Study finds Leipzig Low Emission Zone removed most dangerous particles; NOx remained nearly constant
Leipzig’s Low Emission Zone was established in March 2011, allowing only access of Euro 4 and higher diesel vehicles, with few exceptions. A joint scientific study by the Saxon State Office of the Environment, Agriculture and Geology (LfULG) and the Leibniz Institute for Tropospheric Research (TROPOS) has found that the ban of older vehicles and subsequent modernization of the car fleet over the past six years resulted in slightly reduced PM10 and PM2.5 mass concentrations.
The mass concentration of black carbon (soot particles) emitted mainly from diesel vehicles decreased by up to 60% at the street site. These particles are believed to be most dangerous due to their carcinogenic trace compounds such as polycyclic aromatic hydrocarbons.
The number concentration of ultrafine particles, which can penetrate deep into the lungs, decreased by up to approximately 70%. However, despite modernized diesel vehicles, NOx concentrations did not follow these trends and remained nearly constant. The main achievement of the Low Emission Zone was the improvement of air quality by the reduction of the most dangerous particles, the study concluded.
Thirteen monitoring stations provided data.
The scientists determined the reduction of tailpipe emissions of black carbon and ultrafine particles at a street-site by taking into account the concentrations measured in the urban background. The reduction in black carbon and ultrafine particles was most significant at the measuring station Leipzig Mitte (Leipzig Central).
This is the measuring station at the congested at the inner city ring road. There, the mass concentration of carcinogenic soot particles dropped by approximately 60% and the number concentration of ultrafine particles by ca. 70%.
In terms of the PM mass concentration, this reduction corresponds only to about 5%. Since these particles are however part of the highly toxic fraction of fine particulate matter, the health risk of the population was significantly reduced. The low emission zone was thus a meaningful and successful measure of the city administration of Leipzig to protection of the health of their citizens.— Gunter Löschau, LfULG
Leipzig’s low emission zone covered approximately two thirds of the total city area. At the time of implementation, the City of Leipzig was under heavy criticism, mainly from small and mid-sized enterprises, which were put under pressure to renew their fleet of light duty vehicles to a modern standard.
The modernization of the vehicle fleet accelerated the effect of the low emission zone. However, the proportion of diesel vehicles registered in Leipzig rose from 19 to 26% between 2010 and 2016, with negative consequences. While black carbon and the number concentration of ultrafine particles decreased, the concentration of gaseous nitrogen oxides (NOx) is stagnant and is still too high.
The scientists stressed that efforts still must be made to further improve the air quality in terms of protecting the population. This applies not only to the exceedance of the limit value for nitrogen dioxide (NO2 ), but also for particulate matter.
Gunter Löschau, Alfred Wiedensohler, Wolfram Birmili, Fabian Rasch, Gerald Spindler, Konrad Müller, Andrea Hausmann, Uwe Wolf, Werner Sommer, Mario Anhalt, Volker Dietz, Hartmut Herrmann, Uwe Böhme, Horst-Günter Kath und Holm Kühne (2017): Umweltzone Leipzig – Abschlussbericht (German).