On March 23, 2026, in a decision consequential to regulated Maricopa County businesses and those looking to relocate or expand, the U.S. Environmental Protection Agency (EPA) declined to reclassify the Phoenix-Mesa ozone nonattainment area, including Maricopa County, from “moderate” to “serious” under the 2015 ozone National Ambient Air Quality Standards (NAAQS). As a result, businesses avoid a meaningful step-up in regulatory burden, and the current compliance framework remains intact.