[Ozone: myths and reality].

The extremely noxious gas ozone is of great contemporary interest, revealing also a fascinating history. Its tropospheric concentration has doubled in the past 100 years in the Northern Hemisphere. To answer some of the immediately important questions in relation to ozone, its biological effects and the mechanisms of action in the human organism are reviewed (first effects in man > 160 micrograms/m3, 0.08 ppm). We find out what questions are raised by animal studies to which epidemiologists might seek answers and that we are mostly not able to separate the adverse effects of ozone from those of other summer smog components travelling and interacting additively with it, namely NOx, aldehydes or peroxi-acetyl nitrate (PAN).