The Air Quality Index (AQI) is a number used mostly by government agencies to indicate the level of pollution to the general public. The AQI is also sometimes referred to as Air Pollution Index (API) or Air Quality Health Index (AQHI). As the AQI increases, it can have adverse health effects on a growing percentage of the population, depending on how worse the air quality gets. Most countries have their own way to calculate an AQI, mainly driven by national air quality standards. What you do see in common however is that they divide the AQI measured into ranges and color and label them so it’s easy for people to understand how much risk they run:
Now how does an AQI get calculated? Well, first of all you need to measure the levels of certain gasses as well as the level of particulates in the air over a certain period. The most common components that get measured and which are used to calculate an AQI are:
- Ozone (O3): Ground level Ozone is not directly emitted by something, but is created by sunlight acting on NOx (Nitrogen Oxides) and VOC (Volatile Organic Compound) that exists in the air. Ozone is the primary component of smog and it can cause all kind of respiratory problems, even for instance for healthy people if they exercise under such conditions.
- Sulfur Dioxide (SO2): SO2 is mainly formed by emissions from fossil fuels used by power plants and other industries, but also from large ships. If you breathe in SO2, it can irritate the nose, throat, and airways and creates a risk for people with respiratory problems.
- Carbon Monoxide (CO): CO is emitted by combustion processes, when there is not enough oxygen for complete combustion. Concentrations of CO are mainly high in areas with large concentrations of cars, trucks etc. CO can cause reduction to the oxygen delivery to the body’s organs like the heart and brain. In large concentrations it can even cause dead.
- Nitrogen Dioxide (NO2): NO2 is mainly formed by emissions from cars, buses, trucks, power plants etc., anything that burns fossil fuels. It contributes to respiratory problems as well as the buildup of smog, which both can seriously impact the human health.
- Particulate Matter PM10: Also referred to as Dust Particles, has a size between 2.5 to 10 micrometer. These particles can be caused by grinding operations, dust stirred up by vehicles etc. Particle pollution can contribute to a broad range of health problems.
- Particulate Matter PM2.5: Also referred to as Fine Particles, has a size of 2.5 micrometer or less. These particles can be caused by combustion processes, but also forest fires. Particle pollution can contribute to a broad range of health problems. These Fine Particles are more dangerous then Dust Particles as they are small enough to enter the blood vessels via the lungs.
To get the measurements for an AQI based on the above mentioned elements, governments often use large and expensive monitoring stations. Due to the cost it’s clear you can only have so many per city. It’s nice if you live close to one as then you have a good indication how healthy your living environment is. Wouldn’t it be nice however if there would be a way to increase the number of measuring stations by providing something smaller and more affordable, so that every community, street could have it’s own station and provide data to indicate to the neighborhood how safe it is, that’s what our next blog post will be about.