Zhou, Jiaxu; (2025) Effects of Short-term Exposure to Indoor PM2.5 on Cognitive Performance in Working Age Adults and Implications for Office Buildings. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

BACKGROUND: Fine particulate matter (PM2.5) air pollution is one of the top global risk factors for human health, with some evidence suggesting that long term exposure is associated with potential impacts on nervous system, cognition, and productivity. Little is known about short-term indoor PM2.5 exposure in the workplace and its contribution to these effects. This doctoral thesis aimed to address scientific questions about the impacts of short-term indoor PM2.5 exposure on adults’ cognition, physiological responses, perceived environmental satisfaction, and productivity, and to appraise possible pathways. METHODS: The doctoral research combined two highly complementary studies including a real-world intervention trial in an office building in China (N=60) and a lab-based study in an environmentally controlled chamber in the UK (N=90). Both studies had a control and an intervention condition (via air purifiers), adopting a randomized, single-blind, crossover design. During both conditions, cognitive performance over a wide range of cognitive domains was assessed via a validated neurological test battery supplemented with physiological monitoring (i.e., electrodermal activity, EDA; and heart rate variability, HRV), while subjective assessments of environmental satisfaction and productivity were collected via questionnaire surveys. RESULTS: Elevated indoor PM2.5 levels were found to adversely impact some cognitive domains, particularly memory and attention, but not all aspects of cognitive function. Lower PM2.5 levels were associated with higher HRV indices during cognitive testing, indicating better autonomic nervous system function and greater stress resilience. No significant effects were observed in EDA measures across varying PM2.5 conditions. Mediation analysis showed that elevated PM2.5 exposure decreased HRV Indices, which in turn had a mediating effect on some cognitive skills. Subjective survey outcomes showed that lower PM2.5 levels were associated with higher indoor environmental satisfaction and higher perceived productivity. Mediation effects were observed, with elevated indoor PM2.5 exposure decreasing perceived indoor air quality and satisfaction, which in turn decreased self-reported productivity. CONCLUSIONS: Overall, the doctoral work contributes to a growing body of evidence demonstrating the potential harms of short-term PM2.5 exposure in indoor environments. Consequently, improving air quality by reducing fine PM pollution could mitigate not only adverse physical health outcomes, such as morbidity and mortality, but also broader impacts on cognitive performance and productivity. The research offers comprehensive insights into how indoor PM2.5 affects human cognition and health, underpinning the importance of maintaining low PM2.5 levels in indoor environments. This research not only advances scientific understanding but also has significant implications for building design, public health policy, and workplace management, ultimately contributing to build better and healthier environments. Further research is needed to elucidate a fuller picture of the mechanisms involved in the cognitive and brain effects of PM2.5 by expanding the diversity of physiological markers and neuroimaging techniques, while broadening the demographics of participants, conducting comparative indoor and outdoor PM2.5 toxicity studies, and using interdisciplinary approaches to determine dose-response relationships and develop holistic strategies for a healthy and sustainable world.

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