Indicator 3.2.b Share of the population with excessive exposure to fine particulate matter (PM₂.₅)

3.2.b Share of the population with excessive exposure to fine particulate matter (PM₂.₅)

The indicator measures the proportion of the population whose place of residence is, on an annual average, exposed to fine particulate matter (PM) concentrations exceeding 10 micrograms per cubic metre of air. Fine particulate matter consists of airborne particles that can be inhaled and – depending on their size – penetrate deep into the lungs or even enter the bloodstream. Until 2021, the indicator referred to particles with a diameter of no more than 10 micrometres (PM₁₀). With the revision of the German Sustainable Development Strategy 2025, the focus shifted to smaller particles of up to 2.5 micrometres in diameter (PM₂.₅), as these are considered particularly relevant in terms of adverse health impacts.

The politically defined target stipulates that, by 2030 at the latest, no one should be exposed at their place of residence to PM₂.₅ concentrations exceeding 10 micrograms per cubic metre of air on an annual mean basis. This threshold corresponds to interim target 4 of the air quality guidelines published by the World Health Organization (WHO) in 2021. However, the WHO’s recommended limit value for PM₂.₅ is lower, at 5 micrograms per cubic metre annual mean.

PM₂.₅ originates partly from primary emissions – for example, from industrial processes for energy and heat generation, agriculture, road transport, and residential heating using solid fuels such as wood stoves or fireplaces. It can also form indirectly through so-called secondary particle formation: this occurs when fine particulate matter develops as a result of chemical reactions involving gaseous precursors such as sulphur and nitrogen oxides, ammonia, or hydrocarbons.

PM₂.₅ exposure levels are determined using a combination of modelling outputs and measurement data provided by the German Environment Agency (UBA) and the Länder. For the purposes of this indicator, only data from background monitoring stations in urban and rural areas are included – stations not directly influenced by local emission sources such as traffic or industrial facilities. This ensures a representative depiction of large-scale exposure patterns without distortion from localised "hot spots" of pollution.

The indicator does not represent full spatial compliance with the limit value; rather, it reflects residential locations away from significant emission sources. It therefore does not quantify the absolute exposure level of the entire population or capture seasonal variations. Since localised high-exposure areas are not incorporated into the model, the actual number of individuals with PM₂.₅ exposure above 10 micrograms per cubic metre is likely to be higher than the indicator suggests.

In 2010, the entire population was exposed to PM₂.₅ levels exceeding the threshold of 10 micrograms per cubic metre. In the following years, this share decreased markedly: by 2021, only 28.2% of the population was affected, compared with 15.0% in the previous year. If, however, the WHO guideline value of 5 micrograms per cubic metre were applied as the reference, almost the entire population would still be considered exposed.

In addition to the decline in the share of the population with elevated exposure, the population-weighted annual mean PM₂.₅ concentration has also fallen significantly since 2010. In 2021, the population-weighted mean was 9.3 micrograms per cubic metre – representing a reduction of approximately 42% compared with 2010 (15.9 micrograms per cubic metre).