the risk of exposure to species-specific toxins or allergens and thereby increasing the risk of hypersensitivity pneumonitis. Massive exposure to toxin-producing fungi can occur when moldy organic material is handled. Such exposure can cause exacerbation of allergic disease as well as direct toxic effects such as immunosuppression and cancer (Baxter et al., 1981).
Dose-response data for fungal allergens are unavailable. Standardized protocols for the collection of fungal aerosols are not in wide use, and some of the current methods for quantitation may be unreliable (see Chapter 6). Some studies have reported concentrations of measured viable fungal units (i.e., colony-forming units) in the air of homes that vary over several orders of magnitude both within individual homes, between homes in one community, and between communities (Beaumont et al., 1985; Brunekreef et al., 1990; Su et al., 1992; Verhoeff et al., 1990b).
Of the many different kinds of microorganisms, the fungi are most often associated with allergic disease. Airborne fungal allergens have been implicated in allergic rhinitis/conjunctivitis, allergic asthma, and hypersensitivity pneumonitis. Certain fungi grow saprophytically in the mucous lining of the lungs of patients with allergic bronchopulmonary fungosis or aspergillosis and in the sinuses of people with allergic fungal sinusitis. In addition, conditions favorable to fungal growth correlate positively with respiratory symptom rates as determined by questionnaires (Beaumont et al., 1985; Brunekreef et al., 1989, 1990; Dales et al., 1990; Dekker et al., 1991; Platt et al., 1989; Strachan et al., 1990).
All fungi probably produce allergens that will cause disease with appropriate exposure, although skin test rates vary with allergen sources and the populations chosen for study (Cutten et al., 1988; Giannini et al., 1975; Tarlo et al., 1988). Among people referred for assessment of respiratory atopy, from 1 to 10 percent have positive skin prick tests to one or more fungal allergens (Beaumont et al., 1985). In atopic populations, the percentage of responders can be as high as 27 percent (O'Neil et al., 1988). Skin test reaction rates to fungi in atopic asthmatic patients have been as high as 70 percent (Lopez et al., 1976).
Investigators have measured precipitating IgG antibodies that are specific for soluble allergens of a number of different species of Aspergillus as well as Penicillium, Paecilomyces (Dykewicz et al., 1988), Pleurotus ostreatus (Noster et al., 1976), and Leucogyrophana pinastri (Stone et al., 1989). These antibodies are related to exposure to high levels of small fungal particles, but diseases such as allergic bronchopulmonary aspergillosis (ABPA) and allergic fungal sinusitis (AFS) require additional host factors that are