Note: On Januray 8th 2016, the AQI scale used on the World Air Quality Index project for all stations in India has been updated to better align with the US EPA Standard (This does not apply the DPCC Stations in New Delhi which were already using the standard US EPA Standard).
From the article below, you can understand how to convertion from the NAQI (India National Air Quality Index) to the US EPA AQI is done.
(Tiranga, तिरंगा)
The Indian Central Pollution Control Board has recently announced, in April 2015, the publication of India's National Air Quality Index Standard (NAQI ). All the details on this standard are available from CPCB, wikipedia or from this report from Indian Institute of Technology, Kanpur (iitk.ac.in).
This is actually a very important step forward in the Air Quality world awarness, since the air pollution in each country is very much specific to the country pollution type: For instance because of Dust (in Arabic Peninsula), because of Transport (New Delhi) or topography (Chile).
Fore more information, you can refer to Doctor Sarath Guttikunda's blog on urbanemissions.info, especially this excellent infographics for New Delhi.
And without surprise, the India National Air Quality Index Standard is much more adapted to the "Asian Dust", with AQI values much higher that the US EPA standard for significant particulate matter (PM10 and PM2.5) concentrations. The graphs below are sumurizing the compared AQI for PM10, PM2.5 and Ozone (just move your mouse on the graphs to see the AQI values for each scales).
(Note that the Ozone scale is converted from µg/m3 to ppm, as explained in this article)
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Note: The interesting point to notice is that for PM2.5 pollution (which is most of the the worst pollutant in India jsut like China and Asia in general), an AQI value of 500 for the India NAQI is equivalent to an AQI of 420 in the US EPA Standard - This is because of the NAQI is much more strict than the US EPA, and that is really a good thing about the NAQI.
The consequence is that because the values provided on the Indian National Air Quality portal (done by iitk) are capped to a maximum of 500, the converted AQI on the World Air Quality Index project is a subsequently capped to a maximum of 420. Note that this only applies for readings from the National portal - for New Delhi DPCC stations, the readings are provided as uncapped raw concentration.
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| Range | United States India 0..50 | 50..100 | 100..150 | 150..200 | 200..250 | 250..300 | 300..350 | 350..400 | 400..450 | 450..500 | |
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Historically, the US EPA standard has been used on the World Air Quality Index project for reporting the real-time Air Quality all over the world. After looking at the AQI scales for Latin America, we realized that what makes our world beautiful is its diversity, and are now convinced that having only one unique scale might not be the right solution for all.
For this reason, we are now working on a new feature which will allow users to select the AQI scale which best fits their needs, depending on where they are located in the world, but also depending on the health condition: For instance, for people with asthma or other respiratory problems, there is a real need for an extra safe AQI scale.
While the AQI Scale selection feature is being developed, we will still present the Air Quality information based on the US EPA standard. So if you notice any difference between the values published on India's new National Air Quality Index System and the World Air Quality Index project, this is very likely the reason. Another reason is that we are also promoting the use of the Instant Cast reporting - but India's NAQI reporting system seems to be is already using it.
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For more information about specific countries or continent, please refer to those articles: Thailand and Malysia - India - China - Hong Kong / Canada (Air Quality Health Index) - South America - Australia - Quebec and Montreal - Singapore - Poland - Indonesia .
For information about the 24 hours averaging used or Ozone and Particulate Matter (PM2.5), please refer to those two articles: Ground Ozone Index - PM2.5 Instant Cast
