Date of Award
Doctor of Philosophy (PhD)
Mark T. Hernandez
Biological aerosols (bioaerosols) constitute a significant portion of airborne particulate matter, both indoors and outdoors; however, the extent to which anthropogenic oxidative air pollutants can modify bioaerosols remains unclear. This work isolated the potential for atmospheric ozone to modify important biopolymers in ubiquitous types of bioaerosols. Independent lines of evidence for ozone-mediated modifications of bioaerosols were obtained from environmentally controlled chamber studies designed to challenge bioaerosols with ozone and humidity conditions relevant to the current US EPA NAAQ standards. Before and during different ozone exposures, intrinsic bioaerosol fluorescence was monitored concurrently with the quantity and activity of significant allergens and enzymes present in pure bioaerosols. Results indicate significant decreases in fluorescence intensity, enzyme activity and specific allergen content with ozone exposure, while liberated water soluble organic carbon (WSOC) concomitantly increased over time in all environmental conditions tested.
As judged by real-time intrinsic fluorescence measurements of whole bioaerosols (airborne sporulated Aspergillus spp. and Bacillus subtilis), and the intrinsic fluorescence properties of the liberated bioaerosol WSOC fraction, differences in specific fluorescence began to appear within an hour of bioaerosol exposures to ozone and high humidity. Significant decreases in measureable airborne fungal enzyme activity (beta-N-acetylhexosaminidase) and allergen (Aspf1) content were encountered in response to ozone exposures. On time scales relevant for lower atmosphere environmental ozone bioaerosol exposures, these are the first observations implicating ozone inhibition of key enzymes responsible for fungal spore germination, and antigenic modification of the Aspergillus allergen Asp f 1.
Results from these controlled bioaerosol exposure chamber studies were related to actual environmental aerosol samples that had experienced extreme oxidative stress during a local wildfire. The carbon content and intrinsic fluorescence profiles of WSOC from collected wildfire aerosols indicate that distinct fluorescence patterns from the WSOC present in wildfire emissions changed over the course of the wildfire event in both indoor and outdoor locations, further demonstrating the infiltration potential of wildfire emissions into the indoor environment. Results from this work contribute to a limited body of existing observations documenting the potential impacts of oxidative air pollutants on bioaerosols present in both outdoor and indoor environments.
Gomez, Odessa Mason, "Characterizing Responses of Primary Biological Aerosols to Oxidative Atmospheric Conditions" (2016). Civil Engineering Graduate Theses & Dissertations. 435.