Size- and Time-Resolved Emission Rates of Particulate Matter Mass, Chemical Constituents, and Oxidative Potential from Indoor Sources

Abstract We quantified the time- and size-resolved emission rates of particulate matter (PM) mass, its chemical constituents, and OP (via dithiothreitol assay) from six indoor sources in a test chamber (two types of incense, candle, toaster, humidifier, and cigarette). Both the chemical composition and mass-normalized OP (OPm) varied little temporally. However, both the chemical composition and OPm varied with particle size from <0.25 to 10 μm, with quasi-ultrafine particles (Q-UFPs < 0.25 μm) showing the highest OPm. The particle size distribution of the PM emitted from these sources was mostly unimodal, with both PM10 mass and OP emission rate concentrated in the Q-UFP size range. Given the abundance of Q-UFPs in the emitted PM with their high intrinsic OP, we find that 37 ± 3% of the emitted PM10 mass and OP from these sources has the potential to deposit in the respiratory tract, 45 ± 2% of which deposits in the alveolar region. An exploratory exposure assessment suggests that for an equal dose of PM10 mass and OP originating from these indoor sources vs ambient PM, the emissions from the tested indoor sources will likely result in a 76 ± 10% higher dose of alveolar-deposited mass and OP. Collectively, these results emphasize the need to better quantify the size-resolved toxicological properties of PM from myriad indoor emission sources to reliably estimate the resulting health risks.