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Allegheny Co. Health Dept. Issues Mon Valley Air Pollution Warning; Yet Another H2 Exceedance Noted

Updated: Mar 27

Editor’s Note: This story was updated at 12:53 p.m. Saturday to include information about an H2S exceedance.

Allegheny County Health Department on Saturday morning issued a Mon Valley Air Pollution Warning through its Allegheny Alerts system.

The message read:

An Air Pollution Warning has been issued for the Mon Valley. The 24-hour PM2.5 standard for the Mon Valley has been exceeded at an official monitoring station in the Mon Valley and is likely to continue.

Young children, the elderly, and those with respiratory problems, such as asthma, emphysema, and bronchitis, are especially vulnerable to the effects of air pollution and should limit outdoor activities during this time.

Companies contributing to pollution can contribute by temporarily reducing activities that produce emissions.

More information about fine particulate matter (PM2.5), as well as the current monitored values, can be found (on the ACHD website).

Liberty-Clairton was listed as having the worst Air Quality Index (AQI) in the nation, according to

But PM2.5 wasn’t the only pollutant exceeding regulations. By noon Saturday hydrogen sulfide (H2S) concentrations were so elevated that an exceedance was guaranteed at ACHD’s air quality monitor in Liberty Borough. It’s seventh so far this month at the Liberty monitor.

ACHD announced earlier this month that it would begin sending out Mon Valley Air Pollution warnings when air quality forecasts indicate a potential for poor air quality.

The notices are part of regulations currently, but the step by ACHD provides notice now for residents in the Mon Valley of the potential for poor air quality.

The alerts will be sent out using Allegheny Alerts system, which requires a free subscription. Users can opt to receive notifications via email, text, or phone through the app. Visit to sign up.

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