Marion, Indiana Air Quality
Marion County, Indiana (IN)
→ Stableover 10 years
How Marion, Indiana Air Quality Compares
Marion, Indiana's median AQI of 60is 46% worse than the national average of 41. The area averages 10 unhealthy air days per year. The primary pollutant of concern is Fine Particulate Matter (PM2.5).
Marion, Indiana Air Quality: The Full Picture
Marion, Indiana (Marion 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 2 points between 2014 (58) and 2023 (60), and the five-year median now sits at 57 — inside the "Moderate" 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 310 of 365 monitored days (85% of the year), making it the controlling pollutant for the C grade. The single worst reading logged that year hit an AQI of 259 (Very Unhealthy), while the 90th-percentile day — the level the dirtiest 10% of days reach — came in at 89.
In 2023, Marion County recorded 84 "Good" air days (23% of the 365 days with valid AQI data), 260 "Moderate" days, and 21 days at "Unhealthy for Sensitive Groups" or above. Over the most recent five years on record, monitors logged 50 days that crossed into "Unhealthy for Sensitive Groups" or worse — about 10 per year.
The decade-long trend is essentially flat, with year-to-year median AQI shifting by less than 0.24 points per year on average. The cleanest year in the record was 2017 (median AQI 54), and the most polluted was 2023 (median AQI 60). Because the data come straight from federally certified EPA monitors, these figures track the Indiana 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 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 | 60 | 89 | 259 | 84 | 260 | 21 | PM2.5 |
| 2022 | 56 | 80 | 154 | 101 | 251 | 13 | PM2.5 |
| 2021 | 58 | 81 | 114 | 81 | 278 | 6 | PM2.5 |
| 2020 | 55 | 72 | 144 | 110 | 250 | 6 | PM2.5 |
| 2019 | 58 | 74 | 112 | 78 | 283 | 4 | PM2.5 |
| 2018 | 55 | 73 | 158 | 105 | 249 | 11 | PM2.5 |
| 2017 | 54 | 71 | 122 | 134 | 227 | 4 | PM2.5 |
| 2016 | 55 | 77 | 143 | 111 | 244 | 11 | PM2.5 |
| 2015 | 56 | 74 | 159 | 129 | 233 | 3 | PM2.5 |
| 2014 | 58 | 79 | 209 | 85 | 273 | 7 | PM2.5 |
What This Means for Marion County Residents
Marion, Indiana 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 60 falls in the "Moderate" range.
The primary pollutant affecting this area is Fine Particulate Matter (PM2.5). Over the past 5 years, this area has averaged 10 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
Marion, Indiana has a current median AQI of 60, which falls in the "Moderate" range. The area has received an Air Quality Grade of C (51/100) based on 10 years of EPA monitoring data.
Air quality in Marion, Indiana is stable over the past decade. The median AQI has changed by +2 points from 2014 to 2023.
Marion, Indiana averages 10 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 Marion, Indiana is Fine Particulate Matter (PM2.5). This is the dominant contributor to elevated AQI readings in the Marion County area.
Marion, Indiana averages 10 unhealthy air days per year. Asthma patients should monitor daily AQI readings and limit outdoor activity when AQI exceeds 100. The primary pollutant is Fine Particulate Matter (PM2.5), which is a known asthma trigger.
With a median AQI of 60 (Moderate), outdoor exercise in Marion, Indiana is safe most days, though sensitive individuals should check daily AQI before intense workouts. Marion, Indiana averages 10 days per year when athletes should move workouts indoors.