Trinity, California Air Quality
Trinity County, California (CA)
↑ Worseningover 10 years
How Trinity, California Air Quality Compares
Trinity, California's median AQI of 31is 24% better than the national average of 41. Air quality has worsened by 19 AQI points over the past decade. Residents experience an average of 20 unhealthy air days per year, above the national threshold for concern. The primary pollutant of concern is Fine Particulate Matter (PM2.5).
Trinity, California Air Quality: The Full Picture
Trinity, California (Trinity County) holds an AirHistory Air Quality Grade of C (fair, scoring 51 out of 100), built from 10 years of EPA Air Quality System monitoring. Its median AQI rose 19 points between 2014 (12) and 2023 (31), and the five-year median now sits at 32 — inside the "Good" band on the EPA scale.
The pollutant driving most of the area's AQI readings is Fine Particulate Matter (PM2.5). In 2023, it set the daily AQI on 311 of 311 monitored days (100% of the year), making it the controlling pollutant for the C grade. The single worst reading logged that year hit an AQI of 174 (Unhealthy), while the 90th-percentile day — the level the dirtiest 10% of days reach — came in at 65.
In 2023, Trinity County recorded 209 "Good" air days (67% of the 311 days with valid AQI data), 93 "Moderate" days, and 9 days at "Unhealthy for Sensitive Groups" or above. Over the most recent five years on record, monitors logged 100 days that crossed into "Unhealthy for Sensitive Groups" or worse — about 20 per year.
The decade-long trend is worsening: median AQI has been climbing by roughly 1.01 points per year. The cleanest year in the record was 2014 (median AQI 12), and the most polluted was 2017 (median AQI 57). Because the data come straight from federally certified EPA monitors, these figures track the California 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). Air quality in this area has been declining over the past 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 | 31 | 65 | 174 | 209 | 93 | 9 | PM2.5 |
| 2022 | 34 | 72 | 342 | 227 | 111 | 15 | PM2.5 |
| 2021 | 38 | 168 | 1217 | 201 | 81 | 46 | PM2.5 |
| 2020 | 36 | 81 | 211 | 215 | 100 | 28 | PM2.5 |
| 2019 | 23 | 56 | 113 | 225 | 42 | 2 | PM2.5 |
| 2018 | 54 | 82 | 209 | 117 | 155 | 19 | PM2.5 |
| 2017 | 57 | 91 | 844 | 76 | 116 | 11 | PM2.5 |
| 2016 | 51 | 73 | 97 | 83 | 84 | 0 | PM2.5 |
| 2015 | 12 | 29 | 56 | 67 | 1 | 0 | PM2.5 |
| 2014 | 12 | 44 | 90 | 102 | 10 | 0 | PM2.5 |
What This Means for Trinity County Residents
Trinity, California has received an Air Quality Grade of C (51/100) based on a decade of monitoring data from the EPA's air quality monitoring program. The current median AQI of 31 falls in the "Good" range.
Concerning trends show air quality has been declining, with the median AQI rising by 19 points over the monitoring period. This could be driven by increased development, wildfire smoke, or industrial activity.
The primary pollutant affecting this area is Fine Particulate Matter (PM2.5). Over the past 5 years, this area has averaged 20 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
Trinity, California has a current median AQI of 31, which falls in the "Good" range. The area has received an Air Quality Grade of C (51/100) based on 10 years of EPA monitoring data.
Air quality in Trinity, California is worsening over the past decade. The median AQI has changed by +19 points from 2014 to 2023.
Trinity, California averages 20 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 Trinity, California is Fine Particulate Matter (PM2.5). This is the dominant contributor to elevated AQI readings in the Trinity County area.
Trinity, California averages 20 unhealthy air days per year. With frequent unhealthy air days, asthma patients should use a HEPA air purifier indoors and check AQI before any outdoor activity. The primary pollutant is Fine Particulate Matter (PM2.5), which is a known asthma trigger.
With a median AQI of 31 (Good), outdoor exercise in Trinity, California is generally safe year-round. Trinity, California averages 20 days per year when athletes should move workouts indoors.