08 July 2023

Maricopa County Air Quality Department: Ozone High Pollution Advisory issued for Sunday, July 9

Arizona’s poor air quality can be attributed to the worsening air quality in Maricopa County, which has both the nation’s fastest growing population and the fewest good air quality days. Maricopa County had good air quality on just 4% of days in 2021 (this figure was 25% in 1980).

ARIZONA HAS THE WORST AIR QUALITY IN THE COUNTRY

Ozone: Ground level ozone is formed by a chemical reaction that needs heat from sunlight, nitrogen oxides and VOCs to form.

The months of April through September make up our Valley’s longer-than-normal "ozone season."

"High Pollution Advisory" or "HPA" means the highest concentration of pollution may exceed the federal health standard.

Arizona has the worst air quality in the country.

Arizona is the only state with an unhealthy average AQI, at 101.8.

Nationally, the average AQI was 48.6 in 2021.

Around 96% of counties had good air quality for more than half of days in 2021.

Which states have improving or worsening air quality?

National air quality has improved over the past several decades due to federal and state regulations on vehicles and factories.

Since 1985, the national average AQI has improved by 23.5 points.

Only eight states have had worsening air quality since then, particularly North Dakota, Wyoming, and Arizona.

Indiana and California have had the greatest air quality improvements since 1985.

Which states have the best and worst air quality?

USAFacts