Grade D Air Quality Cities
43 cities with below average air quality
Grade D means below-average air quality with frequent unhealthy days and concerning trends. These cities are scored using EPA Air Quality System data spanning 10 years of daily AQI readings.
All Grade D Cities
| City | State | 5yr Avg AQI | Trend | Worst Pollutant |
|---|---|---|---|---|
| Butler, Ohio | OH | 50 | Worsening | Ozone |
| Codington, South Dakota | SD | 40 | Worsening | PM2.5 |
| Cook, Illinois | IL | 57 | Stable | PM2.5 |
| Dona Ana, New Mexico | NM | 54 | Stable | Ozone |
| Douglas, Colorado | CO | 47 | Worsening | Ozone |
| DuPage, Illinois | IL | 49 | Worsening | PM2.5 |
| Jackson, Mississippi | MS | 46 | Worsening | PM2.5 |
| McLean, Illinois | IL | 48 | Worsening | PM2.5 |
| Siskiyou, California | CA | 41 | Worsening | Ozone |
| Uintah, Utah | UT | 51 | Worsening | Ozone |
| Valley, Idaho | ID | 37 | Worsening | PM2.5 |
| Boulder, Colorado | CO | 50 | Worsening | Ozone |
| Henderson, Kentucky | KY | 53 | Worsening | PM2.5 |
| Neosho, Kansas | KS | 48 | Worsening | Ozone |
| Sanders, Montana | MT | 36 | Worsening | PM2.5 |
| Sangamon, Illinois | IL | 46 | Worsening | PM2.5 |
| Asotin, Washington | WA | 43 | Worsening | PM2.5 |
| Eddy, New Mexico | NM | 47 | Worsening | Ozone |
| SONORA, Country Of Mexico | MX | 44 | Worsening | Ozone |
| Weld, Colorado | CO | 53 | Worsening | Ozone |
| Fresno, California | CA | 68 | Improving | Ozone |
| Jefferson, Colorado | CO | 47 | Stable | Ozone |
| Rock Island, Illinois | IL | 47 | Worsening | PM2.5 |
| Stanislaus, California | CA | 57 | Improving | PM2.5 |
| Winnebago, Illinois | IL | 48 | Worsening | Ozone |
| Imperial, California | CA | 61 | Improving | PM2.5 |
| Kings, California | CA | 64 | Improving | Ozone |
| Placer, California | CA | 54 | Worsening | Ozone |
| Tarrant, Texas | TX | 53 | Worsening | PM2.5 |
| Catano, Puerto Rico | PR | 42 | Worsening | PM2.5 |
| Clark, Nevada | NV | 62 | Stable | Ozone |
| Kern, California | CA | 77 | Improving | Ozone |
| Bernalillo, New Mexico | NM | 59 | Worsening | Ozone |
| El Paso, Texas | TX | 60 | Worsening | PM2.5 |
| Mono, California | CA | 33 | Worsening | PM2.5 |
| Salt Lake, Utah | UT | 57 | Worsening | Ozone |
| Pinal, Arizona | AZ | 66 | Improving | PM10 |
| Harris, Texas | TX | 59 | Worsening | PM2.5 |
| Tulare, California | CA | 75 | Improving | Ozone |
| Plumas, California | CA | 52 | Worsening | PM2.5 |
| Los Angeles, California | CA | 75 | Improving | PM2.5 |
| Riverside, California | CA | 82 | Improving | Ozone |
| San Diego, California | CA | 67 | Stable | PM2.5 |
Frequently Asked Questions
Grade D (Below Average) indicates below-average air quality with frequent unhealthy days and concerning trends. The grade is based on 5-year average AQI (40%), trend direction (30%), unhealthy days per year (20%), and worst pollutant severity (10%).
43 of 1,020 monitored US cities currently have a Grade D Air Quality rating, representing 4.2% of all tracked areas.
Grade D cities experience regular periods where air quality poses health risks, especially for children, the elderly, and people with respiratory conditions. Checking daily AQI readings is recommended.
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