Hey y’all! In light of the new PM2.5 NAAQS that was recently finalized by the USEPA, is there going to be any update to how the PM2.5 AQI is calculated?
I have a basic understanding of how AQI is calculated, and I know that it represented almost like a percentage of the NAAQS. Based on that reasoning, would the calculations under the USEPA 24-hour average for PM2.5 need to be adjusted? Wouldn’t a tighter standard result in a higher AQI number (all other parameters being equal)?
Hi @aea1993
Our map uses the EPA 24 hour standard to display the EPA AQI. Originally, no changes were planned, as the NAAQS only revised annual exposure levels. However, in accordance with The EPA’s announcement here, we will updating our map to reflect the changes to the 24 hour standard.
This will occur in the future, however we do not have a strict timeline right now.
Hi, Kieran.
Have the map and local sensor Web server been updated to use the new scale yet?
Hi @waterem No, this change has not been made yet. The change will be implemented on the map with the release of the next map version. However, we don’t have a timeline for that release.
Along similar lines, will the indoor PurpleAir sensors get a firmware update to reflect the new standards? Asked another way, when the LED is green, can I be sure the raw value is 9.0 or less, or 12.0 or less? Thank you.
Hi @nierenberg
We do plan to update the on-board breakpoints as well. This won’t be included with the next map update, and won’t be soon.
I was a member of the EPA CASAC panel that reviewed the PM2.5 NAAQS. EPA did tighten the annual from 12 to 9 in Feb 2024, and that moves the green to yellow AQI breakpoint from 12 to 9. There were other smaller changes to the AQI but none that normally make a difference, since the daily NAAQS was [unfortunately] left at 35. It should be no higher than 25, which is where Canada will land when they finish revisions to their CAAQS.
@Kieran what’s the latest on PurpleAir implementing these new breakpoints?
…the daily NAAQS was [unfortunately] left at 35. It should be no higher than 25…
George, any articles or documents you recommend if I’m interested in learning more about where the standards should be set?
The annual at 9 is reasonable, but it could have been 8 or even lower. EPA uses the annual as the controlling standard, and the daily as a [now almost useless] backstop. The daily has been at 35 since 2006, while the annual has dropped from 15 to 9. They should drop in sync. More info:
Thank you! ----------------------