by Michael J. Schumacher, M.D.
Metropolitan Tucson is surrounded by mountains, predisposing the area to frequent temperature inversions. During this time the valley fills with colder air containing higher concentrations of air pollutants, as compared with mountain slopes above the temperature inversion layer.
Local sources of air pollution are traffic (greater than 40%), vehicle-generated paved road dust (12%), and dust from unpaved roads (8-10%). Pollution from automobile emissions (mainly nitrogen dioxide) increases in the winter, particularly on days with temperature inversion. As in other cities, use of oxygenated motor fuels contributes to aldehyde and other volatile organic compound pollution.
The average concentration of ozone in the city ranges from 0.022 to 0.042 ppm (parts per million) throughout the Tucson basin, and is tending to increase. Highest levels of ozone generally occur in the summer. Average concentration of nitrogen dioxide range from 0.019 to 0.021 ppm, and particulates 10 microns and smaller range from 12.5 to 30.7 micrograms per cubic meter. Aside from a coal- fired power plant, Tucson has no heavy industrial sources of sulfur dioxide and levels of this pollutant are low.
Symptoms of asthma and other chronic lung diseases are precipitated by increased levels of air pollutants including nitrogen dioxide, ozone, and particulates, and the increased incidence of asthma in the fall and winter may be related to effects of temperature inversion on vehicle-generated pollution. Air pollution in Tucson may also influence the high incidence of allergy in this region, but further research is needed to confirm this.
Posted in: Urban Environment