Environmentalists say that, by their calculations, the Herbert A. Wagner Generating Station in Pasadena has for years released unhealthy levels of a pollutant known to trigger asthma and cause cancer. The EPA has tentatively agreed with that assessment, saying Wagner appears to be emitting unacceptable levels of sulfur dioxide.
But Maryland officials, in mounting a rare challenge by the state of an EPA finding, say that recent improvements have lowered sulfur dioxide pollution around the plant to safe levels. The changes at the plant include a switch to coal that contains less sulfur.
State officials call a Sierra Club analysis — which largely served as the basis for the EPA finding — erroneous, and they are joining nine other states in seeking to avoid a federal designation that could require plant owners to make expensive upgrades to clean up emissions.
Gov. Larry Hogan has made clear he is wary of environmental initiatives that could lead to higher energy costs for consumers. The administration recently opposed plans to expand an energy conservation program that adds to bills and vetoed legislation to boost the use of more expensive renewable energy.
A spokesman for Hogan declined to comment for this article.
There is room for disagreement about the amount of sulfur dioxide pollution coming from the plant because limited data is available. In the four decades since EPA last updated its standard for the pollutant, which largely comes from coal-fired power plants, the number of monitors to measure it has declined by two-thirds. The closest measurements to the Wagner plant are taken in Essex; the next-closest come from upwind, near Washington.
"We do not have a good representation of what the air quality is because of that," said Cristina Fernandez, a regional director in the EPA's Office of Air Program Planning.
As a result, states, environmental groups and the EPA are left to make assumptions and use computer models to estimate how much pollution the Wagner plant is belching into the air — and how significant a health risk it poses.
The EPA is expected to issue a final ruling by the end of this month.
Though state officials say air quality has improved significantly in recent years, the debate has neighbors and clean-air advocates worried. Children are diagnosed with asthma more than twice as often in Baltimore as they are nationally — a possible sign of years of poor air quality generally, and high sulfur dioxide concentrations specifically.
"Nobody's really talking about it, and it's a big problem," said John Garofolo, who lives in a townhouse community just across a cove from the Wagner plant.
In February, the EPA proposed that communities within about 22 miles of the plant, which sits on the Patapsco River at Baltimore City's border with Anne Arundel County, be declared in violation of a sulfur dioxide standard established in 2010.
The area includes parts of Anne Arundel and Baltimore counties, while the agency said it could not determine if Baltimore City air is within the standard because there are no ambient air pollution monitors within its borders.
The agency considers it a public health risk if power plants or industrial facilities too often average more than 75 parts per billion of sulfur dioxide emissions within an hour. It estimates that Wagner exceeds that limit at least four times a year.
Sulfur dioxide is a byproduct of the combustion of many types of fuel; exposure to it for as little as five minutes can cause respiratory problems. It is also a component of particle pollution, which can contribute to heart attacks and lung cancer.
The EPA's analysis was based on modeling provided by the Sierra Club, which joined the Natural Resources Defense Council in suing the EPA over what they called lax enforcement of sulfur dioxide standards. They reached a consent agreement in federal court requiring the EPA to evaluate levels of the pollutant across the country, starting with a batch of decisions due July 2.
The EPA deemed the data "persuasive evidence" that air quality violations are occurring at Wagner.
Officials with the Maryland Department of the Environment disagree. George S. "Tad" Aburn, director of air and radiation management for the department, said the Sierra Club's math is based on old data and conservative assumptions that make it more of a worst-case estimate than a realistic assessment.
Instead, he said, any air-quality designation should be based on current information. The department told the EPA that sulfur dioxide emissions dropped 40 percent after one Wagner unit began burning coal with less chlorine and sulfur, for example, and has provided the agency with its own modeling.
"We feel really confident our analysis is very good and that EPA will, after seeing our analysis, agree with us," Aburn said.
The plant's owner, Talen Energy Corp., declined to comment.
The Sierra Club has countered that Maryland's analysis does not follow EPA protocol. By design, the EPA requires modeling air quality over three years, the group said. Otherwise, "someone would always be jumping up and down and saying, 'Well, today air quality is fine,'" said Zachary Fabish, a Sierra Club attorney.
The group argues that both its data and the state's show unhealthy air quality around the Wagner plant.
Such disagreements with the EPA have been rare, Aburn said, because in the past the state has been able to provide reliable measurements to show whether it meets air quality standards. That's how the state prefers it, he said, so officials may add more monitors in Western Maryland and the Washington region when those areas are evaluated for sulfur dioxide in coming years.
Fernandez said that in contrast to most air-quality enforcement, the EPA is using modeling instead of data to evaluate sulfur dioxide pollution because there are so few monitors to track it. The monitors numbered more than 1,500 during the 1980s, but are now down to fewer than 500 as some were phased out over the years, according to the Sierra Club.
Maryland is not alone in challenging the EPA. Of areas within 12 states that EPA says are in violation of the sulfur dioxide standard, only two agreed with that analysis.
Still, enforcement using modeling has been challenged in court and upheld, said Nick Morales, an associate attorney with the environmental law organization Earthjustice.
"There's really no basis for saying that modeling is somehow a method that is not going to lead to an informed designation," he said.
EPA officials are in the process of comparing the Sierra Club's and Maryland's analyses, Fernandez said.
If the EPA confirms its initial finding that the plant is violating the standard, Maryland officials would have to work with the owners on a plan to reduce sulfur dioxide emissions. That could include investments in equipment known as "scrubbers" or other technological improvements.
Even if the EPA comes to agree with Maryland officials, some question whether more needs to be done to lower sulfur dioxide levels.
Without some sort of enforcement action, there would be nothing holding the Wagner plant's owners to make improvements, said Rena Steinzor, a professor at the University of Maryland School of Law. The Center for Progressive Reform, a think tank she helped found, has criticized Maryland environmental officials for referring fewer polluters to law enforcement in recent years, allowing them to delay promised remedies.
Dr. Gwen DuBois, president-elect of Chesapeake Physicians for Social Responsibility and an internist at Sinai Hospital, called pollution controls at plants "low-hanging fruit." Poor air quality has contributed to 20 percent asthma rates among city children, more than twice the national average, and led to disproportionate numbers of hospital stays and emergency room visits, she said.
"It costs people money; it's just different people than the people causing pollution," she said.
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