The combustion of fossil fuels such as coal, heating oil or motor fuels as well as diesel and petrol produces a large amount of air pollutants which are a major burden on the environment. They have different effects on people and the environment. In addition to air pollutants, emissions also include noise, light, heat, vibrations and radiation.

Due to the harmful effects on health, certain limit values have been introduced for various areas in order to reduce emissions. Air and noise limit values play a decisive role, especially in the environmental zones, which are intended to reduce emissions from road traffic. The main air pollutants are: particulate matter, nitrogen oxide, sulphur dioxide, ozone and carbon dioxide.

Particulate matter (PM)

The tiny dust particles, also known as particulate matter, are produced by combustion processes in vehicles, power stations, ovens and heating systems and are almost invisible. In urban areas, road traffic is a significant source of particulate matter. Abrasion and wear of tyres during braking and driving also play a major role here. Particulate matter is divided into three classes:


  • Particles with a diameter of 10 micrometres (PM10)
  • Particles with a diameter of less than 2.5 micrometres (PM2,5) 
  • Particles that are 1 micron and smaller, known as ultra-fine dust (PM0,1)

Nitric oxide (NOx)

Nitric oxide, also known as nitrogen oxide, is a chemical compound of nitrogen (N) and oxygen (O). As both elements are very reactive, there is not one nitrogen oxide, but rather a collective term for various gaseous compounds, often abbreviated as NOx. Nitrogen oxides are formed during combustion processes, such as in combustion engines and combustion plants for oil, gas and coal. In cities, the main sources are traffic and freight transport. Nitrogen oxides are responsible for air pollution and for many negative environmental impacts:


  • They contribute to particulate matter pollution and thus cause smog
  • Nitrogen oxides are partly responsible for the increased formation of ozone in summer
  • They increase the effect of allergens on asthmatics
  • Plants are damaged and soils and waters are over-fertilised and acidified

Sulphur dioxide (SO2)

Sulphur dioxide (SO2) is a colourless, pungent smelling, water-soluble gas, which is mainly formed during combustion processes of coal and fuel oil as well as other sulphur-containing fuels by oxidation of the sulphur it contains. The primary sources for the SO2 generation are combustion plants, heating systems and motor vehicle traffic with diesel engines. The gas can cause harm to humans and the environment:

  • In the atmosphere, sulphur dioxide turns into sulphate particles, which contribute to the pollution with fine dust (PM10)
  • Sulphur dioxide can damage plants and cause acidification of soil and water
  • It irritates the mucous membranes and can cause eye irritation and respiratory problems

Ozone (O3)

Ozone (O3), a colorless, pungent smelling and toxic gas, is one of the most important trace gases in the atmosphere. Basically, a distinction must be made here between two cases:

  • Stratosphere: At an altitude of 20 to 30 kilometres, ozone is a natural component in the atmosphere and forms the natural ozone layer that protects the earth from the sun's harmful ultraviolet radiation.
  • Troposphere: The ozone found near the ground is harmful and has negative effects on organisms. Here it is formed by intensive solar radiation from precursor pollutants, mainly nitrogen oxides and volatile organic compounds caused by road traffic.


In humans, excessive ozone exposure causes irritation of mucous membranes, damage to the respiratory tract, eyes and lung tissue, and in plants, it affects plant growth, crop yields and quality.

Carbon dioxide (CO2)

Carbon dioxide (CO2) is a colourless, odourless, non-flammable gas which is not a pollutant with toxic properties in the conventional sense. Rather, in the true sense, carbon dioxide is an important, indispensable metabolic product of humans, animals and plants. Only the increase in CO2 concentration has negative consequences, as it contributes significantly to the greenhouse effect. Global warming is not caused by natural processes but by anthropogenic sources. These sources include the burning of fossil fuels for energy production, industry, heating of buildings and motor vehicles.

The consequences of the increase of CO2 particles in the atmosphere are drastic:

  • The earth's climate is warming up, as less heat radiated from the earth can escape into space.
  • This causes sea levels to rise as the polar ice caps and glaciers melt.
  • The precipitation zones are shifting, extreme weather events such as storms and floods or heat waves and droughts are increasing and biodiversity is being threatened.

Noise (dB)

Noise is any annoying loud noise that the ear perceives. This happens when sounds created by vibrations spread in the air as sound waves and hit the ear. The strength of the sound, i.e. the volume, is called sound pressure. The measured value is the sound pressure level, which is expressed in decibels (dB). For many people, noise is a polluting environmental problem. Road traffic noise, which is mainly caused by motor vehicles, is clearly the most important source of noise.

The WHO has set target values for protection:

  • Minimum target: 65 dB(A) during the day and 55 dB(A) at night should not be exceeded to avoid health risks.
  • Medium target: In order to prevent enormous nuisance, the levels of pollution should be reduced to 55 dB(A) during the day and 45 dB(A) at night
  • Optimum protection: In the long term, values of 50 dB(A) during the day and 40 dB(A) at night should be targeted