Development air quality and air pollution control
In order to improve air quality throughout Europe, the EU has defined air quality limits that have been incorporated into German law. These levels are very challenging. Especially for particulate matter, the limits are being met much better today than they were ten years ago. For nitrogen oxide emissions, however, there are still greater challenges.
There are two different limits for particulate matter (PM10) – one for the annual average and one for the daily average. The annual average must not exceed 40 micrograms per cubic meter (μg/m³). The daily average must be no greater than 50 μg/m³, but this value can be exceeded 35 times in a calendar year. These limits for particulate matter (PM10) are largely met in Germany, even at measurement stations next to high-traffic roads. In 2015, only two measurement stations still exceeded the limits. One of these is at the Neckartor in Stuttgart. Even there, success in improving air quality is clearly evident. From 187 overruns in 2005, the frequency of overruns was reduced to around 70 within ten years.
The annual average limit for particulate matter is currently met at every station in Germany. In 2015 once again it was seen that daily limits are exceeded almost exclusively in the winter. The meteorological conditions in winter months are the primary reason for this. Particularly when winter high-pressure zones cover a large area, with low moisture and strong sunlight, the daily limits can be exceeded. In the summer, in contrast, overruns of daily limits are seldom recorded. Levels above the limit are also often observed across large areas. For example, of the 48 stations that had twenty or more days over the limit in the first half of 2014, three-quarters were in the new federal states, which are rather sparsely populated. This indicates that particulate matter levels typically have meteorological causes for the most part.
The example of the particulate matter alarm in Stuttgart at the beginning of 2016 shows that road traffic can hardly be made responsible for levels above the limit anymore. Although fewer vehicles were traveling on the road, particulate matter levels rose significantly on the days when the particulate matter alarm was in effect.
The automotive industry has done its part to minimize particulate matter. In modern passenger cars, particulate matter emissions are essentially irrelevant. According to official data, even in Berlin automobile exhaust contributed only about 7 percent to particulate matter levels. Construction machines, in contrast, had over a 12 percent share. The Federal Environment Ministry has determined that exhaust gases from heating systems and open fireplaces are now responsible for a larger proportion of total particulate matter emissions than motor vehicle engines. An example makes this especially clear: The engine of a fully loaded 40-ton tractor trailer emits the same amount of particulate matter on a trip from Berlin to Hamburg as a smoker who smokes one pack of cigarettes.
In an international comparison, German cities are in an extremely good situation. The particulate matter emissions in the Chinese capital of Beijing are significantly above the levels observed in Germany and reach heights that have never been measured in this country. But attempts to control the levels with driving bans have also failed there. Despite cutting traffic volume in half with driving bans, no significant change in particulate matter levels was achieved. Instead, the influence of weather is also clear in Beijing. The lack of wind is the primary factor for high pollutant levels. Particulate matter levels drop noticeably whenever stronger wind movements are recorded.
In Milan another factor is clear, namely the inversion weather pattern. The temperature curve there tracks the particulate matter curve very closely, and limited driving bans in Milan also could not bring about any change.
Meeting the limits for nitrogen dioxide emissions (NO2) on main traffic routes in cities is still a challenge. This is due not least to the fact that although stricter air-quality limits have been in place in the EU since 2010, the more strict Euro 6 exhaust gas standard for all newly registered diesel passenger cars has only needed to be met since September 2015. As market penetration of these modern drivetrains advances, however, the air quality will become significantly better in upcoming years with respect to nitrogen oxide emissions.
In order to reduce nitrogen oxide emissions at the affected measurement stations in the short term, there are many suitable approaches. Avoiding traffic backups in inner cities with intelligent traffic light controls – known as the green wave – has great potential. Better traffic flow reduces nitrogen oxide emissions by up to one-third, as shown by measurements from the Technical University in Munich and the ADAC. In addition, buses and taxis in inner-city traffic have a substantial impact on NOx emissions, because they are used in inner cities at particularly high levels. Replacement of these fleets with modern, low-pollution buses and cars would appreciably lower NOx emissions in the short term.