The diesel discussion is becoming more objective, the sustainability of diesel technology is increasingly being discussed in a less prejudicial manner among experts, in the media and social networks. Here, we explain the key facts and most dubious details about NOx and particular matter.
Millions of Germans depend on their cars. Many couldn’t even carry out their jobs without a car. Those who have to drive or commute to work frequently chose to buy cars with diesel engines. With good reason: Driving many miles on one tank of fuel and being on the road in an environmentally friendly manner while conserving resources – that was the basic idea many employees had in mind. In the meantime, many diesel cars (and their drivers) have become the pariahs of the nation. The emotional debate surrounding diesel driving bans during the last few years has made large swaths of the population extremely uncertain.
An objective discussion – at last!
he diesel discussion is becoming more objective – finally, one might add. The voices and positions are getting more differentiated. Advantages and actual risks posed by diesel technology are increasingly being discussed in a less prejudicial manner among experts, doctors – especially lung specialists, in the media and social networks. At the same time, factual situation is complex and often confusing. The sustainability of Diesel powertrain technology is mostly measured referring to emission values of CO2, nitrogen dioxide (NOx), and particular matter. Furthermore, actual proposals to improve the environmental audit are often based on highly problematic assumptions – a speed limit on highways, higher gas prices or a statal quorum for electric cars, for example. But how effective would those measures be? But how does a sober environmental audit of diesel vehicles look like?
The exhaust from a diesel engine is a mixture of many substances, including particulate matter and nitrogen dioxide (NOx). Both are particularly harmful to peoples’ respiratory tracts. Question is: How are harmful doses measured, and how are respectable limits gained? Particulate matter currently may not exceed 50 micrograms per cubic meter on streets; the threshold in the case of nitrogen dioxide is even lower at 40 micrograms per cubic meter. Professor Annette Peters, Director at the Helmholtz Center in Munich, was one of those who determined these values many years ago. Today she says: “That was the World Health Organisation’s (WHO) recommendation, which was thought to protect people effectively. It was based on the evaluation of health statistics.” How was the result arrived at? The WHO compared rates of disease and death of urban and rural residents. The lower life expectancy in cities was largely grounded in the presence of NOx, which was a controversial assumption from the start.
Nevertheless, these alleged NOx victims became the strongest argument against the diesel engine. Even now the Deutsche Umwelthilfe (Environmental Action Germany) states that 800,000 people per annum fall ill due to NOx and 13,000 would die from it every year. They sued municipalities in Germany by the dozen. Now more and more cities are issuing driving bans following court rulings. The WHO, by the way, had specifically warned against the equating reference point and threshold value in 2000, the year they published the reference value of 40 micrograms per cubic meter in their guidelines on air quality in Europe.
“The ultimate in dumbing down”
It’s clear to Professor Martin Hetzel, Medical Director at the Red Cross Hospital in Stuttgart, one of the leading lung clinics in the country that “particulate matter alerts are the ultimate in dumbing down, because an alert is a sign of a significant, acute emergency. That is not the case given the particulate matter presence in Stuttgart.” Hetzel knows many patients from his own perspective. That’s another reason the statistical comparisons the WHO based their conclusions on have nothing to do with reality: “There is no such thing as a particulate matter disease of the lung or heart,” he said in the ARD report. “Not a single death can be traced back to particulates or nitrogen dioxide. Those are constructed mathematical models. It just isn’t plausible that these small concentrations of particulates and nitrogen dioxide cause deaths in the manner that is currently being discussed.” Dr. Wolfgang Straff from the German Environment Agency conceded to ARD as well: “There are really no NO2 deaths. It isn’t anything that can be scientifically observed. We can’t break down an illness to one cause.”
Professor Dieter Köhler works at the specialist hospital Kloster Grafschaft in the Sauerland, which is also a leading pulmonology clinic in Germany. The former president of the German Respiratory Society says: “So you compare two groups: urban and rural residents. And a small difference in life expectancy is found. However, this can also be a result of too little exercise, higher alcohol and nicotine consumption and other factors. To draw the conclusion that it is based on particulate matter and nitrogen dioxide is scientifically unacceptable. You’re drawing a conclusion from a coincidental observation, which isn’t tenable.
Locations of the measuring points – based on special interests?
In the meantime the locations of the measuring points in the cities are under discussion. Professor Matthias Klingner, expert and head of the Fraunhofer Institut said on the topic of Germany’s most infamous measuring point at the Stuttgart Neckartor: “You can hardly get any more devious in setting it up. In the middle of a dip, and in a corner, no less. A free exchange between exhaust and air is impossible here.” Klingner sees the regulations for setting up measuring points as clearly violated. “They stipulate placing the measuring devices out in the open and with 70-degree set-up angles.”
Klingner views the regular driving bans in Stuttgart as scare tactics. There are other factors that are much more critical to particulates and nitrogen dioxide concentrations. “’These substances are bound to the earth during longer bouts of rain, so then we measure only seven micrograms per cubic meter of air,” says Klingner. There’s also another reason Klingner doesn’t think the values from the Stuttgart Neckartor are plausible: “If we look at the high numbers, then the cars that are responsible for them are the ones that brake for a traffic light and accelerate again when the lights change. Every car needs an especially high amount of fuel in that case. Therefore those measuring points should be some distance away from the crossing so that those acceleration actions are not measured. But that is how high nitrogen oxide values are generated.”
The scientists wanted to know more exactly how much of a pollution impact the traffic has on the people at the Stuttgart Neckartor. They placed their measuring devices in a student apartment located directly at the six-lane road. What happened then was unexpected: They measured 80 micrograms per cubic meter in the apartment. The cause: a normal household gas boiler. That alone was responsible for the measured value to double the threshold value applicable for the street. Lighting two candles even increased the value in the apartment to 140 micrograms per cubic meter.
Noodles with tomato sauce on a gas stove: 1,300 micrograms nitrogen dioxide
But that wasn’t all. When the students prepared spaghetti with tomato sauce over two gas flames for 15 minutes, the indicator jumped to 1,300 micrograms nitrogen dioxide per cubic meter – more than 30 times the threshold limit outside.
Incidentally, there are no explicit warnings for candles or gas stoves – neither from the German Environment Agency nor from the Environmental Action organization.
The Fraunhofer Institut states that “not one person in Germany dies from engine exhaust pollutants emitted by German cars with a diesel engine.” To the contrary: “In a worldwide comparison, German diesel engine vehicles distinguished themselves through exceptionally low pollutant emissions, even when taking the exhaust manipulations into account.” In any event, the pollutant emissions from diesel engines have been reduced by 84 percent and by 60 percent in gasoline engines in the past 15 years. Modern diesel cars that comply with the Euro 6 standard are among the cleanest means of transportation in general: Such a diesel car emits 80 micrograms of nitrogen oxide per passenger over one kilometer. In contrast, commuter trains with diesel locomotives emit 240 micrograms of nitrogen dioxide per passenger and kilometer, whereas busses even reach 550!
Errors don’t survive over time
Air quality has not only significantly improved in German metropolitan areas over the past 20 years, but has also done so throughout Europe. The nitrogen oxide emissions have fallen from 2.9 to 1.2 million tons annually since 1990. The annual mean rate in rural areas currently lies at 10, in the cities at between 20 and 30 micrograms per cubic meter. The average value on roads with heavy traffic is under 40, and above that only at individual measuring points.
Natural particulate matter pollution in the concentrations that are measured in Germany doesn’t lead to any statistically provable increase in health risks, even in long-term observations. The Environmental Protection Agency (EPA) in the USA therefore has already suspended the 50-microgram limit for particulate matter in 2006. Furthermore, the EPA considers a nitrogen oxide threshold of 103 micrograms per cubic meter to be insignificant as a health hazard. That is the American threshold value right now – a number that isn’t surpassed at any measuring point in Germany.
Professor Martin Hetzel, Medical Director at the Red Cross Hospital in Stuttgart, even suspects “dubious, ideology-driven populism”. He believes: “Of course, you can follow the line of taking traffic out of the cities. But then the method should not be setting threshold limits that aren’t based on any scientific foundation. That’s a mistake.” And mistakes don’t survive history in the long term.