The discussion about influence of air pollution on health is loaded by special problems: methods are not always adequate, special interest exists of the general population and of politicians, more than 100 substances are involved. There is no ascertained knowledge about systemic actions of air pollutants by diffusion or resorption. Local action on bronchopulmonary system can cause or deteriorate otherwise provoked diseases. There are no ascertained results that general air pollution is really the cause of diseases. Deterioration of airways obstruction takes place on patients with hyperreactivity of the airways in the range of 2,5 mg/m3 SO2. It is possible that very sensitive patients also react against lower concentrations. These results were shown on rectangular increases of concentration. Slower increases of the concentrations show less or no effect. The same reactions can be seen by exposure against cold air or other unspecific challenges of these patients. The published data on premature death are in disagreement with corresponding experimental results. For the development of lung cancer the knowledge of tobacco smoking habits is indispensable. In the future long-term studies with high response-rates are necessary. Our basic knowledge today is sufficient to perform such studies. The industrialized society has to solve such questions which also interfere with other more extended problems.