Investigating indoor airborne Aspergillus: Method development, temporal variation, and factors affecting concentrations

Inhalation of mold can cause several health problems, including allergic and asthmatic reactions. Aspergillus is a particularly problematic genus of mold, because it includes species that can infect immunocompromised people. Aspergillus can grow both indoors and outdoors, and its particles are commonly detected in indoor air.; A quantitative Polymerase Chain Reaction (qPCR) assay was developed to detect the Aspergillus genus. QPCR, a DNA-based method, is more sensitive, accurate, and specific than traditional culture-based methods. The developed assay is specific to the Aspergillus genus, and has minimal interference with similar molds. It is also very sensitive, and can reliably detect less than 10 mold conidia equivalents in a sample. To quantify concentrations of airborne Aspergillus particles, the qPCR assay was combined with an upstream process for collecting particles on filters, and extracting and purifying the DNA. Inhibition experiments indicated that the other particulate matter in the air samples did not affect the quantification of Aspergillus.; Once this method was validated, it was used in a 14-month study to explore how construction in a hospital could affect airborne Aspergillus concentrations. A children's hospital was undergoing partial construction, while the remainder continued to serve patients. Patient areas were regularly sampled to investigate if Aspergillus and particulate matter ≤5 mum (PM5) concentrations would be elevated. By periodically sampling in the construction zone and in an adjacent patient area, the effectiveness of the construction containment system was investigated. Results showed that construction was not causing elevated concentrations of Aspergillus in patient areas. In the construction zone, Aspergillus levels were occasionally elevated, and PM5 levels were regularly elevated. However, the containment system appeared effective, because Aspergillus and PM5 remained low in adjacent patient areas.; Based on observations from the longitudinal study, it was hypothesized that foot traffic and/or outdoor Aspergillus concentrations could significantly affect indoor Aspergillus concentrations. Intensive sampling campaigns were conducted in two carpeted lobbies, and samples were analyzed for Aspergillus and PM5 concentrations. A bivariate model was created for each of the pollutants of interest ( Aspergillus and PM5) based on the two variables (foot traffic and outdoor pollutant concentration). The bivariate model was strongly significant for 3 of 4 scenarios for Aspergillus and for 2 of 4 scenarios for PM5, supporting the hypothesis. Seasonal variations were also found, with Aspergillus concentrations higher indoors in September than in March, and higher outdoors in September and May than in March.; Controlled foot traffic experiments were conducted to explore the association of Aspergillus concentrations with walking. Results indicated that resuspension from a carpet was a strongly significant mechanism, and that shedding from people and their clothing could play a secondary role.