UA logo Allergy and Asthma in the
Southwestern United States
Information for patients with allergy and related problems
in the Southwest

Environment and allergic disease               

Air Pollution, Asthma and Allergy 

Which Air Pollutants Cause Respiratory Disease?  
Symptoms of asthma and other chronic lung diseases are often precipitated by increased levels of air pollutants including particulates, nitrogen oxides, ozone and sulfur dioxide, all of which may directly irritate the airways.   The increased incidence of asthma in the fall and winter is probably due to several factors including the effects of temperature inversion on vehicle-generated pollution, combined with the increased incidence of respiratory virus infection at this time of the year, and increased mold spore counts. 

The incidence of allergic respiratory disease is high and continues to increase in populations of urban areas of Westernized countries throughout the world.  There is mounting evidence from epidemiologic and laboratory research of an important cause of allergy in Westernized civilizations: protection from bacterial exposure and bacterial infection in childhood through hygiene and liberal use of antibiotics.  Certain bacterial products appear to affect the developing immune system in childhood by diverting immune responses away from allergy.  Another explanation of this public health problem in developed countries is  air pollution from automobile traffic.  Diesel exhaust, known to boost the formation of IgE antibodies in experimental animals to make them allergic, could play a part in causing allergy in human populations.   Although air pollution is an important trigger for asthma symptoms, it is not considered to be an important cause of allergy as such, because of the low incidence of allergy in polluted non-Western environments.

Air Pollution in Arizona  
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.  Air pollution in Maricopa County (which includes Phoenix) is considerably higher than that in Tucson. 

Air pollutants in Arizona cities are principally nitrogen oxides, ozone, carbon monoxide and particulates.  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.  Detailed daily information on air quality in Arizona can be found on the web sites for Pima CountyMaricopa County and Pinal County.  

Air Pollution in Tucson 
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, and increase during the afternoons when the temperatures are high.  Average concentrations 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. 

For details on levels of ozone, nitrogen dioxide, carbon monoxide, sulfur dioxide and particulates (PM10 and PM2.5) based on current monitoring in Tucson and other localities as compared with all other monitoring stations in the country, go to

Indoor Air
Air inside an air-conditioned home in which there are no smokers, pets or old carpets is usually free of hazardous levels of air pollutants that could cause respiratory disease.  In the  Southwest evaporative coolers, commonly used instead of refrigerated air conditioning, can increase indoor levels of airborne allergens, particularly mold spores.  Tobacco smoke, pets (particularly cats), house dust mites, cockroaches and moldy carpet are common indoor triggers of asthma and rhinitis.

Additional information on air pollution, greenhouse gases, global warming and outdoor air quality may be found on the web sites of the Environmental Protection Agency and the California Environmental Protection Agency.   The Californian site provides well-written information in excellent detail.

Return to menu

Disclaimer:   This site is for educational purposes only.  Any information that you have found in this web site is not intended to replace medical care or advice given to you by your own physicians. You should consider consulting your local medical library and other web sites for additional information. 

Comments and suggestions welcome!   Email:
Content Owner:  Michael J. Schumacher, MB, FRACP, The University of Arizona

Updated  1/2012