Air Quality Rankings for South Carolina (2026)

South Carolina has 18 cities tracked by EPA air-quality monitors, with a state-wide 5-year median AQI of 39 — 2 points cleaner than the national average of AQI 41. Georgetown, South Carolina ranks #1 with the cleanest air (AQI 14, Grade A), while Greenville, South Carolina sits at the bottom (AQI 49, Grade C). The rankings below are computed from the EPA Air Quality System (AQS), which aggregates daily AQI readings from federally certified monitors into annual averages. Cities are sorted by 5-year median AQI (lowest = cleanest = #1). The 5-year window smooths out year-to-year volatility from weather and wildfire events.

Air quality across South Carolina has held roughly steady over the past decade — 10 cities improving, 8 worsening, and 0 stable. That stability makes the state-average ranking a reliable signal of what residents can expect over time.

The dominant pollutant across 9 of 18 South Carolina cities is Fine Particulate Matter (PM2.5). PM2.5 (fine particulate matter) is most often driven by combustion sources — vehicle exhaust, industrial emissions, residential wood burning, and increasingly wildfire smoke. It penetrates deep into lung tissue and the bloodstream and is the air pollutant most strongly linked to long-term health impacts. Other South Carolina cities report Ground-Level Ozone (8), Coarse Particulate Matter (PM10) (1) as their dominant concern.

The fastest-improving city in South Carolina is Colleton, South Carolina, with median AQI falling by 2.3 points per year. Steady improvement at that pace usually reflects fleet turnover (older diesels retiring), upwind power-plant retirements, or tighter regional emissions controls.

The city with the steepest decline is Horry, South Carolina, where median AQI is rising by 1.8 points per year. Rapid deterioration in a single city usually points to either wildfire-smoke exposure (in the West) or a new local emissions source — a power plant, port, or freight corridor coming online.