AirNow/EPA
By Joe Edwards
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Thousands of residents across parts of South Carolina and North Carolina are facing "unhealthy" levels of air pollution early on Friday morning, according to the Environmental Protection Agency's (EPA) AirNow Map.
The map shows a pocket of "unhealthy" ozone and fine particle pollution (PM2.5) encompassing Greenville, Spartanburg, and a portion of neighboring North Carolina.
When air quality reaches the "unhealthy" level, EPA guidelines recommend that sensitive groups—which typically include children, older adults, and those with certain medical conditions—avoid long or intense outdoor activities and to consider rescheduling or moving activities indoors.
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The rest of the population is advised to reduce long or intense activities and take more breaks during outdoor activities.
"The spikes were likely due to a rather stable atmosphere overnight, which trapped pollutants near the surface, aided by emissions from many prescribed fires and wildfires observed across the Southeast U.S. recently," the South Carolina Department of Environmental Services told Newsweek via email on Friday.
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What Is PM2.5?
PM2.5 refers to fine inhalable particles with diameters of 2.5 micrometers or smaller—about 30 times thinner than a human hair. Because of their tiny size, these particles can penetrate into the lungs. PM2.5 can come from direct sources such as construction activity, unpaved roads, fields, smokestacks, and fires, including wildfire smoke.
What Is Ozone?
“Ozone is a secondary pollutant, meaning it's not emitted directly from sources, but is formed through chemical reactions,” AccuWeather meteorologist Brandon Buckingham previously told Newsweek. “These reactions require sunlight and higher temperatures, making warmer months more prone to ozone formation. When air is stagnant, pollutants don't get dispersed, allowing ozone to build up to unhealthy levels.”
How the EPA Measures Air Quality
The EPA employs the Air Quality Index (AQI) to measure air quality across America. It is a scale from 0 to 301+ that rates air quality into six categories which range from good to hazardous, based on to the health risk to the public.
- Green – Good (0 to 50): Air quality is satisfactory, and air pollution poses little or no risk.
- Yellow – Moderate (51 to 100): Air quality is acceptable. However, there may be a risk for some people, particularly those who are unusually sensitive to air pollution.
- Orange – Unhealthy for Sensitive Groups (101 to 150): Members of sensitive groups may experience health effects. The general public is less likely to be affected.
- Red – Unhealthy (151 to 200) Some members of the general public may experience health effects. Members of sensitive groups may experience more serious health effects.
- Purple – Very Unhealthy (201 to 300) Health alert: The risk of health effects is increased for everyone.
- Maroon – Hazardous (301 and higher) Health warning of emergency conditions; everyone is more likely to be affected.
Update 3/27/26, 5:30 a.m. ET: This article was updated with additional information.
Update, 3/30/26, 12:22 p.m. ET: This article was updated with comment from the South Carolina Department of Environmental Services.
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