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This story comes from our partner, 90.5 WESA.

In February, the Allegheny County Health Department announced compliance with federal air quality standards for the first time ever. But compliance with state hydrogen sulfide standards in the Mon Valley has fallen in 2021.

Hydrogen sulfide, or H2S, is a gas with a rotten egg smell that can cause eye, nose and throat irritation, as well as fatigue and respiratory effects like wheezing. So far this year, there have been 33 violations of the state’s 24-hour standard for hydrogen sulfide, which already surpasses the 25 exceedances in 2020. David Good, chief of air monitoring at ACHD, the agency that regulates air quality for the county, said the department projects there will be 55 violations by the end of 2021.

“It’s troubling,” said Ned Mulcahy, staff attorney for the Group Against Smog and Pollution, known as GASP. “It’s not the trend direction we would expect or hope.”

The Liberty air quality monitor, where the exceedances were measured, is about two miles from U.S. Steel’s Clairton Coke Works, the largest emitter of H2S in Pennsylvania. A 2018 study by the University of Pittsburgh and ACHD concluded U.S. Steel was “likely a substantial contributor” to H2S concentrations at the Liberty monitor.

U.S. Steel spokeswoman Amanda Malkowski said the 2018 study does not account for other sources of hydrogen sulfide, which include wastewater treatment facilities and landfills.

Good said the health department has several efforts underway to improve surveillance, including a new permanent H2S monitor installed in North Braddock and another proposed for Clairton. In addition, ACHD is planning a special study of hydrogen sulfide using 10 portable monitors throughout the Mon Valley, slated to begin in the fall and last at least a year.

“The missing link that we have right now is to try to better quantify the other potential sources of hydrogen sulfide,” Good said. “There are contributions from landfills. There are contributions from wastewater treatment plants. But we do not think they’re on the same scale as the contributions that we get from the Clairton Coke Works.”

Mulcahy said the special study has the potential to support enforcement.

“Data is incredibly important to enforcement,” Mulcahy said. “It’s one thing to say, ‘This stinks. Knock it off.’ It’s another to say, ‘Here are the readings. Here are the health standards.’ … It’s having reliable evidence that’s captured by EPA methods with the chain of custody that can be used in court. That’s incredibly important.”

Two proposed regulations could help curtail H2S emissions, including revised coke oven regulations and an episodic weather rule that would require industrial plants to cut emissions during prolonged air inversions. During an inversion, a blanket of cool air traps warm air—and pollution—close to the ground. Severe episodes, like the six-day inversion in December 2019, can cause days of unhealthy air, and researchers predict climate change will make inversions worse. Malkowski said U.S. Steel supports the episodic weather rule.

The Allegheny County Health Department issued a notice of violation to U.S. Steel for exceedances of the state hydrogen sulfide standard in April. The notice covers the 25 exceedances at the Liberty monitor in 2020, and 7 of the exceedances in 2021. Good said ACHD was not able to discuss the ongoing litigation.