Median AQI
46
Good
Iowa · County air quality · 2025
Polk County, Iowa
Median AQI 46 (Good). 58.5% of monitored days rated Good, direct from EPA Air Quality System stations.
- 46
- Median AQI
- 58.5%
- Good-air days
- 0
- Unhealthy days
- 12%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Polk County's air is good on balance, among the more polluted 10% of US counties, a median AQI of 46 with 58.5% of 304 monitored days in the Good band, driven mainly by PM2.5.
- 46
- median AQI · Good
- 58.5%
- days rated Good
- PM2.5
- main pollutant
- 12%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 136.
Data updated July 2026
- Good · 178 d · 58.6%
- Moderate · 124 d · 40.8%
- USG · 2 d · 0.7%
How did Polk County's air break down in 2025?
Across 304 monitored days, 178 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 136 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 304 days monitored. Median AQI: 46 (Good).
Insights: Polk County, Iowa. EPA monitors recorded a median Air Quality Index of 46 across 304 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 178 (59%) fell in the Good band (AQI 0–50), 124 (41%) registered Moderate readings, and 2 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 66, while the worst single-day peak hit 136 (USG). Residents averaged about 17.6 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (202 days), Ozone (100 days), PM10 (2 days). Across the 2020–2025 trend window, good days shifted by -83 and the median AQI moved +4 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 136, usg but never Unhealthy. Nearby counties show comparable readings: Black Hawk (56.6% good, AQI 48); Bremer (87.1% good, AQI 38); Clinton (59.9% good, AQI 45); Harrison (83.0% good, AQI 39); Johnson (71.0% good, AQI 36); Linn (61.2% good, AQI 44).
Air Quality Summary
Good Days
58.5%
178 of 304 monitored days
-16.5pp vs 75% target
Max AQI Recorded
136
USG
Health Grade
Moderate
90th-pct AQI 66
Polk County, Good days share 58.6%
National avg
Share of monitored days at AQI 0-50 (Good band).
Polk County, Unhealthy-or-worse share 0.0%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 304 monitored days across EPA AQI categories.
Good
178
59%
Moderate
124
41%
USG
2
1%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Polk County.
- PM2.5 · 202 days · 66.4%
- Ozone · 100 days · 32.9%
- PM10 · 2 days · 0.7%
Health Impact Assessment
Moderate
Polk County's air quality is rated Moderate based on 58.5% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 58.5% of monitored days in 2025, with a median AQI of 46. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 202 of 304 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Polk County. Best year: 2022 (273 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 261 | 103 | 0 | 2 | 42 | 199 |
| 2021 | 227 | 137 | 1 | 0 | 45 | 110 |
| 2022 | 273 | 92 | 0 | 0 | 41 | 89 |
| 2023 | 168 | 182 | 12 | 3 | 52 | 166 |
| 2024 | 247 | 119 | 0 | 0 | 45 | 93 |
| 2025 | 178 | 124 | 2 | 0 | 46 | 136 |
How does Polk County compare?
How Polk County compares
Good-day share worse than US avg
Polk County 58.5%
Black Hawk County, Iowa 56.6%
US average 76.5%
Median AQI worse than US avg
Polk County 46
Black Hawk County, Iowa 48
US average 38
Unhealthy days / yr about average
Polk County 0
Black Hawk County, Iowa 1
US average 0
Other Counties in Iowa
Air quality comparison for nearby counties in Iowa.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Polk County.
Bay County, Florida
AQI 46 · 60.6% good
Blount County, Tennessee
AQI 46 · 69.6% good
Cache County, Utah
AQI 46 · 61.2% good
Chesterfield County, South Carolina
AQI 46 · 61.2% good
Clark County, Indiana
AQI 46 · 59.7% good
Clark County, Ohio
AQI 46 · 59.4% good
What Polk County's air means for you
The air here stays in the breathable range year-round, with PM2.5 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 46 means for exposure. Health guidance
- See how Polk County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Polk County with its Iowa neighbours before drawing a conclusion about the region. All of Iowa
Based on 304 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Polk County, Iowa? ▼
Polk County has a median Air Quality Index (AQI) of 46, rated "Good." 58.5% of monitored days (178 out of 304) had good air quality in 2025.
What is the main pollutant in Polk County? ▼
The primary pollutant in Polk County is Fine Particles (PM2.5), which was the main AQI driver on 202 days (66% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Polk County have? ▼
In 2025, Polk County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 136.
Is the air quality in Polk County getting better or worse? ▼
Air quality in Polk County is worsening based on 5-year trends (2020-2025). Best year: 2022 with 273 good days. Worst year: 2023 with 168 good days.
What does AQI 46 mean for health? ▼
Polk County's median AQI of 46 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Polk County compare to other counties in Iowa? ▼
Polk County has 58.5% good air days. Nearby counties in Iowa: Black Hawk (56.6% good), Bremer (87.1% good), Clinton (59.9% good), Harrison (83.0% good), Johnson (71.0% good), Linn (61.2% good).
What is the 90th percentile AQI in Polk County? ▼
The 90th percentile AQI for Polk County is 66, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 136 (USG).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.
Every figure on PlainAir is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.