Low Emission Zone in Leipzig effective in reducing particle pollution

22 December 2017

An air quality study in Leipzig, Germany, found that the ambient concentrations of toxic combustion aerosols that are primarily produced by motor vehicles has been reduced by as much as 60-70% since the introduction of a Low Emission Zone (LEZ) in the city. However, the LEZ appeared to have no effect on NOx exposures. The findings are part of a joint scientific study by the Saxon State Office of the Environment, Agriculture and Geology (LfULG) and the Leibniz Institute for Tropospheric Research (Tropos).

The LEZ in Leipzig was established in March 2011, limiting access for diesel vehicles to those certified to Euro 4 and higher emission standards. The ban of older vehicles and subsequent modernization of the car fleet resulted in slightly reduced PM₁₀ and PM_2.5 mass concentrations. However, the mass concentration of black carbon (soot particles) emitted mainly from diesel vehicles decreased by 60% in the city center. Furthermore, the number concentration of ultrafine particles, which can penetrate deep into the lungs, decreased by approximately 70%. These particles are believed to be among the most toxic and carcinogenic pollutants from motor vehicles.

Despite modernized diesel vehicles, NOx concentrations did not follow these trends and remained nearly constant. However, the main achievement of the Low Emission Zone was the improvement of air quality by the reduction of the most dangerous particles—according to the authors of the study.

Leipzig’s LEZ covers 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. However, the final conclusion of the LfULG/Tropos report Effect of the Low Emission Zone on Air Quality was very positive.

Scientists from both institutes investigated air quality changes over the period of seven years. Thirteen monitoring stations in Saxony provided data. Seven of these 13 stations were equipped for the measurement of black carbon and ultrafine particles.

The reduction in black carbon and ultrafine particles was most significant at the measuring station ‘Leipzig Mitte’ (Leipzig Central). This measuring station is located at the congested inner city ring road. There, the mass concentration of black carbon particles dropped by approximately 60% and the number concentration of ultrafine particles by about 70%.

The modernization of the vehicle fleet accelerated the effect of the low emission zone. However, the proportion of diesel vehicles registered in Leipzig increased 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 NOx is stagnant and remains too high.

Source: Tropos Institute | Umweltzone Leipzig Abschlussbericht