What Is the Air Quality in Colleton, South Carolina?
Colleton, South Carolina has an Air Quality Grade of A (excellent) with a 5-year median AQI of 26. The dominant pollutant is Fine Particulate Matter (PM2.5), and air quality has been improving over the past decade.
Colleton, South Carolina Air Quality Snapshot
| Air Quality Grade | A86/100 |
| 5-Year Median AQI | 26 (Good) |
| Most Recent Median AQI (2019) | 26 (Good) |
| Dominant Pollutant | Fine Particulate Matter (PM2.5) |
| 10-Year Trend | Improving (-2.31 AQI/yr) |
| Unhealthy Days (last 5 yr) | 0 |
| National Rank (cleanest = #1) | #95 of 1,020 (9th cleanest percentile) |
| South Carolina Rank | #2 of 18 |
What Does the A Grade Mean?
Colleton, South Carolina earns an A — it is among the cleanest U.S. cities tracked by EPA monitoring, with median AQI averaging just 26 over the past five years. Days in the "Good" category dominate the calendar; air-quality alerts are rare.
Colleton, South Carolina's 5-year median AQI of 26 is 15 points below the national average of 41 — meaningfully cleaner than the typical U.S. metro tracked here. Within South Carolina, Colleton, South Carolina runs cleaner than the state average of 39 — a positive signal that local conditions (terrain, wind patterns, emission sources) are working in residents' favor.
For context within South Carolina: Georgetown, South Carolina currently holds the state's cleanest grade (A, AQI 14), while York, South Carolina sits at the bottom (C, AQI 44).
What's in Colleton, South Carolina's Air?
The dominant pollutant in Colleton, South Carolina is Fine Particulate Matter (PM2.5). Fine particulate matter — particles less than 2.5 micrometers across — comes mostly from combustion: vehicle exhaust, wildfire smoke, residential wood burning, and industrial emissions. Because these particles are small enough to enter the bloodstream, PM2.5 is the pollutant most strongly linked to cardiovascular disease, respiratory illness, and premature death.
Days by Dominant Pollutant (2019)
| Pollutant | Days as Dominant | Share of Year |
|---|---|---|
| Fine Particulate Matter (PM2.5) | 7 | 100% |
Is the Air Getting Better or Worse?
Air quality in Colleton, South Carolina has been improving over the past decade, with median AQI dropping by roughly 2.3 points per year. That is consistent with the broader national pattern — most U.S. metros have seen steady reductions in particulate and ozone pollution since the 2010s as cleaner vehicles and power plants come online.
In 2014, Colleton, South Carolina posted a median AQI of 42. By 2019 that figure was 26 — a drop of 16 AQI points cleaner across 6 years of EPA records.
Year-by-Year AQI in Colleton, South Carolina
| Year | Median AQI | Good Days | Unhealthy Days | Dominant Pollutant |
|---|---|---|---|---|
| 2014 | 42 | 233 | 1 | PM2.5 |
| 2015 | 37 | 252 | 0 | Ozone |
| 2016 | 39 | 264 | 3 | PM2.5 |
| 2017 | 41 | 263 | 0 | PM2.5 |
| 2018 | 36 | 294 | 0 | PM2.5 |
| 2019 | 26 | 7 | 0 | PM2.5 |
Health Context for Colleton, South Carolina
Across the past five years, this area has logged just 0 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 0 days per year, or roughly one every other month. That is a low count by national standards.
For most healthy adults, current air quality in this area does not require any change in behavior. People with severe asthma, COPD, or recent cardiac events should still keep an eye on daily AQI alerts, especially during wildfire season. Because PM2.5 penetrates deep into the lungs and bloodstream, an N95 or KN95 mask provides meaningful protection on smoky or high-particulate days — surgical masks do not.
How This Grade Is Calculated
The AirHistory Air Quality Grade combines four signals: the 5-year median AQI (40% of the score), the 10-year trend direction (30%), the count of unhealthy days per year (20%), and the dominant pollutant type (10%). All four come directly from the EPA Air Quality System (AQS), which aggregates readings from federally certified monitors. Read the full methodology.
Colleton, South Carolina has an Air Quality Grade of A (excellent) with a 5-year median AQI of 26. The dominant pollutant is Fine Particulate Matter (PM2.5), and air quality has been improving over the past decade.
The data source behind this answer is the EPA Air Quality System (AQS). Every figure on the page traces back to that source; the methodology page describes the inputs and the refresh cadence in full detail.
A practical caveat: the headline answer above reflects the most recent the EPA Air Quality System (AQS) vintage; underlying data is often revised for months after first publication, and the right reference for any specific decision is whichever vintage is current at the time of the decision. The as-of date is stamped on every page.
Source: EPA Outdoor Air Quality Data, 2026.