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.
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.
Michael J. Schumacher, MB, FRACP, The University of Arizona