Clark, Illinois Air Quality
Clark County, Illinois (IL)
↓ Improvingover 10 years
How Clark, Illinois Air Quality Compares
Clark, Illinois's median AQI of 36is 12% better than the national average of 41. The area averages 1 unhealthy air days per year. The primary pollutant of concern is Ground-Level Ozone.
Clark, Illinois Air Quality: The Full Picture
Clark, Illinois (Clark County) holds an AirHistory Air Quality Grade of B (good, scoring 73 out of 100), built from 10 years of EPA Air Quality System monitoring. Its median AQI fell 3 points between 2014 (39) and 2023 (36), and the five-year median now sits at 34 — inside the "Good" band on the EPA scale.
The pollutant driving most of the area's AQI readings is Ground-Level Ozone. In 2023, it set the daily AQI on 358 of 358 monitored days (100% of the year), making it the controlling pollutant for the B grade. The single worst reading logged that year hit an AQI of 136 (Unhealthy for Sensitive Groups), while the 90th-percentile day — the level the dirtiest 10% of days reach — came in at 51.
In 2023, Clark County recorded 320 "Good" air days (89% of the 358 days with valid AQI data), 33 "Moderate" days, and 5 days at "Unhealthy for Sensitive Groups" or above. Over the most recent five years on record, monitors logged 6 days that crossed into "Unhealthy for Sensitive Groups" or worse — about 1 per year.
The decade-long trend is improving: median AQI has been dropping by roughly 0.63 points per year. The cleanest year in the record was 2020 (median AQI 31), and the most polluted was 2014 (median AQI 39). 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.
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10-Year AQI Trend
The solid line shows the median AQI each year. The dashed line shows the 90th percentile (worst 10% of days). This area has seen measurable air quality improvement over the decade.
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 | 36 | 51 | 136 | 320 | 33 | 5 | Ozone |
| 2022 | 34 | 45 | 101 | 296 | 15 | 1 | Ozone |
| 2021 | 34 | 46 | 84 | 344 | 19 | 0 | Ozone |
| 2020 | 31 | 45 | 97 | 347 | 16 | 0 | Ozone |
| 2019 | 34 | 47 | 74 | 314 | 13 | 0 | Ozone |
| 2018 | 32 | 48 | 101 | 337 | 21 | 1 | Ozone |
| 2017 | 39 | 51 | 101 | 211 | 29 | 1 | Ozone |
| 2016 | 38 | 54 | 101 | 175 | 27 | 1 | Ozone |
| 2015 | 39 | 61 | 87 | 182 | 28 | 0 | Ozone |
| 2014 | 39 | 51 | 90 | 185 | 26 | 0 | Ozone |
What This Means for Clark County Residents
Clark, Illinois has received an Air Quality Grade of B (73/100) based on a decade of monitoring data from the EPA's air quality monitoring program. The current median AQI of 36 falls in the "Good" range.
Encouragingly, air quality here has been improving, with the median AQI dropping by 3 points over the monitoring period. This trend suggests continued investment in emission controls and cleaner energy.
The primary pollutant affecting this area is Ground-Level Ozone. Over the past 5 years, this area has averaged 1 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.
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Frequently Asked Questions
Clark, Illinois has a current median AQI of 36, which falls in the "Good" range. The area has received an Air Quality Grade of B (73/100) based on 10 years of EPA monitoring data.
Air quality in Clark, Illinois is improving over the past decade. The median AQI has changed by -3 points from 2014 to 2023.
Clark, Illinois averages 1 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 Clark, Illinois is Ground-Level Ozone. This is the dominant contributor to elevated AQI readings in the Clark County area.
Clark, Illinois averages 1 unhealthy air days per year. This is relatively low, making it a reasonable choice for asthma sufferers. The primary pollutant is Ground-Level Ozone, which is a known asthma trigger.
With a median AQI of 36 (Good), outdoor exercise in Clark, Illinois is generally safe year-round. Clark, Illinois averages 1 days per year when athletes should move workouts indoors.