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Liberty-Clairton Area Dealt More Unhealthy Air Quality, More H2S Exceedances

The Mon Valley was dealt another bout of unhealthy air Wednesday morning, with residents in the Liberty-Clairton area again waking up to the worst air quality in the nation according to AirNow.gov, a U.S. Environmental Protection Agency website that tracks the Air Quality Index (AQI) throughout the country.

AQI soared into the red, unhealthy-for-everybody range this morning, peaking at 163. An air dispersion report issued Wednesday by the Allegheny County Health Department (ACHD) noted a strong surface inversion occurred today.

The forecast, sourced from the state Department of Environmental Protection (DEP) said:

Fine particulate levels will be at their highest between 4 and 10 a.m. this morning, then the breaking inversion along with a southeast wind will send overall averages down into the mid to high moderate range for the overall daily average.

While Wednesday’s report called for somewhat better air dispersion conditions for tomorrow morning, it did forecast another moderate-to-strong surface inversion early Thursday.

But it wasn’t just fine particulate levels that were elevated in the Mon Valley this week – concentrations of hydrogen-sulfide (called H2S for short, it’s a colorless gas recognized by its distinct rotten-egg odor) were also high. 

In fact, the 24-hour average concentration of H2S at ACHD’s air quality monitor in Liberty Borough was 0.009 ppm Tuesday, exceeding Pennsylvania’s standard of 0.005 ppm. Levels of hydrogen sulfide at the Liberty monitor were so high Wednesday that by 8 a.m. another exceedance was guaranteed.

That means that on four of the last six days, levels of H2S were over the regulatory limit, and the intervening days weren’t much better: The average concentration at the Liberty monitor was 0.005 ppm on both May 16 and May 17. Over this same six-day period, concentrations at the North Braddock monitor flirted with regulatory limits but did not exceed them.

“How many more hydrogen-sulfide exceedances need to happen in the Mon Valley before the Allegheny County Health Department provides an update on the enforcement order it issued to U.S. Steel over this very issue?” GASP Executive Director Rachel Filippini asked.

By way of background: GASP has long called on ACHD to track down the source of the county’s H2S problem, and on April 1 the department finally took action, issuing a Notice of Violation to U.S. Steel covering 25 exceedances that occurred in 2020 and seven in the first quarter of 2021 at the Liberty monitor. Eight exceedances of the state’s 24-hour H2S standard that occurred at the North Braddock monitor December 2020 through March 2021 were not included.

This type of notice is the first step for any enforcement action –  including civil penalties of up to $25,000 per violation per day – for air pollution sources. U.S. Steel had 14 days to schedule a meeting with ACHD to discuss the NOV before ACHD may proceed with further enforcement action. 

No further information about the notice or U.S. Steel’s response is available on the ACHD website. GASP submitted a formal Right to Know request to glean more information and will provide an update when that request is granted.

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