What Is the Air Quality in Union, Oregon?
Union, Oregon has an Air Quality Grade of B (good) with a 5-year median AQI of 27. The dominant pollutant is Fine Particulate Matter (PM2.5), and air quality has been improving over the past decade.
Union, Oregon Air Quality Snapshot
| Air Quality Grade | B76/100 |
| 5-Year Median AQI | 27 (Good) |
| Most Recent Median AQI (2023) | 26 (Good) |
| Dominant Pollutant | Fine Particulate Matter (PM2.5) |
| 10-Year Trend | Improving (-0.88 AQI/yr) |
| Unhealthy Days (last 5 yr) | 20 |
| National Rank (cleanest = #1) | #101 of 1,020 (10th cleanest percentile) |
| Oregon Rank | #4 of 23 |
What Does the B Grade Mean?
Union, Oregon 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 27. Sensitive groups will see occasional caution days, but the typical resident will not need to change behavior based on air quality.
Union, Oregon's 5-year median AQI of 27 is 14 points below the national average of 41 — meaningfully cleaner than the typical U.S. metro tracked here. Within Oregon, Union, Oregon runs cleaner than the state average of 34 — a positive signal that local conditions (terrain, wind patterns, emission sources) are working in residents' favor.
For context within Oregon: Jefferson, Oregon currently holds the state's cleanest grade (A, AQI 28), while Douglas, Oregon sits at the bottom (C, AQI 36).
What's in Union, Oregon's Air?
The dominant pollutant in Union, Oregon 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) | 360 | 100% |
| Coarse Particulate Matter (PM10) | 1 | 0% |
Is the Air Getting Better or Worse?
Air quality in Union, Oregon has been improving over the past decade, with median AQI dropping by roughly 0.9 points per year. That is consistent with the broader national pattern — most U.S. metros have seen steady reductions in particulate and ozone pollution since the 2010s as cleaner vehicles and power plants come online.
In 2014, Union, Oregon posted a median AQI of 34. By 2023 that figure was 26 — a drop of 8 AQI points cleaner across 10 years of EPA records.
Year-by-Year AQI in Union, Oregon
| Year | Median AQI | Good Days | Unhealthy Days | Dominant Pollutant |
|---|---|---|---|---|
| 2014 | 34 | 255 | 6 | PM2.5 |
| 2015 | 38 | 254 | 11 | PM2.5 |
| 2016 | 24 | 297 | 0 | PM2.5 |
| 2017 | 31 | 277 | 11 | PM2.5 |
| 2018 | 32 | 282 | 6 | PM2.5 |
| 2019 | 26 | 313 | 0 | PM2.5 |
| 2020 | 27 | 300 | 9 | PM2.5 |
| 2021 | 27 | 304 | 7 | PM2.5 |
| 2022 | 28 | 283 | 4 | PM2.5 |
| 2023 | 26 | 305 | 0 | PM2.5 |
Health Context for Union, Oregon
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.
Union, Oregon has an Air Quality Grade of B (good) with a 5-year median AQI of 27. The dominant pollutant is Fine Particulate Matter (PM2.5), and air quality has been improving over the past decade.
This answer pulls from the EPA Air Quality System (AQS), the authoritative federal source for U.S. air quality and pollution monitoring. The headline number above is the direct answer; what follows is the additional context most readers need to use the answer for a real decision rather than just a fact lookup.
For readers turning this answer into action: cross-reference against the underlying the EPA Air Quality System (AQS) record before acting on time-sensitive decisions. The site renders the data as it was published; subsequent revisions can shift the picture, and the live federal data is always the authoritative current reference.
Source: EPA Outdoor Air Quality Data, 2026.