Union, South Dakota Air Quality
Union County, South Dakota (SD)
→ Stableover 8 years
How Union, South Dakota Air Quality Compares
Union, South Dakota's median AQI of 44is 7% worse than the national average of 41. The area averages 2 unhealthy air days per year. The primary pollutant of concern is Ground-Level Ozone.
Union, South Dakota Air Quality: The Full Picture
Union, South Dakota (Union County) holds an AirHistory Air Quality Grade of B (good, scoring 67 out of 100), built from 8 years of EPA Air Quality System monitoring. Its median AQI rose 1 points between 2014 (43) and 2021 (44), and the five-year median now sits at 40 — inside the "Good" band on the EPA scale.
The pollutant driving most of the area's AQI readings is Ground-Level Ozone. In 2021, it set the daily AQI on 155 of 273 monitored days (57% of the year), making it the controlling pollutant for the B grade. The single worst reading logged that year hit an AQI of 167 (Unhealthy), while the 90th-percentile day — the level the dirtiest 10% of days reach — came in at 64.
In 2021, Union County recorded 179 "Good" air days (66% of the 273 days with valid AQI data), 90 "Moderate" days, and 4 days at "Unhealthy for Sensitive Groups" or above. Over the most recent five years on record, monitors logged 5 days that crossed into "Unhealthy for Sensitive Groups" or worse — about 1 per year.
The decade-long trend is essentially flat, with year-to-year median AQI shifting by less than 0.17 points per year on average. The cleanest year in the record was 2019 (median AQI 37), and the most polluted was 2021 (median AQI 44). Because the data come straight from federally certified EPA monitors, these figures track the South Dakota 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 |
|---|---|---|---|---|---|---|---|
| 2021 | 44 | 64 | 167 | 179 | 90 | 4 | Ozone |
| 2020 | 39 | 56 | 141 | 304 | 61 | 1 | Ozone |
| 2019 | 37 | 56 | 97 | 306 | 58 | 0 | Ozone |
| 2018 | 43 | 62 | 112 | 256 | 106 | 3 | Ozone |
| 2017 | 41 | 58 | 100 | 278 | 87 | 0 | Ozone |
| 2016 | 38 | 57 | 112 | 295 | 69 | 2 | Ozone |
| 2015 | 43 | 61 | 108 | 243 | 120 | 2 | PM2.5 |
| 2014 | 43 | 61 | 100 | 244 | 121 | 0 | PM2.5 |
What This Means for Union County Residents
Union, South Dakota has received an Air Quality Grade of B (67/100) based on a decade of monitoring data from the EPA's air quality monitoring program. The current median AQI of 44 falls in the "Good" range.
The primary pollutant affecting this area is Ground-Level Ozone. Over the past 5 years, this area has averaged 2 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
Union, South Dakota has a current median AQI of 44, which falls in the "Good" range. The area has received an Air Quality Grade of B (67/100) based on 10 years of EPA monitoring data.
Air quality in Union, South Dakota is stable over the past decade. The median AQI has changed by +1 points from 2014 to 2021.
Union, South Dakota averages 2 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 Union, South Dakota is Ground-Level Ozone. This is the dominant contributor to elevated AQI readings in the Union County area.
Union, South Dakota averages 2 unhealthy air days per year. This is relatively low, making it a reasonable choice for asthma sufferers. The primary pollutant is Ground-Level Ozone, which is a known asthma trigger.
With a median AQI of 44 (Good), outdoor exercise in Union, South Dakota is generally safe year-round. Union, South Dakota averages 2 days per year when athletes should move workouts indoors.