The US EPA, in February 2024, has changed the AQI breakpoint table. This official website shows that, linked to at the bottom of this note.
The notice about the change is also included, as the second link below
Essentially, here’s an example of how the change affects things. Let’s say you have an AQI of 25. In the old system, that would mean if just based on PM2.5, that your PM2.5 pollutant value would be 6. However, in the new system, an AQI of 25 means that the PM2.5 pollutant value would be 4.5.
Put another way, if you had a PM2.5 pollutant value of 4, that would translate to an AQI of (4/(12-0)(50-0)) = 0.3350 = ~17
But, with the new system, if you had a PM2.5 pollutant value of 4, that would translate to an AQI of (4/(9-0)(50-0)) = 0.4450 = ~22
These are BIG differences. Further, while I see mechanisms to change the PM2.5 correction algorithm (from say, US-EPA to Canada-CCCE), or to show US vs Canadian AQI colors and values, I don’t see any way to change the calculation rules to choose this new US-EPA set of breakpoints.
What is PurpleAir’s plan, if any, to incorporate an option to use the new US-EPA AQI breakpoints in their products? What will be the ‘default’ set of breakpoints going forward? The old or the new?
Thanks!
JPB