10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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The Effects of Alpha-pinene and Toluene in the Presence of UV, Ozone, and Humidity on Bioaerosols in a Laboratory Rotating Drum
SEAN KINAHAN, Don Collins, Yong-Le Pan, Aimable Kalume, Matthew Tezak, Keiko Salazar, Gabriel Lucero, Steven Storch, Cathryn Reyna, Joshua Santarpia, Sandia National Laboratories
Abstract Number: 1363 Working Group: Bioaerosols
Abstract A Goldberg rotating drum was established in a BSL-1 laboratory to age aerosols in the presence of controlled levels of relative humidity (RH), ozone, and UV light. More recently, a series of mass-flow controllers and permeation tubes were incorporated to achieve controlled, reproducible concentrations of volatile organic compounds (VOCs), with the focus to date on toluene and α-pinene. Gaseous species are continuously introduced along a center-axis using a gas-permeable expanded Teflon tube to maintain stable reaction conditions, while also maintaining a low velocity exchange of gases to prevent the disruption of the aerosol population. Three types of bioaerosols were produced to investigate the effects of these variables both individually, and with other input conditions expected to have combinatory effects. Specifically, a spore-forming species, Bacillus thuringiensis al Hakam, a vegetative species, E. coli, and a virus, MS-2, were grown according to established laboratory protocols and aerosolized through an ultrasonic nozzle at a particle size of 2-3 µm, depending on the organism. Changes in the bioaerosol population size and fluorescence were monitored using real-time aerosol instrumentation including a Wideband Integrated Bioaersosol Sensor (WIBS 4A), an Aerodynamic Particle Sizer (APS), and an Army Research Laboratory developed Single Particle Fluorescence Spectrometer (SPFS), which excites particles at both 263 and 351 nm wavelengths.. Additionally, viability and genomic signature were investigated in aerosol samples collected using an AGI-30 impinger, allowing a comparison of an aged sample to the corresponding time zero sample. For Bacillus thuringiensis, UV light was found to be the primary driver of aging, with very minor effects of RH, ozone, and VOCs. Statistically significant increases in aging were observed for E. coli when exposed to UV light and toluene compared to UV light alone or toluene alone, despite UV light being the primary driver. Lastly, exposure to UV light and high RH resulted in increased aging in the presence of both VOCs for the virus, MS-2. In most cases, the magnitude of change in PCR signature did not correlate with the magnitude change in viability, even when the same overall trend was present, which also indicates differences in the decay of detectability and viability.