Comparative Analysis of Indoor and Outdoor TSP Concentrations in Bombay, Toronto, and Zagreb

Air pollution concentrations in urban areas vary in both time and space (Munn, 1981). Time variations are strongly influenced by changes in human activities. Several activities occur repeatedly at regular intervals thus producing cycles in air pollution changes, like daily variations in CO concentration due to the change in traffic density or seasonal variations in air pollution (e.g., from heating systems which in moderate climates operate mainly in cold months). Spatial patterns of pollution concentrations over a given area depend on the number, type, strength, and distribution of various sources, and on the diffusion potential of the atmosphere. Such patterns will change somewhat according to prevailing weather conditions. However, the basic ~nderlying pattern of air pollution concentrations over a given area generally remains fairly constant with some areas having higher levels most of the time (e.g., busy downtown) than the other areas (e.g., suburbs). Most urban areas employ networks of stationary air monitoring stations to measure levels of air pollutants. Such networks serve a useful purpose in that they indicate both spatial and temporal variations in concentrations of an air pollutant. The purpose of this monitoring is to protect human health by assuring that concentrations have not exceeded health-based concentrations or standards. The assumption that a set of ambient air pollution measurements adequately delineate a person's exposure is now being questioned. First, most people move about during their daily activities, from areas of relatively low pollution concentrations to high ones and back again. Secondly, persons spend on the average 80 to 90 percent of their time indoors breathing indoor, not outdoor, air. Lastly, several studies have shown that indoor air pollution can be quite high depending on climatic conditions, building construction, and lifestyle factors (e.g., cooking practices and cigarette smoking).