State of American Air Quality 2026

Executive Summary

After analyzing a decade of EPA Air Quality System data across 1,020 US cities, this report finds a nation divided on air quality. While 24% of monitored cities show meaningful improvement in their 5-year average AQI, 16% are trending in the wrong direction — many driven by wildfire smoke intrusion that is rewriting the air quality map of the American West.

The national average AQI stands at 39, which falls in the Good category by EPA standards. However, this average masks dramatic regional variation. 50 cities earn an A grade for consistently clean air, while 4 cities receive an F — meaning residents face persistently unhealthy conditions. The average city experienced 21 unhealthy air days over the past five years.

PM2.5 particulate matter is the dominant pollutant in 531 cities, while ozone leads in 452. The PM2.5 dominance reflects both vehicle emissions in urban corridors and the growing influence of wildfire smoke, which can transport fine particles hundreds of miles from burn sites. Cities that once enjoyed reliably clean mountain air now face episodic spikes that drag down their overall scores.

This report ranks every analyzed city, identifies the most improved and most declined metros, breaks down state-level performance, and examines the pollutants driving these trends. The data makes clear: where you live matters enormously for the air you breathe, and the map is shifting.

Wildfire Impact Analysis

Wildfire smoke has emerged as the single largest disruptor of US air quality trends since 2020. Cities in California, Oregon, Washington, Montana, and Colorado — many of which historically had excellent air quality — now face episodic PM2.5 spikes that can push daily AQI readings above 300 (Hazardous). 531 cities in our dataset identify PM2.5 as their primary pollutant of concern, a figure that has grown significantly as wildfire seasons lengthen.

The impact extends well beyond fire-adjacent regions. Smoke plumes from western wildfires regularly reach the Midwest and East Coast, temporarily degrading air quality in cities hundreds of miles from the nearest burn. This phenomenon means that even cities with strong regulatory controls on local emissions can see their annual statistics worsened by distant fires.

Regional Patterns and Pollutant Breakdown

Two pollutants dominate the national air quality picture: PM2.5 fine particulate matter and ground-level ozone. PM2.5 is the primary concern in 531 cities, driven by vehicle emissions, industrial sources, and increasingly by wildfire smoke. Ozone dominates in 452 cities, primarily in sun-intensive southern and western regions where vehicle exhaust and industrial emissions react with sunlight.

Urban vs. suburban differences are also notable. Dense urban cores tend to have higher baseline AQI from traffic and industrial emissions, while suburban and exurban areas can see wider seasonal swings — excellent air quality for much of the year punctuated by wildfire smoke events or summer ozone formation.

Methodology

This report analyzes EPA Air Quality System (AQS) monitoring data from 2014 through 2023, covering 1,020 cities across 54 states. Each city's Air Quality Grade is computed using a proprietary scoring model that weights: 5-year average AQI (40%), trend direction (30%), annual unhealthy days (20%), and worst contaminant severity (10%). Trend direction is calculated via linear regression of annual median AQI values. Cities are classified as "improving" (slope < -0.5), "stable" (-0.5 to 0.5), or "worsening" (> 0.5). Data processing pipeline details are available on our methodology page.