[Croup and air pollutants: results of a two-year prospective longitudinal study].

The Reutlingen/Tübingen/Rottenburg region in Baden-Württemberg is characterized by medium and small sized towns and rural areas. In 1986/87 875 cases of croup were registered there by the treating physicians during a 24-months period. In consideration of meteorological and virological "disturbing variables" the influence of the measured air pollution by SO2, NO, NO2, CO, ozone and dust on croup frequency was computed by means of statistical regression methods. For the months September till March, the main manifestation period of croup, weak but statistically significant influences of the daily means of NO and NO2 were found, for the whole year influences of NO, NO2, and CO. During the winter months temperature correlates positively and velocity of wind negatively, both statistically with significance, to croup frequency. The essential conditions of croup are individual and familiar disposition on the one hand, virus infections on the other. Air pollution of a concentration like given in the investigated region was found to be a weak additional factor that favours the manifestation of croup.