Exposure Assessment of Indoor and Occupational Aerosols - Consensus reports have identified associations between exposure to damp indoor environments, microbial growth and adverse respiratory health effects. Inhalation exposure of fungal bioaerosols found within these damp contaminated environments continues to be an area of great public concern especially for residents residing in or returning to these water damaged environments following natural disasters or flooding events. To assess the risk of exposure, the development of standard exposure assessment methods to identify and quantify microbial bioaerosols is critical, in order to determine sources, metabolic byproducts and biomarkers of exposure. Building upon the research conducted in previous years, NIOSH continued ongoing projects in FY20 to better understand the adverse health effects caused by fungal exposure. Sequencing-based studies conducted previously have identified fungal yeasts, which are often overlooked, as sources of personal exposure. Basidiomycota yeasts are prominent in indoor contaminated environments, but their role in adverse health effects has remained relatively uncharacterized. To address this knowledge gap, species-specific primers, probes, and a quantitative polymerase chain reaction (qPCR) method were developed to provide the detection and quantification of Vishniacozyma victoriae (syn. Cryptococcus victoriae). This species-specific qPCR assay was then used to detect and quantify V. victoriae in dust samples from homes participating in the New York City Neighborhood Asthma and Allergy Study (NAAS). In addition, the influence of housing factors and health effects associated with V. victoriae exposure in homes of children from low and high asthma prevalence neighborhoods in the New York metropolitan area were examined. The results from this study will provide new insight into the association between fungal yeast exposure and airway diseases. Along with exposure to fungal components including spores, hyphae and submicron fragments, exposure to fungi also includes secondary byproducts of fungal metabolism, such as mycotoxins. In FY20, a manuscript titled ?Effect of storage temperature and duration on concentrations of 27 fungal secondary metabolites spiked into floor dust from an office building? was published in the Journal of Occupational and Environmental Hygiene. This manuscript reported that fungal secondary metabolites in floor dust, including mycotoxins, quickly degraded at room temperature, whereas storing them under refrigeration or freezing conditions slowed degradation. This study demonstrated that storage temperature influenced degradation of the metabolites more than storage time. The rapid degradation of the secondary metabolites at room temperature may indicate that the concentrations of those metabolites, especially mycotoxins, are likely to be low in indoor settled dust. NIOSH had previously documented substantial matrix effects associated with the quantification of the metabolites in dust samples using the high-throughput HPLC-MSMS method. A standard addition method to compensate for substantial matrix effects was further investigated in FY20. Currently, the importance of using internal standards in the analysis of multiple fungal metabolites in floor dust samples is being examined by comparing the concentrations of the secondary metabolites measured with internal standards to those without internal standards. In addition to the examination of secondary metabolite storage conditions, experiments to assess stability of standard materials during storage at multiple storage conditions for extended time periods were also completed in FY20. Using the assessment of fungal DNA sequences from 500 dust samples previously collected from 50 schools, the organisms Fusarium graminearum and F. culmorum were identified, along with the mycotoxin, deoxynivalenol, from 48.1% and 83.4% of the samples, respectively. Examination of fungal secondary metabolite profiles for the floor dust samples will continue in FY21.
