It’s a hot July day and 86-year-old John Zavacky is chatting with friends in the South Side Market House’s Senior Center. In the background, an air conditioner hums while drawing the warm outside air into the cavernous main room.

Zavacky, a lifelong Pittsburgher, says the air quality is much better than it used to be. He can distinctly remember the city’s smoggy past.

"I mean, you can look out and see whatever you’re looking at," he said. "Before, with all the smoke and the stuff from the coke ovens, it was bad. The steel mills, especially the coke ovens, once they fired up there was smoke, flames, all over Hazelwood, Oakland, Greenfield, Squirrel Hill.”

Although the city is a far cry from the old adage “hell with the lid off,” Pittsburgh still struggles with pollution.

“Air quality in the Pittsburgh region was not good 249 days in 2016 – that’s about two-thirds of the time,” Breathe Project executive director Matthew Mehalik said.

Pollution brings negative health effects, Mehalik said, including higher rates of asthma and lung cancer. According to the American Lung Association's "State of the Air" report with data from 2014-16, Allegheny County was in the top 2 percent of counties for the risk of cancer from air toxins. The region, which includes parts of western Pennsylvania, West Virginia and Ohio, ranked 10th worst out of the 201 studied.

Using monitors spread out across the country, the Environmental Protection Agency tracks pollution under PM 2.5, or fine particles, and ozone to measure local air quality.

The agency then takes the worst number of the two measurements as the day’s air quality. For example, the index on July 26 was 65 – moderate, with the main pollutant as PM 2.5.

John Graham, a senior scientist with the Clean Air Task Force, studies western Pennsylvania air quality and said PM 2.5 pollution can come from many sources such as diesel trucks, trains, ordinary cars and burning coal.

“When you’re driving your car and you see a diesel truck in front of you, and the truck is going up a hill, you might see some black smoke coming out of the exhaust pipe,” he said.

But Graham says heavy industry, such as the U.S. Steel’s Clairton Coke Works, is one of the biggest contributors.

Ozone, a toxic gas, is also a contributor to air pollution. It mainly comes from traffic and is created by chemical reactions between exhaust and sunlight. It’s different from PM 2.5 in that it’s more of an issue in the summer.

Pollution levels under 50 are considered green, or good. Yellow, or moderate, means the air is acceptable, but there may be some health concerns for those extremely sensitive to pollution. Next is orange as unhealthy for sensitive groups – the elderly, children and those with heart and lung problems. That’s followed by red – plain unhealthy – and purple – very unhealthy. The scale tops out at hazardous with an upper ceiling of 500 and a sinister looking burgundy.

Pittsburgh hasn’t seen the extreme upper range of the spectrum for many years, but yellow and orange days are common.

According to EPA data, in 2017 the Pittsburgh area had only 105 days rated green for PM 2.5 pollution – that’s about 29 percent. Yellow was the most common with 250 days, but there were several dips into the upper end of the scale. Nine days reached orange, and a single day hit red.

That’s in step with the past decade – going back to 2010, green days ranged between 24 and 38 percent.

Ozone was a bit better in 2017, with nearly 70 percent of days classified green. Of the rest, most were rated yellow, with only nine days clocking in as orange. That’s also in step with the past decade – apart from July 30, 2018, the last time ozone reached red levels in southwestern Pennsylvania was one day in 2013.

Graham said that in 2000, pollution in western Pennsylvania has steadily declined in line with national trends. That’s been driven by shifts away from coal to cleaner energy sources, as well as stricter vehicle emissions regulations.

Local PM 2.5 pollution bucks the trend around 2014, when a small increase begins. Each subsequent year, the monitors measure a rise in levels.

Graham said year-to-year levels do have some variance, thanks to local meteorology and weather patterns. But the trend is still visible in the data’s three-year averages.

The increase is quite small – only about a microgram – and it’s mostly happening at the Liberty monitor, which measures emissions from Clairton Coke Works from about 2 miles away.

“I would guess that’s probably the most likely culprit,” he said. “When we see a different trend in particles, then it says there must be something else going on that’s sort of independent of the national trends.”

U.S. Steel did not respond to repeated requests for comment, but the Allegheny County Board of Health agrees the manufacturing company is causing the increase. It recently fined U.S. Steel $1 million for violating pollution standards. Health department director Dr. Karen Hacker said the recent upward trend is very concerning.

“We told them if they do not get their emissions in control, that we will tell them to shut down two of their batteries,” Hacker said.

Batteries, or rows of coke ovens, are used to cook coal into coke for steel production.

Jim Kelly, the Health Department's manager of environmental health, said the demand is a deviation from how the agency has dealth with polluters in their past, but that it's a needed change.

“That would be two of their oldest, and dirtiest, operating batteries,” said Kelly.

Kelly said the Liberty monitor is currently failing the EPA’s air quality standards, and that’s why the board is pushing U.S. Steel to reduce emissions.

However, he said the negative impacts of the coke works are confined to a small area measured by the Liberty and North Braddock (located on the border of North Braddock and East Pittsburgh) monitors. He said there’s too much focus on the Liberty monitor, and that painting the whole metro area’s air quality as poor based on it isn’t accurate.

“You take those two monitors out of the equation; the rest of our monitors are well below the standard,” he said. “The Braddock monitor is below the standard as well, but it’s higher than we would prefer, and that’s why it will be part of that emission reduction strategy.”

The Clean Air Task Force’s John Graham said he agrees that the Liberty monitor doesn’t tell the whole story, but for a different reason – he said air pollution still affects the whole metro area.

“The Liberty monitor is the one that most often has the worst air, but it’s only a third of the time based on these AQI numbers,” Graham said. “The same is true of the ozone numbers – almost every site is prone to having the worst pollution at least some of the time.”

In 2017, the Liberty monitor registered the worst air quality in the region on 35 percent of days –the largest portion by far.

Graham cautions that’s not a measure of air quality, just distribution. Even perfectly clear days are determined by the monitor registering the worst air quality that day. However, locations other than the Liberty monitor still set the day’s air quality standard the majority of the time.

“The whole air shed is prone to high air pollution,” he said.

Mehalik agrees, citing 2016 EPA data on the region’s best performing monitor – North Park. The detector is located on the roof of the North Park Golf Course in Wexford.

“The North Park monitor registered in the 50th percentile nationally,” Mehalik said. “So our best monitor is still in the worst half of measured particulate matter pollution in the country.”

In short, Pittsburgh's best monitor is still worse than half of all the monitors in the United States.

In addition, Graham said the EPA’s standards that define acceptable levels of air pollution may be too loose. To determine the standards, the agency spends years reviewing health studies and crafts the safe air quality levels based on the data. But the whole process takes years, Graham said, which means the data is often years old by the time the new standards are implemented.

“By the time they actually get the standard set based on the health evidence, the health evidence they’re using is now five or maybe even 10 years old,” Graham said. “This is just an issue with the way our regulatory system works.”

Graham says that the EPA’s standards are out of step compared to the goals set by Canada and the World Health Organization. He pointed to the American standard for the fine particle pollution of PM 2.5 as an example, as both Canada and the WHO's goals are more stringent than it.

“The daily standard in Canada might be 25, whereas our daily standard is 35,” Graham said. “The annual standard for the World Health Organization, they recommend 10, whereas our standard in the U.S. is 12.”

However, Jim Kelly said there’s an important distinction in the difference between goals and standards. The World Health Organization sets numbers that are ideals, he said, as a way to push for better air quality. In contrast, failing the EPA’s standards carries significant consequences.

“In our country, our national ambient air quality standards are standards. There are consequences when you fail those standards,” Kelly said. “We have a Clean Air Act that requires you to do something, it requires you to set those standards, and it requires punitive measures when you violate those standards.”

Still, Graham said any level of pollution has the potential for negative health effects.

“As our air quality improves, we’re able to really test what happens from an epidemiological standpoint what the health effects are at lower and lower levels of air pollution, because you can’t really test really clean air if you don’t have it.” he said “We haven’t yet found a level below which it’s perfectly safe to breathe those fine particles – they still seem to have health effects, negative health effects.”

PM 2.5, for example, affects cardiovascular and respiratory health. Long-term exposure may increase the risk of cancer. The elderly, young children and those with existing medical issues are the most at risk for pollution.

“If we only look at those values that are above the air quality standard, I think we are potentially missing a number of times when the pollution might really still be harmful,” Graham said.

*This story was updated on Monday, Aug. 6 at 12:55 p.m. to correct the most recent day rated Red for ozone levels. It was July 30, 2018, not one day in 2013.