Diesel Emissions: Fact Check

Following we post an article by the journalist Susan Djahangard from the German weekly „Die Zeit“ (No. 43) from October 19, 2017 (p. 34) concerning the topic: “Reality check for the industry: Are more and more people in Germany dying from lethal car emissions?”

German NGO Deutsche Umwelthilfe (DUH) issued what sounds like a dramatic warning last week: In just one year, there were 12,860 premature deaths owing to the »diesel exhaust poison« nitrogen dioxide. According to DUH's calculations, this was four times as many as in fatal road accidents. Not only is this a large number, but DUH claims that it is increasing - that is the result of a study by the European Environment Agency to which DUH refers: it reports that the number increased by twenty percent last year, i.e. around 2000 more premature deaths.

It is clear to DUH who is responsible for this. Jürgen Resch, General Manager of DUH, is quoted in a press release: »The shockingly high number of premature deaths due to the "diesel exhaust poison" nitrogen dioxide is the result of criminal practices by the car manufacturers.« Nor is the government free from blame: Diesel cars pollute the inner-cities »with the blessing of the Federal Motor Transport Authority (KBA)«. DUH refers to compromises between the federal government and the automobile industry following the diesel scandal.

The figures come from the Air Quality in Europe report 2017, a new study by the European Environment Agency. This agency based in Copenhagen belongs to the European Union, and its remit is to inform politicians and the general public. So what about these almost 13,000 »premature deaths« in Germany caused by the »diesel exhaust poison, nitrogen dioxide«?

First we have to clarify how dangerous nitrogen dioxide is. The gas is a primary product of ozone and particulate matter, and therefore has indirect effects on human health. Particulates are considered to be carcinogenic. However, DUH refers to the part of the study that concerns itself with the direct effects of nitrogen oxides. They damage the breathing apparatus, and effects on circulatory ailments are also probable. »A healthy person is relatively insensitive to nitrogen dioxide, however it can be damaging for people with ailments such as asthma,« says Annette Peters, an epidemiologist at the Helmholtz Canter in Munich.

How harmful and from what concentration is still a matter of debate. 40 micrograms per cubic meter per year is permitted in Germany, and the World Health Organization recommends the same. A much higher limiting value of 950 micrograms per cubic meter applies in workplaces. Peters explains: »We can assume that only healthy people work there. A higher concentration is not dangerous to them. However, people with previous ailments use public spaces and the lower limiting value is appropriate.« Moreover, people are only at the workplace for a limited time. Matthias Klingner, Head of the Fraunhofer Institute for Transport and Infrastructure Systems, has intensively studied the subject of pollution from exhaust emissions. He disagrees: »Looking at the limiting value in workplaces, I can only come to the conclusion that the nitrogen oxide density in the outside air cannot be harmful to health.«

The European Environment Agency used two different limiting values for its calculations. In one instance the authors assumed damage to health from a level of 20 micrograms per cubic meter. One of the three authors of the study, Alberto González Ortiz, explains: »We followed the recommendations of the WHO. There are initial studies suggesting that even a lower concentration has an effect. This is why we also calculated the effects of a concentration above only ten micrograms per cubic meter. The results with the higher limiting value are however more reliable, as they are based on stronger evidence.« The number of »premature deaths« changes considerably depending on the limiting value used. If one uses the lower limiting value of ten micrograms as a basis, the study arrives at a figure of 44,960 premature deaths in Germany, or three times as many.

Apart from the limiting value, it is important to understand what the scientists have actually calculated. Premature deaths are those that occur before the theoretical life expectancy has been reached. If the influencing factor, in this case nitrogen dioxide as an airborne pollutant, were not present, it would have been possible to prevent the premature death. The 12,860 premature deaths in Germany were therefore not healthy people who suddenly dropped down dead, but people whose life was shortened. As a second factor the Environment Agency calculated the years of life that were lost. According to this, 133,000 years of life were lost as a result of nitrogen oxide pollution. Applying this to the number of premature deaths, this would meanaround ten years per premature death.

The figures are not the result of pathological tests. The scientists are working with statistical models in which the probability is calculated that premature deaths will occur as a result of nitrogen oxide pollution. These are therefore estimates.

»I consider it to be scientifically untenable to statistically eliminate all other influencing factors and attribute the effect exclusively to nitrogen dioxide«, says Matthias Klingner of the Fraunhofer Institute. Annette Peters at the Helmholtz Center defends the model-based calculations: »They are very useful for estimating trends and approximate numbers over a period of years. However the results are vague in many respects.« So whether one trusts in these models or not – they are not precise.

Yet DUH not only gives the number of deaths, it also knows who is responsible: the car manufacturers and the Federal Motor Transport Authority. Is that plausible?

Hardly. Firstly, nitrogen oxide emissions have been reduced over the longer term, by almost sixty percent since 1990 according to the Federal Environment Agency. And secondly, not only diesel cars are responsible for nitrogen oxide pollution. While it is true that the major part of nitrogen oxide air pollution comes from road traffic, the energy sector, agriculture and private households also emit major amounts of nitrogen oxides. More nitrogen oxides in the air can therefore not be ascribed directly to diesel cars. Thirdly, the nitrogen oxide pollution established by the study is also connected to the method of measurement. »We use the measurement data to produce maps showing the concentration of nitrogen oxides. This year we also included traffic hotspots. This gave us a more precise picture, especially concerning hotspots in major cities. This is why we found a higher level of nitrogen oxide pollution«, says González Ortiz, the author of the study. The result of the study has nothing to do with an actual increase in pollution as suggested by DUH.

The DUH nonetheless sticks to its arguments: It is true that overall nitrogen oxide pollution has declined, and only part of the nitrogen oxides comes from road traffic, Dorothee Saar, head of the department for transport and clean air, admits. »However, nitrogen oxide pollution is high in the inner cities and limiting values are regularly exceeded with no sanctions.« This may well be true. But it is no explanation for the increase in numbers.

The assertion of DUH that the study established an increase in premature deaths in Germany because car manufacturers are switching off their exhaust aftertreatment is wrong. As the author of the study, González Ortiz, says: »We cannot associate the diesel scandal with the higher pollution levels in this year's report, and neither have we attempted to prove such as causal relationship.«

Author: Susan Djahangard

Note: This text was translated from a German article published in: Die Zeit, October 19, 2017 (No. 43, p. 34).

Original article (German)

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