Health effects of air pollutants

In a given population, not all individuals are affected equally by the same environmental hazard. Substantial variations in sensitivity to an exposure may occur, due to age, nutritional status, genetic predisposition and state of general health, which are important determinants of individual vulnerability. Risk assessments need to be made for particular high-risk groups such as infants and young children, the elderly, pregnant women and their foetuses, the nutritionally deprived, and individuals suffering from some diseases. It is especially important to identify these high-risk groups because they will usually be the first to experience adverse health effects as the level of the pollutant increases. For example, a recent study showed higher values of lead in blood in children living near a lead smelter than in adults in the same area. Often, only a small subset of the population may experience high levels of exposure to air pollution, and the doses received by the general population are so low that only vulnerable high-risk groups are severely affected. Any excess mortality due to a pollutant may therefore be restricted to a small section of the population, so mortality rates for entire populations can often be weak and insensitive indicators of environmental health effects.

Estimates of health damage from air pollution are difficult to calculate. In a recent analysis of summer smog episodes in the UK, for example, the number of additional hospital admissions for respiratory disorders in the summer of 1993 was estimated to be around 180. This represents some 0.1% of all such hospital admissions in the UK during that period. There may also be estimations for smaller populations where the information on exposure to air pollution is more precise and underlying assumptions are more reliable.