Grade B Air Quality Cities
490 cities with good air quality
Grade B means good air quality with occasional moderate pollution days. These cities are scored using 10 years of EPA Air Quality System data, weighted across 5-year median AQI (40%), trend direction (30%), unhealthy days per year (20%), and worst-pollutant severity (10%).
What "Grade B" Actually Means
A Grade B means a 5-year median AQI in the upper "Good" or low "Moderate" range (typically 45-65), generally clean trends, and a manageable count of unhealthy days. These are reliably good places to live for air quality, with occasional caution days for sensitive groups during pollution events or hot summer afternoons.
The general population does not need to change behavior in a Grade B city. People with severe asthma, advanced COPD, recent cardiac events, or in late-stage pregnancy should still pay attention to AQI alerts during the worst windows — typically summer ozone peaks and the occasional wildfire smoke event.
Grade B and Daily Life
Outdoor activity is unrestricted on most days. Schools run normal outdoor PE and recess. Healthy adults can train, bike, run, and exercise as planned. The main daily-life adjustment: people in the most-sensitive subgroups should ease off intensity when AQI climbs above 80 on the worst days.
Long-Term Health Picture
Long-term residence in Grade B cities is associated with health outcomes close to those in Grade A cities. The biggest health upside from local advocacy in Grade B areas comes from preventing slippage into worse territory during pollution events and ensuring local industrial/transportation growth does not erode current air quality.
Where Grade B Cities Cluster
Grade B is the most common rating for low-to-mid-density U.S. metros that are not directly downwind of major emission sources. Many Northeast, upper Midwest, and Mountain West cities fall here.
Among the 490 Grade B cities tracked here, the largest concentrations are in OH (25), NC (25), PA (25), IN (21), FL (20). The dominant pollutant in these cities is Ozone (247 cities), followed by PM2.5 (230), PM10 (11).
All Grade B Cities
Frequently Asked Questions
A Grade B means a 5-year median AQI in the upper "Good" or low "Moderate" range (typically 45-65), generally clean trends, and a manageable count of unhealthy days. These are reliably good places to live for air quality, with occasional caution days for sensitive groups during pollution events or hot summer afternoons.
490 of 1,020 monitored US cities currently have a Grade B Air Quality rating, representing 48.0% of all tracked areas.
The general population does not need to change behavior in a Grade B city. People with severe asthma, advanced COPD, recent cardiac events, or in late-stage pregnancy should still pay attention to AQI alerts during the worst windows — typically summer ozone peaks and the occasional wildfire smoke event.
Outdoor activity is unrestricted on most days. Schools run normal outdoor PE and recess. Healthy adults can train, bike, run, and exercise as planned. The main daily-life adjustment: people in the most-sensitive subgroups should ease off intensity when AQI climbs above 80 on the worst days.
Grade B is the most common rating for low-to-mid-density U.S. metros that are not directly downwind of major emission sources. Many Northeast, upper Midwest, and Mountain West cities fall here.
/methodology
The this entity category groups every U.S. air quality and pollution monitoring entity sharing this attribute. The list above is the data; the paragraphs below explain what the grouping means against the broader the EPA Air Quality System (AQS) distribution and how to read the relative rankings within the category.
For readers using this category as a starting point, the per-entity detail pages linked from the table above carry the underlying the EPA Air Quality System (AQS) data in full. The category-level view is the filter; the per-entity pages are the actual answer.
Source: EPA Outdoor Air Quality Data, 2026.