Indoor air pollution

A book review by Valerio Ferracci
National Physical Laboratory
[email protected]
ECG Bulletin July 2024

People in developed countries spend approximately 90% of their time indoors, however, indoor air pollution is often overlooked relative to outdoor air quality. This book[1] provides a comprehensive exploration of this issue.

While most air quality management policies focus on outdoor pollution, there is a growing recognition of the importance of indoor air quality. The issue has become all the more relevant following the COVID-19 pandemic, which highlighted the role of indoor environments in virus transmission, and when addressing the energy efficiency of buildings, ensuring insulation and air tightness are accompanied by efficient ventilation.[2] As people spend most of their time indoors, indoor environments contribute disproportionately to personal exposure, which is why it is important to understand the processes affecting indoor air quality.

The book highlights the major challenges in studying indoor air: the heterogeneity of indoor environments, each accompanied by different sources of pollutants; and the difficulties (logistical and financial) of performing measurements using complex instrumentation in representative indoor environments.
​The initial chapter focuses on indoor pollutants in homes, offices, and schools, as well as in other microenvironments such as restaurants, hair salons, and fitness centres. Each section offers insights into the diverse sources and impacts of indoor pollution. The following chapter focuses on outdoor air as a source of indoor pollution, and discusses how species such as nitrogen dioxide, ozone and particulate matter can infiltrate from the outdoors. The roles of ventilation, filtration and building air-tightness are also explored. Conversely, the opposite process can also occur, and a subsequent chapter explores indoor emissions as sources of outdoor pollution, considering in particular, halogenated compounds, typically used as flame retardants and stainproofing additives, and how they can bioaccumulate in outdoor environments.

A chapter authored by Nicola Carslaw (a speaker at the RSC/IOP Indoor Air event[3]) examines the gas- and mixed-phase chemistry occurring in indoor environments. Photolysis tends to be less important due to lower light levels, but interactions with surfaces become more important. Chemical reactions between ozone (infiltrated from outdoors) and terpenes (from cleaning and personal care products) can lead to the formation of a variety of products, some of them harmful to health

An account of bioaerosols in indoor environments follows, made all the more relevant since the COVID-19 pandemic (note the book was published in 2019, prior to the first UK national lockdown). A thorough account on the methods used to monitor bioaerosols, and the challenges associated with them, is provided.

Lastly, the book delves into the impact of indoor air on pollution exposure and health. The negative health effects of indoor pollutants (e.g. asthma exacerbation, as well as decreased cognitive performance) are illustrated, along with recommendations on how to reduce exposure by limiting ingress of outdoor pollution and reducing indoor sources.

Overall, the volume offers a comprehensive insight into the scientific aspects and implications of indoor air pollution, serving as a valuable resource for researchers, students, consultants, and policymakers in understanding and addressing this important issue.
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References
1. Indoor Air Pollution (Issues in Environmental Science and Technology Volume 48), ed. R. M. Harrison and R. E. Hester, Royal Society of Chemistry, Cambridge, 2019. ISBN 978-1-78801-514-1.
2. ECG Bulletin, pp. 20-21, January 2022.
3. ECG Bulletin, pp. 10-11, January 2020.