Cook, Illinois Air Quality
Cook County, Illinois (IL)
→ Stableover 10 years
How Cook, Illinois Air Quality Compares
Cook, Illinois's median AQI of 57is 39% worse than the national average of 41. Residents experience an average of 18 unhealthy air days per year, above the national threshold for concern. The primary pollutant of concern is Fine Particulate Matter (PM2.5).
Cook, Illinois Air Quality: The Full Picture
Cook, Illinois (Cook County) holds an AirHistory Air Quality Grade of D (poor, scoring 49 out of 100), built from 10 years of EPA Air Quality System monitoring. Its median AQI fell 2 points between 2014 (59) and 2023 (57), and the five-year median now sits at 57 — inside the "Moderate" band on the EPA scale.
The pollutant driving most of the area's AQI readings is Fine Particulate Matter (PM2.5). In 2023, it set the daily AQI on 252 of 365 monitored days (69% of the year), making it the controlling pollutant for the D grade. The single worst reading logged that year hit an AQI of 223 (Very Unhealthy), while the 90th-percentile day — the level the dirtiest 10% of days reach — came in at 93.
In 2023, Cook County recorded 104 "Good" air days (28% of the 365 days with valid AQI data), 227 "Moderate" days, and 34 days at "Unhealthy for Sensitive Groups" or above. Over the most recent five years on record, monitors logged 92 days that crossed into "Unhealthy for Sensitive Groups" or worse — about 18 per year.
The decade-long trend is essentially flat, with year-to-year median AQI shifting by less than 0.10 points per year on average. The cleanest year in the record was 2022 (median AQI 54), and the most polluted was 2014 (median AQI 59). Because the data come straight from federally certified EPA monitors, these figures track the Illinois county the monitors physically sit in rather than a city boundary.
Get Cook, Illinois's next air-quality update
Subscribe for Cook, Illinois air-quality updates by email. No spam, unsubscribe anytime.
10-Year AQI Trend
The solid line shows the median AQI each year. The dashed line shows the 90th percentile (worst 10% of days).
Air Quality Day Breakdown
Number of days per year in each EPA AQI category. Green = Good (AQI 0-50), Yellow = Moderate (51-100), Orange = Unhealthy for Sensitive Groups (101-150), Red = Unhealthy or worse (151+).
Year-by-Year Data
| Year | Median AQI | 90th Pct | Max AQI | Good Days | Moderate | Unhealthy+ | Pollutant |
|---|---|---|---|---|---|---|---|
| 2023 | 57 | 93 | 223 | 104 | 227 | 34 | PM2.5 |
| 2022 | 54 | 76 | 151 | 117 | 240 | 8 | PM2.5 |
| 2021 | 59 | 89 | 156 | 87 | 257 | 21 | PM2.5 |
| 2020 | 58 | 84 | 164 | 86 | 260 | 20 | PM2.5 |
| 2019 | 58 | 79 | 133 | 80 | 276 | 9 | PM2.5 |
| 2018 | 59 | 86 | 177 | 86 | 260 | 19 | PM2.5 |
| 2017 | 55 | 87 | 177 | 114 | 232 | 19 | PM2.5 |
| 2016 | 56 | 80 | 169 | 115 | 233 | 18 | PM2.5 |
| 2015 | 57 | 79 | 195 | 73 | 285 | 7 | PM2.5 |
| 2014 | 59 | 80 | 143 | 76 | 281 | 8 | PM2.5 |
What This Means for Cook County Residents
Cook, Illinois has received an Air Quality Grade of D (49/100) based on a decade of monitoring data from the EPA's air quality monitoring program. The current median AQI of 57 falls in the "Moderate" range.
The primary pollutant affecting this area is Fine Particulate Matter (PM2.5). Over the past 5 years, this area has averaged 18 unhealthy air quality days per year, days when sensitive groups (children, elderly, those with respiratory conditions) should limit outdoor activity. The American Lung Association's State of the Air report provides additional context on long-term health risks from air pollution exposure.
Related Cities in Illinois
Frequently Asked Questions
Cook, Illinois has a current median AQI of 57, which falls in the "Moderate" range. The area has received an Air Quality Grade of D (49/100) based on 10 years of EPA monitoring data.
Air quality in Cook, Illinois is stable over the past decade. The median AQI has changed by -2 points from 2014 to 2023.
Cook, Illinois averages 18 unhealthy air quality days per year over the past 5 years. On these days, sensitive groups including children, the elderly, and those with respiratory conditions should limit outdoor activity.
The primary pollutant affecting Cook, Illinois is Fine Particulate Matter (PM2.5). This is the dominant contributor to elevated AQI readings in the Cook County area.
Cook, Illinois averages 18 unhealthy air days per year. With frequent unhealthy air days, asthma patients should use a HEPA air purifier indoors and check AQI before any outdoor activity. The primary pollutant is Fine Particulate Matter (PM2.5), which is a known asthma trigger.
With a median AQI of 57 (Moderate), outdoor exercise in Cook, Illinois is safe most days, though sensitive individuals should check daily AQI before intense workouts. Cook, Illinois averages 18 days per year when athletes should move workouts indoors.