South Philly refinery, a big polluter, shut down 6 months ago. So, do we have cleaner air?

The vast Philadelphia Energy Solutions refining complex was the single largest stationary source of air pollution in the city before it shut down after a catastrophic June 21 fire. So it would be reasonable to assume the city’s air quality has improved in the six months since the largest oil refinery on the East Coast suspended fuel production.

But hard numbers are elusive that conclusively demonstrate the air quality has improved. Data collected by the refinery at its fence line, and from a government air monitor less than a half-mile from the PES refinery, do not show steep declines in pollution after the refinery ceased production.

Environmental advocates say the air sensors pick up only some refinery emissions, and much depends upon the direction that the wind is blowing. The city’s Public Health Department is reluctant to draw conclusions based on short-term data, and says it keeps watch on emissions over the entire region.

“It’s difficult to say if it’s better or not because that term is so variable, and right now we’re tracking that type of thing over an entire year,” said James Garrow, spokesperson for the city’s Air Management Services, which regulates air emissions.

Several readers posed questions about the impact of the closure to Curious Philly, the forum through which Inquirer reporters answer queries about the city and the region. The questions about the refinery are timely because PES declared bankruptcy after it shut down and it may be sold early next year. Several potential bidders propose restarting fuel production, which, by its nature, emits air pollution.

Worries about air emissions and their impact on surrounding neighborhoods were a dominant theme at public hearings conducted this summer by Mayor Jim Kenney’s Refinery Advisory Group, which explored possible uses of the 1,300-acre refinery site.

“It is clear that the refinery has been a significant source of air pollution in Philadelphia,” the advisory group said in its final report. “It is also clear that exposure to certain air pollutants poses health risks, and that a reduction in air pollution can be expected to lead to better health outcomes.”

But the advisory group’s report seemed to anticipate the current fog of inconclusive data, noting that it is difficult to tie a reduction in refinery emissions directly to a reduction in the air pollution that affects any specific community or population “because there are other relevant risk factors and pollution sources involved."

The advisory group’s final report notes that Philadelphia’s air quality has improved over the years as environmental standards have tightened, cleaner fuel standards went into effect, and heavy industry declined. In two decades, average annual fine particulates in Philadelphia air have declined by nearly 50% and ozone levels, while still higher than federal standards, have also declined significantly, the report said.

The refinery’s performance has also improved over time, the report said. Since 2014, annual releases of air toxics from the refinery dropped by about 38% from 2011 to 2013 figures. Still, the city has issued seven Notices of Violation to PES since 2012 for exceeding pollution limits, though the violations were not serious enough to require closure or major improvements.

Though its performance has improved somewhat, the refinery is still estimated to be responsible for a staggering amount of pollution: About 9% of the city’s emissions of fine particulates, and 20% of greenhouse gases. It emitted 464,284 pounds of toxic materials in 2016, or more than half of the toxic emissions from large sources in Philadelphia. About 10% of those materials are known carcinogens, such as benzene and dioxin.

The city’s air-emissions permit for the refinery is 255 pages long, and includes an inventory of hundreds of potential pollution sources, including boilers, heaters, flares, processing units, and storage tanks, of which there are more than 100 on-site, the oldest of which went into service in 1908. Just one pollution source at the refinery, the main boiler house that produces steam for processing units, is allowed to annually emit up to 253.7 tons of nitrogen oxides, 152.6 tons of sulfur dioxide, 417 tons of carbon monoxide, 50.6 tons of particulates, and 34 tons of volatile organic compounds.

“It’s a complicated facility with lots of different types of air pollution," said Joseph Otis Minott, executive director of the Clean Air Council, a frequent legal adversary of the refinery. “Some are going to have an impact on the immediate community, some going to have an impact on the global community.”

Experts are reluctant to link a single source of pollution to specific health impacts, which can take decades to manifest themselves.

Though the National Cancer Institute estimates that Philadelphia has the highest cancer rate of any large city in the country, and it also has an asthma hospitalization rate three times higher than the state average, the advisory group report noted that the cancer risk from exposure to air toxics in neighborhoods near the refinery is comparable to the cancer risk rates in Center City, which has little exposure to refinery emissions.

The refinery could process up to 335,000 barrels of oil a day, or 14 million gallons. With the closure of PES, production of the fuel, and its associated emissions, has shifted to other refineries in the region or to plants in other parts of the United States, or in Europe, Canada, and India. While the refinery was responsible for 20% of the city’s greenhouse-gas emissions, those gases are still being emitted into the atmosphere, elsewhere.

One expert believes that the refinery’s shutdown can already be measured in reduced regional levels of ground-level ozone, or smog, which is produced from pollutants emitted by motor vehicles, power plants, and industrial manufacturing -- such as refining.

Philadelphia reported only 10 "Ozone Action Days” this past summer -- days when the air was unhealthy to breathe -- down from 14 to 18 days recorded in the previous three years. This year’s decline occurred during a period of reduced rainfall, which would normally increase the number of days with excessive ozone, said Marilyn V. Howarth, director of community engagement at the University of Pennsylvania’s Center of Excellence in Environmental Toxicology.

“Closure of the refinery contributed to the improvement of the air quality and the health of Philadelphians," Howarth told a City Council hearing in November, citing the reduced number of ozone alerts.

Aside from the ozone data, there are two primary sources of ambient-air measurements located near the refinery, but both have shortcomings, according to experts.

The city maintains an air-monitoring station at 24th and Ritner Streets, about 2,000 feet from the refinery fence line and the racks where tanker trucks fill up with gasoline, diesel, and heating oil from the refinery. That air-sampling station is primarily concerned with measuring “criteria pollutants” identified by the U.S. Environmental Protection Agency to comply with the Clean Air Act — particulate matter, nitrogen dioxide, ozone, carbon monoxide, sulfur dioxide, and lead.

The air-sampling station captures usual activity at the refinery only if the wind is blowing from the southwest, said Peter DeCarlo, a Drexel environmental engineering professor. For instance, on June 21, the day of the giant refinery fire that spewed clouds of combusted hydrocarbons as well as more than 3,000 pounds of deadly hydrofluoric acid into the atmosphere, the monitor at 24th Street measured nothing unusual, he said.

Under a consent agreement, PES operates air monitors on the eastern and western boundaries of its property to measure particulate matter, ozone, sulfur dioxide, lead, carbon monoxide, nitrogen oxides, hydrogen sulfide, and benzene. The refinery posted the results until its website went offline in the summer. The emission data later reappeared on a new website, http://pesrm.info, which PES notified the EPA about on Nov. 21, said David Sternberg, a spokesperson for the EPA’s Region 3 in Philadelphia.

The fence-line measurements are raw data for public information, and neither the city nor the EPA actively analyzes the information. It is also posted in a digital format that is not easy to analyze, said DeCarlo.

The EPA uses emissions data collected directly from various refinery units — point-source data — to tally up the plant’s output of pollutants.

“As for interpreting the fence-line monitoring data, there are no emission limits associated with the data,” said Sternberg. “Emission limits at PES are associated with specific point sources and not fence-line monitoring.”

For many advocates of keeping the refinery closed, getting hung up about the absence of definitive data is akin to failing to see the forest for the trees.

“That is the city’s single largest stationary source of air pollution,” said DeCarlo, of Drexel. “Shutting it down has got to have some sort of positive impact, right?”