Arizona Air Quality Information

Introducing The New High Pollution Watch

Have you ever seen the words "High Pollution Advisory" on the digital signs above the highways? Or have you ever heard of a Health Watch? In the past, ADEQ issued High Pollution Advisories when air pollution levels were expected to exceed the federal health standard and Health Watches when levels were expected to approach the federal health standard. Now, ADEQ is improving this messaging system, keeping some things the same but making some important changes as well.

First of all, ADEQ is introducing its new "High Pollution Watch" (HPW). High Pollution Watches will be issued when there is potential for a pollutant (ozone, PM10, or PM2.5) to exceed the federal health standard. HPW's are issued further in advance of High Pollution Advisories (HPA) and designed to be an outlook for potential poor air quality. Like the HPA, the HPW is associated with Air Quality Index (AQI) values above 100.

So, how do the High Pollution Watch (HPW) and High Pollution Advisory (HPA) work together? Suppose it's Wednesday and ozone is forecast to have an AQI value of 101 on Thursday, 105 on Friday, and then 90 on Saturday. An HPA would be issued for Thursday since there is a high probability of ozone exceeding the standard. An HPW would be issued for Friday since there is a potential for ozone to exceed the standard, however there is not yet enough confidence to issue an HPA. Nothing would be issued for Saturday since the AQI is forecast below 100. Then on Thursday, if conditions remain favorable for ozone to exceed the standard on Friday, or confidence is higher that it will, the HPW would be upgraded to an HPA. However, if it turns out that ozone is no longer expected to be above 100 AQI, the HPW would be cancelled and nothing would be issued for Friday.

The benefit of the High Pollution Watch (HPW) is that it will alert the public of air quality that could pose a risk to their health, while providing enough time for people to make plans to avoid, or help improve, pollution. We encourage people to plan ahead to carpool, work from home, or take the bus. Then, once the HPW is upgraded to a High Pollution Advisory, the public should be prepared to put their plans in motion and limit their exposure (especially sensitive individuals).

Last but not least, ADEQ is retiring the Health Watch (HW). By definition, HWs were associated with AQI values of 90-100. However, this range of values was a somewhat arbitrary range chosen to represent when a pollutant was expected to approach the standard. Also, since the 90-100 AQI range is a typical occurrence during the summer, it led to over messaging of the HW. And thirdly, there was some confusion in the naming terminology between Health Watch" and "High Pollution Advisory," where one had "Health" and the other had "High Pollution." Retiring the HW will ensure more consistent and meaningful messaging.