The use of aerometric network data has been criticized before on the grounds that it might give an unreliable picture of population exposure. However, the extensive data obtained from networks is still being used for studies of health effects of air pollution. This study uses a rigorous approach in analyzing these data to test their suitability for studies of acute health effects of air pollution. New York City, with one of the most extensive aerometric networks, consisting of 40 air pollution monitoring stations, is taken as an example. Three years of hourly SO2 readings and bi-hourly readings of smokeshade have been analyzed. The use of one aerometric station to represent the daily exposure of the population of New York City as has been done in previous studies is shown to be invalid. The use of individual monitoring stations of the New York City aerometric network to represent the day-to-day exposure to SO2 and smokeshade of the populations surrounding these monitoring stations is examined, with results showing that further work will be necessary before such an approach is justified.