Mold was nominated to the NTP for toxicological characterization and based on their inhalation, mycological, and immunological expertise, NIOSH was engaged as a partner to conduct multiple sub-chronic (13-week) exposure studies to individual organisms or mixtures of molds mimicking a real-world exposure. NIOSH has developed a system that allows for precisely controlled exposures to particulates via inhalation. This approach overcomes a number of limitations associated with previous mold exposure studies in experimental animal models that have used less relevant means of exposure to assess fungal toxicity. The acoustical generation system (AGS) developed as part of this partnership delivers fungal test articles to mice in a manner that simulates natural indoor fungal contaminant exposure. Aspergillus fumigatus was selected as a model organism for the initial studies. In FY15 NIOSH conducted a 13-week sub chronic toxicology study to examine systemic effects of fungal exposures in B6C3F1/N mice. NIOSH has begun to optimize exposure conditions for two additional fungi of interest, beginning with Aspergillus versicolor, and then Stachybotrys chartarum (mycotoxin producing and non-producing chemotypes). Pilot studies were conducted with Stachybotrys chartarum and preliminary data suggests that the resulting pulmonary inflammatory responses differ following exposure to this organism as compared to the previously evaluated Aspergillus fumigatus. In FY15, the NTP study design was approved for 13 week toxicology studies using these organisms. The projects conducted as part of this interagency agreement support the NTP mission through the development of analytical reagents for improved species-specific identification of fungi and to better evaluate the health effects associated with fungal exposures. The knowledge gained from these projects will assist in the development of improved testing methods for the quantification of environmental fungi, as well as generate data that will strengthen the scientific base for fungal exposure risk assessment. These projects will additionally address specific NIOSH and NIEHS research goals for reducing environmental and occupational causes or contributing factors to acute and chronic illness and disease in worker populations as well as children.
