How to convert from Air Quality Index (AQI) to Mass Concentration (micrograms per cubic meter)

Since there has been a lot of confusion around air quality index (AQI) and mass concentration, I’ve attached a simple converter from the Clean Air Initiative (CAI), an Asia-based air pollution research and advocacy group that we belong to.

There are plenty of background discussion, but basically, AQI or API is a local, China and HK-based number that is made up and based on its own local standard. So, what is a 50, or “Class I – Excellent” may actually be a worse classification back in your home country. So, most experts always recommend you either get the data in mass terms (micrograms per m3) or convert the API.

This simple excel program lets you do that. Once you do that, you can interpret the numbers using the standard of your choice. Common international standards can be found here.

Enjoy!

Asian Air Pollutant Index (API) to concentration converter

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How to convert from Air Quality Index (AQI) to Mass Concentration (micrograms per cubic meter)

  1. David Scoins says:

    Thank you immensely for this conversion table. I’ve been fighting with the lack of information for hours. Article by me on http://www.scoins.net thanks you publicly.

    • Louie Cheng says:

      Hi David,

      You’re very welcome. If you havent already, also check out the excel conversion sheet and the online calculator, if you don’t feel like doing this manually.

      At the lower levels, there is frequently a big difference between AQI and mass concentration.

      • David Scoins says:

        I had done that already, thanks.
        For the big peak we were all writing about on the 12th, the SEPA figures for Jan were 232 on the 11th and 174 on the 12th. If that is perhaps the mean API for the day, is it PM2.5 or PM10 or something else? How come their figures are so low? I’ve just looked at the last three months on their figures, paralleling what Vance Wagner did, and I get a mean of 75 and a standard deviation of 40. This does not fit with the AQI we read from the US embassy. What have I misunderstood, pray?

        • Louie Cheng says:

          David, API and AQI are completely different and calculated differently. The API is the scale used by the Chinese Monitoring Center. The AQI is by AirNow, adopted by the US Consulate. For this reason, we recommend all PM2.5 discussions use mass concentration (micrograms per cubic meter) that allows for an apples to apples comparison.

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