Pittsburgh Area Getting Another Blast Of Canada Wildfire Smoke

PITTSBURGH, PA —If you thought the Canada wildfire smoke problems had vanished from Western Pennsylvania, think again. The Allegheny County Health Department is warning that the county likely will have elevated concentrations of fine particulate matter, known scientifically as PM2.5, on Wednesday and Thursday.

The state Department of Environmental Protection is expected to issue an Air Quality Action Day alert for one or both days.

Fine particulate matter refers to very small particles in the air that are less than 2.5 microns or less wide. What does that mean? There are about 25,000 microns in an inch. So insignificantly sized are they that are about 30 times smaller than a human hair.

An Air Quality Action Day is declared when the air quality index is predicted to be Code Orange or higher. On an Air Quality Action Day, children, the elderly, and those with respiratory problems, such as asthma, emphysema, and bronchitis, are vulnerable to the effects of air pollution and should limit outdoor activities.

Here's the latest from the National Weather Service: