Effect of Ozone, Clothing, Temperature, and Humidity on the Total OH Reactivity Emitted from Humans

People influence indoor air chemistry through their chemical emissions via breath and skin. Previous studies showed that direct measurement of total OH reactivity of human emissions matched that calculated from parallel measurements of volatile organic compounds (VOCs) from breath, skin, and the whole body. In this study, we determined, with direct measurements from two independent groups of four adult volunteers, the effect of indoor temperature and humidity, clothing coverage (amount of exposed skin), and indoor ozone concentration on the total OH reactivity of gaseous human emissions. The results show that the measured concentrations of VOCs and ammonia adequately account for the measured total OH reactivity. The total OH reactivity of human emissions was primarily affected by ozone reactions with organic skin-oil constituents and increased with exposed skin surface, higher temperature, and higher humidity. Humans emitted a comparable total mixing ratio of VOCs and ammonia at elevated temperature-low humidity and elevated temperature-high humidity, with relatively low diversity in chemical classes. In contrast, the total OH reactivity increased with higher temperature and higher humidity, with a larger diversity in chemical classes compared to the total mixing ratio. Ozone present, carbonyl compounds were the dominant reactive compounds in all of the reported conditions

How Does Personal Hygiene Influence Indoor Air Quality?

Humans are known to be a continuous and potent indoor source of volatile organic compounds (VOCs). However, little is known about how personal hygiene, in terms of showering frequency, can influence these emissions and their impact on indoor air chemistry involving ozone. In this study, we characterized the VOC composition of the air in a controlled climate chamber (22.5 m3 with an air change rate at 3.2 h-1) occupied by four male volunteers on successive days under ozone-free (∼0 ppb) and ozone-present (37-40 ppb) conditions. The volunteers either showered the evening prior to the experiments or skipped showering for 24 and 48 h. Reduced shower frequency increased human emissions of gas-phase carboxylic acids, possibly originating from skin bacteria. With ozone present, increasing the number of no-shower days enhanced ozone-skin surface reactions, yielding higher levels of oxidation products. Wearing the same clothing over several days reduced the level of compounds generated from clothing-ozone reactions. When skin lotion was applied, the yield of the skin ozonolysis products decreased, while other compounds increased due to ozone reactions with lotion ingredients. These findings help determine the degree to which personal hygiene choices affect the indoor air composition and indoor air exposures

Carbonyl Sulfide (OCS) in the Upper Troposphere/Lowermost Stratosphere (UT/LMS) Region: Estimates of Lifetimes and Fluxes

Abstract Carbonyl sulfide (OCS or COS) is a ubiquitous trace gas and plays a role in forming stratospheric sulfate aerosol particles, thereby influencing climate. In this study, whole‐air samples containing OCS were collected onboard a passenger aircraft (IAGOS‐CARIBIC) from the upper troposphere/lowermost stratosphere (UT/LMS, 10–12 km) region and analyzed with CryoTrap–GC–AED system in the laboratory. Global OCS mixing ratios are presented and by using the OCS measurements in conjunction with other trace gases, an atmospheric OCS lifetime of 2.1 ± 1.3 years, and lowermost stratospheric OCS lifetime of 47 ± 16 years were determined. A total flux of 137 GgS a−1 of OCS from the troposphere into the stratosphere was estimated, and the stratospheric sink estimate yielded 55 ± 23 GgS a−1 of OCS. The 60% smaller sink can be interpreted as 82 GgS a−1 OCS which is transported back from the stratosphere into the troposphere

Assessment of aldehyde contributions to PTR-MS <i>m/z</i> 69.07 in indoor air measurements

Proton transfer reaction-mass spectrometry (PTR-MS) has been widely used for monitoring outdoor and indoor volatile organic compounds. For outdoor air, mass-to-charge-ratio m/z 69.07 is usually assigned to isoprene. Isoprene is also a major component of human breath and therefore abundant in occupied indoor environments. Mass 69.07 as an indicator of indoor isoprene can suffer interference resulting from fragmentation of aldehydes [V. Ruzsanyi, et al., Multi-capillary-column proton-transfer-reaction time-of-flight mass spectrometry, J. Chromatogr. A, 2013, 1316, 112-118], which are also abundant indoors, especially when ozone is elevated [C. J. Weschler, Roles of the human occupant in indoor chemistry, Indoor Air, 2016, 26, 6-24]. As part of the Indoor Chemical Human Emission and Reactivity (ICHEAR) campaign we examined this effect in human-occupied chamber studies, in the absence and presence of ozone. We find that such interferences do occur when ozone reacts with both human skin oil and cotton-based clothing. In the presence of humans and 35 ppb ozone, PTR-mass 69.07 was three times higher than the isoprene mixing ratio measured independently by GC-MS. To investigate this effect, we measured the fragmentation patterns of aldehydes and examined the contribution of different aldehydes to m/z 69.07 in the ICHEAR experiments. Nonanal, and its contribution to m/z 69.07, could be quantified reliably for clothing and human dermal emissions under the experimental conditions. In contrast, decanal is difficult to quantify, since compounds other than decanal fragment to m/z 157.16, its MH+ peak, which also makes it difficult to estimate decanal's contribution to m/z 69.07

Total OH Reactivity of Emissions from Humans: In Situ Measurement and Budget Analysis

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