Local authorities, health and environment

Health effects of air pollution

One way of classifying the health effects of pollutants is to make a distinction between two broad categories: acute (i.e. short-term) and chronic (i.e. long-term) effects. For each of these categories, the effects can range in severity from death to minor illness or discomfort. For example, dust and other polluting particles in air can have acute effects, such as immediate irritations to eyes and throat, or hospitalisation and even deaths from respiratory failure or heart attacks, caused by severe episodes of air pollution. For some pollutants there may be a threshold level of exposure, below which no health effect is evident, e.g. SO2. For others, there may be no threshold, and some effect may occur whatever the level of exposure is, e.g. benzene.

Estimated health impact of ambient air pollution in Europe
Indicator of health deficiency Proportion of the health deficiency attributed to the pollution Estimated number of cases (annual)
Cough and eye irritation in children 0.4-0.6% 2.6-4 million
Lower respiratory illness in children 7-10% 4-6 million
Lower respiratory illness in children causing a medical visit 0.3%-0.5% 17-29 thousand
Ambulatory visits due to respiratory disease 0.2-0.4% 90-200 thousand
Decrease of pulmonary function by more than 5% 19% 14 million
Incidence of chronic obstructive pulmonary disease 3-7% 18-42 thousand
Hospital admissions due to respiratory disease 0.2%-0.4% 4-8 thousand
WHO European Center for Environment and Health, Concern for Europe's tomorrow, 1995
Epidemiology(Click for more details)
Epidemiology is the study of the distribution and the determinants of health-related states and events in populations, and the application of this study to the control of health problems. Epidemiological methods have been widely used to generate and test hypotheses on cause-effect relationships and to evaluate interventions.

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.Dispersal of air pollutants

Some epidemiological evidence on the health effects of air pollution in children
Country or area Exposure (*) Association found with increased exposure
France, 1989 Mixed industrial pollution Increased rhinitis and school absenteeism
Czech Republic, 1992 PM10, SO2, NOx Infant and respiratory mortality increased with PM10 exposure
Switzerland, 1989 NO2 Increased respiratory symptoms
Germany, 1991 TSP, NO2 Increased croup
Alpine Region, 1993 SO2, NO2, O3 Reduced lung function
Higher asthma
Netherlands, 1993 SO2, NO2, PM10 and BS Increased wheezing and use of bronchodilator
Finland, 1991 SO2, NOx, H2S, TSP Increased respiratory infections
Italy, 1992 Outdoor air pollution and passive smoking Increased asthma
(*) SO2: sulphur dioxide, NOx : nitrogen oxides, NO2 : nitrous dioxide, O3 : ozone, TSP : Total suspended particulates, H2S : hydrogen sulphide, PM10 : particulate matter less than 10 microns, BS : black smoke.
Source: summarised from D. Briggs, C. Corvalen, M. Nurminen, WHO/UNEP/USEPA, "Linkage methods for environment and health analysis"


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