plus the US and Canada.

The convention is a framework convention that is supplemented with more specific protocols. So far 8 such protocols have been worked out and signed. Five of them are in force.

Air pollution can be transported across national borders, and it is therefore not always possible for individual countries to regulate the air quality and the deposition of harmful compounds by national regulation. An effective abatement of air pollution requires international collaboration. The Geneva Convention forms the framework of the only forum on the European continent where the common problems in relation to air pollution can be addressed.

The first protocol deals with financing of the technical scientific basis. Within this framework data have been collected, air and precipitation quality have been measured, and model calculations of the atmospheric dispersion have been carried out since 1985. By means of emission prognoses and model calculations it is further possible to evaluate the future pollution and the results of planned regulation. This has played a key role in later negotiations on protocols that aim at regulating emissions of sulphur dioxide, nitrogen oxide, hydrocarbons, heavy metals and POP.

The culmination of this work is the Gothenburg Protocol, which was signed in 1999. It is both a "multi-pollutant" and a "multi-effect" protocol aiming at reducing acidification, eutrophication and damages from tropospheric ozone. The strategy is a comprehensive effort against transboundary pollution with sulphur dioxide, nitrogen oxide, hydrocarbons and ammonia.

Danish emissions and targets for the four compounds in the Gothenburg Protocol
The diagram shows Danish emissions in the reference year 1990 and in 2000. Further are shown the emission ceilings that Denmark is committed to as signatory to the Gothenburg Protocol and the adoption of the EU directive on national emission ceilings.
Both within the UN Economic Commission for Europe (ECE) and at EU level, work is done to control transboundary air pollution. For Denmark the results are identical.

(Source: Danish Environmental Protection Agency)

The objectives of the Gothenburg Protocol

The protocol has been negotiated on the basis of model calculations founded in national mapping of critical loads and the costs of reducing emissions. And it puts ceilings for emissions of the four mentioned compounds for each country in 2010.

The protocol operates with fixed targets for improvement of the state of the environment in all the areas comprised. The emission reductions, however, are carried out where it is most cost-effective, i.e. where the benefits to the affected areas are largest, and where actions have so far been taken at least towards emission control and further efforts therefore will be relatively cheap.

When the protocol is fully implemented in 2010 Europe's emissions of sulphur must be reduced by at least 63%, NOx emissions by 41%, VOC emissions by 40% and emissions of ammonia by 17% - all relative to emissions in 1990.

The protocol also sets out strict limit values for emissions from specific sources, e.g. incineration plants, power plants, chemical treatment plants plus cars and lorries. It is required that the best available technology is used in order to keep emissions down. VOC emissions from products like paints and aerosols must also be reduced. Finally, farmers must take specific measures in order to control emissions of ammonia. Guidelines decided in connection with the protocol suggest a series of abatement technologies and economic instruments for the emission reductions in the relevant sectors, including transport.

It is estimated that when the protocol is implemented, European areas suffering from too high acidification levels will be reduced from 93 mill ha in 1990 to 15 mill ha in 2010. Areas suffering from too high a degree of acidification will have fallen from 165 mill ha in 1990 to 108 mill ha.

The number of days with too high ozone levels will be halved. That means that the number of life years lost as a consequence of chronic effects of ozone loads will be about 2.3 mill. lower in 2010 than in 1990. And there will be about 47,500 fewer premature deaths as a result of ozone and particles in the atmosphere. The amount of vegetation that is exposed to too high ozone levels will be reduced by 44% compared to 1990.

The EU directive on national emissions

In parallel with ECE also the EU has taken action to reduce long-range transport of air pollution. The principal objective is the same: a cost-effective comprehensive reduction of impacts of acidifying, eutrophying and ozone forming compounds (SO2, NOx, VOC and NH3). The EU Commission has calculated proposed emission ceilings for each of the 15 EU countries - the socalled NEC (National Emission Ceiling) directive, which was adopted in October 2001.

In spite of a common basis for calculations the results are different, primarily because no account is taken of areas that are sensitive to acidification in Norway, which is not a member of the EU. For Denmark the ceilings for the four compounds are identical.

Consequences for Denmark

Danish emissions of SO₂, NO_x, VOC and NH₃ are already so strictly regulated that the required reductions will be achieved if current legislation and existing environmental goals are fulfilled. For nitrogen oxide, however, the fulfilment will to some extent depend upon electricity export and Denmark's implementation of the Kyoto Protocol.

It is also worth noting that even full compliance with the Gothenburg Protocol can only be considered a preliminary goal. It will not be sufficient to fully protect Danish nature and environment.

The hole in the sky
– the CFC gasses and the Montreal Protocol

CFC (chloro-fluoro carbons) is a common name for a series of industrially produced gasses. They are under normal conditions extremely stable and completely nontoxic. They have therefore had a series of practical applications, e.g. as heat medium in refrigerators, as propellant in spray cans or fire extinguishers, and in the production of insulating foam. For many years they were considered an environmental asset.

In the beginning of the 1980's, however, it became evident that their great stability might be the explanation of a newly observed global environmental threat: the depletion of the atmosphere's ozone layer.

Depletion of the ozone layer

Ozone (O₃) is at low altitudes an air pollutant that harms both vegetation and human health. In the stratosphere 15-50 km above the ground, however, ozone provides a necessary shield against biologically active ultraviolet radiation from the sun - the so-called UV-B radiation. The great stability of the CFC gasses and thus their long lifetime in the atmosphere mean that they can be mixed only poorly in the stratosphere. Here they are broken down by the ultraviolet radiation and form free chlorine atoms that transform ozone to ordinary oxygen. In a chain process a single CFC molecule can decompose many ozone molecules.

Depletion of the ozone layer will result in an increase of the UV-B at ground level and a range of unwanted effects. Most feared is the increased incidence of i.a. skin cancer. It is, thus, estimated that a 1% reduction of the ozone layer will increase the risk of nonmelanomium by 2%. The significance for the far more dangerous malignant melanomium is, however, less clear.

Sunlight is an essential condition for higher forms of life. For humans the lack of sunlight can cause serious health and sometimes mental problems. But direct radiation from the sun also contains ultraviolet radiation that is harmful to biological systems. Normally it is partly filtered out by the ozone layer in the stratosphere. It is therefore a serious matter if the ozone layer is depleted.

On a larger scale i. a. plankton algae can be harmed. As they constitute the first link in the marine food chain, it may have consequences that can escalate through the whole system.

International efforts

Already in 1985 the Vienna Convention on the Protection of the Ozone Layer was signed, and in 1987 the more concrete Montreal Protocol. It has later been tightened, in step with the provision of new knowledge on ozone depleting compounds and the possibilities for phasing them out. The industrialised countries committed themselves to stopping the use of the five most important CFC's before 1996, whereas the developing countries must stop the use before 2010. There are also agreements for three halones (similar compounds that contain bromine), which have been used especially for fire extinguishers. Further, it has been planned to phase out a series of substitutes with minor ozone depleting efficiency.

The development in Denmark and the World

Denmark has rapidly outphased the use of ozone depleting compounds. For practical reasons the effect of all the relevant compounds is expressed in terms of the most important CFC, CFC-11. In 2001 the Danish consumption measured as CFC11 equivalents had fallen by 99%.

Also internationally phasing out has been successful, although a fall in the production of CFC has been accompanied by rising production of the less harmful substitutes. In the future the most important challenges will be to ensure that the developing countries can meet the requirements of the Montreal Protocol to phase out HCFC (hydrochloro fluorocarbons) and methyl bromide, to fight illegal trade and, finally, to identify and control new ozone depleting compounds.

The problem thus appears to be on its way towards a solution. But even with fulfilment of the most recent international agreement, the ozone layer will not be fully restored until approx. the middle of this century.

Danish consumption of ozone depleting compounds
Since international work with protection of the ozone layer started in the beginning of the 1980's, the Danish consumption of ozone depleting compounds has by and large been phased out. Here is shown - in amount of controlled ozone depleting compounds - the consumption expressed in terms of CFC11 equivalents.

(Source: Danish Environmental Protection Agency).
         

The global average of the CFC-11 concentration
Although the global mean value of CFC-11 concentrations appears to have peaked, it will take at least decades before the impact on the ozone layer is below the critical level.

(Source: IPCC).
            

The ozone column over Denmark
The average ozone column over Denmark has, since measurements started in 1978, fallen by about 10%. Under cloud-free conditions, when people preferably enjoy the sunlight, the harmful ultraviolet radiation increases by nearly 15%. Nevertheless, this is still significantly less than possible exposure during the summer holiday in Southern Europe.

(Source: DMI).

Global warming
– the greenhouse gasses and the Climate Convention

The importance of the composition of the atmosphere for the energy balance of the earth and thus for the global climate has been recognised since the beginning of the 19th century. In the 1890's the Swedish meteorologist Arrhenius calculated that the doubling of the concentration of CO₂ could result in a global warming of 5-6°C. In the 1930's it became evident that the temperature was indeed increasing, but it did not receive much attention. Partly because it was considered almost an advantage, partly because such questions generally lost in the competition for political attention against social problems after the First World War, the economic depression in the 1930's, and the prelude to the Second World War.

In the years after the Second World War scientific interest in the phenomenon increased, but not until an international conference on "Green house effect, climate change and ecosystems" in 1985, was it politically recognised that it could be a problem with global impact on the environment.

Danish emissions of carbon dioxide (CO₂) and other greenhouse gasses
Danish emissions of carbon dioxide increased slowly up to the middle of the 1990's and are now slightly decreasing. The values in 1975, 1990 (reference year) and 2000 were nearly identical, about 50 Mt. per year. Emissions of other greenhouse gasses, expressed in CO₂ equivalents, have been almost constant since 1990.

(Sources: NERI, Risø, Danish Energy Agency)
      

Stabilisation scenario
To stabilise the content of carbon dioxide in the atmosphere at twice the "natural" level (550 ppmv), it requires that global emissions are halved in the next decade and then further reduced.

(Source: IPPC).

The threat of climate change

The increased greenhouse effect and the threat of anthropogenic global warming have a time perspective reaching many centuries ahead. And it is a far more controversial phenomenon than the depletion of the ozone layer.

Different areas on Earth will be affected differently, and not all negatively. Denmark, seen in isolation, will be fairly well situated if plans for the expected climate changes are made in time - especially within forestry and in connection with construction of large infrastructures. A rising sea level resulting from global warming can, however, also in Denmark cause problems in low lying coastal areas.

Generally the developing countries will be hit hardest, since they are both the most vulnerable and have the poorest possibilities for adaptation. Necessary action to reduce emissions of greenhouse gasses affects all society's sectors for many years and will in the developing countries conflict with a justified wish for economic development.

The IPCC stabilisation scenarios

Partly as a result of the Brundtland Report on environment and development, the UN Environment Programme (UNEP) and the World Meteorological Organisation (WMO) established the so-called Intergovernmental Panel of Climate Change (IPCC) in 1988. IPPC has i.a. investigated the goal that the atmospheric content of carbon dioxide and other climate gasses shall be stabilised at a level twice the level before the industrialisation accelerated in the beginning of the 19th century. In this scenario, the global impact will be acceptable, but certainly not without environmental problems. To achieve this goal, however, the global emissions - after an almost unavoidable increase for some decades, must be halved compared to the present level before 2100, and then in the following decades be further reduced. And that must be accomplished simultaneously with a situation where the world population probably doubles, and the developing countries will increase their material standard of living. Thus a goal that is significantly more ambitious and farsighted than that of the Brundtland Commission. On a per capita basis this will require much more extensive reduction of emissions in countries like Denmark. This may not be technically impossible, but, politically, a great challenge.

Only very limited Danish areas are virgin nature, and the large fraction of this is found along the coast. In warmer climate with rising sea level, low lying areas that are comprised by the EU birds directive will be threatened.

The Climate Convention

After a series of preparatory meetings the UN organised in 1992 in Rio de Janeiro a world conference on environment and development. Here 155 parties signed a framework convention on climate change (UNFCCC). It aims at a stabilisation of the concentration of greenhouse gasses in the atmosphere. The ultimate objective is quoted in the margin.

The convention thus expresses a general intention and recognises that climate changes cannot be avoided completely. What will then be considered an acceptable combination of "dangerous, "sufficient" and "sustainable" will depend upon political considerations.

Between politics and science

The convention came into force in 1994, and subsequently a series of meetings have taken place with the signatories in the COP (Conference of the Parties). The third and so far most important conference took place under great public attention in Kyoto, Japan, in December 1997. It was concluded with the adoption of a protocol, applying to carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O) and hydrofluoric carbons (HFC), perfluoro carbons (PFC) and sulphur hexa fluoride (SF₆). Freon compounds that are both greenhouse gasses and ozonedepleting substances, were not considered, because they are already regulated in the Montreal Protocol.

The targets of the Kyoto Protocol

With respect to specific emission reductions, however, only modest results were obtained. The industrialised countries, including Russia and Eastern Europe, must - together - reduce their total emissions of greenhouse gasses - expressed as CO₂ - by 5.2% in the period 2008-2012 compared to 1990 levels. A few countries were permitted directly to increase their emissions. These modest reductions have later been undermined, i.a. it has been permitted to set off emissions against sinks for carbon dioxide, i.a. forestation. Further, since some countries, including the US, are not likely to participate, it is very doubtful whether the target will be reached.

On the average the EU countries must reduce their emissions of greenhouse gasses by 8%. In the subsequent distribution of reduction figures, Denmark accepted to reduce emissions by 21%. In 2002 a regulation was issued limiting the use of the potent greenhouse gasses HFC, PFC and SF₆. However, in practice the total contribution is modest. In 2003 the Danish Government will consequently present a number of concrete proposals on tools to be used to reach the reduction target for the most important greenhouse gasses - especially carbon dioxide. This will in the years to come be Denmark's greatest environmental challenge.

Literature

(Please note that some Danish institutions have changed their name over the years.)

Aniansson, B. (ed.), 1982: Acidification today and tomorrow. Swedish Ministry of Agriculture, Environment'82 Committee. Stockholm.

Bach, H., Christensen, N., Kristensen, P., 2002: The State of the Environment in Denmark, 2001. NERI Technical Report No. 409. National Environmental Research Institute, Roskilde.

Danish Energy Agency, 1996: Denmark's Energy Futures. Ministry of Environment and Energy, Copenhagen.

Danish Environmental Protection Agency, 1992: Industrial Air Pollution Control Guidelines, Vejledning fra Miljøstyrelsen Nr.9, 1992. Danish Environmental Protection Agency, Copenhagen.

Danish Ministry of Environment and Energy, 1996: Energy 21: The Danish Government´s Action Plan for Energy 1996, Copenhagen.

EMEP (Co-operative programme for monitoring and evaluation of the long range transmission of air pollutants in Europe) publishes yearly reports through the Norwegian Meteorological Institute.

European Environment Agency, 1999: Environment in the European Union at the turn of the century. Environmental assessment report No. 2. European Environment Agency, Copenhagen.

European Environment Agency, 2001: Environmental signals 2001. Environmental assessment report No. 8. European Environment Agency, Copenhagen.

Forsuringsudvalget, 1984: Environment and energy (In Danish: Miljø og Energi) In Danish with an English summary. National Agency of Environmental Protection, Copenhagen.

Heidam, N.Z., 2000: The Background Air Quality in Denmark 1978-1997. NERI Technical Report No. 341. National Environmental Research Institute, Roskilde.

IPCC (Intergovernmental Panel on Climate Change) has published three Assessments in 1992, 1996 and 2001, and a series of special reports. All publications can be downloaded from the internet at: www.IPCC.ch

Ministry of the Environment, 1988: Environment and development: The Danish Government´s action plan. Ministry of the Environment, Copenhagen.

Moe, M., 1995: Environmental Administration in Denmark. Environment News No.17. Danish Environmental Protection Agency, Copenhagen.

National Agency of Environmental Protection, 1973: Environmental Protection Act. National Agency of Environmental Protection, Copenhagen.

National Environmental Research Institute (DMU) publishes various technical reports and data, in many cases in English. They can be downloaded as PDF files at DMU´s homepage: http://fagligerapporter.dmu.dk

Ministry of the Environment and Energy, 2000: Climate 2012: Status and Perspectives for Denmark´s Climate Policy. Ministry of the Environment and Energy, Copenhagen.

United Nations, 2000: Protocol to the 1979 convention on longrange transboundary air pollution to abate acidification, eutrophication and ground-level ozone. A short version on the Gothenburg Protocol can be found at: http://www.unece.org/env/lrtap/multi_h1.htm

WHO (World Health Organization), 2000: Air quality guidelines for Europe; second edition. WHO Regional Publications, European Series No. 91. Regional Office for Europe, Copenhagen.

World Commission on Environment and Development, 1987: Our Common Future, Oxford University Press.

Information (also often in English) can be obtained on the following homepages:

- Danish Ministry of the Environment: www.mim.dk
- Danish Environmental Protection Agency: www.mst.dk
- National Environmental Research Institute: www.dmu.dk
- Danish Energy Agency: www.ens.dk