What Is the Air Quality in Saint Louis, Minnesota?
Saint Louis, Minnesota has an Air Quality Grade of B (good) with a 5-year median AQI of 39. The dominant pollutant is Fine Particulate Matter (PM2.5), and air quality has been stable over the past decade.
Saint Louis, Minnesota Air Quality Snapshot
| Air Quality Grade | B65/100 |
| 5-Year Median AQI | 39 (Good) |
| Most Recent Median AQI (2023) | 44 (Good) |
| Dominant Pollutant | Fine Particulate Matter (PM2.5) |
| 10-Year Trend | Stable (-0.18 AQI/yr) |
| Unhealthy Days (last 5 yr) | 20 |
| National Rank (cleanest = #1) | #427 of 1,020 (42th cleanest percentile) |
| Minnesota Rank | #12 of 21 |
What Does the B Grade Mean?
Saint Louis, Minnesota earns a B — air quality is reliably in the safe range for most residents most of the time, with a 5-year median AQI of 39. Sensitive groups will see occasional caution days, but the typical resident will not need to change behavior based on air quality.
Saint Louis, Minnesota's 5-year median AQI of 39 is 2 points below the national average of 41 — meaningfully cleaner than the typical U.S. metro tracked here. Within Minnesota, Saint Louis, Minnesota runs more polluted than the state average of 36 — local sources or geography are concentrating pollution above the state's typical reading.
For context within Minnesota: Cook, Minnesota currently holds the state's cleanest grade (A, AQI 12), while Cass, Minnesota sits at the bottom (C, AQI 32).
What's in Saint Louis, Minnesota's Air?
The dominant pollutant in Saint Louis, Minnesota 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) | 190 | 52% |
| Ground-Level Ozone | 168 | 46% |
| Coarse Particulate Matter (PM10) | 6 | 2% |
| Nitrogen Dioxide | 1 | 0% |
Is the Air Getting Better or Worse?
Air quality in Saint Louis, Minnesota 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, Saint Louis, Minnesota posted a median AQI of 47. By 2023 that figure was 44 — a drop of 3 AQI points cleaner across 10 years of EPA records.
Year-by-Year AQI in Saint Louis, Minnesota
| Year | Median AQI | Good Days | Unhealthy Days | Dominant Pollutant |
|---|---|---|---|---|
| 2014 | 47 | 216 | 0 | PM2.5 |
| 2015 | 40 | 289 | 1 | PM2.5 |
| 2016 | 34 | 323 | 1 | Ozone |
| 2017 | 36 | 307 | 0 | Ozone |
| 2018 | 39 | 284 | 2 | Ozone |
| 2019 | 38 | 306 | 1 | PM2.5 |
| 2020 | 40 | 279 | 1 | PM2.5 |
| 2021 | 37 | 283 | 10 | Ozone |
| 2022 | 36 | 322 | 0 | Ozone |
| 2023 | 44 | 221 | 8 | PM2.5 |
Health Context for Saint Louis, Minnesota
Across the past five years, this area has logged just 20 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 4 days per year, or roughly one every other month. That is a low count by national standards.
For most healthy adults, current air quality in this area does not require any change in behavior. People with severe asthma, COPD, or recent cardiac events should still keep an eye on daily AQI alerts, especially during wildfire season. 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.
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.
Saint Louis, Minnesota has an Air Quality Grade of B (good) with a 5-year median AQI of 39. 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.