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Air Pollution and Health Research


Introductory concepts.

This page is intended to give a very brief introductory overview of some of the salient issues regarding research into urban air pollution and health. It will outline examples of some of the research being conducted. 
For a more detailed account of this page with special reference to research being undertaken in Manchester and elsewhere, please click here.
 
Man-made air pollution has probably been a hazard to the human species ever since fire was discovered. Natural hazards uch as bush-fires and volcanic eruptions have been around for much longer of course!
  • What are the risks to health? 
  • How big are they? Are they getting bigger or smaller? 
  • Are some people more susceptible than others ? 
Industrial complex

What are the Purposes of Air Pollution and Health Research? 

The first and obvious answer to this question is that the researcher should try to determine whether or not there is a causal relationship between an environmental exposure and an adverse effect on health. This is much more difficult than most lay people believe. Several criteria must be fulfilled. You may wish to consult a page on asthma and air pollutants as an example. However, even if one establishes that a particular specified hazard can be responsible for some unwanted health effect, this level of information on its own is of limited practical use. What is really needed is a quantitative measure of the likelihood of an adverse health effect (i.e. the risk) for a given level of exposure.

Another necessity is to determine the exposure-response relationships for mixed exposures, and the interaction between these and other risk factors. Having established causation, and exposure-response relationships (no mean task), it may be important to translate these into health economic terms. In other words one might need to respond to questions such as: 

What degree of environmental change, and at what cost would produce what extent of health benefit?.
This information is very important for standard setting. Any interventions, especially costly ones, should be properly evaluated so as to ensure that the resource is being well utilised.

Some Difficulties with Research

Difficulties pervade study design, implementation and interpretation. For example in relation to the issue of "causation", three important difficulties need to be considered:

Bias. Essentially this results from not comparing like with like - for example it may be that people who respond and participate in an epidemiologic study, might be more likely to be concerned about ill health effects, and perhaps suffer from them, than individuals who decline to participate.

Confounding. Rather than present an epidemiologic definition of this, consider the following scenario:

Assume a study shows that in a particular city, on days with a high level of pollution, there are more admissions to hospital of elderly people with fractures of the hip. Should one conclude therefore that in some way or another pollution causes hips to fracture? The alternative, more likely explanation is that in certain bitterly cold weather conditions, some pollutant concentrations are more likely to be increased because of "temperature inversion". However, those same weather conditions are also likely to be associated with slippery iced ground, and folk are therefore more likely to slip and injure themselves.
Chance. If a study is small, it may result in a false negative effect because the numbers of subjects are too small, to show an increase in risk, for example in relatively rare conditions like leukaemia. On the other hand, if a large number of statistical tests are carried out, especially in a relatively indiscriminate fashion, it is likely that by chance a number of them will appear to be "statistically significant" - a false positive interpretation may then result.

Current research in Air Pollution and Health

Click here for further information.