With its location in a basin, the city of Aachen is at a climatic and air hygiene disadvantage compared to other cities, which has a negative impact on the level of air pollution, for example, and at times to a high and intolerable degree.
Clean air plans must be drawn up for areas in which the air pollutant limit values of the EU Air Quality Directive have been exceeded or are at risk of being exceeded. These plans set out measures to reduce air pollution. As long as the effect of the measures does not lead to compliance with the limit values, the plans must be updated. In Aachen, a clean air plan was drawn up for the first time in 2009. The last one was in 2022. As the limit values have been clearly complied with since then, there is currently no update.
Spa areas
Particular attention must be paid to the air hygiene situation in the two Aachen spa areas of Burtscheid and Monheimsallee. These areas, located to the north and south-east of the city centre, are subject to considerably higher requirements than the general EU limit values for particulate matter nitrogen dioxide (North Rhine-Westphalia Health Resorts Act and quality standards for the designation of health resorts), so-called health resort guide values.
For a long time, compliance with these spa-specific requirements was not guaranteed, particularly during periods of low air exchange. Current air hygiene studies from 2016 in the two spa areas now show that even the particularly strict spa area guidelines can be met.
Today, the main emitter in the spa areas themselves and in the nearby spa fringe areas is motorized road traffic. By means of green planning measures and a solid fuel ordinance that has been in force since 2010, a significant reduction in domestic fuel emissions has also been achieved through the implementation of already known traffic reduction scenarios to ensure the sustainable quality of the spa areas. This is also associated with a reduction in excessive noise emissions in some areas.
Clean air plan 2022
Thanks to a clear strategy, the city of Aachen has been on the right track for years to sustainably improve air quality in the urban area. Despite the talc and diesel emissions scandal, which had a massive impact on air pollution control in the cities, pollution levels of particulate matter (PM10) and nitrogen dioxide (NO2) have fallen continuously.
The relevant limit values for particulate matter (40 µg/m³ as an annual average and a maximum of 35 days with a daily average > 50 µg/m³) have been clearly complied with for many years. Among other things, the Aachen Solid Fuel Ordinance issued in 2010 has made an important contribution here. The WHO recommendation for PM 10 of 20 µg/m² as an annual average, which applies until 2020, has been met or undercut for several years at the Wilhelmstraße measuring station. The annual average value measured at Wilhelmstraße in 2021 is 18 µ/m³. Although this exceeds the WHO recommendation, which was lowered to 15 µg/m³ from September 2021, the value is still well within the acceptable range for a large city. Irrespective of this, the city of Aachen continues to focus on the issue of particulate matter in its air pollution control strategy as a precautionary measure for its population.
In the case of nitrogen dioxide (NO2), the success of the measures was rather modest for a long time. Even though the values have fallen continuously and the limit value at the state measuring station on Wilhelmstrasse - as a significant marker for traffic-induced emissions - was below the applicable limit value of 40 µg/m³ NO2 for the first time in 2019, there were still exceedances at individual pollution hotspots at the city's own measuring stations.
Against this backdrop and in view of the lawsuit filed by Deutsche Umwelthilfe (DUH) against various clean air plans (including Aachen) several years ago, a multi-stage immediate action program was presented to politicians in autumn 2019. Targeted key measures are intended to make an effective contribution to further reducing NO2 pollution in Aachen. The focus is on:
- (Further) optimization of the bus fleet through SCRT retrofitting and early procurement of new buses (EuroVI and electric) (2019)
- the introduction of a 30 km/h speed limit along the entire ring of avenues and on a section of Monheimsallee (2019/2020),
- the promotion of cycling by expanding the cycle path network, the cycling infrastructure and improving the range of services,
- the improvement of public transport services for commuters and shopping traffic,
- the expansion of electromobility and field trials with other low-emission drive types.
In addition to the local measures, the nationwide software update and the buy-back premium for diesel cars have also contributed to the reduction in NO2 pollution.
In 2020, the annual average NO2 limit of 40 µg/m³ was undercut for the first time at all Aachen measuring stations - including the city's own. Further reductions were recorded at individual points in 2021.
With this third update of the Aachen Clean Air Plan, which came into force on May 1, 2022, the new immediate action program will be integrated into the existing, comprehensive catalog of measures of the Aachen Clean Air Strategy.