10/20/2026
The Allegheny County Health Department is issuing a Mon Valley Episode Watch for Tuesday, October 20, 2026.
The Episode Warning runs parallel with the Pennsylvania Department of Environmental Protection issuing a Code Orange (Unhealthy for Sensitive Groups) Air Quality Alert for the Monongahela Valley (Mon Valley).
High pressure over the area will result in limits to air mixing and trap pollutants close to the surface for several hours in the morning on Tuesday. The result will be several hours in the Code Orange or higher range.
The Code Orange was specifically issued for fine particulate matter (PM 2.5) is based on a 24-hour average, where individual hours will have concentrations higher (and lower) than the forecast.
Code Orange (Unhealthy for Sensitive Groups)
Sensitive groups include people with heart or lung disease, older adults, children and teenagers, pregnant women, minority populations, and outdoor workers.
Sensitive groups should make outdoor activities shorter and less intense. It’s OK to be active outdoors but take more breaks. Watch for symptoms such as coughing or shortness of breath. People with asthma should follow their asthma action plan and keep quick relief medicine handy. People with heart disease should monitor symptoms such as palpitations, shortness of breath, or unusual fatigue may indicate a serious problem. If you have any of these, contact your health care provider.
Companies in the Mon Valley contributing to pollution are required to temporarily reduce activities that produce emissions.
PM 2.5 is a type of particle pollution that comes from many different sources. Fine particles (2.5 micrometers in diameter and smaller) come from power plants, industrial processes, vehicle tailpipes, woodstoves, and wildfires.
Particle pollution causes several serious health problems, including coughing, wheezing, reduced lung function, asthma attacks, heart attacks and strokes. It also is linked to early death in people with heart or lung disease.
Get the latest local updates on air quality by enrolling in Allegheny Alerts for free.
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The Allegheny County Health Department's mission is to protect, promote, and preserve the health and well-being of the more than 1.2 million people who call Allegheny County home.
