ABSTRACT
Historically, only qualitative standards were available to estimate the levels of air pollution in a city. These standards usually consisted of generalized descriptions of health effects (as seen in
Fumifugium
, above) or, in the case of the Great London Smog Disaster of 1952, statistics on the number of excess deaths or hospital admittances. These are after-the-fact measures of air pollution. It was only well into the latter half of the 20th century that instruments became available to monitor air pollution levels on a real-time basis. Instruments also made possible the setting of numerical standards for health and welfare as management tools.
