Human personal air pollution clouds in a naturally ventilated office during the COVID-19 pandemic

Shen, Yang; Muthalagu, Akila; Serrano, Viviana González; Licina, Dusan

doi:10.1016/j.buildenv.2023.110280

Cited by 9 publications

(5 citation statements)

References 97 publications

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“…In addition, in typical indoor environments with pronounced spatial gradients of air pollutants, CO 2 and NH 3 levels can be elevated in the perihuman microenvironment beyond those represented by the assumption of a well-mixed indoor environment, leading to elevated personal exposure. − Future work exploring the effect of human gaseous emissions on personal exposure is warranted.…”

Section: Results and Discussionmentioning

confidence: 99%

Physiology or Psychology: What Drives Human Emissions of Carbon Dioxide and Ammonia?

Yang,

Bekö,

Wargocki

et al. 2024

Environ. Sci. Technol.

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Humans are the primary sources of CO 2 and NH 3 indoors. Their emission rates may be influenced by human physiological and psychological status. This study investigated the impact of physiological and psychological engagements on the human emissions of CO 2 and NH 3 . In a climate chamber, we measured CO 2 and NH 3 emissions from participants performing physical activities (walking and running at metabolic rates of 2.5 and 5 met, respectively) and psychological stimuli (meditation and cognitive tasks). Participants' physiological responses were recorded, including the skin temperature, electrodermal activity (EDA), and heart rate, and then analyzed for their relationship with CO 2 and NH 3 emissions. The results showed that physiological engagement considerably elevated per-person CO 2 emission rates from 19.6 (seated) to 46.9 (2.5 met) and 115.4 L/h (5 met) and NH 3 emission rates from 2.7 to 5.1 and 8.3 mg/h, respectively. CO 2 emissions reduced when participants stopped running, whereas NH 3 emissions continued to increase owing to their distinct emission mechanisms. Psychological engagement did not significantly alter participants' emissions of CO 2 and NH 3 . Regression analysis revealed that CO 2 emissions were predominantly correlated with heart rate, whereas NH 3 emissions were mainly associated with skin temperature and EDA. These findings contribute to a deeper understanding of human metabolic emissions of CO 2 and NH 3 .

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Section: Results and Discussionmentioning

confidence: 99%

Physiology or Psychology: What Drives Human Emissions of Carbon Dioxide and Ammonia?

Yang,

Bekö,

Wargocki

et al. 2024

Environ. Sci. Technol.

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“…Future research can consider measuring air velocities at multipoints or simulating airflow field using computational fluid dynamics to investigate the relationship between air movement and indoor nanoparticle dynamics. Finally, future studies should consider more robust approaches to examine the ultrafine particle and ozone distribution around humans generated from ozone–human chemistry, such as multipoint measurements at various points in a room and in the peri-human microenvironment …”

Section: Resultsmentioning

confidence: 99%

“…6) alternated between the table and the sampling station every 30 min while staying in the chamber. This adjustment aimed to investigate the potential difference in ultrafine particle levels between the bulk air and the peri-human microenvironment (termed the “personal cloud effect” − ).…”

Section: Methodsmentioning

confidence: 99%

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Influence of Ventilation on Formation and Growth of 1–20 nm Particles via Ozone–Human Chemistry

Yang,

Müller,

Wang

et al. 2024

Environ. Sci. Technol.

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Ozone reaction with human surfaces is an important source of ultrafine particles indoors. However, 1−20 nm particles generated from ozone−human chemistry, which mark the first step of particle formation and growth, remain understudied. Ventilation and indoor air movement could have important implications for these processes. Therefore, in a controlled-climate chamber, we measured ultrafine particles initiated from ozone−human chemistry and their dependence on the air change rate (ACR, 0.5, 1.5, and 3 h −1 ) and operation of mixing fans (on and off). Concurrently, we measured volatile organic compounds (VOCs) and explored the correlation between particles and gas-phase products. At 25−30 ppb ozone levels, humans generated 0.2−7.7 × 10 12 of 1−3 nm, 0−7.2 × 10 12 of 3−10 nm, and 0−1.3 × 10 12 of 10−20 nm particles per person per hour depending on the ACR and mixing fan operation. Size-dependent particle growth and formation rates increased with higher ACR. The operation of mixing fans suppressed the particle formation and growth, owing to enhanced surface deposition of the newly formed particles and their precursors. Correlation analyses revealed complex interactions between the particles and VOCs initiated by ozone−human chemistry. The results imply that ventilation and indoor air movement may have a more significant influence on particle dynamics and fate relative to indoor chemistry.

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“…Moreover, we expect that NCAs generated from ozone–squalene reactions would be more pronouncedly distributed close to the reactive surface relative to the bulk air . This may imply that the NCA level can be higher in the peri-human microenvironment than in room air (the phenomenon termed “personal cloud” − ). Such a spatial variation of NCAs generated from ozone–squalene chemistry merits future examination.…”

Section: Resultsmentioning

confidence: 99%

Nanocluster Aerosols from Ozone–Human Chemistry Are Dominated by Squalene–Ozone Reactions

Yang,

Licina

2024

Environ. Sci. Technol. Lett.

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Nanocluster aerosols (NCAs, <3 nm particles) are associated with climate feedbacks and potentially with human health. Our recent study revealed NCA formation owing to the reaction of ozone with human surfaces. However, the underlying mechanisms driving NCA emissions remain unexplored. Squalene is the most abundant compound in human skin lipids that reacts with ozone, followed by unsaturated fatty acids. This study aims to examine the contribution of the squalene−ozone reaction to NCA formation and the influence of ozone and ammonia (NH 3 ) levels. In a climate-controlled chamber, we painted squalene and 6-hexadecenoic acid (C16:1n6) on glass plates to facilitate their reactions with ozone. The squalene−ozone reaction was further investigated at different ozone levels (15 and 90 ppb) and NH 3 levels (0 and 375 ppb). The results demonstrate that the ozonolysis of human skin lipid compounds contributes to NCA formation. With a typical squalene-C16:1n6 ratio found in human skin lipids (4:1), squalene generated 40 times more NCAs than did C16:1n6 and, thus, dominated NCA formation. More NCAs were generated with increased ozone levels, whereas increased NH 3 levels were associated with the stronger generation of larger NCAs but fewer of the smallest ones. This study experimentally confirms that NCAs are primarily formed from squalene−ozone reactions in ozone−human chemistry.

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Human personal air pollution clouds in a naturally ventilated office during the COVID-19 pandemic

Cited by 9 publications

References 97 publications

Physiology or Psychology: What Drives Human Emissions of Carbon Dioxide and Ammonia?

Physiology or Psychology: What Drives Human Emissions of Carbon Dioxide and Ammonia?

Influence of Ventilation on Formation and Growth of 1–20 nm Particles via Ozone–Human Chemistry

Nanocluster Aerosols from Ozone–Human Chemistry Are Dominated by Squalene–Ozone Reactions

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