What is an AQI?
AQI is the abbreviation for Air Quality Index. As the name suggests, this is an indicator that allows you to assess the air quality as a whole with a single value.
How is an AQI constructed?
The purpose of an AQI is to show pollution levels in a way that allows us to quickly understand the impact exposure will have on our health.
Not all pollutants have the same effect on health at the same concentration. For example, benzene is carcinogenic from concentrations as low as 1 µg / m3, but ozone does not begin to have significant effects until 100 µg / m3!
An AQI brings together the concentration values (expressed in µg / m3) of all these different pollutants in relation to the impact they have on health. Thus, the higher the value of the AQI, the more polluted the air and the greater the health risk. On the other hand, a low AQI means fresh air and a low health impact.
Why are there so many different AQIs?
Most AQIs are linked to local laws and regulations. Because all countries and regions develop their policies and laws differently, a lot of AQIs are needed to measure air pollution and uphold the specific laws. To add to this, most countries’ AQIs are based on different thresholds, with different pollutants taken into account, different calculation methods, and a different number of categories. There is a European AQI, a Chinese AQI, a Canadian AQI, one for the United States, and more… It's not easy to find your way around if you want to compare pollution on a global scale!
The Plume Air Quality Index
At Plume Labs, we have carefully studied the various AQIs. We observed two things. The first was that none of these AQIs were based on commonly accepted health impact thresholds, and the second none of the AQI thresholds had any concrete meaning for individuals.
To address these issues, we built our own: the Plume Air Quality Index. The Plume AQI has seven levels of pollution, or thresholds. These thresholds are linked to the exposure limits outlined by the World Health Organisation. Each category represents the amount of time it is safe to spend in that level of pollution. For example: one year (PAQI < 20), one day (PAQI <50), one hour (PAQI <100).
In practice, this means that if an individual’s average daily exposure exceeds 50 Plume AQI, they may start to experience negative health impacts.
The seven levels of pollution are:
The overall Plume AQI is determined by whatever pollutant is measuring the highest. For example: if you have readings of 10 VOCs, 25 PM2.5, 30 PM10, and 50 NO2, the overall Plume AQI will be 50.