As part of the European Public Health project IMCA II validity and practicability of "air pollution" as a respiratory health indicator were analyzed. The definitions of air quality as an indicator proposed by the WHO project ECOEHIS and by IMCA I were compared. The public availability of the necessary data was checked through access to web-based data-bases. Practicability and interpretation of the indicator were discussed with project partners and external experts. Air quality serves as a kind of benchmark for the good health-related environmental policy. In this sense, it is a relevant health indicator. Although air quality is not directly in the responsibility of health policy, its vital importance for the population's health should not be neglected. In principle, data is available to calculate this IMCA indicator for any chosen area in Europe. The indicator is relevant and informative, but calculation and interpretation need input from local expert knowledge. The European health policy is well advised to take air quality into account. To that end, an interdisciplinary approach is warranted. The proposed definition of air quality as a (respiratory) health indicator is workable, but correct interpretation depends on expert and local knowledge.