Childhood asthma and outdoor air pollution in Oporto area

The influence of outdoor air pollution, on childhood asthma, is not yet completely understood, especially a long exposition to low but persistent pollutants levels. This paper presents the relationship between air pollution, as sulphur dioxide (SO2) and black smoke (BS), and asthmatic attacks on children living in the Oporto area, during the period between 1983 and 1987, when its levels ranged below the official "security" ones. There was no correlation between daily levels of SO2 or BS, and the asthmatic attacks rate. However, for longer periods, as months and quarters, an increased positive correlation was found, but only with SO2 (r = 0.334, p = 0.01; r = 0.473, p = 0.07, for month and quarter periods, respectively). These data suggest that, neither SO2 nor BS seem to be direct bronchospasm inductors, at least when its levels stay between the relatively low limits observed. On the other hand, the longer exposition to SO2 appears to lower the threshold of the asthmatic children to other bronchospasm stimulus.