Criticism of the limit value for nitrogen oxides is justified. Instead of just banning diesel cars, we should talk about fine dust again. You do not need to be afraid of candles.
Big red candles, a smell of fir wood and a touch of secrecy are now in the air. So begins a Christmas carol that every child learns in elementary school – and if you do it a post on Facebook believes that this has spread in recent weeks and then also begins poisoning all Christmas lovers.
The post claims that candles from an advent wreath emit more nitric oxide than would be allowed in the European Union. With this one, we want to make fun of the discussion about the control of air pollution and the bans of driving with diesel.
The bill that is established in the mail is nonsense. But the statement that it is necessary to question the limit value for nitrogen oxides is not totally false.
What is the debate about nitrogen oxides?
Nitrogen oxides are gases. Our air is not only composed of oxygen and carbon dioxide (CO2), it also buzzes around other connections depending on the altitude and geographical location. This is nothing special at first.
Whenever something burns, nitrogen oxides are produced: cigarettes, spark plugs, gas stoves, fireplaces, diesel engines (ie internal combustion engines) – the hotter the flames, the more all these things produce nitrogen oxides. The flames in diesel cars are getting hotter. Because the hotter the flame, the less fuel the car consumes.
When we talk about nitrogen oxides, we usually mean nitrogen dioxide (NO2). There is also nitric oxide (NO) – but as soon as the nitric oxide is released in the air, it reacts with other gases and becomes quite direct in NO2, the dioxide of 39; nitrogen. This is why NO2 is much more relevant than NO.
To find out how much nitrogen dioxide comes from an advent wreath, we interviewed Stefan Thomann, among others. He is a chemist at European Association of Candles. He says there are currently several studies in which researchers are measuring how candles increase the concentration of nitric oxide in the room.
However, Thomann says that there are several problems with the bill in the Facebook post.
Problem 1: The unit
Facebookpost wants to specify the concentration of nitric oxide in "ng" – in nanograms. It's like comparing the prices of apples and pears in milligrams at the fruit counter: nonsense. The unit is much too small. because Nitrogen oxides are measured in micrograms. The EU-wide limit value for nitrogen oxides is currently included 40 micrograms of nitric oxide per cubic meter of air the annual average. 40 micrograms correspond to 40,000 nanograms. The bill uses the wrong unit.
Problem 2: The size of the room
As I said – we measure the concentration of nitrogen oxide in the air Microgram per cubic meter of air. A room of 20 square meters and whose ceilings are 3 meters high has a total of 60 cubic meters of airSo you would need 2400 micrograms of nitric oxidebring concentration back to the room at the edge of the EU.
Hong Kong scientists tested nitrogen oxide emissions from five different candles in 2005. The candle that emitted the most nitric oxide produced in total 280 micrograms. when four candles completely burn, so you have 1120 micrograms Nitric oxide, which is distributed in the chamber. With 60 cubic meters of air, we would be around 18.5 micrograms of nitric oxide per cubic meter of air. This is below the 40 microgram limit imposed by the EU.
Problem 3: Inside and outside
Various studies, cited by the World Health Organization, show that nitric oxide flies faster indoors – so concentration does not increase forever, even if you turn on the gas stove and do not broadcast it not. Indeed, nitrogen oxides decompose on surfaces. A study showedthat an increased value in the interior in about an hour reached the previous level again.
An advent wreath, which only briefly increases the concentration of nitrogen oxides, therefore can not be compared to the situation of people who live all their lives near an area. big street.
So, does the limit make sense?
CORRECTIV interviewed many experts and read the studies that justify the limit. The fact is that there are so many disciplines related to nitrogen oxides that no one knows perfectly. Meteorologists, doctors, physicists, politicians – no one neglects the conflict. Because it's way too complex.
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the Pneumologist Dieter Köhler on a war against the limit of the EU. He drives a diesel himself and says that nitrogen oxides can not be so bad because smokers breathe with each cigarette up & # 39; to 600 micrograms one of them. Whether it makes a difference that one smokes voluntarily or involuntarily on a highway, his bill interests him, but not.
the The meteorologist Ulrike Dauert The Federal Environmental Agency knows exactly how to measure nitrogen oxides in the air. However, the reason is that the limit and the amount of harmful air harmful to people do not fall within their area of expertise.
Martin Lutz, Who makes the plans of clean air for Berlin, can not understand why now now immediately the limit is in question, which has been established for centuries. He works every day to ensure that the 40 micrograms are not exceeded in all the streets of Berlin. That nitrogen oxides are harmful, he finds "arschklar".
the Wolfgang Straff, doctor was part of a team that conducted a study on behalf of the Federal Environment Agency to prove the dangers of nitrogen oxides. He says: The law is there, now you have to stick to it. But diesel drivers would think only of themselves.
What was the same with the fine dust?
What all experts have in common is powerlessness. About why and when the debate is over. Why all of a sudden talk about nitrogen oxides, but nobody talks more about fine dust and CO2. Fine dust is much more dangerous than nitric oxide. It makes you sick, it's proven – statistically significant. The fine dust is so fine that it can enter the blood through the lungs. And each car produces particles – they are created when the disc brakes stop the car, they are produced every kilometer of tire wear, they come up from the ground when cars have passed for a long time.
the physicist Gerhard Scheuch has been working in environmental research for almost twenty years. He also spent six months with the US Environmental Protection Agency.
This authority initially reached the value of 40 micrograms per cubic meter before. In a study of the 90s.
Scheuch says: "For some substances, there is not a limit that will make them definitely deadly." Nitric oxide is one of these substances.
Politics needs clear statements, but science is not
It is unclear to what value and under what conditions the gas is harmless. The task of scientists, however, is to know exactly – so that politics can make decisions to protect the population. Politics needs neither doubt nor complexity – politics needs laws.
"Then you have to weigh in as a scientist, and be careful," says Scheuch in an interview with CORRECTIV. With nitrogen oxides For example, there were studies given that in asthmatics already at a concentration of 100 micrograms per cubic meter, changes in the lungs observed. And still other studies in which we could not find anything.
In research groups, which must define a danger threshold, it is agreed that their own results are not always statistically proven. "We doubt it, of course," says Scheuch.
However, no study has been done on people who live long in a street where the concentration of nitrogen oxides is high. Because you should hurt the subject with it. Force them to breathe the bad air 24 hours a day. Although smokers do so voluntarily, their lungs sometimes have a break. If you lie in bed and smoke two cigarettes, you can open the window so that it does not stink in the room. Anyone who looks stinky in front of the window is not lucky.
Therefore, possible damage to nitrogen oxides can only be suspected based on animal experiments, calculations and statistics.
How the limit came to the world
1989 – In "Study of six cities"At Harvard University, researchers have compared the air quality in six US cities with mortality," said physicist Gerhard Scheuch, "the hype around clean air has begun. .
It has turned out that the inhabitants of polluted cities die earlier. The researchers found a clear Link between particles and lung diseasesIn contrast, the results on nitric oxide were not statistically relevant.
1997 – The World Health Organization (WHO) publishes a report suggesting the 40-microgram limit for the first time. This study says:
"While it is possible to trust meta-analysis, symptoms and illnesses can also be associated with other processes, so you should interpret the results with caution." Other studies have attempted to relate nitric oxide levels to changes in lung function. little significant, Many studies could no effect see what happens in human studies. " (Translations and highlights from CORRECTIV)
Explanation: Most studies on nitric oxide at this stage were conducted on mice and rats. Mice were much more likely than rats. In experiments with monkeys, no change was found.
"Based on a background concentration of 15 micrograms per cubic meter and because health effects occur with an increase in concentration of 28.2 micrograms or more, an annual recommendation of 40 micrograms is proposed. "
Explanation: Number 28.2 kidnaps researchers a study, who found a connection between homes with gas cookers and respiratory diseases in children. In gas fireplaces, nitric oxide concentration was greater by about 28.2 micrograms. The children in these apartments were more likely to cough. This effect was only observed in infants from two years of age – this was not the case for babies.
"This value will prevent the worst influences", this continues in this year's WHO study. Exactly as Gerhard Scheuch had said: researchers play safety.
the report also cited a test in which researchers observed hamsters: they had to live 40 hours per week with a nitrogen dioxide concentration of 3760 micrograms per cubic meter. For eight weeks. They remained perfectly healthy.
1999 – The European Council gives a guideline out. This is an "alarm threshold". of 400 micrograms Nitrogen dioxide per cubic meter of air needs to be warned of the population.
2002 – European Council and European Parliament to choose the action program for the environment – a statement of intent that does not yet name concrete values.
2005 – The WHO publishes a new report on the quality of the air. There are two important things in it. First, nitric oxide is a good indicator. When there is a lot of nitric oxide in the air, it burns a lot. This is why there are more particles and other products of combustion. Secondly, in the studies on nitric oxide, other products of combustion could have been the cause of the disease. What part of the exhaust air cocktail makes people sick, it's hard to say. "There is still no solid foundation for setting a benchmark for nitrogen dioxide," the study says.
2008 – The European Council and the European Parliament decide on a new directivewhich replaces the old. This is also the new limit: 40 micrograms of nitrogen dioxide per cubic meter, The limit does not apply to jobs – who works in the industry can 950 micrograms per cubic meter breathe. There are two reasons. The first is that the 40 microgram limit is designed to protect even asthmatics and toddlers. Most of the time, they do not work in the industry.
The second is that no health restrictions were observed when people who worked at much higher concentrations of nitric oxide were observed. It was already in 1997 in the WHO study.
2010 – The directive becomes the law. European countries must now respect the limits. Ute Dauert, a meteorologist at the Federal Environment Agency, told CORRECTIV: "At the cut-off point, the EU Commission has taken over a WHO recommendation dating from 1999, so that the current state of affairs In the end, it's a political compromise that comes in. "
Since then there is more than 500 measuring stations in Germany, which measure the concentration of nitrogen oxides in the air. Operating a station costs around 100,000 euros a year, said Martin Lutz of the Berlin Senate at CORRECTIV.
Basically, Germany spends around 50 million euros on monitoring a gas whose toxic effects have not yet been proven. Which says a lot: how much nitric oxide is in the air, can also be closed to other harmful components of the air. If you live in an area where the burden is heavy, you should have the right to know it.
2015 – VW is flying: the automaker has handled its diesel cars. They had emitted more nitrogen oxides to consume less fuel.
For Martin Lutz, head of air pollution control in Berlin, everything was clear. "We thought nitric oxide levels would not go down because people were buying so much SUVs," he says. "In addition, more and more people are ordering online, so there is more delivery traffic." But now, he had proof that it was not just the people sitting in the cars, but also the people who were building them.
Diesel is the main polluter of nitrogen oxides in cities. But they are not the only polluters. Gasoline engines emit CO2 in the air. And all cars produce fine dust.
If it is after the WHO would be the limit for the finest particles (PM2.5), which is also the most dangerous at 10 micrograms per cubic meter. But this value has not been supported by the EU. the Limit value for particles in Germany is included 25 micrograms per cubic meter. Twice as recommended by WHO.
For nitric oxide, for which it is not clear if and when it will make you sick, the EU has adopted the strict and cautious recommendation.
For particles, where it is clear that you are going to get fed up, the EU did not do it.
February 2018 – A research group will analyze the number of deaths in Germany due to nitrogen oxides. But researchers do not investigate, they do not sound the doors of residents and do not hear their bronchi. You count. Do a meta-analysis of other meta-analyzes.
The fact that this study is not quite obvious can be explained, for example, by the fact that it is not the effects of nitric oxide on the lungs that have been analyzed – but the cardiovascular system. To do this, write the researchers, there was enough data. Unfortunately not on lung diseases.
It is also ironic that spatial analysis has remained a pure hypothesis. The researchers did not look on the street and watched the diseases that people are dying of. Together they calculated the number of people who died from cardiovascular disease in Germany. Then they calculated together the number of people living in Germany subjected to increased pollution by nitric oxide. Then, they deduced how many cardiovascular deaths have died because of nitric oxide could.
It is not only laymen in statistics who will be suspicious. Also the Ministry of Environment and Climate Protection of NRW. Originally, the federal government had provided the research group with data on the Ruhr area – but did not want it to be published. Why, the ministry explains this:
"The results of the study are, in our opinion, not appropriate for making independent statements about premature deaths / disease burden due to NO2 exposure in the specific model region." such as age distribution in the population and medical care, which have an influence on the results, have not been taken into account in our opinion.
During the implementation of the study, we had a close technical exchange with the Federal Environment Agency and presented our technical and methodical concerns from the beginning of the process. Prior to publication, we only had drafts and excerpts from the global report on model regions. For this, we still had some outstanding questions regarding the methodology, the expression and the comparability of the results. Since these issues could not be clarified conclusively and the general context of the report did not develop, we decided in October 2017 not to approve the publication of the Modellregion Ruhrgebiet. "
NRW experts did not find the study useful.
May 2018 – Hamburg imposes this first driving ban for diesel cars to meet the limits of nitrogen oxide.
This is an indicator
Nitrogen oxides are the subject of a public debate indicator for a good air. a marker valuefrom which we can deduce other pollutants in the air. Few nitrogen oxides identical to those of free breathing.
It's like putting the performance of a primary school kid on math lessons.
Of course, mathematics is important – and of course, no matter how much nitric oxide in the air. But a child who writes only mathematics – so all the limits observed – can still write five years in German and sit still.
Good students are generally good at many subjects. However, diesel and gasoline have a weak point: for diesel, it is nitrogen dioxide. For gasoline, it is CO2.
Diesel cars now have the misfortune that their very low point has become the indicative value of a good performance. Respectively: For a good air. Whenever a city wants to show off its air-to-air testimonials, everyone is content to look at the nitrogen oxide index.
It's so complicated. Among them, diesel owners, who must now leave their cars for testimony on the air quality of some cities. Because a research group proposed twenty years ago a value to which everyone clings now. Because the EU has made this value the law. And maybe because Nitrogen oxide looks so dangerous dangerous – after choking.
Note: 21.12.2018: In an earlier version of the article, we have described in the third paragraph the nitrogen in the form of CO2 and therefore as one of the main constituents of air . We corrected that.
An advent wreath, which only briefly increases the concentration of nitrogen oxides, can not be compared to the situation of people who live all their lives close to a great deal. street.