Atmospheric immissions and their impact on air quality

An atmospheric immission is the concentration of a pollutant measured in ambient air at a particular location. Pollutants may originate from human activities or natural sources and can be present as gases, smoke, dust or other airborne particles, altering the natural composition of the atmosphere.

Atmospheric immissions matter because they can affect human health, other living organisms and natural resources. Air pollutantsAir pollution caused by atmospheric contaminants is one of the most critical and complex environmental problems we face today, both because of its global r...
Read more can also damage soil and water, altering terrestrial and aquatic ecosystems. Their concentrations are regulated through environmental legislation that establishes limit values for certain pollutants.

While atmospheric emissionsAtmospheric emissions are pollutants released into the air from both human activities and natural sources. The main anthropogenic sources include industry,...
Read more originate from a particular source, such as an industrial process or an aircraft engine, immissions refer to pollutant concentrations in ambient air. These concentrations can be measured at specific locations using air qualityAir quality refers to the state of the air we breathe and its composition in terms of pollutants present in the atmosphere. It is considered good when poll...
Read more monitoring stations.

Tropospheric ozone (O₃)Tropospheric ozone (O₃) or ground-level ozone is a gas found in the lowest layer of the Earth's atmosphere, the troposphere, which extends up to 10 kilomet...
Read more is an example of a secondary air pollutant formed when certain compounds released by combustion engines and other sources react in the atmosphere. These photochemical reactions, driven by sunlight, produce ozone at ground level, where it can affect human health and the environment.

What is an atmospheric immission?

Immissions represent the concentrations of pollutants present in ambient air following their emission, transport, dispersion and possible atmospheric transformation. During these processes, pollutants may undergo physical and chemical changes as they interact with other atmospheric constituents.

These pollutant concentrations, or atmospheric immissions, express the amount of a pollutant present in a given volume of air. They therefore differ from atmospheric emissions, which refer to pollutants released into the atmosphere by a particular source.

Scientific studies are used to assess the health and environmental effects of air pollutants and support the establishment of concentration limit values. These assessments help define protective thresholds and criteria for evaluating air quality.

Differences between emissions and immissions

The relationship between atmospheric emissions and immissions is not necessarily proportional. Once released, a pollutant may undergo chemical and physical reactions, as well as transport and dispersion processes influenced by weather conditions and the surrounding environment.

The main differences between the two concepts are as follows:

Emissions

• Represent the quantity of a pollutant released into the atmosphere from an individual source or group of sources.
• May occur continuously or intermittently.
• May originate from an identifiable point source or from diffuse sources.
• May be released as gases, solid particles or liquid aerosols.
• May result from both human activities and natural processes.
• Are commonly quantified in units of mass per unit of time, such as g/h or kg/year.
• May decrease significantly or cease when the emitting activity stops.

Immissions

• Represent the concentration of a pollutant at a particular location and time.
• Legal limit values for certain pollutants are established using scientific evidence and health and environmental protection criteria.
• Compliance with air quality limit values helps protect human health and ecosystems.
• Are commonly expressed as mass per unit volume, such as µg/m³ or mg/m³.
• Air quality monitoringControlling air quality is an essential task in order to enjoy optimal environmental conditions for healthy human development and to keep the environment i...
  Read more stations and sensor networks measure these concentrations to assess air quality in a given area and track changes over time.
• Changes in pollutant concentrations are not always proportional to changes in emissions because of meteorological conditions, dispersion and atmospheric chemical processes.

Graphical illustration of atmospheric emissions and immissions

How are atmospheric immissions measured?

One of the main challenges in protecting human health and well-being is determining the concentrations of substances that can affect air quality. Environmental legislation establishes criteria for assessing pollution levels and defining the measures needed to protect people and the environment.

Regulating atmospheric immissions involves assessing pollutant concentrations and their potential effects. Competent authorities establish limit values and other air quality objectives for specific pollutants, while geographical characteristics, industrial activity and population distribution influence the design of monitoring networks.

Effective pollution control requires reliable air quality monitoring systems, including sensor networks capable of providing representative measurements. These networks can complement official reference monitoring stations and extend the geographical coverage of air quality data. Measurements should be carried out systematically and continuously, supported by appropriate calibration and quality control procedures.

Analysing the collected data makes it possible to determine pollutant concentrations in a particular area and identify periods when established limit values are exceeded. Correct interpretation requires consideration of averaging periods, meteorological conditions and the requirements of applicable air quality legislation.

When legal limit values are exceeded, the competent authorities must assess the situation and take the measures required under the applicable legislation. Affected individuals and communities may also use available administrative and legal mechanisms to request environmental protection measures. Identifying emission sources and analysing pollutant dispersion can help determine the most appropriate corrective actions.

Continuous monitoring of atmospheric immissions helps detect pollution episodes, assess the effectiveness of emission reduction measures and provide objective information to support environmental management and public health protection.