Mason, Washington Air Quality
Mason County, Washington (WA)
↓ Improvingover 10 years
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 | 24 | 53 | 106 | 313 | 49 | 1 | PM2.5 |
| 2022 | 23 | 58 | 125 | 302 | 60 | 3 | PM2.5 |
| 2021 | 22 | 43 | 70 | 339 | 22 | 0 | PM2.5 |
| 2020 | 23 | 52 | 397 | 312 | 36 | 9 | PM2.5 |
| 2019 | 28 | 53 | 75 | 305 | 56 | 0 | PM2.5 |
| 2018 | 28 | 56 | 168 | 304 | 55 | 6 | PM2.5 |
| 2017 | 25 | 57 | 156 | 301 | 60 | 2 | PM2.5 |
| 2016 | 27 | 51 | 72 | 327 | 39 | 0 | PM2.5 |
| 2015 | 29 | 53 | 102 | 316 | 45 | 1 | PM2.5 |
| 2014 | 27 | 53 | 80 | 319 | 46 | 0 | PM2.5 |
What This Means for Mason County Residents
Mason, Washington has received an Air Quality Grade of B (76/100) based on a decade of EPA monitoring data. The current median AQI of 24 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 Fine Particulate Matter (PM2.5). Over the past 5 years, this area has averaged 3 unhealthy air quality days per year — days when sensitive groups (children, elderly, those with respiratory conditions) should limit outdoor activity.