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The invisible killer – The science behind air quality, productivity and health in the workplace

When prioritising where you should invest time and money into your workplace it can be a difficult balancing act. When you have stakeholders who value different things and targets to meet independently of that, it may feel as if you can’t please everyone.

However, our latest research suggests that indoor air quality (IAQ) could hold the key to unlocking a number of challenges found in the workplace by decision makers. Good indoor air quality is proven to improve productivity, wellbeing and health, be listed as the highest priority for employees when it comes to office features and could even help bring employees back to the office and keep them motivated in their role.

With all this in mind we’ve put together a guide on the science behind air quality, productivity and health to help you better understand its impact on the workplace.

What are the causes of air pollution?

When air pollution is discussed, the conversation usually focuses on man-made sources, but there are various pollutants that can be attributed to the natural environment. This includes sources such as smoke from wildfires, ash from volcanoes, dust from sandstorms and salt from sea spray. Most air pollution, however, is anthropogenic – meaning that it is caused by human activity. 

Fossil fuels

The combustion of fossil fuels – coal, crude oil, and natural gas – is one of the main sources of air pollution. In fact, these fuels begin polluting our air long before they’re even burned when they are mined, transported and processed. When burned to produce energy for electricity and transportation, fossil fuels emit a number of air pollutants, including carbon monoxide, carbon dioxide, sulphur dioxide and particulate matter. 


The use of pesticides and fertilisers to grow mass-produced crops emit pollutants, such as ammonia and nitrous oxide, into the surrounding air. Other significant contributors to poor air quality include animal waste and the entire livestock production process, including the raw materials, fossil fuels and deforestation involved. 


Transport is one of the main sources of air pollution, contributing to over half of all nitrous oxide emissions globally. Traffic-related air pollution (TRAP) is one of the biggest offenders in this category, particularly in urban areas. Another major offender is the aviation sector – if it were a country, it would be the sixth largest producer of greenhouse gas emissions.

Waste disposal 

Improper disposal of waste can be a significant source of air pollution, as dangerous chemicals are released into the surrounding air. Burning the waste of four of the biggest contributors to plastic pollution – CocaCola, PepsiCo, Unilever and Nestlé – generates a staggering 4.6 million tonnes of carbon dioxide annually. 

Indoor sources

Pollutants are often generated and accumulate indoors, causing poor indoor air quality in our homes, offices, and public spaces. 

Sources include: 

  • Chemicals from cleaning products, varnishes, air fresheners, candles
  • Mould 
  • CO2 from building occupants
  • Tobacco smoke
  • Dust and animal dander
  • Asbestos in building materials
  • Dust mites
  • Gases and PM2.5 from cooking

Environmental factors include: 

  • Inadequate temperature
  • High or low humidity
  • Insufficient ventilation

What are the effects of air pollution? 

Air pollution can affect anyone, at any stage of their life, causing a wide and complex range of health issues. In some cases, damage can be gradual and may not become apparent for many years.

Short-term effects include: 

  • Respiratory illnesses like pneumonia and bronchitis
  • Irritation of nasal passages, airways, eyes and skin
  • Headaches, dizziness and nausea 
  • Coughing, sneezing and shortness of breath
  • Exacerbation of asthma

Long-term effects include: 

  • Strokes 
  • Cardiovascular disease 
  • Respiratory disease 
  • Lung cancer 
  • Reduced life expectancy 

Air pollution is a complex topic that is still being widely researched. Emerging evidence suggests that air pollution may have links to cognitive function, causing premature decline, dementia, and mental health issues in children.

What are the main pollutants?

Many particles and gases, both natural and man-made, contribute to air pollution. Exposure to different pollutants vary in terms of severity of health and environmental effects, but long-term exposure to any of the key pollutants can cause significant health implications, and can sometimes even be fatal. The World Health Organization (WHO) recently published updated air quality guidelines relating to the key air pollutants, which governments can work towards to improve the quality of our air.

Particulate Matter

The term particulate matter (PM) describes a mixture of solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, or smoke, are large or dark enough to be seen with the naked eye. Others are so small they can only be detected using an electron microscope.

Carbon Dioxide

Carbon dioxide (CO2) is a naturally occurring, colourless, odourless gas that makes up 0.04% (400ppm) of the air we breathe. Human and animal respiration and combustion are the main sources of indoor CO2, which means concentrations are significantly higher indoors than outdoors.

Total Volatile Organic Compounds

Volatile Organic Compounds (VOCs) are compounds that can become gases or vapours: Total Volatile Organic Compounds (TVOCs) is the collective term referring to a group of common VOCs. Examples include acetone, benzene and formaldehyde, and they are often emitted from construction and furnishing products.

Nitrogen dioxide 

Nitrogen dioxide (NO2) is a highly reactive gas that is produced alongside nitric oxide (NO): together they are known as nitrogen oxides or oxides of nitrogen (NOx). NO2 is caused by combustion, primarily the combustion of fuels. The main source of these emissions comes from road vehicles, but other significant sources include power plants, industrial processes and central heating.

Ground-level ozone

Ozone (O3) is a gas found in the Earth’s upper atmosphere and at ground level. Stratospheric ozone, a naturally occurring gas in the upper atmosphere, is not harmful and protects us from ultraviolet rays. At ground level, tropospheric ozone is created by chemical reactions between nitrogen oxides and VOCs – this type of ozone is a harmful pollutant.

Carbon monoxide 

Carbon monoxide (CO) is an invisible, odourless and tasteless gas. It is produced when fuels like gas, oil and coal burn without sufficient oxygen: main sources are vehicle emissions, industrial activities and cigarette smoke. There are also some natural sources of CO, including volcanoes and wildfires.


Radon (Rn) is a naturally occurring, radioactive gas that is invisible, odourless and tasteless. It is formed by the radioactive decay of the small amounts of uranium that occur naturally in rocks and soils. Once formed, it can enter buildings through cracks in walls, doors and windows.


Lead (Pb) is a naturally occurring element which can be found in the Earth’s crust. While it has some industrial uses, it has been acknowledged as a dangerous substance for decades, and can cause extreme damage to our health. Key sources of lead in the air include ore and metal processing, lead-acid battery production and piston-engine aircraft fuel. It was also commonly found in petrol for road vehicles, until it was widely banned two decades ago.

Sulphur dioxide 

Sulphur dioxide (SO2) is a colourless gas with a strong smell, which is produced when fuels containing sulphur, such as coal and oil, are burned. Sources of this include vehicle use, heating, and cement manufacturing; it also causes secondary air pollution by contributing to the formation of ozone, and producing sulphates through chemical reactions, which contribute to PM.

Relation to indoor and outdoor air quality

When people think about poor air quality, they tend to focus on outdoor air pollutants such as car exhausts or factory fumes, and if indoor air quality is discussed, it is usually treated as a separate issue. However, the two are very much linked, and a great deal of our exposure to air pollution actually occurs when we are inside. 

  • We spend more than 90% of our time indoors (U.S. Environmental Protection Agency, 1989)
  • Indoor concentrations of pollutants are often two to five times higher than typical outdoor concentrations (U.S. Environmental Protection Agency, 1987) 
  • The combined effects of ambient air pollution (pollution in your immediate surroundings) and household air pollution are associated with 6.7 million premature deaths annually. (World Health Organisation, 2022)

Concentrations of outdoor pollutants rise and fall constantly because of changes in weather, climate, and human activity. For example, outdoor pollutants can build up in the lower atmosphere as a result of temperature inversions. During periods of cold weather, warm air rises into the upper atmosphere and traps cold air beneath it, causing pollutants to build up at low altitudes. 

Concentrations can also rise quickly in the mornings during rush hour traffic, but subside once traffic diminishes and wind and heat clear the air of excess pollutants. The Earth essentially has its very own natural air-purifying technology that spreads outdoor pollutants far and wide.

Unfortunately for humans, indoor pollutants are not always exposed to any similar processes to reduce their concentrations. Ventilation brings in outdoor air, often referred to as ‘fresh air,’ to dilute indoor contaminants, but this can inadvertently introduce even more pollutants to the inside environment.

Outdoor air pollutants can also infiltrate indoor air in ways that may not be immediately obvious: through open windows and doors, and cracks in walls, doors and window sealants. And to make matters worse, there are also many indoor sources that create more pollution, including everyday items like carpets, furniture and cleaning products.

Due to the fact we are indoors so much, prolonged exposure to indoor air pollution at any level can result in significant long-term health impacts. It is abundantly clear that steps need to be taken to increase awareness of the threats which are presented by indoor air pollution. 

What needs to be done to improve air quality? 

Air pollution might be the largest environmental public health threat on the planet, but thankfully, it is one that we can solve if we take action immediately. We need to improve education about the dangers of air pollution, while demanding greater transparency when it comes to gaining access to air quality data. 

Other important steps include:

  • Reducing energy consumption and burning less coal
  • Lessening the impact of the transport industry
  • Setting clearer, stricter and more ambitious standards
  • Taking action within communities to find innovative solutions
  • Enshrining the improvement of air quality in legislation 

In order to improve air quality and tackle global warming, change needs to happen on a national and global scale. But actions at the individual and community level are also important – we can work together to create a healthier planet for us and generations to come.

Impact of air quality on health

The various harmful gases and particles that pollute our air, such as sulphur dioxide, carbon monoxide and total volatile organic compounds (TVOCs), can have serious effects on our health. 

These pollutants impact our bodies in many ways, affecting key systems and organs. Many people naturally assume that the damage from air pollution is limited to the respiratory system, but research shows harm goes far beyond this, causing heart disease, different types of cancers, and impacting pregnancy and foetal development. Awareness of these health impacts is certainly growing – in this year’s survey commissioned by AirRated, 73% of respondents agreed with the statement: ‘I understand how indoor air quality impacts my health.’ 

Emerging evidence also shows links between air pollution and cerebral function, with scientists investigating links with increased risk of severe mental illness and development of dementia.

While COVID-19 has dominated the news for the past three years, and nearly 7 million people have now lost their lives as a result (as of February 2023), the deadly health impacts of air pollution rarely make front page headlines – despite the yearly death toll being treble those caused by COVID-19.

Health effects of air pollution

The heart and circulatory system 

There’s abundant research showing that air pollution impedes cardiovascular function (National Center for Biotechnology Information, 2018). Toxic air has a significant and wide-reaching impact on the circulatory system and heart; according to the World Health Organization (WHO), over 20% of cardiovascular deaths are attributed to exposure to polluted air (World Heart Federation, 2019). The majority of premature deaths linked to outdoor air pollution are from heart disease and stroke. 

Charities like the British Heart Foundation are also conducting ongoing research into the damage that toxic air causes to the heart. This happens when blood vessels become restricted, causing them to be narrower and harder, and blood pressure rises – all of which strain the heart. Pollutants can also increase the likelihood of blood clots and cause abnormal heart rhythm. This increases the risk of heart attack and stroke among those with existing heart conditions, and can also cause completely new heart issues to develop.

Lung function 

The effects of air pollution on the lung is perhaps the most widely discussed health impact of exposure to poor air quality. Research shows that long-term exposure to air pollution can hinder proper lung development in children, while toxic air is equally harmful to older members of the population too (King’s College London, 2018).

Lung health declines steadily as we age, and inhaling air pollutants only serves to compound this deterioration. Long-term exposure to pollutants such as particulate matter, ground-level ozone and radon has been linked to the development of lung disease in later life, and can even directly cause lung cancer. A US study of over 7,000 participants between the ages of 45 and 84 years, found a direct connection between exposure to ambient air pollutants, and increasing emphysema and worsening lung function (Jama Network, 2019).


Asthma is a lifelong condition that affects the airways of the lungs, and manifests itself through coughing, wheezing and shortness of breath. The symptoms are usually manageable and not too disruptive, but asthma attacks can be triggered by allergies or high levels of pollution, and can potentially be fatal.

According to Asthma UK, two thirds of asthma sufferers report the condition being worsened by poor air quality, which is a result of the airways being narrowed, and particulate matter being inhaled directly into the lungs.

In April 2021, scientists conducting a study at Lehigh University in Pennsylvania identified a severe type of asthma and concluded that it’s likely induced by early childhood exposure to by products of burning fossil fuels. This is the first study of its kind to demonstrate air pollution as a direct cause of non-Th2, the most challenging type of asthma to control.


Following a China-based study, the International Agency for Research on Cancer (IARC), classified air pollution and particulate matter as carcinogens (Chinese Journal of Cancer, 2014). This means that these pollutants are direct causes of cancer in humans. The most common type of cancer associated with poor air quality is lung cancer, with risk levels being higher in built-up areas. However, a recent study carried out in Hong Kong suggests that PM2.5 could be linked to breast, liver and pancreatic cancers (Cancer Epidemiol, Biomarkers and Prevention, 2016).

IAQ in the workplace

Sick Building Syndrome: How IAQ in the workplace is making us sick

From the 1960s, many occupants of newly built homes, nurseries and offices, started to report nonspecific symptoms associated with the time they spent inside a building. 

Complaints became so prolific that a decade later the mainstream media coined the term ‘office illness.’ By 1986, WHO research estimated that 10-30% of newly built offices in the west had indoor air problems, and ‘sick building syndrome’ was formally identified. Respected organisations such as the Health and Safety Executive (HSE) have carried out extensive research on SBS, finding that poor indoor air quality is a major contributor. 

The reason is that post-war buildings were built as airtight, centrally-heated structures, with no consideration for airflow or ventilation. Indoor air quality was simply not understood as a threat to human health. 

Symptoms of SBS:

  • Lung inflammation (pneumonitis) 
  • Tightness of the chest
  • Difficulty breathing
  • Allergy-type symptoms
  • Itchy eyes
  • Irritated airways
  • Coughs and runny noses
  • Fatigue
  • Headaches
  • Difficulty concentrating
  • Body aches
  • Fever
  • Chill

People with preexisting respiratory or allergy problems will usually have more severe symptoms; for example, asthma sufferers may have more asthma attacks, or more serious asthma attacks and people prone to headaches may experience them more frequently or to a greater degree.

SBS and workforce effects: absenteeism and presenteeism

While SBS describes acute health and comfort symptoms linked to time spent inside a building, its effects trigger two types of behavioural changes within a workforce. 

Absenteeism is the term used to describe an employee being away from work for more than is reasonable or usual; presenteeism describes being present at work, but performing at low levels due to feeling unwell.

We spend around a third of our lives in the office, or roughly 90,000 hours over an average lifetime. Academic studies have found presenteeism costs the UK economy around £4k per employee a year, as unwell people were seen to perform at only 84% of full capacity. A 2020 UK survey found that absenteeism and presenteeism combined cost the economy almost £92 billion in 2019, with productivity on the decline. 

And then there’s been the pandemic, which has driven a massive trend for hybrid working patterns. This, alongside a rise in time off due to mental health issues – now the biggest reason for long-term absence – means that offices need to be places that people want to return to. Employment itself has been shown to be vital for mental health while well-designed environments are regularly acknowledged for improving and protecting mental wellbeing.

How a healthy building leads to a healthy business

Workforce productivity: the COGfx Global Buildings study

Professor Joseph Allen, one of the leading experts on healthy buildings, determined absolutely that good indoor air quality increases occupant productivity and wellbeing.

“Just like we’ve made great gains in public health around sanitation, water quality, and food safety, indoor air quality is going to be part of that conversation moving forward.”

– Professor Joseph Allen,

Conducted by Harvard T.H. Chan School of Public Health, the three-year COGfx Global Buildings study culminated in 2017, by comparing human performance and wellbeing across 100 offices around the world.

During ‘Study 1: Indoor Environmental Quality’ – a year-long global experiment – Allen’s team placed sensors at workers’ desks, and handed them a custom-made phone app that delivered brief cognitive function tests throughout the day. Volunteers also took a short survey asking if they suffered headaches, dizziness or had trouble sleeping each day.

“When volunteers worked in well-ventilated conditions (which lowered the levels of CO2 and VOCs), they scored 61% higher than when they worked in typical office building conditions” says Professor Allen. “When they worked in the cleanest conditions, with even lower CO2 levels and higher ventilation rates, their scores climbed 101%”

Study 2: Buildingonomics: The Impact of Working in a Green Certified Building on Cognitive Function and Health, found that green-certified buildings increased occupant cognition by 26% and health and wellbeing overall, compared to non green-certified buildings. 

For Study 3: Global Buildings, the effects of PM2.5 and CO2 , the team assessed 302 employees in urban office buildings in six countries (China, India, Mexico, Thailand, the United States of America, and the United Kingdom). The study took a year and concluded that for every decrease in the levels of exposure through ventilation and filtration, there is an equal increase in cognitive function.

“The results showed the biggest improvements in areas that tested how workers used information to make strategic decisions and how they plan, stay prepared, and strategise during crises.”

– Joseph G. Allen, The Harvard Business Review.

Ultimately, results showed occupants’ cognitive function test scores doubled in good indoor air environments. The cost of running better ventilation systems to heighten employee performance came in at $14–40 per person per year, while the estimated ROI (in improved productivity in faster response times and increased accuracy), was measured at between $6,500 and $7,500 per person per year. Not only that, senior managers made better decisions when in healthier air environments.

More recently, in Allen’s 2020 book Healthy Buildings: How Indoor Spaces Drive Performance and Productivity (co-written with Harvard Business School lecturer John D. Macomber), Allen outlines the bottom-line gains of healthy air, citing research that estimates improved air quality could add $20 billion annually to the US economy.

Looking for support?

If you’re considering what you can do about your indoor air quality, or not sure whether it’s worth putting focus into IAQ, you can book a free ‘no-obligation’ consultation with one of our workplace consultants by leaving your details below.