Key airborne pollutants--the impact on health.

Current appreciations of the effect on health of classical air pollutants including nitrogen dioxide, sulphur dioxide, particulate matter, carbon monoxide and ozone, depend upon modern techniques of epidemiological research. These techniques, which are powerful and able to detect small effects, depend upon the power of modern computers and, though the theory was understood, their application was not possible for most research workers before about 1980. The methods involve handling large data sets and the application of complex methods of regression analysis. Dealing statistically with the many confounding factors that obscure and interact with the effects on health of air pollutants is possible using these methods. Early concerns about the adequacy of handling confounding factors have recently been allayed. This review considers short-term impacts, long-term impacts and areas where further research is required.