PITTSBURGH (AP) — The Allegheny County health department has announced a fine of more than $1.8 million against U.S. Steel over emissions of hydrogen sulfide at its Clairton coke plant in western Pennsylvania that officials say have exceeded Pennsylvania’s ambient air quality standards.

Officials said the fine, based on data from the Liberty Borough air monitoring station since January 2020, represents the first penalty the department has issued against a single source over hydrogen sulfide emissions.

Residents have long complained about such emissions, which have a rotten-egg smell and according to the federal Centers for Disease Control and Prevention can irritate the eyes and respiratory system. Residents and environmental groups have urged stricter pollution limits on the plant, which produces fuel used in steel manufacture.

Last fall, the company announced cancelation of a planned $1.5 billion emission control upgrade to its Mon Valley Works and the shutdown of three batteries at the Clairton plant.

U.S. Steel said in a statement that it “remains committed to doing its fair share” to protect air quality in the communities in which it operates, but questioned whether it was responsible for the hydrogen sulfide emissions, the Pittsburgh Post-Gazette reported.

The company said the health department “bases the fine on data obtained from the Liberty air monitor that collects data from multiple sources, most of which have no relation to U.S. Steel’s operations.”

The company said it had tried to study all impacts and identify all contributing factors of hydrogen sulfide at the air monitor jointly with the health department “but those efforts have been unsuccessful.”