Oxidative Potential and Lung-Deposition of Size-Resolved Aerosols Emitted from Common Indoor Sources
P. S. GANESH SUBRAMANIAN, Saman Haratian, Mohammad Heidarinejad, Brent Stephens, Vishal Verma, University of Illinois Urbana-Champaign
Abstract Number: 498
Working Group: Health-Related Aerosols
Abstract
Oxidative potential (OP) quantifies the ability of particulate matter (PM) to induce oxidative stress in humans and is used as a surrogate of PM toxicity. Although people spend most of their time indoors, the lung-deposited OP exposure from PM emitted indoors is still unknown. In this study, we collected size-resolved PM emitted from common household sources [incense (patchouli), incense (frankincense), cigarettes, toasters, ultrasonic humidifiers running on tap water, and unscented candles in the presence of a wind-draft] in a clean-controlled-environmental-chamber. Our goal is to evaluate the size-resolved emission rates, mass-normalized OP (OPm) using dithiothreitol (DTT) assay, and chemical composition of PM from these sources. Lung-deposited exposures were calculated by integrating the size-resolved data with the multiple-path particle dosimetry (MPPD) model and compared with total respirable exposures (i.e., fine PM; PM2.5) for both mass and OP of the PM emitted from indoor sources.
Preliminary results revealed that submicron particles (<1 μm) constituted over 95% of the total PM mass emitted from incense (both fragrances), cigarettes, and toasters. Notably, OPm increased with decreasing particle size for the emissions from the few sources characterized thus far (i.e. both fragrances of incense), aligning with previous findings on ambient PM. Exploratory exposure assessment revealed that only 18.3%, 11%, 16.6%, and 20.9% of the PM2.5 emitted from incense (patchouli), incense (frankincense), cigarette, and toaster emissions, respectively got deposited in the pulmonary regions. Similarly, lung-deposited OP was also a very low fraction of total emitted PM2.5-OP [i.e. 20.8% and 13.3% of the PM2.5-OP for incense (patchouli) and incense (frankincense) emissions, respectively]. Notably, ultrafine PM (UFP; Dp<0.25 μm) constituted around 59±20% of the emitted PM mass but constituted a larger fraction of lung-deposited PM (80±16%) and OP (77±19%), due to higher intrinsic OP of UFP. These preliminary results reveal that respirable exposures conducted using bulk PM2.5-OP overestimate lung-deposited dose of potentially toxic PM and emphasize the need for size-resolved measurements to reliably estimate PM-induced health-effects.