[Experiences and considerations from 50-year pursuit of ozone effects on man].

High average ozone concentrations near ground are typical of places with efficient air exchange to higher atmospheric layers, e.g. health resorts with favorable climate and little anthropogenic air contamination. Warning about harmful effects of ozone may be misleading unless its role as a natural component of the air is considered. Distinguishing between "clean air ozone" in contrast to "smog ozone" is helpful for an understanding of the problem. For lack of quantitative surveys, tolerance limits for ozone had to be set without regard for interactions with other harmful air constituents and for adaptation effects.