Introduction

The London smog of 1952 triggered research into the effects of air pollutants on health. A trickle of new epidemiological studies that began in the late 1980s and turned into a flood in the 1990s, provided evidence that day-to-day variations in the already low concentrations of particles and other pollutants were associated with effects on health. Less certain, but probable, is that public concern about air pollution and its effects will not abate. These factors mean that efforts to control air pollution will need to be maintained and focused upon those measures that are most likely to provide a good return in terms of benefit as balanced against cost. Pollution of the air by particles is also not a new phenomenon; indeed, of the commonly studied air pollutants smoke, consisting of course of a particulate aerosol, was the first pollutant to be complained of and studied in detail.