PITTSBURGH (KDKA) — Allegheny County’s air quality improved during 2018, according to new Health Department data.

A report released by the Allegheny County Health Department today shows 2018 was the cleanest year on record for PM 2.5 at the Liberty-Clairton area monitor. It’s one of nine monitors throughout the region that measure levels of PM 2.5, or fine inhalable particles, in the air.

The Health Department certifies its data from these monitors yearly and sends it to the U.S. Environmental Protection Agency for quality assurance. The EPA is required to periodically review this data, as well as set national air quality standards, under the federal Clean Air Act.

In 2018, the annual value of PM 2.5 at the Liberty monitor was 11.5 mg/cm, says the Health Department. Not only is that lower than the monitor’s 2017 value of 13.4 mg/cm — it’s lower than the EPA standard of 12 mg/cm. The monitor’s 24-hour PM 2.5 value was also lower than the EPA standard and its 2017 value. Based on this data, the Health Department says, the Liberty monitor has attained EPA standard.

According to County Executive Rich Fitzgerald, this marks the first time the Liberty monitor has met the EPA standard. All of the county’s other PM 2.5 monitors were already in compliance with the EPA standard, according to previous Health Department data.

The Health Department attributes these improvements in air quality to policy changes it made to enforce the Clean Air Act more aggressively, including fining U.S. Steel’s Clairton Coke Works $1.6 million in 2018 — the largest fine issued in ACHD history, according to a press release from the Health Department.

“We have worked diligently to address the issues at the Liberty monitor, and the 2018 data is showing that significant progress is being made,” the Health Department’s director, Dr. Karen Hacker, said in a press release. “In addition to meteorological influences, we believe these improvements at the Liberty monitor are a result of strong enforcement actions, fines and penalties, and consequent improvements made at U.S. Steel’s Clairton Coke Works.”