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UPDATED: Unhealthy Air Quality Returns to Mon Valley as Allegheny County Experiences 51st H2S Exceed

Editor’s Note: This story was updated at 1-:17 a.m. Dec. 17 to include information and updated chart to reflect an H2S exceedance that took place Thursday.

Horrific air quality returned to the Mon Valley this week, with the showing AQI NowCast values at Allegheny County Health Department’s air quality monitor in Liberty borough soared to 164, on Tuesday which is considered unhealthy.

How bad has it been? Fine particulate matter (otherwise known as PM2.5) averaged 82.6 ug/m3 over the first 12 hours of the day Tuesday. The federal health-based 24-hour average standard is 35 ug/m3, and ACHD on Tuesday morning issued a Mon Valley Air Pollution Warning alerting residents that there’s been a PM2.5 exceedance at the Liberty monitor.

You can learn more about Mon Valley Air Pollution Warnings here.

During periods of unhealthy air quality, the EPA suggests that people with heart or lung disease, older adults, children, and teens should avoid strenuous outdoor activities, keep outdoor activities short, and consider moving physical activities indoors or rescheduling them to reduce exposure to air pollutants.

But that wasn’t the only air quality issue on our radar: Allegheny County also reached a grim benchmark this week – Monday, Tuesday, and Thursday marked the 50th, 51st, and 52nd days this year that concentrations of hydrogen sulfide (AKA H2S AKA that gross rotten egg odor) exceeded Pennsylvania’s 24-hour average at the air quality monitor in Liberty borough. 

It’s worth noting that H2S values were so high Tuesday morning, that an exceedance was guaranteed by 5 a.m.

The ongoing issue remains a concern at GASP.

“That more than doubles the 2020 tally at the Liberty monitor with 17 others at Allegheny County Health Department’s air quality monitor in North Braddock,” our Executive Director Patrick Campbell said. “GASP has been following the data closely and can tell you that residents in the Mon Valley have told us the issue is taking a real toll on their physical and mental wellness.”

Residents also took to Twitter to express their frustration and anger:

When I went outside this morning I could immediately tell that something was wrong. If you live in Allegheny County, please stay inside today as much as possible. — Katrina Eames (@katrinaeames) December 14, 2021

While ACHD issued an H2S-related enforcement order against U.S. Steel’s Clairton Coke Works in April, officials haven’t said word one since.

“At this point, it’s inexcusable that our public health officials have refused to offer more information about what’s causing these elevated levels of H2S in the Mon Valley, what they are doing to remedy the issue, and how they are holding U.S. Steel accountable for the part it plays in this mess,” Campbell said. “Residents deserve better than the silent treatment when it comes to matters of public health.”

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