This indicator shows the dynamics of emissions of total suspended particles (TSP), primary particles smaller than 10 µm (PM₁₀) and particles smaller than 2.5 µm (PM_2.5) in the period 2000–2012 and the structure of particles as regards pollution sources.

In terms of pollution sources, we distinguish between primary and secondary particles. Primary particles come directly from sources on the ground, while secondary particles are a result of various transformations in the polluted atmosphere. Particles may be of natural (pollen, dust, sea salt, smoke from wildfires, meteoric dust, volcanic ash, etc.) or anthropogenic origin (a result of emissions from energy facilities, industry, transport, agriculture, small heating units, etc.). Depending on their source, particles can be of various chemical composition, shape or state of matter.

In 2012, emissions of total suspended particles (TSP) amounted to 24 kt, which was 1.5% less than in 2000. Emissions of primary particles smaller than 10 µm (PM₁₀) increased by 1.5% in the period 2000–2012. In 2012, they represented 82% of emissions of total suspended particles (20 kt). In the same period, emissions of primary particles smaller than 2.5 µm (PM_2,5) increased by 15%. Emissions of PM_2,5 particles represented 70% of emissions of total suspended particles (17 kt). Particles smaller than 2.5 µm represent as much as 85% of emissions of particles smaller than 10 µm. In the period 2000–2012, emissions of particles sized between 2.5 µm and 10 µm decreased by 41%. In 2012, PM_2,5 emissions were 9% higher than in 2005.

In the period 2000–2012, the greatest decrease in emissions of particulate matter (TSP, PM_10, PM_2,5) was recorded in industrial processes, electricity and heat generation and the use of solvents. In the same period, the greatest increase in emissions of particulate matter was recorded in transport and the use of fuels in households and the commercial sector. Increased emissions of particulate matter from households were partially a result of favourable prices of firewood compared to other energy sources used for heating.

The main source of particulate matter is combustion of fuels in households, largely due to the use of firewood in inefficient, old boilers using solid fuels or in other devices in which combustion of wood biomass is less than optimal. The share of this source increases proportionately with the decreasing size of particles, which means that PM_2,5 particles prevail in emissions from wood biomass combustion.

The main source of total suspended particles is the use of fuels in households and the commercial sector (60%), followed by agriculture (22%) and transport (9%). The situation is similar as regards PM₁₀ particles, for which the use of fuels in households and the commercial sector contribute 70% to total emissions of primary particles smaller than 10 µm, while agriculture contributes 12% and transport 9%. As regards PM_2,5 particles, the most important source is small heating units that contribute 81% to the total emissions of primary particles smaller than 2.5 µm, while transport contributes 8%.

With 9.7 kg of primary PM₁₀ particles per capita in 2011, Slovenia was ranked the third among EU-28 countries. The highest emissions per capita in 2011 were recorded in Estonia (31.6 kg/capita), while the lowest emissions were recorded in the Netherlands (1.7 kg/capita).

In order to reduce PM₁₀ emissions in Slovenia, the Operational programme for the protection of ambient air against pollution caused by PM₁₀sets out the following measures:

• reduction of emissions from heating devices at the national, regional and local levels;
• reduction of emissions from road transport at the national, regional and local levels
• reduction of emissions from industrial sources;
• reduction of emissions from construction operations.

Measures to reduce emissions of primary and secondary PM₁₀ particles in ambient air include improvement of energy efficiency and combustion processes, replacement of solid fossil fuels with natural gas and renewable energy sources, introduction of stricter emissions standards for motor vehicles and consistent implementation of environmental legislation.

Primary PM₁₀ particles are solid particles with a diameter of 10 μm or less that are directly emitted into the atmosphere (PM₁₀). Secondary PM₁₀ particles, or precursors of PM₁₀ particles, include NO_x, SO_x and NH₃, which are transformed into solid particles with a diameter of 10 μm or less as a result of physical-chemical reactions.

Inhaling of particles may cause more frequent and more severe respiratory and cardiovascular diseases, which increases the possibility of early death. Recently, most research is directed into studying the impact of fine particles on human health. Smaller particles pose a greater hazard to human health as they penetrate deeper into the respiratory system. Particles larger than 10 μm stay in the upper part of the respiratory tract (nasal cavity, paranasal sinuses), while particles smaller than 10 μm travel to the lower part. Particles smaller than 2.5 μm can penetrate deep into the lungs.