Is the Air Quality Good in Cook, Illinois?
No — air quality in Cook, Illinois is below the U.S. average. The city earns a Grade of D (poor) on a 5-year median AQI of 57 (Moderate), with 92 unhealthy-air days over five years (about 18 per year). Residents with asthma, heart disease, or young children should treat daily AQI forecasts as a real input.
Who Can Safely Breathe the Air in Cook, Illinois?
Treat daily AQI forecasts as essential input. On flagged days, sensitive groups (asthma, COPD, heart disease, pregnancy, young children, older adults) should limit outdoor exertion and keep windows closed. A HEPA air cleaner sized to a bedroom or family room can cut indoor PM2.5 by 80%+ during smoke or pollution events. Because PM2.5 penetrates deep into the lungs and bloodstream, an N95 or KN95 mask provides meaningful protection on smoky or high-particulate days — surgical masks do not.
Across the past five years, this area has logged 92 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 18 days per year. That is roughly typical for a U.S. metro, with most caution days clustered in summer (ozone) or wildfire season.
Cook, Illinois Air Quality Snapshot
| Air Quality Grade | D49/100 |
| 5-Year Median AQI | 57 (Moderate) |
| Most Recent Median AQI (2023) | 57 (Moderate) |
| Dominant Pollutant | Fine Particulate Matter (PM2.5) |
| 10-Year Trend | Stable (-0.10 AQI/yr) |
| Unhealthy Days (last 5 yr) | 92 |
| National Rank (cleanest = #1) | #1002 of 1,020 (98th most polluted percentile) |
| Illinois Rank | #23 of 23 |
What Does the D Grade Mean?
Cook, Illinois earns a D — air quality falls below the U.S. average, with a 5-year median AQI of 57. Residents with asthma, COPD, heart disease, or young children should watch daily AQI forecasts and limit outdoor exertion when alerts go out.
Cook, Illinois's 5-year median AQI of 57 is 16 points above the national average of 41 — meaningfully more polluted than the typical U.S. metro tracked here. Within Illinois, Cook, Illinois runs more polluted than the state average of 45 — local sources or geography are concentrating pollution above the state's typical reading.
For context within Illinois: Clark, Illinois currently holds the state's cleanest grade (B, AQI 34), while Rock Island, Illinois sits at the bottom (D, AQI 47).
What's in Cook, Illinois's Air?
The dominant pollutant in Cook, Illinois is Fine Particulate Matter (PM2.5). Fine particulate matter — particles less than 2.5 micrometers across — comes mostly from combustion: vehicle exhaust, wildfire smoke, residential wood burning, and industrial emissions. Because these particles are small enough to enter the bloodstream, PM2.5 is the pollutant most strongly linked to cardiovascular disease, respiratory illness, and premature death.
Days by Dominant Pollutant (2023)
| Pollutant | Days as Dominant | Share of Year |
|---|---|---|
| Fine Particulate Matter (PM2.5) | 252 | 69% |
| Ground-Level Ozone | 97 | 27% |
| Nitrogen Dioxide | 8 | 2% |
| Coarse Particulate Matter (PM10) | 8 | 2% |
Is the Air Getting Better or Worse?
Air quality in Cook, Illinois has held roughly steady over the past decade, with year-to-year shifts in median AQI of less than half a point. That stability makes the city's long-run grade a reliable signal of what residents can expect day-to-day.
In 2014, Cook, Illinois posted a median AQI of 59. By 2023 that figure was 57 — a drop of 2 AQI points cleaner across 10 years of EPA records.
Year-by-Year AQI in Cook, Illinois
| Year | Median AQI | Good Days | Unhealthy Days | Dominant Pollutant |
|---|---|---|---|---|
| 2014 | 59 | 76 | 8 | PM2.5 |
| 2015 | 57 | 73 | 7 | PM2.5 |
| 2016 | 56 | 115 | 18 | PM2.5 |
| 2017 | 55 | 114 | 19 | PM2.5 |
| 2018 | 59 | 86 | 19 | PM2.5 |
| 2019 | 58 | 80 | 9 | PM2.5 |
| 2020 | 58 | 86 | 20 | PM2.5 |
| 2021 | 59 | 87 | 21 | PM2.5 |
| 2022 | 54 | 117 | 8 | PM2.5 |
| 2023 | 57 | 104 | 34 | PM2.5 |
How This Grade Is Calculated
The AirHistory Air Quality Grade combines four signals: the 5-year median AQI (40% of the score), the 10-year trend direction (30%), the count of unhealthy days per year (20%), and the dominant pollutant type (10%). All four come directly from the EPA Air Quality System (AQS), which aggregates readings from federally certified monitors. Read the full methodology.
More about Cook, Illinois
Cook, Illinois has an Air Quality Grade of D (poor) with a 5-year median AQI of 57. The dominant pollutant is Fine Particulate Matter (PM2.5), and air quality has been stable over the past decade.
The data source behind this answer is the EPA Air Quality System (AQS). Every figure on the page traces back to that source; the methodology page describes the inputs and the refresh cadence in full detail.
A practical caveat: the headline answer above reflects the most recent the EPA Air Quality System (AQS) vintage; underlying data is often revised for months after first publication, and the right reference for any specific decision is whichever vintage is current at the time of the decision. The as-of date is stamped on every page.
Source: EPA Outdoor Air Quality Data, 2026.