The Pittsburgh region’s bad air history isn’t history after all, according to the American Lung Association’s 20th annual “State of the Air” report released Wednesday.

The report found worsening daily and annual soot pollution in the tri-state metro region for the three-year period, 2015 through 2017, along with higher levels of ground-level ozone, the principal component of unhealthy smog.

Allegheny County was the only county outside of California to receive failing grades in both soot categories and ozone.

But the region wasn’t alone in registering poorer air quality. While there were more regions where air quality has improved there were also many regions that experienced more days of high ozone levels and short-term airborne particle spikes in the three years covered by this year’s report than in the previous report for 2014-2016.

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“Residents of Pittsburgh and the metro area should be aware that we’re breathing unhealthy air, driven by local emissions, upwind sources, and extreme heat as a result of climate change, placing our health and lives at risk,” said Kevin Stewart, the ALA’s director of environmental health for advocacy and public policy.

The report ranked the 12-county Pittsburgh-New Castle-Weirton metro area 28th worst in the U.S. for ozone. It was ranked 37th worst last year.

And even as many other regions showed progress in reducing soot pollution, the tri-state region ran counter to that trend, ranking 7th worst nationally in annual airborne particle emissions and 10th worst in daily spikes exceeding healthy limits.

As it has for 19 of the 20 years the Lung Association has published a report, Los Angeles remains the metro area with the worst ozone pollution. The Fresno, Calif., metro area has had the worst annual particle pollution, and Bakersfield, Calif., is ranked 1st for short-term soot pollution.

Mr. Stewart said many eastern metro regions registered reduced annual levels of fine airborne particles during the three years covered by the report as power plants switched fuel from dirty coal to cleaner burning natural gas and vehicle emissions also improved.

But the Pittsburgh metro region has more industry than most, and its daily and annual soot pollution levels were significantly higher in this year’s report than they were in the previous report.

“The [particulate matter] levels are driven by local industry,” Mr. Stewart said. “Other metro areas don’t have that level of industry and not all metro areas have as many monitoring stations near obvious industrial sites. And its river valleys also trap pollution along the ground.”

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While the report states that “most of the nation has much cleaner air quality than even a decade ago,” and the national trend is toward reduced soot pollution, ozone levels are up in more regions that not, a product of warmer temperatures from 2015 through 2017.

According to the report, those years were the hottest recorded in global history.

Mr. Stewart said the warming climate not only makes ozone more likely to form, but also makes it harder to keep in check once it does.

According to the Lung Association, both ozone and particle pollution are dangerous to public health and can increase the risk of premature death and serious health effects such as lung cancer, asthma, cardiovascular damage, and developmental and reproductive harm.

The Lung Association’s air pollution “report card” uses the latest available quality-assured local, state and federal pollution data to calculate its rankings.

Mr. Stewart said the Clean Air Act has been successful in reducing emissions, but air quality is “not close to where we want to be.” He said the ALA supports more stringent emissions standards.

“Current controls,” he said, “are inadequate to protect public health.”

Dr. Karen Hacker, director of the Allegheny County Health Department, which regulates and enforces air emissions in the county, said the ALA’s report is “a reminder that air quality continues to be one of the most pressing public health challenges in our area.”

She said the department has ramped up enforcement efforts in the past two years, and will continue to aggressively hold polluters accountable. She said the department is working to reduce emissions of sulfur dioxide and particulate matter measured by the Liberty air monitor, downwind from U.S. Steel’s Clairton Coke Works in the Mon Valley.

“The Liberty monitor is the only monitor in the county that is out of attainment with EPA standards for sulfur dioxide and particulate matter, and addressing this issue is a top priority,” Dr. Hacker said.

She said the department will soon submit the county’s portion of a federally required state emissions control plan, which will address the county’s failure to meet soot limitations. The department is also working on formulating new coke oven rules to deal with fugitive emissions at the Clairton coke plant.

“We all want and deserve clean air, and we will continue to use all of our tools to improve the air that we all breathe,” Dr. Hacker said. “But we cannot do this alone, and we call upon industry leaders, such as U.S. Steel, to address all non-compliance issues and improve our air quality.”

Don Hopey: dhopey@post-gazette.com, 412-263-1983, or on Twitter @donhopey