1) The currently heavily debated limit of 40 micrograms of nitrogen dioxide per cubic meter of air is based mainly on epidemiological studies. To clarify: Epidemiology is a recognized scientific discipline, which, in its main objective, follows the goal to identify long-term risks of environmental and lifestyle factors for the population and to assess their significance. Large observational numbers, diverse observational situations, and complex mathematical models, supported by toxicological studies, are used to distinguish causal relationships from coincidental events.
2) Numerous questions can only be answered with the methods of epidemiology, since nobody would expose people to a "controlled experiment" with exposure to pollutants over years and decades. The well accepted finding that smoking is harmful to health was established through epidemiological studies.
3) There is no scientific doubt that exposure to air pollutants poses a health risk to the population, not only with regard to respiratory and lung diseases, but also, for example, with regard to cardiovascular diseases.
4) However, there is no method that would allow a physician to determine the extent to which components of air pollution have contributed to a patient's lung disease.
5) Selected experts from a wide range of disciplines regularly evaluate the current state of knowledge in an international body of the World Health Organization (WHO). The limits to air pollutants recommended by WHO are designed to minimize the health risk to the population as much as possible. There is no question about the scientific expertise of WHO's high caliber international panel.
6) For nitrogen dioxide, which is an indicator of other air pollutants, this benchmark is currently set at 40 micrograms per cubic meter of air. Such a value needs to be reasonable for particularly sensitive people (including children, the elderly, patients with pulmonary and cardiac diseases), as no one can escape the inhalation of the ambient air - 24 hours a day. The DZL has no reliable new findings, which would give reason to correct this current benchmark.
7) The German threshold value is based on the guideline recommendations of the WHO, but also takes into account additional factors such as technical feasibility. Which measures are taken, to what extent and in what order of time in order to counter regional exceedances of the threshold values is also a political decision. Of course, the proportionality of the measures must be kept in mind.
8) In the current discussion on nitric dioxide, populistic scientific statements experienced a rapid increase in interest in the media. On the other hand, the "classical" reaction pattern of science, offering carefully considered and balanced statements in selected publication organs to the population and decision-makers fell completely behind. It will be necessary to consider how the concerned science organizations can prepare better for this phenomenon in the future as political decisions should be based on sound scientific evidence.
Prof. Dr. Werner Seeger (Chairman and speaker)
for the management board of the German Center for Lung Research (Deutsches Zentrum für Lungenforschung, DZL)
The original press release on the DZL website.
