Air Quality Rankings for Iowa (2026)
Iowa has 16 cities tracked by EPA air-quality monitors, with a state-wide 5-year median AQI of 42 — roughly matching the national average of AQI 41. Cerro Gordo, Iowa ranks #1 with the cleanest air (AQI 18, Grade B), while Scott, Iowa sits at the bottom (AQI 52, Grade B).
How Iowa Compares
Iowa has 16 cities tracked by EPA air-quality monitors, with a state-wide 5-year median AQI of 42 — roughly matching the national average of AQI 41. Cerro Gordo, Iowa ranks #1 with the cleanest air (AQI 18, Grade B), while Scott, Iowa sits at the bottom (AQI 52, Grade B). The rankings below are computed from the EPA Air Quality System (AQS), which aggregates daily AQI readings from federally certified monitors into annual averages. Cities are sorted by 5-year median AQI (lowest = cleanest = #1). The 5-year window smooths out year-to-year volatility from weather and wildfire events.
Air quality across Iowa has held roughly steady over the past decade — 8 cities improving, 7 worsening, and 1 stable. That stability makes the state-average ranking a reliable signal of what residents can expect over time.
The dominant pollutant across 13 of 16 Iowa cities is Fine Particulate Matter (PM2.5). PM2.5 (fine particulate matter) is most often driven by combustion sources — vehicle exhaust, industrial emissions, residential wood burning, and increasingly wildfire smoke. It penetrates deep into lung tissue and the bloodstream and is the air pollutant most strongly linked to long-term health impacts. Other Iowa cities report Ground-Level Ozone (2), Coarse Particulate Matter (PM10) (1) as their dominant concern.
The fastest-improving city in Iowa is Scott, Iowa, with median AQI falling by 1.1 points per year. Steady improvement at that pace usually reflects fleet turnover (older diesels retiring), upwind power-plant retirements, or tighter regional emissions controls.
The city with the steepest decline is Bremer, Iowa, where median AQI is rising by 0.5 points per year. Rapid deterioration in a single city usually points to either wildfire-smoke exposure (in the West) or a new local emissions source — a power plant, port, or freight corridor coming online.
Full Iowa Ranking
| # | City | 5yr Avg AQI | Current AQI | Worst Pollutant | Trend | Grade |
|---|---|---|---|---|---|---|
| 1 | Cerro Gordo, Iowa | 18 | 19 | PM10 | Worsening | B |
| 2 | Bremer, Iowa | 38 | 42 | Ozone | Worsening | C |
| 3 | Harrison, Iowa | 40 | 44 | Ozone | Worsening | C |
| 4 | Woodbury, Iowa | 40 | 43 | PM2.5 | Worsening | C |
| 5 | Montgomery, Iowa | 41 | 44 | PM2.5 | Improving | B |
| 6 | Lee, Iowa | 42 | 47 | PM2.5 | Stable | B |
| 7 | Pottawattamie, Iowa | 42 | 49 | PM2.5 | Stable | C |
| 8 | Van Buren, Iowa | 43 | 46 | PM2.5 | Improving | B |
| 9 | Palo Alto, Iowa | 43 | 46 | PM2.5 | Improving | B |
| 10 | Muscatine, Iowa | 44 | 49 | PM2.5 | Improving | B |
| 11 | Polk, Iowa | 44 | 52 | PM2.5 | Stable | C |
| 12 | Black Hawk, Iowa | 45 | 53 | PM2.5 | Improving | B |
| 13 | Johnson, Iowa | 48 | 53 | PM2.5 | Worsening | C |
| 14 | Linn, Iowa | 49 | 54 | PM2.5 | Worsening | C |
| 15 | Clinton, Iowa | 51 | 54 | PM2.5 | Improving | C |
| 16 | Scott, Iowa | 52 | 53 | PM2.5 | Improving | B |
Air quality data for Iowa is sourced from the EPA Air Quality System (AQS), which monitors outdoor air quality at thousands of stations nationwide.
Frequently Asked Questions
Cerro Gordo, Iowa has the best air quality in Iowa with a 5-year average AQI of 18 and a Grade B (75/100). Its dominant pollutant is Coarse Particulate Matter (PM10) and the long-run trend is worsening.
Scott, Iowa has the worst air quality in Iowa with a 5-year average AQI of 52 and a Grade B (66/100). Its dominant pollutant is Fine Particulate Matter (PM2.5).
Iowa has 16 cities with EPA air quality monitoring data, covering 2014-2023 of daily AQI measurements aggregated into annual averages.
Iowa's state-wide 5-year median AQI is 42, roughly matching the national average of AQI 41. Air quality across Iowa has held roughly steady over the past decade — 8 cities improving, 7 worsening, and 1 stable. That stability makes the state-average ranking a reliable signal of what residents can expect over time.
Fine Particulate Matter (PM2.5) is the dominant pollutant in 13 of 16 monitored Iowa cities. PM2.5 (fine particulate matter) is most often driven by combustion sources — vehicle exhaust, industrial emissions, residential wood burning, and increasingly wildfire smoke. It penetrates deep into lung tissue and the bloodstream and is the air pollutant most strongly linked to long-term health impacts.
Iowa cities log an average of 2 days per year at "Unhealthy for Sensitive Groups" or worse, based on EPA monitor data over the last five years. Across all 16 Iowa cities tracked, that totals 182 unhealthy days over the period.
Cities ranked by 5-year average AQI (lower is better). Grades factor in average AQI, trend direction, unhealthy days, and dominant pollutant.
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.