The results of the lymphocyte-nucleolar test in 1985 and 1986 yielded distinct differences between the exposed children (Wiesbaden, Frankfurt) and the children in the control areas (Freiburg, Starnberg, i.e. an increased number of compact, activated lymphocyte-nucleoli in the former. These results are in harmony with the clinically determined findings on enlarged and fissured tonsils as well as enlarged mandibular and cervical lymph glands as an expression of heightened reactivity of the lymphatic tissue to a long-term burden by environmental factors such as e.g. air pollution.