2024 Author: Eric Donovan | [email protected]. Last modified: 2023-12-16 21:13
First nitrogen oxides, now CO2. The emissions scandal at Volkswagen is spreading. But what do the individual substances that come out of the exhaust mean? We present them at a glance.
Some car emissions are harmful to health, others to the climate or nature. After the VW scandal initially hit the headlines with nitrogen oxides that are harmful to the lungs, the car manufacturer now had to admit irregularities in CO2 levels. But what exactly do the various pollutants mean? We list them.
Nitrogen oxides (NOx):
Nitrogen oxides that are harmful to health, such as nitrogen monoxide and dioxide, only occur in tiny amounts in nature. They come mainly from cars, but also from coal, oil and gas power plants. Diesel engines emit much more NOx than gasoline engines. The substances can attack the mucous membranes and lead to coughing, breathing difficulties and eye irritation. Asthmatics are particularly at risk. But they can also affect the heart and circulation. Plants are damaged in three ways: NOx are poisonous for leaves and lead to over-fertilization and acidification of the soil.
In addition, nitrogen oxides contribute to the formation of fine dust and ground-level ozone. Technically, NOx can be converted into harmless nitrogen (N2) and oxygen (O2) using a three-way catalytic converter in gasoline engines. However, there are still residues of NOx. In diesel engines, the breakdown of NOx is much more difficult - it can be achieved by injecting a urea solution into the exhaust gas flow.
Among the NOx, only laughing gas (nitrous oxide / N2O) is important for the greenhouse effect. It does not harm health in the present concentrations. Laughing gas comes mainly from fields with lots of artificial nitrogen fertilizers. The currently most important NOx is nitrogen dioxide (NO2).
NO2 limit values air:
"Nitrogen dioxide (NO2), which mainly comes from vehicle exhaust gases, is developing into the number one pollutant," writes the Federal Environment Agency (UBA). In 2014, the NO2 concentration exceeded the annual mean limit of 40 micrograms per cubic meter at more than half of the measuring stations on roads with heavy traffic. Then authorities must ensure a reduction in NO2 with air pollution control plans. In addition, the EU Commission can initiate so-called infringement proceedings, which can lead to fines. According to the UBA, such a procedure is currently in progress against Germany because the annual limit value has been exceeded. Citizens can also sue the authorities for compliance with the limit values.
NOx limit values car:
The limit value in car exhaust for all nitrogen oxides combined in the EU is 80 milligrams per kilometer (mg / km) for diesel engines and 60 mg / km for gasoline engines. The value required by the US environmental protection agency EPA is the equivalent of 43.5 mg / km on average. However, the US control systems are not uniform and regulations may vary from state to state.
Ozone (O3):
In sunlight, NOx together with organic substances and oxygen form ozone. Since the auto catalytic converter and corresponding technologies in power plants led to the reduction of NOx in the air, the ozone peaks have also decreased. However, the average O3 pollution increased - mainly because cars emit less nitrogen monoxide (NO) and this breaks down ozone at night. Ozone irritates the mucous membranes, eyes and lungs. It can cause respiratory problems. As with NO2, asthmatics are particularly at risk, but also workers and athletes outdoors and children with their high metabolism.
O3 limit values air:
If the ozone concentration reaches 180 micrograms or more per cubic meter of air for an hour, state authorities have to inform people via radio stations, for example, and indicate what to do. People who are sensitive to ozone should refrain from strenuous outdoor activities. From the alarm threshold of 240 micrograms per cubic meter, this applies to the entire population.
particulate matter
These tiny particles are created either directly in car engines, power stations, industry or when smoking cigarettes, or indirectly through nitrogen oxides and other gases. The fine particles get into the lungs and even enter the bloodstream. They can lead to inflammation of the airways, but also to thrombosis and heart disorders. Fine dust emissions were particularly high in the GDR and have fallen significantly in Germany since 1985.
Fine dust limit values for cars:
Many cities have set up environmental zones to reduce their particulate matter levels. Only cars with a green (rarely also yellow) sticker are allowed into these. The badges are only available for cars that comply with certain emissions standards - which almost all new cars in recent years do. The environmental zones were an important instrument to reduce fine dust in large cities, said UBA President Maria Krautzberger some time ago. Now a transport policy is required that leads away from the motor vehicle and towards buses, trains or bicycles.
Green sticker
The main aim of the green stickers was to reduce particulate matter emissions. According to the UBA, NO2 emissions are currently causing problems. According to the UBA, the previous stickers are of little help here, as diesel cars with a green sticker still emitted considerable amounts of nitrogen oxides.
Carbon dioxide (CO2):
Although it is harmless to humans, it is also the most important greenhouse gas and 76 percent responsible for human-made global warming. According to the UBA, road traffic causes around 17 percent of all greenhouse gas emissions in Germany - carbon dioxide plays by far the largest role here. There are ever more economical engines, but at the same time ever larger cars with more horsepower and a rapidly increasing transport by truck. Greenhouse gas emissions from traffic rose by as much as 0.6 percent between 1990 and 2014.
CO2 limit values for cars:
In 2015, car manufacturers in the EU have to achieve an average limit of 130 grams of CO2 emissions per kilometer for their car fleets. In 2021, only 95 grams will be allowed. In the USA, the CO2 limit values are slightly higher. The specification of the US environmental agency EPA provides for a limit value for cars of around 140 grams per kilometer for vehicles registered in 2016. By 2025, this limit will gradually decrease to around 89 grams per kilometer. However, individual states can be stricter. (dpa)
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