Most people will recognize the phenomenon: When sitting for a longer time in an enclosed space together with many others, the air “gets bad”. But what does that mean – for which functions of our body? And why? And are other things going on in the air we breathe? And what is “good enough”? The investigation presented on this website explores two particular elements of these questions:
- Oxygen and CO2
- Particulate Matter (PM) in two forms – PM2.5 and PM10
Oxygen and CO2:
The ideal air to breathe should contain between 19.5% and 23.5% Oxygen. However, as we inhale Oxygen, we exhale Carbon dioxide (CO2) – and when in an enclosed room without refreshing the air and replenishing the oxygen entailed in it, the oxygen concentration will fall simply due to the presence of people breathing – while the CO2 concentration will rise. Too much CO2 in the air, however, can compromise our health – typically showing up as headaches, dizziness, tiredness or through other, more severe symptoms that emerge as CO2 levels rise (see further below some more detail).
What is normal – and what is too much? Normal outdoor CO2 concentration is in the range of 250-400 ppm; between 400 and 1000 ppm can be found in enclosed spaces that have good air exchange (ppm means “parts per million” and measures the mass of a chemical) . Upwards of 1000ppm, people begin complaining about drowsiness, and beyond 2000 ppm poor concentration and loss of attention begin. The accepted standard for classrooms is 1000 ppm, something measured usually only when the rooms are empty; while countries vary in whether or not they set standards formally, Austria – where Vienna International Schools is located – has building legislation that defines 1000 ppm as the maximum concentration, noting that 1,400ppm should definitely not be exceeded. Often, however, these standards seem to be exceeded – e.g. a study in classrooms in California found concentration levels of up to 2200.
Particulate Matter (PM):
Particulate Matters (PMs) are a mix of many things that circulate in the air we breathe – emitted from various sources such as construction, roads or fields, or also as a result of chemical reactions. PMs may be solid or droplets that would be liquid, including things such as dust, dirt or smoke. Based on their size, PMs are classified as:
- PM10 – such particulate matters can be inhaled since they are less than 10 micrometers in diameter; 10 micrometers are about as large as a single cotton thread;
- PM2.5 – such particulate matters can be inhaled even more easily since they are by a fourth smaller than PM10 particles in diameter.
Most of us will never know that we are surrounded by either PM10 and PM2.5; just to get a sense – 100 micrometers are the equivalent of 0.1 millimeters and commonly thought to be the smallest unit that can still be seen with the naked eye. The World Health Organisation (WHO) has issued Guidelines for Indoor Air Quality that also cover Particulate Matters; these Guidelines state that safe levels of PM10 are at under 20 micrograms per cubic meter (a more conservative standard than the EU’s standard which defines safe Indoor Air Quality at under 40 micrograms per cubic meter); for PM2.5, the WHO guidelines set the standard for safe levels at 10 micrograms per cubic meter.
What does Air Quality mean for our Cognitive Functions?
Multiple studies have confirmed the negative relationship between our ability to think and take on cognitive tasks and either CO2 concentration or various PM concentration.
The relationship between CO2 concentration in the air and our cognitive functions has been studied for quite some time, often with a particular focus on school buildings and classrooms.
CO2 at higher concentration levels has been shown to limit the brain’s ability to focus and to process information. For example, a study of schoolchildren’s educational attainment in Scotland found an inverse relationship between CO2 concentration in classrooms and children’s educational progress. High CO2 concentration in air also has other negative health effects, for example increasing the risk of flue transmission between students.
The relationship between PMs and the brain’s functioning has been studied mostly only over the past five to 10 years. A large study undertaken recently in China found that long-term PM exposure can compromise someone’s abilty to reason, to write and solve math problems. – but looked mostly to older grown-ups and years of exposure. Even if indoor air quality in terms of PM concentration has not been examined exhaustively, many studies have confirmed that even short-term exposure can lead to cognitive decline.
Indoor Air Quality 