This indicator shows past energy-related emissions of individual substances and total emissions of ozone precursors, acidifying substances and particulate matter.

Ozone precursors are substances that contribute to the formation of ground-level ozone. Ozone precursors are nitrogen oxides (NO_x), carbon monoxide (CO), methane (CH₄) and non-methane volatile organic compounds (NMVOC). Tropospheric or ground-level ozone has adverse effects on both human health and the ecosystem. High concentrations of ground-level ozone have been shown to adversely affect the human respiratory system, especially the lungs, while in the environment, high concentrations of ozone decrease yields, cause leaf damage and decrease disease resistance. Ozone is also capable of causing damage to plastics and rubbers.

Acidifying substances are sulphur dioxide (SO₂), nitrogen oxides (NO_x) and ammonia (NH₃). Acidification causes substantial damage to the ecosystem, buildings and materials (corrosion). NO_x and NH₃ lead to eutrophication (excess nitrogen in soil and water).

Particulate matter emissions are classified into primary PM₁₀ (particulate matter with a diameter of 10 μm or less, emitted directly into the atmosphere), and secondary PM₁₀ or PM₁₀ precursors (the fraction of NO_x, SO₂ and NH₃ emissions which, as a result of photo-chemical reactions in the atmosphere, transform into particulate matter with a diameter of 10 μm or less). The inhalation of such particles may increase the frequency and severity of a number of respiratory problems, which may increase the risk of premature death. The smaller particles, which can go deeper into the lungs, are especially dangerous.

For all air pollutants, energy-related emissions decreased in the treated period. This is especially true for SO₂ emissions that were 93 % lower in 2007 than in 1990, whereby approximately half of this reduction was achieved by the year 2000. The reason was the installation of desulphurisation devices on thermal power plants and the use of fuel with a lower sulphur content. In 2007, the emissions of the Šoštanj Thermal Power Plant reduced by 18 % due to flue gas exhausts from units 1-3 being connected to the desulphurisation device of unit 4. In 2007, energy sources contributed 92 % of total SO₂ emissions. Emissions of non-methane volatile organic compounds substantially reduced as well, being 51 % lower in 2007 than in 1990. This reduction was predominantly caused by the use of catalytic converters for the after-treatment of motor vehicle exhaust gases and a substantial increase in the share of diesel fuel in total motor fuel consumption. In 2007, emissions reduced by 4 % due to reductions in industry and transport-related emissions. In 2007, the share of energy-related emissions amounted to 59 %. The smallest reduction was evident in NO_x emissions (by 21 %). With regard to the year 2000, these emissions reduced by 9 %. This reduction was caused by European standards defining the permissible content of substances in the exhaust gases that are met by using catalysts and implementing primary measures in thermal power plants. On the other hand, industry-related emissions increased (due to including emissions from the construction sector – construction machinery, in the year 2000 and economic growth in 2005 and 2006) as well as emissions in the household sector that increased due to a growth in the use of liquid fuels (until 1999). In 2007, a 5 % reduction in emissions was noted due to reductions in energy consumption in the industrial sector (natural gas) and in wider use (fuel oil). All NO_x emissions are energy-related. In 2007, 96 % of ammonia emissions (NH₃) originated in agriculture and the remainder in transport. Transport emissions have been increasing due to a higher number of cars with catalytic converters. Since the year 2000, these emissions increased by 11 % and by 0.4 % since 2007.

Particulate matter with a diameter of 10 μm or less is also an atmospheric pollutant but its records were set up only in the year 2000 so there is no quantified objective for its reduction. Following a chequered trend until 2003, energy-related emissions slowly reduced between 2004 and 2006 (at an average annual rate of 2.3 %), while a more substantial reduction was evident in 2007 (7 %). In 2007, energy-related emissions represented 83 % of total emissions that stood at 7.4 kt.

Carbon monoxide (CO) emissions, which are fully energy-related, were substantially lower in 2007 than in 1990 (61 %). This was due to swift reductions in transport emissions after 1996 (due to European standards), as transport is by far the largest source (almost 70 %). In 2007, they amounted to 99.3 kt.

In 2007, total emissions (non-energy related and energy-related) amounted to, for SO₂, 14.2 kt, which is almost 13 kt less than the 2010 target; NO_x 44.6 kt (0.9 % lower than target emissions); NMVOC 39.3 kt (1.7 % less than the 2010 target) and NH₃ 18.5 kt (7.5 % less than target emissions). The year 2007 was the first year when emissions of all substances in Slovenia were below 2010 target values. We need to be aware however, that targets for NO_x emissions can still be jeopardised, as the consumption of liquid fuel in transport is rapidly growing, while liquid fuel consumption in wide use increased in 2008, which means that growth in transport will no longer be offset by reductions in wide use.

Detrimental environmental effects of air pollutants can be classified into three groups: acidification and eutrophication that have a detrimental effect on the ecosystem and therefore an indirect effect on human health and ground-level ozone and dust particles that have direct detrimental effects on human health. The impact of emissions of individual air pollutants on these environmental impacts can be estimated by using weighting factors.

If we compared data to the year 1990, emissions of acidifying substances and ozone precursors decreased by 38 % and 20 % respectively by the year 2000. This reduction in emissions continued after the year 2000 with emissions of acidifying substances reducing by 54 % and emissions of ozone precursors by 19 % by the year 2007 compared to the year 2000 (Figure 3). Particulate matter emissions (primary and secondary particulate matter) were 45 % lower in 2007 compared to the year 2000.

In 2007, ammonia contributed the largest share to total emissions of acidifying substances (over 95 % coming from non-energy related sectors – agriculture), followed by NO_x, in Slovenia generated only by the combustion of fuel, and SO₂ (16 %). Energy sources contributed 57 % of total emissions. The weighted total emissions of acidifying substances indicate that the highest factor is that of NH₃, followed by SO₂ and NO_x. This helps us to understand the high share of non-energy related sectors in total emissions (43 %). In the 2000-2007 period, the reduction in emissions was mostly influenced by reductions of SO₂ emissions from large thermal power plants and from wider use (Figure 5).

In 2007, more than half of the emissions of ozone precursors related to NO_x emissions, followed by NMVOC, CO and a minimum contribution by CH₄ (Figure 4). Energy sources contributed 84 % of total emissions. The highest weight in calculating total emissions is that of NO_x, followed by NMVOC, with CO and CH₄ weights being substantially lower (9 and 70 times lower respectively). It is for this reason that changes in total emissions are similar to changes in NO_x and NMVOC emissions. The main source is transport.

Contributing pollutants to particulate matter or dust particles emissions are SO₂, NO_x and NH₃ that are the source of secondary particulate matter and PM₁₀. The same as is the case with ozone precursors, the highest share in total emissions is held by NO_x followed by NH₃, SO₂ and PM₁₀ (Figure 4). Again, the majority of emissions relate to transport. In 2007, energy sources contributed 80 % of total emissions. The reduction in emissions is predominantly due to reductions in SO₂ emissions.

As regards environmental impacts, the common point for all emission groups is NO_x. It holds the largest share in emissions of ozone precursors and particulate matter emissions (51 % and 59 % respectively) and is only slightly behind NH₃ (by 3 percentage points) in emissions of acidifying substances. This allows us to conclude that a reduction of NO_x emissions efficiently reduces all of the above mentioned adverse environmental impacts. The continued reduction of these emissions in 2007 is therefore very positive, the question however remains about trends for 2008, as statistical data on energy consumption for 2008 indicate a substantial growth in the sale of motor fuels in transport as well as the sale of fuel oil in wider use. In order to continue improving air quality, measures determined by both the Operational Programme for Complying with National Emission Ceilings for Atmospheric Pollutants as well as the Operational Programme for Limiting Greenhouse Gas Emissions by 2012 will have to be implemented, especially in the field of transport. An analysis of the implementation of the Operational Programme for Limiting Greenhouse Gas Emissions by 2012 has shown that the implementation of measures is unsatisfactory especially in the area of transport.