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UPDATED: Mon Valley Experiences More Air Quality Exceedances, ACHD Says Conditions to Persist Throug

Editor’s Note: This story was updated at 4:10 p.m. on Saturday, Nov. 7 to reflect updated air quality data and table.

Levels of hydrogen sulfide were so high through 8 a.m. Saturday at the Liberty monitor that it’s mathematically impossible NOT to exceed the state’s 24-hour standard – the fourth such exceedance this week and the 24th of the year in Allegheny County, according to preliminary data from the health department.

The county experienced two air quality exceedances Friday when the concentration of hydrogen sulfide at the Liberty monitor was more than double the state limit. The concentration of fine particulate matter (PM2.5) at the Liberty monitor also exceeded the federal health-based regulatory standard.  There were also H2S exceedances on Wednesday, Nov. 4, and Thursday, Nov. 5.

Adding insult to injury, the highest one-hour concentration of H2S at the Liberty monitor for all of 2020 — 0.056 ppm — occurred between 8 p.m. and 9 p.m. Friday.

And health officials said not to expect a reprieve from poor air quality until early next week: Stagnant conditions causing poor air dispersion exacerbating air pollution is expected to persist through at least Tuesday.

Saturday also marks the third consecutive Code Orange Air Quality Action Day, according to a press release issued by the state Department of Environmental Protection.

“The concentrations of these air pollutants at the Liberty monitor are alarmingly high and reinforce the need for ACHD to make good on its commitment to draft new episodic weather regulations,” GASP Executive Director Rachel Filippini said. “Residents in the Mon Valley are suffering and need real leadership and swift action from Allegheny County Chief Executive Rich Fitzgerald, ACHD, and industrial polluters like U.S. Steel.”

She added: “ACHD strongly encouraged residents and businesses to voluntarily help reduce air pollution. U.S. Steel needs to tell the public what steps its taking to protect local residents’ health.”

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