2022's 4th Exceedance of PA’s H2S Air Quality Standard Noted in Mon Valley; Still No Word from ACHD

Updated: Sep 9

Sadly, if you live in the Mon Valley, this likely isn’t news: Air quality was terrible early Saturday, with AirNow.gov showing “unhealthy” NowCast AQI values that were – for a time – the worst in the nation.


Users took to the CMU CREATE Lab’s SmellPGH app to share their complaints and concerns, describing physical symptoms like nausea, headaches, scratchy throats, and respiratory trouble.


One user noted the lack of action from the Allegheny County Health Department (ACHD), writing, “You are ruining our quality of life.” Many, many others lamented the overpowering stench.


The culprits? Air quality monitor data showed elevated concentrations of many pollutants Saturday but undoubtedly hydrogen sulfide (H2S) – a flammable, colorless gas produced during the coke-making process (among other things) that smells like rotten eggs – played a part.


Exposure to low concentrations of hydrogen sulfide may cause irritation to the eyes, nose, or throat. It may also cause difficulty in breathing for some asthmatics. The EPA says exposure to low concentrations of hydrogen sulfide may also cause headaches, poor memory, tiredness, and balance problems.   


People usually can smell hydrogen sulfide at concentrations as low as 0.0005 parts per million. Concentrations exceeded that threshold handily on Saturday.


In fact, the H2S concentration at Allegheny County Health Department’s air quality monitor in Liberty Borough averaged 0.007 ppm over the full day. That exceeds Pennsylvania’s 24-hour average limit of 0.005 ppm. Saturday marked the fourth exceedance so far this year at the Liberty monitor.

For those trying to keep track: H2S concentrations at the Liberty monitor exceeded the Pennsylvania 24-hour average standard 54 times last year – which was more than twice 2020’s numbers. There were 18 other such exceedances at Allegheny County Health Department’s air quality monitor in North Braddock Borough.


Despite the regularity with which these exceedances occur and our regular calls to action asking ACHD to do better when it comes to communicating the issue with residents, Chief Operating Officer Patrick Dowd and health department leadership have so far refused to weigh in on the issue publicly.


We’ve said it before and we’ll say it again now: We don’t know why ACHD has refused to be more transparent on this issue. 


“Their silence is telling residents plenty,” GASP Executive Director Patrick Campbell said. “We are again asking Mr. Dowd to do everything in his power as chief operating officer to create a more robust communications plan for the air quality program.”


What do we know about what might be causing all these H2S exceedances? We know that ACHD issued an H2S-related enforcement action against U.S. Steel’s Clairton Coke Works in April 2021 (as well as an associated press release), but unfortunately, no other details have since been provided to the public.


“These H2S exceedances and bouts of unhealthy air happen too frequently for residents to hear nothing from health officials,” Campbell said. 



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