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The Mon Valley Stinks (Literally): Sky-High H2S Concentrations Cause Air Quality Exceedances

Updated: Apr 3

Editor’s Note: This story was updated at 9:25 a.m. on Thursday, July 29 to include additional information about an air quality exceedance that occurred on Wednesday, July 28. The associated chart was also updated to reflect the new data.

Hydrogen sulfide concentrations at Allegheny County Health Department’s air quality monitors in Liberty and North Braddock boroughs were sky-high Tuesday morning – so high that by 10 a.m. exceedances of the state’s 24-hour average standard were guaranteed.

On Wednesday, Liberty experienced another H2S exceedance, with the North Braddock monitor seeing concentrations that were right up to but not over the regulatory limit.

That makes 33 exceedances of the H2S standard in the past seven months at the Liberty air quality monitor and 12 at North Braddock. 

“For perspective, that’s already more H2S exceedances than in all of 2020 and just three shy of making this the worst year we’ve seen since 2017,” GASP Executive Director Rachel Filippini said. “Clearly, we have an issue here – one that health officials are remiss in not addressing publicly.”

GASP is again calling on – nay, demanding – ACHD publicly address these exceedances – both in general and as they happen. 

For the uninitiated: Hydrogen sulfide, or H2S for short, is a colorless gas that’s recognizable by its rotten-egg odor. It’s a stench that those in the Mon Valley – and folks downwind of it – deal with all too often.

“Residents are routinely impacted by the pungent odor and deserve to be informed about what’s going on at U.S. Steel’s facilities to cause the H2S issue, as well as what the department is doing to hold the company accountable,” Filippini said. “They also deserve to know when there have been H2S air quality exceedances. That kind of public disclosure helps build trust and helps hold polluters responsible.”

Enough’s enough, ACHD.

There has been no update regarding the April 1 notice of violation (NOV) issued to U.S. Steel for prior exceedances of the hydrogen sulfide ambient air quality standard at the Liberty monitor.  

That NOV covers 25 exceedances in 2020 and seven more from the first quarter of 2021. It did NOT include eight exceedances of Pennsylvania’s 24-hour H2S standard that occurred at the North Braddock air quality monitor from December 2020 through March 2021.

The public is also in the dark on the current status of the joint notice of violation issued to U.S. Steel by the health department and the Environmental Protection Agency in 2017 covering issues at the Edgar Thomson facility.

“We understand that issues connected to that NOV are still ongoing but certainly there must be some details that officials could share with the public,” Filippini said. “It’s been years since there’s been an update, yet troubling emissions issues continue at the facility in Braddock. Residents deserve better – and at the very least they deserve an update.”

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