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Pulmonologist and epidemiologist on the consequences of fine dust

Interview with pulmonologist and epidemiologist
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Z ur person: Prof. Dr. Holger Schulz (photo left) Deputy Director at the Institute for Epidemiology at the Helmholtz Zentrum München, Head of the Department of Lung Epidemiology

About: Prof. Dr. Martin Hetzel (photo right) pulmonologist and cardiologist, managing director of the Association of Pneumological Clinics, Chairman of the South German Society for Pneumology

The interview is part of our new series 'The Truth About ...'. In five episodes, auto motor und sport answers the most important questions about the diesel future, electric cars and the right way to buy a car. Episode 1: The truth about the future of diesel starts in Issue 6/2019, which you can buy here.

Mr. Schulz, is the scientific basis our air limit values ​​are really as poor as some pulmonologists claim?

Schulz: No, you certainly can't say that. They are based on a great number of epidemiological studies that have been carried out in Europe, the USA and Asia. In addition, studies on cell cultures are carried out in order to identify mechanisms of how pollutants work. The third pillar is exposure studies, also with volunteers, where people are exposed to certain substances for a certain period of time and then examined, for example, how the lung function changes, whether inflammation markers are found in the lungs or blood, or whether there are changes in the heart and blood Circulatory system there.

But it is precisely the epidemiological studies that are criticized by a group of pulmonologists around Dieter Köhler. Martin Hetzel is one of the co-authors of their thesis paper.

Mr. Hetzel, what do you criticize about epidemiological studies?

Hetzel: In the cohort studies the Loss of life due to respiratory and heart diseases of people who live in rural areas and of people who live close to traffic, calculated assuming a statistical life expectancy. In addition, population-related pollution was calculated from the data from the measuring stations. Then a connection was established between the calculated region-related lifetime loss and the corresponding pollution. This is called correlation. Small differences in the lifespan of rural and urban populations can be seen here. The middle onesLifetime differences are less than 10 hours. From this correlation, the NO2 was inadmissibly ascribed to the cause. In the last step, from the mean lifetime loss, using inadmissible mathematical methods, it is possible to deduce 6000 deaths. There are no deaths from environmental NO2 pollution that is causally attributable to NO2. Hence the statement: 'There are no nitric oxide deaths.'

Are your studies really that clumsy?

Schulz: No, we are much further on there. We have methods in which the pollutant load is determined for each individual test person at their place of residence. This then automatically does not result in a city-rural comparison, because the pollutant values ​​also differ greatly in the city, depending on whether I live on a busy street or not. The second aspect is the assessment of the health risk. So: How much life do I lose, for example, when I am exposed to pollutants? The models are not suitable for determining what the individual loses in lifetime. It is about an assessment in the population, for example to give politicians something to compare different risk factors. For example, a smoker loses an average of 8 to 10 years of life.

Mr. Hetzel, you also criticize the lack of consideration of disruptive factors. What is meant by that?

Hetzel: Risks of premature death due to lifestyle - for example tobacco consumption or obesity - have an impact many times more on the lifetime. These disruptive factors were not measured, but estimated. The slightest changes in the estimated disturbance variables that are introduced into the mathematical model then lead to different results. If the disruptive factors have a much stronger effect than the environmental pollutants, then adequate consideration through estimates in the mathematical model is not possible.

Is there anything to this criticism?

Schulz: You can't say that like that. The models are adjusted for this, and in such studies one also looks at subgroups, i.e. only smokers or only non-smokers, people with or without lung diseases and so on. This is usually not published, but it plays an important role in the evaluation. If I see that this consideration also leads to a stable result, I can assume a reliable statement.

When comparing it with smoking, a calculation error was discovered in your paper . Does that mean that all statements are invalid?

Hetzel: No, on the contrary. The way in which it is now trying to match the arguments put forwardreply is clear evidence of their strength. Why is? The Federal Environment Agency published a few years ago that fine dust in environmental concentrations leads to 47,000 deaths annually in Germany. We attacked the plausibility of this statement by calculating the time in which a smoker inhales the same amount of fine dust as a person who inhales the limit value concentration of 50 µg /m³ fine dust for 80 years without interruption. We have specified this time as “less than 2 months”. The basic assumption was based on a higher amount of condensate per cigarette than is permitted according to an EU standard. Now we have submitted the invoice for the legally permissible amount of condensate: The duration is 2.1 months. In doing so, we are not playing down the harmful effects of tobacco consumption. We take the daily in-vivo experiment tobacco consumption as a plausibility test on the question of the deadly effect of fine dust in environmental concentrations. Whether it is less than 2 months or 2.1 months: The fact that smokers generally do not drop dead after 2.1 months is one of many arguments against the one-sided interpretations of epidemiological studies on the harmful effects of fine dust 'v-A_-interview__frage'> As a pulmonologist, you advise calmness in view of the pollutant levels measured. Do you still need limit values?

Hetzel: The NOX concentrations currently measured at the measuring points do not pose a health risk. This is proven by the serious evaluation of scientific studies, and our everyday experience speaks for it. We treat many people with bronchial asthma who are regularly exposed to much higher levels of NO2 indoors than is measured at the measuring points. However, they do not report any interior-related symptoms. If you cook with gas stoves at home, NO2 concentrations of over 1,000 µg /m³ can quickly occur. If apartments are heated with gas boilers in winter, apartment NO2 concentrations of over 100 µg /m³ are not unusual. You can achieve these indoor concentrations with just a few burning candles. The pulmonologists would have noticed if these situations regularly triggered asthma symptoms.

As an argument against the low limit values, the requirements from other areas of life are often used .

If NOX is so dangerous, how can it be that the limit value 40 micrograms applies on roads, but I have to withstand 950 micrograms at many workplaces and possibly also a gas boiler at home hanging on the wall?

Schulz: What we do know is that children who live in apartments with gas heaters develop a slightly lower lung volume and suffer from an increased risk of asthma. In the workplace, however, we compare different things: 40 micrograms is a 24-hour andAnnual mean value and 950 micrograms an eight-hour value. At work we have healthy adults, but in the ambient air we also have children and the sick. For other pollutants such as asbestos, doctors also allow higher values ​​for workplaces. Nevertheless, from our point of view, there is nothing against lower limit values ​​in the workplace.

But do residents really live shorter on a busy street?

Schulz: There is it's a good study from Europe that evaluated 25 cities. Based on the WHO's fine dust recommendation of 10 micrograms, people would live half a year to a year longer.

And with nitrogen oxides?

Schulz: There is the study by the Federal Environment Agency, in which my institute was also involved, which estimated the long-term burden of disease in Germany at 6,000 premature deaths due to cardiovascular diseases. But here, too, the following applies again: This is a 'measure', it is not a death like in a car accident. The point is only to show that there are measurable effects and, if necessary, to compare the effect with other risk factors.

Mr. Hetzel, your explanation was only accepted by around 110 pulmonologists signed. However, the pulmonologist association has 3,800 members. Why doesn't the majority take part?

Hetzel: There was no vote. After our statement was sent to the members of the DGP, within a few weeks more than 100 pulmonologists declared their readiness to publicly represent the arguments put forward. That doesn't mean that the other club members disagree. In addition, the 3,800 members are not all pulmonologists. One should not primarily vote on scientific content. A few days after our arguments were published, the Federal Association of Pulmonologists, in which many resident pulmonologists are organized, captured such a mood by means of a quick poll: The majority spoke out against the retention of the applicable statutory pollutant limit values.

We always read from 70,000 studies on air pollutants. Could it be that there really are that many?

Schulz: Yes, it can be. Air pollutants have been studied for decades. One could now ask: why are you still researching when you already know the result? However, the pollutants are constantly changing. For example sulfur dioxide, which was in the media in connection with forest dieback in the 80s, but it also damages the respiratory tract. Today this is no longer an issue, just like the coarse soot in diesels, which is now filtered out. Today we have problems with ultrafine particles, some of which are highly toxic. These are not like NO2 orParticulate matter measured, but we can use NO2 as an indicator as both come mainly from traffic. In short: where there is NO2, there are also ultrafine particles, and the values ​​rise in parallel. The particle filter has already achieved a great deal in terms of particle mass, but it does not filter out very small particles sufficiently.

Then it is counterproductive that modern diesels with their SCR systems reduce NO2. That means you don't have the indicator.

Schulz: Exactly. However, NO2 also has its health effects and must be reduced. We would have to establish the measurement of the ultrafine particles, at least in different places in Germany. We have optimized the engines in the direction of achieving less and less exhaust gas mass, but on the other hand we are getting more and more ultrafine particles that have virtually no mass. Here it would make sense to speak to the engineers of the automotive industry in order to design the technology in such a way that overall as few harmful emissions as possible escape.


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