How do breath and skin emissions impact indoor air chemistry?

Abstract

People are an important source of pollution indoors, through activities such as cleaning, and also from “natural” emissions from breath and skin. This paper investigates natural emissions in high‐occupancy environments. Model simulations are performed for a school classroom during a typical summer in a polluted urban area. The results show that classroom occupants have a significant impact on indoor ozone, which increases from ~9 to ~20 ppb when the pupils leave for lunch and decreases to ~14 ppb when they return. The concentrations of 4‐OPA, formic acid, and acetic acid formed as oxidation products following skin emissions attained maximum concentrations of 0.8, 0.5, and 0.1 ppb, respectively, when pupils were present, increasing from near‐zero concentrations in their absence. For acetone, methanol, and ethanol from breath emissions, maximum concentrations were ~22.3, 6.6, and 21.5 ppb, respectively, compared to 7.4, 2.1, and 16.9 ppb in their absence. A rate of production analysis showed that occupancy reduced oxidant concentrations, while enhancing formation of nitrated organic compounds, owing to the chemistry that follows from increased aldehyde production. Occupancy also changes the peroxy radical composition, with those formed through isoprene oxidation becoming relatively more important, which also has consequences for subsequent oxidant concentrations.

The atmospheric chemistry of indoor environments

“…As well, human skin and soiled clothing are important sinks for ozone and sources of VOCs. 175,176,249 These VOCs can lead to SOA formation. 96 Other recent studies have shown how soiled clothing protects us from gas-phase oxidants but can also enhance dermal exposure to chemical pollutants.…”

Secondary product creation potential (SPCP): a metric for assessing the potential impact of indoor air pollution on human health

“…There were no indoor emissions of VOCs, but VOC mixing ratios outdoors were typical for a polluted urban area. 23 In the absence of indoor sources, indoor VOC mixing ratios were determined by the outdoor values and the air exchange rate (AER), which was set to 0.76 h À1 for the standard scenario. 17,24 It was assumed that there were indoor lights, as well as attenuated outdoor light, with 3% of ultraviolet (UV) and 10% of visible light from outdoors assumed to be transmitted through windows.…”

The impact of clothing on ozone and squalene ozonolysis products in indoor environments

“…Less well recognized is the role of the occupants themselves. High concentrations of volatile organic compounds have been measured in human breath, which can lead to an increase in the concentrations of these species indoors [1][2][3] . Primary emissions of volatiles from skin have also been measured 4 .…”