| Air filters from 15 sites, including 6 hospitals, in the Southeastern, Mid-Western, and Southwestern United States were examined for evidence of fungal colonization. Light and scanning electron microscopy procedures combined with recoveries in culture demonstrated that filter media made from cotton/synthetic fiber blends, both panel and bag-type, and HEPA-type microglass filters supported the in situ growth and reproduction of fungi. Moreover, the fungi were capable of producing a range of volatile organic compounds (VOCs) that may contribute to the sick building syndrome.;In laboratory studies unused filter media were colonized readily by fungi, particularly Aspergillus spp. and Cladosporium spp. These same fungi were among the most common recovered from field studies. Certain species, such as Epicoccum nigrum and Beauvaria sp., that have been considered to be indicators of outdoor air were shown to colonize air filter materials. Both laboratory and field studies showed that treatment of air filter media with antimicrobial compounds retarded colonization, but the antimicrobials were of varied efficacy dependent in part upon humidity and nutrient substrates.;Extensive air and bulk material sampling for fungi was carried out at one hospital after outbreaks of infection of 15 patients by Aspergillus fumigatus, supposedly related to construction activities. Aspergillus nidulans, not A. fumigatus, originated from within the building and the air handling system. High densities of A. fumigatus were located in the plant mulching material on the grounds immediately surrounding the building. Modification of the air flow at the main entrance and more stringent maintenance of the air filtration system correlated with a decreased incidence of Aspergillosis even while construction continued.;Fungi colonizing air filter media were found with GC-mass spectrometry to produce a range of volatile organic compounds (VOCs), particularly benzene derivatives and 2-ethyl-1-hexanol. These compounds were emitted directly from colonized unused filter media and from air filters colonized by fungi during their use in air handling systems. Contaminated air filter media may be directly involved in the sick building syndrome. |
