Emission and oxidative potential of PM2.5 generated by nine indoor sources

Abstract

Indoor particulate matter (PM) sources pose great danger to air quality. This study used an environmental chamber to measure mass-normalized oxidative potential (OPM, a metric for intrinsic toxicity) and emission rates of nine indoor PM2.5 sources, including mainstream tobacco smoke, side-stream tobacco smoke, mosquito repellent coil, incense, moxa, scented candles, tobacco-heated e-cigarettes, liquid-heated e-cigarettes, and mosquito repellent electric mat. A dithiothreitol assay was used to measure the oxidative potential. A mass balance-based model was fitted to PM2.5 mass concentration records to calculate PM2.5 emission rates. Volume-standardized oxidative potential (OPV) exposure was calculated in a model room based on PM2.5 emission rate, and OPM obtained in this study. Overall, combustion sources were more detrimental than non-combustion sources. The highest and lowest mean OPM was found in the PM2.5 samples from side-stream tobacco smoke (99.5 pmol/min/μg) and the liquid-heated e-cigarette (1.3 pmol/min/μg), respectively. PM2.5 emission rates of indoor sources varied from 3153.9 μg/min (mainstream tobacco smoke) to 4.0 μg/min (scented candle). In the modeling room, PM2.5 from mosquito repellent coil showed the highest mean OPV (5.9 nmol/min/m3), although its mean mass concentration ranked second. OPV exposure caused by first-hand tobacco-heated e-cigarettes in one day was comparable to that caused by ambient PM2.5.