Oxidative Potential of the Particulate Matter Emitted from Common Household Sources

P. S. GANESH SUBRAMANIAN, Zhuying Dai, Vishal Verma, University of Illinois Urbana-Champaign

     Abstract Number: 136
     Working Group: Indoor Aerosols

Abstract
Oxidative potential (OP) is a metric, which quantifies the ability of particulate matter (PM) to induce oxidative stress in humans and cause adverse health effects. Although people spend over 80% of their time indoors, the OP of PM emitted from indoor sources are largely unknown. We collected PM emitted by commonly used household sources (unscented-candles, scented-candles, incenses, cigarettes, ultrasonic-humidifiers, and essential-oil-diffusers) in a clean-controlled-environmental-chamber and measured their chemical composition and PM emission rates (PER). Three different assays; dithiothreitol (OP_DTT), glutathione (OP_GSH), and hydroxyl radical generation (OP_OH) were used to quantify OP. Finally, we performed an exploratory exposure assessment using this dataset for a representative room volume (50 m³, 0.7 Air Changes per hour) scenario.

Preliminary results showed that PER was highest for cigarettes (~1400 μg/min), followed by incenses (400-600 μg/min), and lower than 100 μg/min for the other sources. The PER from unscented-candles was substantially higher (~50x) in presence of a wind-draft. Over 75% of the total PM-mass comprised of organic-matter for cigarette and incense emissions, while over 50% consisted of elemental-carbon for unscented-candles in the presence of wind-draft.

Unscented-candle emissions in presence of a wind-draft showed the highest intrinsic OP_DTT and OP_OH, while OP_GSH was highest for cigarette emissions. This higher intrinsic OP_DTT and OP_OH could be attributed to the high elemental-carbon content of PM emitted from candles during wind-draft. Ultrasonic-humidifier and essential-oil-diffuser emissions had the lowest intrinsic OP_DTT and OP_OH, but their OP_GSH were comparable with the other sources. Experiments are underway for further OP and chemical composition measurements for other indoor sources, such as air fryer, toaster, room freshener, coffee maker and laser printer.

Inhaled mass of PM_2.5 and subsequent OP exposure, originating from most of these sources exceeded those from ambient PM_2.5 exposure (assuming ambient PM_2.5 concentration 7.4 μg/m³, typically present in North America). Emissions from humidifier fed with tap-water showed the highest inhaled dose of PM_2.5, OP_DTT­, and OP_GSH exposure amongst all the tested sources. These exploratory results suggest that PM_2.5 emissions from some of these sources could pose a higher health risk than outdoor emissions in regions with low ambient PM_2.5 concentrations.