1 Department of Clinical Epidemiology and Social Medicine, St. Thomas' Hospital Medical School, London
Unfortunately we do not know, at this point in time, which components of air pollution are really the causative agents associated with respiratory symptoms or respiratory diseases, whether it be in the adult or in the child. All that we can say is that air pollution is bad for health, and I would like to emphasize that it is not only air pollution but also other factors that are related to symptoms or disease in both the child and the adult.
ACUTE EFFECTS
When we consider the effects of air pollution, we ought to consider two major types. First, the acute (smog) episode: in London, 1952, we had one of the severest episodes that has ever occurred in the world. There were about 3,000 excess deaths in men and women aged 45 years and over. There were about eight excess deaths in children aged less than 1 year. We could not find any evidence of excess mortality in children older than 1 and below 24 years of age.1 More recently Lawther and my own group have followed up approximately 1,000 children born just before the 1952 smog; that is to say, who were exposed in this smog episode at less than 1 year of age. We contrasted them with a control group, and have not been able to identify any harmful effects in terms of symptoms or lung function among the survivors. However, it is quite clear that air pollution in the first year of life does have an effect on mortality from respiratory disease and other conditions,2 but we cannot show an effect in later periods.