The AQI is an "index" determined by calculating the degree of pollution in the city or at the monitoring point and includes five main pollutants - particulate matter (see SIM-10-2008), ground-level ozone, sulfur dioxide, carbon monoxide and nitrogen dioxide. Each of these pollutants have an air quality standard which is used to calculate the overall AQI for the city. Simultaneously, one can also establish the limiting pollutant(s), resulting in the estimating AQI.
In numbers, AQI is represented between 0 to 500 with 0 representing good air and 500 representing hazardous air. For better understanding and presentation, the AQI is broken down into six categories, each color coded with the number scale.
- Good (green) is for numbers 0 through 50 and means satisfactory air quality
- Moderate (yellow) is 51-100 and is for acceptable air quality
- Unhealthy for Sensitive Groups (tan) is 101-150 and means sensitive individuals with sensitive skin may be affected
- Unhealthy (red) is 151-200 and almost everyone may experience problems.
- Very unhealthy (pink) 210-300 is a health alert, where everyone may have health problems
- Hazardous (purple) over 300 numbers may contribute to emergency health problems and will affect most people
Establishing this number in a forecast mode is not an easy exercise, as it involves modeling of emissions, dispersion of the pollutants depending on local meteorology and terrain, and presentation. However, a number of platforms (and groups) are established and in use, for the readers to choose and learn (and apply). We conducted a workshop on this topic in collaboration with WMO and IITM, in India and hope you will benefit from the material.
For dissemination, options are limitless and there are innovative ways to present the information to public and media - via balloons (in Paris), via websites (links below), via photo journals (in Beijing), via digital exhibition (in Madrid) and lasers (in Helsinki).
