U.S. society from asthma at more than $6.2 billion (K. B. Weiss et al., 1992b), an increase of 39 percent over the estimated cost of the disease in 1985. Despite the lack of exactitude, the size of these costs and the fact that they represent an increasing trend argue for careful attention not only to the effects of allergy in causing asthma but also to the litany of other conditions that are more commonly thought to be associated with ''allergies." Allergic rhinitis (hay fever), for example, is a disease of dramatic proportions in this country; although not life-threatening, it nevertheless is estimated to affect some 35 million Americans (17 percent of the population) at some point in their lives. The direct and indirect costs associated with such a burden of disease are not trivial and point to the importance of serious consideration of the effects of indoor allergens on the public's health.

To a majority of people, the indoor environment has always been considered a refuge from the dangers of the outdoors, offering protection from weather, wild animals, and, in modern times, air pollution—long seen as primarily an outdoor phenomenon. In more recent times, however, reduced ventilation in energy-efficient buildings has stimulated debate and concern about increasing indoor pollutant concentrations. Much of the concern has focused on potential carcinogens, with radon and environmental tobacco smoke being good examples. But other agents and potential health effects are beginning to receive increasing consideration, and among these are the indoor allergens.

Evidence is mounting that allergy has a fundamental, causal relationship

FIGURE 1-1 Amount of time spent indoors, outdoors, and in transit by most Americans.

Sources: NRC, 1981; Spengler and Sexton, 1983.



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