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On the 12th Day of Stench-mas My Health Department Gave to Me… The Cold Shoulder

If you live in or near the Mon Valley, you have our condolences. The stench has been TERRIBLE lately.

How terrible?

Today marks the 12th day in a row that hydrogen sulfide (H2S) concentrations at the Allegheny County Health Department’s air quality monitor in Liberty exceeded Pennsylvania’s 24-hour-average standard.

Of course, you don’t need us to tell you it stinks. But we thought you might like knowing the run we’re on is unprecedented in recent years.

GASP reviewed hourly H2S data through 2017 and determined that this 12-day H2S exceedance streak is the longest stretch of stench at the Liberty monitor over that time period.

Check out this graph we crafted showing every H2S exceedance by date since 2017:

A few insights to consider:


  • This latest spate of exceedances at the Liberty monitor puts Allegheny County solidly on track for 2023 to be the worst year for exceedances since 2017.

  • According to air monitor data, November, as luck would have it, is the stinkiest month for us here in Allegheny County.

  • On the flip side, January is most stank-free by quite a big margin.

  • Talking about patterns: There has been an exceedance on June 29 in six of the past seven years, and on the “good year” (2020), we were only 0.001 ppm away from a perfect seven for seven.

Despite this long stretch of abysmal H2S levels, ACHD has provided the public with zero updates regarding the ongoing exceedances and what it is doing to stem the issue.

“For residents, the past two weeks must have felt like a horrible version of ‘Groundhog Day’ - one without Bill Murray or laughs,” GASP Executive Director Patrick Campbell said. “Every day for the past 12 days, our neighbors have dealt with outrageous levels of industrial stench and associated physical symptoms.”


He added:


“These exceedances have been a known issue for years. Residents need to know what their public health officials are doing to address this issue. GASP is AGAIN calling on ACHD to be transparent.”

Editor’s Note: To make an air quality complaint regarding H2S, residents can use ACHD’s online system or reach the department at 412-578-8103.




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