What are diesel engine emissions?
Diesel engine emissions are the exhaust gases produced by a diesel engine during operation. This is a mixture of substances of varying composition. However, there are substances that are always contained in diesel engine emissions, including carbon dioxide, carbon monoxide, nitrogen oxides and diesel soot. The proportions of the respective substances vary depending on the type of engine.
What are the dangers of diesel engine emissions?
It is not possible to describe a general danger from diesel engine emissions due to the fluctuating ingredients. However, information can be provided for the main components. On the one hand, there are the carbon oxides. As carbon monoxide (CO), it is poisonous. If it is present as carbon dioxide, it can lead to suffocation. CO2 has a higher affinity to attach itself to the red blood cells than O2. It therefore displaces the oxygen molecules in the blood and leads to death by asphyxiation after prolonged exposure. It also contains nitrogen oxides, which are also toxic and irritating to the mucous membranes, as they form acids in combination with water and cause chemical burns.
Debate about diesel engine emissions measured values
Due to the debate about exceeding limit values and the associated threat of a driving ban for diesel vehicles, the discussion about is on diesel engine emissions everyone’s lips. There is no question that nitrogen oxides are harmful. However, the level of the limit values is questionable. Part of the discussion relates to the measurement itself, whether it was carried out in a meaningful way. In order to be able to prove that the air we breathe is polluted, the corresponding measurement should be taken at breathing height.
This is also confirmed by our measurement technicians, who regularly carry out measurements at the workplace and advise employers on this point (you can contact our measurement technicians here ).
If the measuring stations are located on a busy road, the exposure is of course enormous. But is this measurement also representative of the surrounding roads, which are less busy? How comparable are measurements taken at different heights? As long as there is no standardized and comparable measurement method, these will remain the cornerstones of the discussion.
What do the doctors say?
The other part of the discussion is driven by various doctors who openly question the current limit values. The current limit for nitrogen dioxide is 40µg/m³ of air. In a statement, the well-known pneumology professor Prof. Dr. med. Dieter Köhler describes the main points that have led to this debate. On the one hand, the high death figures associated with NO2 appear to be subject to systematic errors, as the practical work of pneumologists never shows “deaths caused by particulate matter and NOx, even with a careful medical history”. However, with a death rate of over 10,000/year, this anamnesis should be more common.
Köhler starts his argument at this point and describes the errors in the data analysis.
- Correlation becomes causality: A large number of studies on air pollution are based on data sets with similar patterns.
- Confounding factors: These were not taken into account, although it is known that factors such as smoking, lifestyle habits and medical care influence the incidence of disease and mortality a hundred times more than the increase in risk due to air pollution.
- Threshold value and toxicity: Most studies on air pollution do not have a threshold value. However, if toxicity is taken as a basis, there should be such a value (as with any poison). Similarly, there should be a more or less clear symptom picture of poisoning by nitrogen oxides. However, this does not seem to be the case and the lack of this poisoning pattern suggests the influence of other disturbing factors, as it is also not possible to clearly explain how nitrogen dioxides can cause such a wide range of diseases.
- Falsification: Normally, falsification would have to be carried out to verify the study results, i.e. test groups would have to be deliberately confronted with very high and very low doses. This is of course ethically unacceptable. However, Köhler argues that smokers voluntarily expose themselves to a very high dose and that such a study could therefore be carried out.
A harmful effect remains undisputed, but these arguments shed new light on the current limit values. It raises the question of how sensible and useful this value is and whether an objective reassessment of the current values should not be carried out, especially as this threatens a driving ban in many cities. Federal Transport Minister Scheuer (CSU), who also considers a review of the measurement locations to be sensible, takes the same view. CDU Secretary General Paul Ziemiak puts it somewhat exaggeratedly, but very aptly: “If I end up […] holding the measuring device directly in the exhaust pipe, then that is not representative of the air in a city”.
Sources:
[1]: Source Featured image: © Bartolomiej Pietrzyk / 123RF.com
[2]: https://blog.gsa-messgeraete.de/?p=1061&preview=true
[3]: https://www.chemie.de/lexikon/Stickoxide.html
[4]: https://www.bund.net/mobilitaet/schadstoffe/stickoxide/
[5]: https://www.lungenaerzte-im-netz.de/fileadmin/pdf/Stellungnahme__NOx_und__Feinstaub.pdf
[6]: https://www.aerzteblatt.de/archiv/200863/Feinstaub-und-Stickstoffdioxid-(NO-sub-2-sub-)-a-critical-assessment-of-the-current-risk-discussion
[7]: https://www.aerzteblatt.de/nachrichten/100676/Schadstoffdebatte-spaltet-Regierung