Feature: A brief history of indoor air quality

Professor Paul Harrison explains how our understanding of indoor air quality has changed over time. 

The importance of good indoor air quality has been recognised since the mid-1800s, but it wasn’t until the 1970s that interest really peaked.

Specific interest in indoor air quality started in the Scandinavian countries, notably Denmark and Sweden, and soon spread to the US and to other European nations.

Initial topics of interest included radon, tobacco smoke, formaldehyde, volatile organic compounds, house dust mites and sick building syndrome (SBS) and then dampness and mould.

UK history

In the UK, significant attention to the issue of indoor air quality and its impact on health only began in earnest with the 1991 House of Commons Select Committee Enquiry on Indoor Pollution which acknowledged the importance of indoor air to the health and wellbeing of people at home and in offices.

The Committee concluded, amongst other things, that ‘there appears to be a worryingly large number of health problems which could be connected with indoor pollution and which affect very large numbers of the population’, and recommended that the Government should ‘develop guidelines and codes of practice for indoor air quality in buildings which specifically identify exposure limits for an extended list of pollutants….’

In response to this, in 1993, the then Department of the Environment (now Defra) published a booklet entitled ‘Good Air Quality in Your Home!’ (DOE, 1993).

The purpose of this was to inform interested individuals about common indoor air pollutants, including where they come from and how they can be tackled. Soon afterwards, the Department of the Environment established an interdepartmental group on indoor air quality and commissioned an in-depth review of the health effects of common indoor air pollutants, the results of which were published as a series of reports by the newly established MRC Institute for Environment and Health.

aerial view of city during daytime

At that time a cross-departmental initiative resulted in the establishment of a significant UK research programme on indoor and outdoor air pollution and an annual meeting to review its progress; this started in 1997 and still continues today.

In 2003, responding to the renewed domestic interest in indoor air quality, the UK Indoor Environments Group was established with the specific aim of co-ordinating and providing a focus for UK activity concerned with improving indoor environments for people.

International interest

In parallel with these activities, the European Collaborative Action on indoor air quality and its impact on man was established.

This was responsible for the publication of a large number of highly influential reports on indoor air pollutants and their effects on health. Later, the European Commission established its Expert Working Group on Indoor Air Quality to review progress and policy developments in this area.

At the same time, two major international conference programmes were running that encouraged the dissemination of research findings on indoor air quality: ‘Indoor Air’ and ‘Healthy Buildings’.

In addition, the European Commission has over the years funded a number of significant research, review and information dissemination programmes on indoor air quality, including ‘EnVIE’, ‘INDEX’ and ‘Healthy Air’.

The World Health Organisation has also played a significant role in the indoor air quality arena, publishing, in 1999, a book on ‘Strategic Approaches to Indoor Air Policy-Making’ and specific guidelines for a number of indoor air pollutants in 2010. WHO also made a very important contribution to the understanding of the global health relevance of IAQ when it published, in 2007, its report ‘Indoor air pollution: national burden of disease estimates’.

In this report WHO stated that, in 2000, indoor air pollution was responsible for more than 1.5 million deaths and 2.7% of the global burden of disease, mostly due to the use of solid fuels for cooking and heating.

The question of guideline values for indoor air pollutants has been addressed by a number of European countries, including especially Germany, Sweden and Norway; France is particularly active in this area having established its ‘Indoor Air Quality Observatory’ in 2001.


In the UK, in 2004, through its Committee on the Medical Effects of Air Pollutants (COMEAP), the Department of Health proposed guideline values for five key indoor pollutants: NO2, CO, formaldehyde, benzene and benzo(a)pyrene, and more recently, in 2019, Public Health England (now UKHSA) published its ‘guidelines for volatile organic compounds in indoor spaces’.

The importance of VOC emissions from building materials and consumer products has been widely recognised and has driven a number of national labelling schemes and also the establishment of a European committee to determine harmonized reference values for a large number of VOCs.

In recent years, in the UK, interest in the importance of indoor air quality for health has received a further significant boost by the publication of three highly influential documents: ‘Every breath we take: the lifelong impact of air pollution’ (RCP/RCPCH, 2016), ‘The inside story: health effects of indoor air quality on children and young people’ (RCPCH, 2020) and NICE guidance on indoor air quality at home (2020).

In addition, the Institute of Air Quality Management recently published a comprehensive Indoor Air Quality guidance document (IAQM, 2021) to assist qualified practitioners in the assessment of indoor air quality.

Also important at a policy level is the recent establishment in the UK of a Cross-Government Working Level Group on IAQ.

This aims to ensure a joined-up approach across government departments and other governmental bodies on IAQ.

Member organisations are the Department of Health and Social Care (DHSC, Chair and Secretariat), UK Health Security Agency (UKHSA, formerly PHE), Cabinet Office, Defra, Department for Levelling Up, Housing and Communities (DLUHC, formerly MHCLG), BEIS Office for Product Safety and Standards (OPSS), Department for Education (DfE), Ministry of Justice, NHS Test and Trace, Health and Safety Executive (HSE).

Group members aim to share knowledge and activities relevant to IAQ, with the objective of identifying any barriers to action and, potentially, ways to move beyond them, as well as potential opportunities for cooperation.

A wide range of indoor pollutants and pollutant sources have been identified as being of significance over the past few decades.

The most important from a health perspective are: asbestos and man-made mineral fibres; bacteria, mould spores and endotoxins; carbon monoxide (CO); halogenated organic compounds; dust mite, cockroach and pet allergens; Environmental Tobacco Smoke (ETS; also referred to as second-hand tobacco smoke); formaldehyde; lead (in paints); oxides of nitrogen (NOx); particles (PM10 and smaller); polycyclic aromatic hydrocarbons (PAHs); radon; and volatile organic compounds (VOCs), including fungal and bacterial metabolites. Newer concerns include flame retardants, phthalates and microplastics.

It is worth noting here that a major impediment, historically, to conducting large-scale studies on the effects of IAQ on health has been the very high cost and time-consuming nature of analysing and monitoring the concentration of indoor pollutants. Fortunately, the development of technologies such as IoT
and ultra-low power and low-cost sensors is now enabling this kind of research to be conducted more easily and cheaply.

by Prof. Paul Harrison, in association with Sensyqo.


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2 years ago

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