A pulmonologist explains the limits for particulate matter and nitrogen oxides in Germany for "complete nonsense", more than 100 colleagues jump at him, and the Federal Minister of Transport rejoices: If so many scientists together, that is "a signal" to rethink the current measurement practices ,
So far, so simplified. After all, the position paper, which is now being talked about everywhere and written by Dieter Köhler, the former vice president of the German Society of Pneumology (DGP), was sent to 3800 DGP members at the beginning of January. But only 112 have signed it up to date, so less than three percent of the lung experts asked. This indicates that a very large majority of lung experts in Germany do not share Kohler's view.
Far more lung experts consider air pollution to be a concern
The official position of the colleagues united in the DGP is also quite different: "Air pollutants endanger our health - especially those of children, the elderly and the sick," the association announced in November 2018. Experts had then created a corresponding dossier for the DGP. On 100 pages with hundreds of footnotes they summarize the state of knowledge of the research.
Her conclusion: "Negative health effects also occur below the current European limit values in Germany." For the German population is currently "no optimal protection against diseases caused by air pollution given." Therefore "a lowering of the legal limit values is necessary" - thus even more stringent guidelines.
The Federal Association of Pulmonologists, Sleep and Respiratory Medicine (BdP) has also taken a stand. "Minimizing the effects of air pollutants endangers efforts to minimize the risks and dangers of air pollution!" Warns Frank Heimann, chairman of the BdP, in a statement. The association unites more than 1200 pulmonologists in Germany.
The pollutants in the debate, how they develop and what they know about their effect on health, we have compiled for you in the following overview:
Where do nitrogen oxides come from?
Nitrogen oxides have no natural source, but arise when coal, oil, gas or wood are burned. In cities, according to the Federal Environment Agency, 60 percent of the nitrogen oxides are from the traffic. Petrol engines make virtually no nitrogen oxides, so the discussions focus on diesel.
Which limits apply to nitrogen oxides?
Across Europe, there is a limit of 200 micrograms of nitrogen dioxide (NO2) per cubic meter of air per hour. It should not be exceeded more than 18 times a year. In addition, there is a limit of 40 micrograms per cubic meter of annual average air, which is also recommended by the WHO.
How do nitrogen oxides affect the body?
Nitrogen dioxide is a corrosive irritant gas. It mainly enters the body when it breates and penetrates to the lungs. Above a certain level, it can irritate the respiratory system causing chest pain, shortness of breath and coughing. People who are exposed to increased exposure to nitrogen dioxide for an extended period of time are at increased risk for asthma, respiratory infections, and cardiovascular disease. Particularly at risk are persons with underlying diseases as well as children, as their respiratory tracts are still developing.
However, the effects of nitric oxides are difficult to isolate. Instead, most studies are so-called observational studies: For this purpose, researchers are analyzing the level of nitrogen oxide exposure in certain areas and how many people there are suffering from a heart attack, for example.
These types of studies all have one weakness: they can never be absolutely sure that nitric oxides are actually responsible for the diseases being observed and not other factors such as particulate matter. To reduce the risk of such bias as much as possible, researchers calculate the influence of other known factors. Nevertheless, the results never provide absolute security.
What is clear, however, is that nitrogen oxides, along with ammonia and other gases, are a source of particulate matter - the other group of air pollutants in the current debate.
How does fine dust develop?
Fine particles are particles smaller than ten micrometers (PM10). One micrometer equals one millionth of a meter. The vast majority comes from natural sources. For example, volcanoes blow large amounts of particles into the air. Forest fires and desert sand also contribute to the dust and particulate matter in the air. Over time, the particles are distributed widely in the atmosphere, so that the load with the distance to the source decreases significantly depending on the weather.
Humans produce dust and particulate matter mainly through combustion processes in industry. If one considers only the particles that are particularly harmful to health below 2.5 microns (PM 2.5), the most important causes, according to industrial processes, are mainly households and small consumers as well as traffic. Households produce fine dust, for example through fireplaces and heaters, as well as waste incineration plants.
In traffic, in addition to the abrasion of brakes and tires, the combustion process in the Otto engine in particular contributes to the particulate matter load. In modern gasoline engines with direct injection, particularly small particles smaller than 0.1 microns (ultrafine particles, UFP) are produced.
Which limits apply to particulate matter?
For particles below 2.5 microns (PM 2.5), the EU has a limit of 25 micrograms per cubic meter of annual average air. It is much lower in the US, where only 10 micrograms are allowed, which is the WHO recommendation.
How does particulate matter affect the body?
The problem with particulate matter: the smaller the particles, the more they penetrate the body when inhaled. The larger particulate matter, the PM10, remains mostly in the upper respiratory tract, ie the throat, trachea, or bronchi. By contrast, PM2.5 reaches the alveoli.
The ultrafine particles can even pass into the bloodstream and thus in principle reach all body regions and cause damage there. It is believed that UFP, among other things in the blood vessels trigger inflammation processes in the vessel walls and thus promote arteriosclerosis and the formation of blood clots.
Which diseases causes particulate matter?
Unlike nitrogen oxides, the harmful effects of particulate matter are clearly demonstrated. Particulate matter irritates the respiratory tract and mucous membranes, causing respiratory problems such as coughing, dyspnoea, and asthma. The particles can also be involved in the development of lung cancer. If they get into the blood, they also cause damage there, the risk of cardiovascular diseases - cardiac arrhythmia, arteriosclerosis and infarction - increases.
People who already have respiratory or heart problems are particularly at risk from particulate matter, according to the World Health Organization, including children and the elderly.
Conclusion: Both nitrogen oxides and particulate matter are considered by health professionals to be harmful to health, and the effects of particulate matter can be better scientifically proven than those of nitrogen oxides. For both pollutants one can not make a clear statement about the concentration at which the substances are definitely harmful. The current limits are partly based on WHO recommendations, but are ultimately politically determined.