Dirk Messner, President of the German Environment Agency (UBA), said: "The improvement in air quality is good news and shows that environmental policy is effective. The Federal government, states and local authorities which have invested so much in cleaner air will see their success reflected in the low levels of air pollution. It has been ten years since compliance with the NO2 limit adopted back in 1999 for the sake of human health is mandatory. Despite some successes, there are still scores of cities across Germany which exceed this limit. Currently, the number is 19, but when all the data has been evaluated that number could grow to between 25 and 30.” The main source of nitrogen oxides in cities is road traffic and diesel passenger cars in particular. Dirk Messner said: “Today’s diesel cars with the Euro 6d-TEMP emissions standard have low on-road nitrogen dioxide emissions, which accounts for the decrease in NO2 pollution. This is proof that we could have already complied quite a while ago with the limit values in cities had older diesel passenger cars been cleaner both on the test bench and under real road conditions. One thing is clear: having fewer cars on the roads in our cities is the best guarantee for cleaner air.”
The decline in average NO2 concentrations of about three micrograms per cubic metre at measuring stations near road traffic is due to several factors. These include local measures, such as speed limits, driving bans or the deployment of low-emissions buses; national measures, such as software updates and the annual renewal of the vehicle fleet, and meteorological phenomena which affect the spread of air pollutants. Modelling has shown that software updates and fleet renewal in 2019 resulted in mitigation of one to two micrograms NO2 per cubic metre air. Three quarters of that mitigation is due to new, cleaner vehicles and only one fourth to the effect of software updates.
With a view to protecting public health, NOx emissions must remain low throughout vehicle service life. The further development of European emission standards (post-Euro-6/VI legislation) should envision raising the requirements of durability in exhaust after treatment systems. In addition, the regularly scheduled emissions inspection should include measurements of NOx emissions to verify the efficiency of nitrogen oxide catalytic converters and detect possible defects in good time.
Particulate matter (PM10): 2019 marked the lowest levels of particulate pollution since measurements began in the late 1990s. For the first time, there was compliance with the limit value in the whole country (no more than 35 days per year with daily mean levels over 50 µg/m³ of air, and a maximum annual mean of 40 µg/m³ of air). Dirk Messner said: "What initially sounds like a success unfortunately falls short when it comes to the protection of health. Particulate matter is a far greater problem than nitrogen oxides – globally and in Germany. The limit values for particulate matter were set more than 20 years ago and are in urgent need of adjustment to the state of the art in scientific knowledge gained by the World Health Organization (WHO). As long as there is no compliance with the much lower guidelines recommended by the WHO, human health is not yet adequately protected against particulate matter. In the European Green Deal, the EU Commission has determined that limit values must be revised, and we are recommending the same, namely that particulate matter limits become stricter, for the sake of people’s health.”
Based on scientific studies, the WHO guideline for PM10 concentrations is a maximum annual mean of 20 µg/m3. The rationale is based on evidence of the health risk of exposure to particulate matter. According to the Global Burden of Disease Study by the Institute for Health Metrics and Evaluation (IHME), particulate matter air pollution ( PM2,5 ) accounted for about 2.9 million deaths worldwide in 2017. This compares with the classic risk factors smoking and alcohol, where related deaths amount to 7 million (smoking) and 2.8 million (alcohol). Particulate matter is one of the 10 risk factors with the highest disease burden worldwide, in Europe and in Germany. The IHME estimates there are some 415,000 related deaths per year in Europe. UBA’s own calculations indicate an annual average of about 44,900 attributable deaths in Germany.
In 2019, 13 percent of all measuring stations failed to comply with the WHO annual mean guideline. Roughly one-third (36%) of all the measuring stations were not in compliance with the WHO air quality guidelines for the 24-hour average (more than 50 µg/m³ on a maximum three days per year). Dirk Messner said: “Although emissions of particulate matter from combustion engines have been in decline for a while, emissions from agriculture and wood firing in particular must be reduced.”
Ozone: Ozone pollution was at average levels in 2019 compared to the previous 20 years. Unusually high temperatures of 40° Celsius and higher in late July 2019 caused many exceedances of the information and alert thresholds (180 and 240 µg/m³ of air, respectively) and a maximum of 300 µg/m³ air. Furthermore, all 260 stations exceeded the long-term objectives for the protection of health (maximum of 120 µg/m³ of air as an 8-hour average), as was the case in the year before, and on an average 24 days per station. Compliance with the WHO guideline of 100 µg/m3 air as an 8-hour mean failed again, as it has the past. Ozone is formed during intense solar radiation by complex reactions of precursor substances, usually nitrogen oxides and volatile organic compounds. Most nitrogen oxides are generated by traffic, whereas volatile organic substances are formed by solvents such as varnishes and paints, adhesives and cleaning agents. However, many types of plants also release volatile organic compounds (biogenic VOC or BVOC) and are further sources of ozone precursors beside man-made emissions. In addition to factors such as plant characteristics and pest infestation, the extent of the impact of BVOC on ozone formation also depends on air temperature and plant water supply. Temperatures of more than 30° Celsius and adequate water supply result in a sharp increase in BVOC emissions and thus to increased ozone formation. Dirk Messner said: “Heat waves will become more frequent in the course of climate change, which might also mean high ozone peaks. We must make clear cuts in the man-made emissions of ozone precursors to minimise health risks.”
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