Saint Charles, Missouri Air Quality
Saint Charles County, Missouri (MO)
→ Stableover 10 years
How Saint Charles, Missouri Air Quality Compares
Saint Charles, Missouri's median AQI of 45is 10% worse than the national average of 41. The area averages 6 unhealthy air days per year. The primary pollutant of concern is Ground-Level Ozone.
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 | 45 | 87 | 147 | 156 | 74 | 15 | Ozone |
| 2022 | 42 | 64 | 129 | 206 | 32 | 7 | Ozone |
| 2021 | 41 | 54 | 119 | 209 | 34 | 2 | Ozone |
| 2020 | 39 | 54 | 112 | 216 | 25 | 4 | Ozone |
| 2019 | 42 | 58 | 151 | 202 | 38 | 4 | Ozone |
| 2018 | 42 | 71 | 147 | 190 | 47 | 8 | Ozone |
| 2017 | 44 | 71 | 159 | 185 | 56 | 4 | Ozone |
| 2016 | 44 | 77 | 151 | 154 | 48 | 12 | Ozone |
| 2015 | 42 | 74 | 126 | 174 | 37 | 3 | Ozone |
| 2014 | 43 | 84 | 126 | 166 | 40 | 8 | Ozone |
What This Means for Saint Charles County Residents
Saint Charles, Missouri has received an Air Quality Grade of C (63/100) based on a decade of monitoring data from the EPA's air quality monitoring program. The current median AQI of 45 falls in the "Good" range.
The primary pollutant affecting this area is Ground-Level Ozone. Over the past 5 years, this area has averaged 6 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 Missouri
Frequently Asked Questions
Saint Charles, Missouri has a current median AQI of 45, which falls in the "Good" range. The area has received an Air Quality Grade of C (63/100) based on 10 years of EPA monitoring data.
Air quality in Saint Charles, Missouri is stable over the past decade. The median AQI has changed by +2 points from 2014 to 2023.
Saint Charles, Missouri averages 6 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 Saint Charles, Missouri is Ground-Level Ozone. This is the dominant contributor to elevated AQI readings in the Saint Charles County area.
Saint Charles, Missouri averages 6 unhealthy air days per year. Asthma patients should monitor daily AQI readings and limit outdoor activity when AQI exceeds 100. The primary pollutant is Ground-Level Ozone, which is a known asthma trigger.
With a median AQI of 45 (Good), outdoor exercise in Saint Charles, Missouri is generally safe year-round. Saint Charles, Missouri averages 6 days per year when athletes should move workouts indoors.
The this entity record above pulls directly from the EPA Air Quality System (AQS). What follows is the per-entity context — how this entity sits in the broader U.S. air quality and pollution monitoring distribution and which underlying factors drive the headline numbers.
The methodology behind every numeric value on this page is publicly documented on the the EPA Air Quality System (AQS) portal and described in detail on this site’s methodology page. Refresh cadence varies by underlying series; the page surfaces the as-of date for each number so readers can trace any figure back to the source release.
For readers using this page as a decision input, the related-entity pages elsewhere on the site provide the comparison set. The most useful comparison for this entity is typically a peer within U.S. counties and states with similar size, similar exposure, or similar geography — not the national-level summary alone.