Air Pollution and Health
Good indoor air quality, good lighting and noise levels ensure school environments are a good place to work and learn. This page contains information about the links between some of the metrics measured by the SAMHE monitor and health.
CO2 and attention levels
High carbon dioxide (CO2) levels in rooms have been linked with increased drowsiness and headaches, which can mean it is harder to learn. We have all had the experience of feeling sleepy in a room that feels "stuffy"; this could be our bodies telling us that CO2 levels might be high.
High CO2 levels are also known to impact how well people's brains work. One study on adults found that increasing CO2 levels from around 600 ppm to 1400 ppm reduced test scores by 50%. High CO2 levels are also linked with increased absences from school, so avoiding high CO2 levels can help improve attendance.
However, CO2 itself is not a dangerous gas. High CO2 levels is an indicator of poor ventilation, which can cause issues with damp and mould and spreading of respiratory illnesses. For more information about ventilation, please take a look at our ventilation guidance for schools. The World Ventil8 Day Website and National Engineering Policy Centre pages also give useful insight into the importance of ventilation. Carbon dioxide should certainly not be confused with Carbon monoxide (CO), since Carbon monoxide is a dangerous gas.
CO2 levels and airborne infection risk
The main source of carbon dioxide (CO2) in most classrooms is the CO2 coming from peoples' exhaled breath. In the absence of combustion or other CO2 sources, CO2 is a good measure of the proportion of air within a classroom that has already been breathed out by someone else: this is called 'rebreathed air'.
When someone has a respiratory infection, like SARS-CoV-2 for COVID-19 or the influenza virus for the flu, they will exhale small virus particles that can be transported by air currents and mixed with the air in the room. If these particles are then breathed in by someone else, this could potentially lead to that person becoming infected by the virus: infection via this transmission route is called 'airborne infection'.
If the concentration of CO2 within a room is high, this indicates low ventilation per occupant, that is, the air within the room is not being renewed very much and the proportion of rebreathed air is larger than it would be in a better ventilated room.
If someone within the room happens to be infected with a respiratory virus, this means that (all else being equal) there is then a larger chance that the air within the room might contain infected particles that could infect someone else. CO2 concentration is only a partial indicator for airborne infection risk, it does not indicate the risk for other transmission routes by which someone might become infected with a respiratory virus; for example, transmission via close contact with someone who is carrying the virus.
Other air quality metrics and health
Outdoor air pollution is a major health issue, according to the World Health Organisation. Poor quality air indoors can also cause ill health, and is important as most people in the UK spend the majority of their time indoors. Health issues arising from poor air quality can be chronic (developing gradually after breathing in poor air over long periods, often many years), or acute (developing quickly due to exposure to high levels of a specific pollutant). Asthma is a chronic condition with acute episodes (asthma attacks) which can be triggered by exposure to high spikes in air pollution. Other immediate effects of exposure to pollutants can include irritated eyes, nose or throat, headaches and dizziness. Removing the source, taking the affected person away from the source, and/or ventilating the room, are usually appropriate solutions.
Relative humidity can be another important factor. For example, if humidity is frequently high (over 65%), it can create a breeding ground for dust mites and mould, which are common allergens, can exacerbate asthma, and can result in other health conditions.
Volatile Organic Compounds are emitted from many different sources, both indoor and outdoor, including paints, cleaning products, air fresheners, spray deodorants, and cooking. There are many different VOCs, some with known health effects, and some with unknown health effects.
More research is needed about the effects of VOCs and other indoor air pollutants on health, as there is uncertainty around what levels of pollutant or periods of exposure cause specific health conditions. The Inside Story report reviewed the existing evidence and gives more information about the health effects of indoor air quality on children and young people.
More information
For worksheets about indoor air pollution and health, aimed at primary-school children, see the Inside Story resources page.