Thousands of residents in communities across parts of Mississippi and California have been advised to stay indoors as much as possible because levels of fine particle pollution (PM2.5) have reached an “unhealthy” level, as of Sunday, February 8, at 4.30 a.m., according to the AirNow Map, produced by the Environmental Protection Agency (EPA). 

Areas Affected by ‘Unhealthy’ Air 

The AirNow map shows an affected area in California that includes a large section of the Plumas National Forest, parts of Highway 395 near the Herlong junction, and several towns along Highway 70, including Portola, Mable, and Beckwourth. 

In Mississippi, a pocket of PM2.5 is lingering over coastal areas—including Long Beach, Gulfport, and Biloxi—and extending inland to affect Highway 67, Wortham, Saucier, and Orange Grove.

What Is PM2.5?

The EPA classifies PM2.5 as tiny particles of pollution, 2.5 micrometers or less in size, which is smaller than a strand of hair. It warns that PM2.5 can be one of the most dangerous forms of air pollution because the particles are so small they can be inhaled, unknowingly, penetrating deep into the lungs and bloodstream, exacerbating existing health conditions or triggering symptoms ranging from coughing and eye, throat, and nose irritation to chest tightness and shortness of breath.  

What Should Residents Do When PM2.5 Is Elevated?

When AirNow records “unhealthy” levels of PM2.5 in the atmosphere, the EPA advises everyone to take steps to reduce their exposure. 

This includes reducing the length and intensity of outdoor activities—such as choosing to walk rather than run.  

Those in sensitive groups, including older adults, children, and people with pre‑existing heart or lung conditions, should avoid exposure as much as possible and limit outdoor activities, postponing them until air quality improves.

PM2.5 can also affect indoor air quality. So the EPA advises people in affected areas to avoid burning candles, woodburners, and indoor fires, and to consider using an air filter or purifier to keep the air clear. 

Where Does PM2.5 Come From?

PM2.5 can come from a variety of sources, including smoke from wildfires and smokestacks, emissions from power or industrial plants and vehicles, or dust from construction sites and unpaved roads. 

How Does The EPA Measure And Communicate Air Quality? 

Alongside the AirNow Map, which highlights areas with elevated levels of air pollution across America, the EPA also uses the Air Quality Index (AQI) to measure and communicate air quality.

The AQI is a standardized system with a scale from 0 to 500 that color‑categorizes air quality from Good to Hazardous:

• 0-50: Good. The air quality is satisfactory and poses little or no risk.
  
• 51-100: Moderate. The air quality is acceptable; however, a small number of unusually sensitive individuals may be affected.

• 101-150: Unhealthy for Sensitive Groups. Members of sensitive groups (children, older adults, and people with heart or lung disease) may experience health effects, but the general public is less likely to be affected.

• 151-200: Unhealthy. Everyone may begin to experience health effects, but sensitive groups may experience more serious effects.

• 201-300: Very Unhealthy. When air pollution reaches this level, the risk of health effects is increased for everyone.
  
• 301-500: Hazardous. Health warnings of emergency conditions are issued by the EPA as the entire population is more likely to be affected.