There is a recognized association between bronchial hyperresponsiveness, atopy (skin test reactivity), and COPD. Studies have demonstrated that the risk of bronchial hyperresponsiveness is related to skin test reactivity (Cockroft et al., 1984; Lebowitz et al., 1991, Peat et al., 1987; Sears et al., 1989). The index rises with the number of positive skin tests and the magnitude of the skin test reaction to each allergen. Therefore, an individual with many strongly positive skin tests to many allergens is much more likely to show bronchial hyperresponsiveness than an individual with no skin test reactivity. The association between atopy, bronchial hyperresponsiveness, and COPD may be explained by three alternative models (Sparrow et al., 1988). First, cigarette smoke may cause inflammation and mucosal damage, resulting in three unrelated by-products: atopy, bronchial hyperresponsiveness, and COPD. Second, when a person has atopy and therefore bronchial hyperresponsiveness, exposure to cigarette smoke leads to COPD. Third, cigarette smoke, atopy, and bronchial hyperresponsiveness are independent factors that contribute to the development of COPD.

SICK BUILDING SYNDROME

Sick building syndrome (also known as tight building syndrome, closed building syndrome, and new building syndrome) is a term given to nonspecific building-related illness. Figure 2-11 shows the relationship between these and other diseases and conditions that may occur in indoor environments and the general approach to their evaluation and management. Sick building syndrome describes a constellation of symptoms including mucosal irritation, fatigue, headache, and occasionally, lower respiratory symptoms and nausea. Patients or workers report that symptoms increase with the amount of time spent in certain buildings and tend to improve when they leave that building. Symptom prevalence rates associated with indoor environments vary tremendously, from less than 5 percent to as much as 50 percent.

For the majority of cases of sick building syndrome, the cause is unknown. A contribution by allergy has been considered unlikely since atopy or specific sensitivity to indoor allergens often is not found. Nevertheless, people with allergic disease frequently are the individuals who are most affected when an indoor air quality problem is occurring. A definitive conclusion that indoor allergens are not related to sick building syndrome awaits further study, particularly with respect to fungal allergens.

SPECIFIC BUILDING-RELATED ILLNESS

Specific building-related illness is defined as illness caused by identifiable toxic, infectious, or allergenic agents, which can be detected by appropriate



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