NICOLE JONIEC'S biggest regret, five years after moving into a century-old townhouse in South Philadelphia with her husband and their two cats, is that she didn't zoom out a little more when she had checked out her new address on Google Maps.

Joniec, 37, who works at the Free Library, said she now feels "silly" that she didn't realize how close they would live to the ancient, sprawling refinery on the banks of the Schuylkill then owned by Sunoco and which today - with a new owner, Philadelphia Energy Solutions - is booming with crude oil fracked in North Dakota.

Now she thinks about the South Philly refinery a lot - on the hot summer nights when the couple shut the windows of their not-air-conditioned home to keep out foul odors, or when she wonders if the industrial site is why her 43-year-old husband is experiencing breathing problems for the first time in his life.

"I don't think we'd have bought it if we'd known it was so close to the refinery," Joniec said of their home. In recent years, she and many others in communities like Girard Estates, West Passyunk and Southwest Philadelphia have been alarmed by the surge in mile-long oil trains rolling through their neighborhoods, by the thick black smoke that came from a January "flaring" incident at the refinery, and now by politicians' talk of a massive "energy hub" that would bring new jobs to the banks of the Schuylkill . . . but also even more air pollution.

As the candidates in the 2015 mayoral contest have mostly raced to embrace the energy-hub proposal, there's been little debate about air pollution from the Philadelphia Energy Solutions refinery, even as it spews tons of toxic chemicals every year into the city's skies and continues to be flagged by regulators for contributing to the region's smog problem, one of the worst in the nation.

In 2013, according to the latest statistics available from the U.S. Environmental Protection Agency, the site - the largest oil refinery on the East Coast - let loose 701,284 pounds (or more than 350 tons) of hazardous air pollutants, including roughly 29 tons of benzene, a potent carcinogen, and many more tons of other toxins that experts say can contribute to breathing problems such as asthma.

Despite new spending on pollution controls that have reduced those numbers since Philadelphia Energy Solutions took control of the refinery in the summer of 2012, city air-quality inspectors cited the plant last fall for a number of alleged violations during 2013, including emissions of nitrogen oxide, or NOx - a key component of smog - and carbon monoxide, as well as flaring and work-rules violations. The company is appealing the citation.

Officials for Philadelphia Energy Solutions (PES) - a joint venture between Sunoco and the the Carlisle Group global-investment firm - said they were unable to comment for this article. PES recently filed for an initial public offering, or IPO - a move that would raise $300 million from Wall Street and would help expand its operations.

The IPO filing means that PES is in a "quiet period" and can't talk to the media.

In a January interview with Philadelphia magazine before the "quiet period," PES CEO Philip Rinaldi promised to be a responsible corporate citizen and to work to allay the concerns of environmentalists But he said that broader opposition to the ambitious, if vague, energy-hub plan is rooted in naivete. "If that's what you want to do, if you want to have all windmills and solar panels, that's great," he said then. "It's not practical, it's not going to work. The society's not going to run that way. Responsible people know that."

Rinaldi's high-profile push for an energy hub with new middle-class jobs - which would bring massive amounts of natural gas fracked in upstate Pennsylvania's Marcellus Shale region into Philadelphia by yet-to-be-built pipelines - gets an endorsement from most of the major mayoral hopefuls.

But neighbors of the refinery are wary of the future. Some post anxiously about pollution on neighborhood Facebook pages, and a few are moving, or at least thinking about it.

One Girard Estates resident, who posts on Facebook as Katie Marie and didn't want to use her real name because of job concerns, said she and her neighbors were not reassured when city officials insisted that a consistent odor last summer - one that was compared to cat urine - wasn't coming from Philadelphia Energy Solutions but from a different refinery operating across the Delaware River in Paulsboro, N.J.

"We still occasionally smell the emissions, but it's never as bad as it was this past summer," she said in an email interview. "I hope this summer is better - living in the shadow of an unregulated refinery and raising a kid frankly scares the crap out of me. I think making South Philadelphia an 'energy hub' is a step back into the 19th century."

A refinery since 1866

Arguably, it is. Philadelphia has hosted some type of refinery at the South Philadelphia site since 1866 - one year after the assassination of Abraham Lincoln, when the U.S. crude-oil industry was just getting started with a push from John D. Rockefeller. Over the next 149 years, the complex has grown under multiple owners and has had its share of tragedy - most famously the 1975 Gulf Oil blaze that killed eight firefighters - while pumping prosperity into Philadelphia's economy and pollution into its air.

It appeared that the site might close in 2012, but creation of Philadelphia Energy Solutions and the North Dakota domestic oil boom saved about 875 well-paying union jobs.

Despite advances in pollution control that began around the time of the first Earth Day in 1970, the shutdown of other factories amid the end of the Industrial Revolution has solidified the refinery's rank as the city's largest stationary source of air pollution. Officials estimate that the plant accounts for more than 70 percent of toxic air emissions in Philadelphia, and nearly one-third of the total for the entire region.

The continued pollution is a cause for concern for advocates and public-health experts alike, who note that Philadelphia has one of the highest rates of childhood asthma in the nation. Dr. Marilyn Howarth of the University of Pennsylvania's Center of Excellence in Environmental Toxicology said the asthma rate of about 26 percent among kids in some of the city's poorest neighborhoods is three times the national average. The city's traffic congestion contributes heavily to the problem, but so do industrial sources.

"The refinery has traditionally contributed a great deal of pollution to the Philadelphia region, and as the refinery operations increase . . . you can only reasonably expect these emissions to increase," Howarth said. The Philadelphia region currently fails to meet federal clean-air standards for ozone and small-particulate matter, two crucial pollution yardsticks.

An EPA analysis of South Philadelphia toxic pollution released last fall found that the vast majority of emissions in the neighborhood came from the refinery and that 11 percent - nearly 40 tons - were known carcinogens, largely benzene. The two biggest sources - roughly two-thirds of the total - were sulfuric acid and hydrogen cyanide.

"Those are acids," said Howarth of the sulfur-laced emissions, "and they are very strong pollutants. They may not cause cancer, but they certainly contribute to asthma and would irritate the airways for people with chronic pulmonary disease."

Joe Minott, executive director of the Clean Air Council in Philadelphia, said he's troubled by the political rush toward the energy-hub plan with little discussion of both why the city would double down on fossil-fuel industries in an era of growing alarm about climate change, and about the pollution costs of the project.

"You can't site in Philadelphia except next to where people live, and that's worrisome," Minott said. "These are not clean industries."

But cautionary voices like Minott's are few and far between. Environmental concerns are competing against both Chamber of Commerce-style boosterism and the hundreds of jobs the refinery provides to members of the steelworkers' union.

Enthusiastic backers of refinery growth include the city's pro-union Democratic boss, U.S. Rep. Bob Brady - beneficiary of a political fundraiser hosted by PES chief Rinaldi. Even one of the more-progressive candidates in the mayor's race, ex-councilman Jim Kenney, named Rinaldi to his economic-development advisory group, while Kenney's spokesman raised a few hackles when she was quoted saying that "clean air doesn't do our citizens a lot of good if they can't afford to live here." Only one candidate, former judge Nelson Diaz, has stressed limiting air pollution in any push for energy jobs.

For now, the loudest voices for balance are coming from the shadows of the refinery stacks.

"I'm all for the jobs aspect," said neighbor Joniec, although she'd prefer cleaner jobs in renewable energy. "To not follow through with the air regulations and whatever checks need to be done, that's where it's a major concern."