Environmental factors and atmospheric pollutants.

Respiratory infections result from complex interactions between the infectious organism and the host, and exposure to environmental pollutants may alter host resistance. The atmospheric pollutants implicated in respiratory infections include acidic aerosols, particles, nitrogen dioxide, ozone, sulfur dioxide, and household allergens. An extensive epidemiological literature has been established linking environmental tobacco smoke to increased occurrence of lower respiratory tract infections in children; exposure to smoke from cooking and heating fires may also increase the risk of serious infections. Experimental evidence suggests that exposure to nitrogen dioxide and acidic aerosols may impair specific host defense mechanisms. Individuals with underlying lung or heart disease, as well as infants and the elderly, are among those most susceptible to the effects of environmental pollutants. Efforts should be directed toward reducing the exposure of children to environmental tobacco smoke and products of unvented combustion while investigations continue.