Abstract
Humans are a potent, mobile source of various volatile organic compounds (VOCs) in indoor environments. Such direct anthropogenic emissions are gaining importance, as those from furnishings and building materials have become better regulated and energy efficient homes may reduce ventilation. While previous studies have characterized human emissions in indoor environments, the question remains whether VOCs remain unidentified by current measuring techniques. In this study conducted in a climate chamber occupied by four people, the total OH reactivity of air was quantified, together with multiple VOCs measured by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) and fast gas chromatography–mass spectrometry (fast-GC–MS). Whole-body, breath, and dermal emissions were assessed. The comparison of directly measured OH reactivity and that of the summed reactivity of individually measured species revealed no significant shortfall. Ozone exposure (37 ppb) was found to have little influence on breath OH reactivity but enhanced dermal OH reactivity significantly. Without ozone, the whole-body OH reactivity was dominated by breath emissions, mostly isoprene (76%). With ozone present, OH reactivity nearly doubled, with the increase being mainly caused by dermal emissions of mostly carbonyl compounds (57%). No significant difference in total OH reactivity was observed for different age groups (teenagers/young adults/seniors) without ozone. With ozone present, the total OH reactivity decreased slightly with increasing age.
Highlights
People spend on average 80%∼90% of their time indoors and more than 60% in their home residence.[1−5] the indoor air quality plays an important role in human health as people are exposed to numerous chemical compounds for long periods within their indoor home environment.[6,7]
In the presence of oxidants such as ozone or the hydroxyl radical (OH), oxidation products can be formed.[15−19] Besides, indoor OH concentrations have been measured and modeled in several studies that indicate the common occurrence of levels on the order of 105 molecules cm−3.20−24 Despite the application of advanced measurement technology in recent studies, the following question remains: Are we measuring all of the OH reactive species related to indoor human emissions? The question can be addressed by measurements of total OH reactivity, which provides a direct measurement of the total loss rate of OH radicals in the air
When this value is compared to the sum of the OH reactivity contributed by the individually measured species, any difference will indicate that the characterization of species has been insufficient
Summary
People spend on average 80%∼90% of their time indoors and more than 60% in their home residence.[1−5] the indoor air quality plays an important role in human health as people are exposed to numerous chemical compounds for long periods within their indoor home environment.[6,7] The degree of exposure is even higher while movement restrictions are in force, e.g., associated with pandemic outbreaks.For the last 20−30 years, the main focus of indoor research has been on building-related emissions such as building materials, furnishings, and paints; numerous volatile organic compounds (VOCs) have been measured from such sources.[8−13] with improved manufacturing techniques, these emissions gradually decreased, increasing the relative importance of emissions from occupants themselves.Humans are a potent, mobile source of chemicals in indoor environments. The question can be addressed by measurements of total OH reactivity, which provides a direct measurement of the total loss rate of OH radicals in the air. Several hundred bioeffluent VOCs are known to be emitted via breath and skin.[14] In the presence of oxidants such as ozone or the hydroxyl radical (OH), oxidation products can be formed.[15−19] Besides, indoor OH concentrations have been measured and modeled in several studies that indicate the common occurrence of levels on the order of 105 molecules cm−3.20−24 Despite the application of advanced measurement technology in recent studies, the following question remains: Are we measuring all of the OH reactive species related to indoor human emissions? When this value is compared to the sum of the OH reactivity contributed by the individually measured species, any difference will indicate that the characterization of species has been insufficient. Studies made outdoors have revealed significant differences between measured and calculated reactivity.[25−28] The missing fraction in comparison to known species gives important insights into possible unknown primary emission sources and secondary products
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
