ABSTRACT
The famous London fog of 1952 left no doubt about the human health risks associated with air pollution and in particular airborne particulates. An estimated 4000 excess deaths were attributed to the fog (Ministry of Health, 1954), which was due to a considerable extent to coal combustion. The result was the general recognition that levels of air pollution should be regulated. This led to the Clean Air Acts of the United Kingdom (1956) and the United States (1970). These Acts set air quality standards whose enforcement required networks of monitors. By the early 1970s the UK had over 1200 monitoring sites measuring black smoke (BS) and sulphur dioxide (SO2).
