Although indoor air pollution is the more serious source of reactions for the chemically susceptible, one should not minimize the danger of outdoor, or ambient, sources of pollution.
Outdoor air pollution is by its very nature variable and intermittent. That is, the intensity of the “smog” frequently depends on local weather conditions. In general, the worst spells of outdoor air pollution occur during stagnant, humid, foggy, or rainy days. This type of weather is apt to be more common in winter. Summer has its own problems, too, with more cars on the road giving off copious fumes from their overheated engines.
Chicago is a particularly good city in which to study this problem. As a storm approaches from the west, air pollution is swept into the city, from the industrial center in the south, by the counterclockwise winds swirling around a low pressure area. When the storm center passes through the city, the winds shift suddenly to the north and east, which clears the air of its major pollutants. Thus, both pollution and the lack of pollution are sharply accentuated by the geography of this area.
Chicago contains four major sources of outdoor air pollution. The greatest is the petroleum refinery area at the extreme northern border of Illinois and Indiana. The reader will recall Nora Barnes’ onset of sickness upon driving through the smog of this industrial zone. Some patients from Michigan prefer to take the ferry from Ludington to Milwaukee and then drive down to Chicago from the north, simply to avoid passing through the area.
The second major source of pollution comes from a refinery area adjoining the ship canal, southwest of Chicago. A third, more diffuse source centers around a paint manufacturing plant on the south side, which is located near several other foci of heavy industry.
The fourth area is the Loop, Chicago’s famous business district. Here automobile and railroad odors are major pollutants. Expressways and diesel railways radiate, spokelike, from the Loop, spewing chemical contamination into the environment.
Depending on the direction and force of the winds, pollutants from these four sources frequently mingle in a noxious cloud, and the contaminated blanket of air they have created is pushed now in one direction, now another. Hardly anyone can escape the influence of this smog, although the south side of the city usually suffers the most, and the lakeside “Gold Coast” the least.
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