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Mon Valley Sees 5 Straight Days of H2S Exceedances & Stench; ACHD Remains Mum on Fix

It was a gorgeous weekend in Pittsburgh. There were blue skies, unseasonably warm temperatures, and plenty of sunshine. In the Mon Valley, though, all that fall splendor was spoiled by a rotten-egg stench that some SmellPGH users said caused physical symptoms like a sore throat, eye irritation and nausea.

The cause of that stench? We’d bet the farm high concentrations of hydrogen sulfide (H2S for short) at Allegheny County Health Department’s air quality monitor in Liberty Borough were to blame.

How bad was it? ACHD monitor data show H2S concentrations at the Liberty monitor handily exceeded Pennsylvania’s 24-hour standard for five straight days - Thursday, Friday, Saturday, Sunday and today.

That means H2S concentrations at ACHDs Liberty air quality monitor exceeded PA’s 24-hour average standard on 11 of 15 days Oct. 23 through Nov. 6. It also means that exceedances in 2023 at the Liberty monitor (81) have already outpaced 2022 (when there were 78 such exceedances).

The 2023 Liberty total now guarantees this will be the second-worst year for H2S exceedances since 2017.

“And with 55 days left in 2023, we’re actually on pace to leap-frog 2021 for the absolutely worst year since 2017,” GASP attorney Ned Mulcahy noted.

Why do we continue to raise a stink about the issue? Because exposure to the levels of hydrogen sulfide we see (way too often) in the Mon Valley can cause irritation to the eyes, nose, or throat as well as headaches, poor memory, tiredness, and balance problems. It may also cause difficulty in breathing for some asthmatics, according to the Agency for Toxic Substances and Disease Registry.

If you’re now asking, “What is the source of all this H2S?” a 2022 ACHD study that concluded, "based on all available data and resources, H2S exceedances that occurred at the Liberty site during the period of Jan. 1, 2020 through March 1, 2022 can be attributed entirely to emissions originating at US Steel's Clairton coking facility."

Then, days after the study was published, ACHD issued a $1.8 million enforcement order against U.S. Steel over the H2S emissions issue. The company appealed the order and the case is ongoing.

State Department of Environmental Protection emissions inventory shows U.S. Steel’s Clairton Coke Works emitted – on average – more than 120 tons of H2S annually from 2010 to 2020, making it the largest stationary source in the state.

Despite the possibility of the Liberty monitor facing the worst year of H2S exceedances since 2017, and despite the public outcry about how the stench impacts residents’ health and quality of life - at Board of Health meetings, on social media, and via CREATE Lab’s Smell PGH app - ACHD has remained pretty much mum on the matter.

That’s why GASP is again publicly asking ACHD: Is there something going on at U.S. Steel’s Clairton Coke Works to cause these H2S values? Has the air quality program been in contact with the company?

“Mon Valley residents don’t deserve their lives and health interrupted by these days-long periods of stench and exceedances,” Campbell said. “We understand that the H2S case against U.S. Steel is ongoing, but that doesn’t absolve the health department of its duty to enforce Pennsylvania’s 24-hour H2S standard and protect residents.”

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