Americans across four US states told to stay indoors due to lung-damaging toxins filling the air

Hundreds of thousands of Americans across four states are waking up to a dire warning to stay indoors as the air outside has become hazardous to breathe.

Air quality meters from the US Environmental Protection Agency (EPA) sounded the alarm Monday morning in Pennsylvania, Georgia, Alabama, and Oklahoma as readings reached ‘unhealthy’ levels for all residents.

In Pennsylvania, the EPA’s air quality-tracking system AirNow detected an extremely hazardous pocket of polluted air forming around the Pittsburgh suburbs just 10 miles south of the city.

Live tracking data captured sharply elevated levels of PM2.5, microscopic particles composed of toxic compounds or heavy metals that are small enough to penetrate the lungs, exacerbate respiratory issues like asthma, and contribute to heart attacks.

In the South, a 110-mile swath across eastern Oklahoma has been declared unhealthy by the EPA, and an 83-mile-long pocket centered over Columbus, Georgia is dealing with highly polluted air Monday morning.

The increased levels have been tied to recent wildfire smoke exacerbating a condition called stagnant air, where little to no wind and high atmospheric pressure trap pollution near ground level. 

Air quality levels are measured on a scale from 0 to 500: good (0–50) carries little risk, moderate (51–100) may affect sensitive individuals, unhealthy for sensitive groups (101–150) poses increased risk, and unhealthy (151–200) impacts everyone, limiting outdoor activity.

In Glassport, Pennsylvania, the Air Quality Index (AQI) reached 192, while readings in parts of Oklahoma, Georgia, and Alabama exceeded 150.

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To understand the impact of stagnant air on cities, it’s helpful to look at atmospheric pressure. Pressure is measured in millibars, with normal sea-level pressure being 1,013 millibars.

Anything between 1,015 and 1,020 millibars is considered a high pressure system, with strong pressure exceeding 1,030 millibars, especially in the winter.

In Glassport, air quality-tracking website IQAir revealed that pressure had reached 1,031 millibars Monday morning, causing sinking air from above that warms and compresses as it descends. 

Stagnant air means the air around you is barely moving, like it’s stuck under a lid, so pollution, smoke, car fumes, and other particles can’t blow away or mix higher up in the atmosphere, causing them to build up near the ground where we breathe.

While the AQI directly over Pittsburgh has remained at ‘moderate’ levels, that entire region of western Pennsylvania is stuck under a high pressure system trapping more pollutants than normal.