Indoor nitrogen dioxide pollution and respiratory symptoms of school children.

The influence of indoor nitrogen dioxide exposure on respiratory symptoms of school children was investigated in a case-control study. The election method used was useful in obtaining symptomatic children, but insufficient indefining cases and controls without additional information. No relationship between indoor NO2 and respiratory symptoms was found. Bias may have been present, especially because of the high mobility of the study population. Attempts to estimate historical exposure were inaccurate. Therefore the results do not exclude that an association between indoor NO2 and respiratory symptoms exist.