Tiffany Mellers jogs behind her two daughters as they pedal their bikes along a ribbon of packed sand along Long Island Sound. “They are good girls,” Mellers said. “They deserve a healthy life.”

Behind them, a 500-foot tall candy-stripe smokestack, a fixture of Bridgeport’s waterfront for nearly five decades, rises in the distance. A third generation of residents is now growing up in its shadow.

But today this old giant is merely a vestige of this region’s coal-fired past. New England is virtually coal-free.

For some, the red-and-white stack of Harbor Station conjures memories of a prosperous industrial past. But for Mellers, it’s a reminder that this largely poor and minority city has borne a heavier pollution burden over the past half-century than its wealthier neighbors. Nearly 40 percent of children in Bridgeport grow up in poverty, more than three times the rate in the rest of Fairfield County. And 14 percent – substantially higher than the national average – have asthma, including Mellers’ two daughters.

Today, Harbor Station looks lifeless as Tiffany and her daughters play on the beach. Like most of New England’s coal plants, it now runs infrequently. Last year, it operated at only 4 percent of its capacity, down from about 86 percent in 2008.

Jeff Kohut, a lifelong Bridgeport resident, said the last time he can remember smoke spewing from the plant was two years ago, during a waterfront baseball game.

“Going back to the 1960s and early 1970s, Bridgeport was quite prosperous in an industrial sense. There were more factories and smoke-belching power plants,” Kohut said. “Even back then it was considered sort of the dirty ragamuffin step child of Fairfield County, so the negative environmental image goes quite a way back.”

A changing fuel mix

Last week President Obama launched a major drive to limit carbon pollution from power plants in a bid to stem climate change. At the program’s core: A directive to develop federal carbon emissions rules for new and existing power plants.

New England, in some ways, is ahead of the curve. Many aging New England coal plants, which emit large quantities of soot and mercury as well as planet-warming greenhouse gases, have retired in the past decade or converted to natural gas. Of the six still connected to the region’s electric grid, two are in the process of closing.

“Natural gas is killing coal plants, but more natural gas infrastructure may be adverse to health and climate in the long run. It’s a paradox.” -N. Jonathan Peres, Conservation Law Foundation Stringent environmental regulations and a steep drop in the cost of natural gas in recent years caused this dramatic change in the region’s energy profile.

The change comes with tradeoffs. Tax rolls will take a hit in some communities, while an increased reliance on natural gas has some experts raising questions about the role this alternative fossil fuel, which comes with its own set of environmental issues, should play in the transition from coal.

“Natural gas is killing coal plants, but more natural gas infrastructure may be adverse to health and climate in the long run. That’s the paradox,” said N. Jonathan Peres, an attorney for the Boston-based Conservation Law Foundation.

In 2000, coal accounted for roughly 18 percent of the region’s electricity generation while natural gas accounted for about 15 percent. In 2012, just 3 percent of New England’s electricity was generated by coal, while 52 percent came from natural gas. Another 13 percent was from renewable fuels, such as hydroelectric and solar power.

The New England trend mimics a nationwide one. In 2003, coal provided 51 percent of all electricity in the United States, compared with 37 percent last year.

“A collapse in gas prices and minimal load growth in the region have done a lot to displace what coal there was,” said David Schlissel, a regulatory attorney and electric utility rate consultant in Massachusetts.

Gas prices fell in 2009 as large reserves of natural gas were tapped with new technologies, such as horizontal drilling and hydraulic fracturing, or fracking. Average natural gas prices in New England in 2013 were 32 percent lower than in 2012. Meanwhile, the price of coal stayed about the same. Wholesale electricity prices in the region have reflected this sharp drop in natural gas prices.

The difference between the price at which they can sell power and the price of generating that power is just not adding up for coal plant operators, Schlissel said. That has meant reduced revenue for coal plant owners and reduced generation time for coal plants.

In 2008, Bridgeport Harbor Station’s coal unit operated for 8,304 hours, about 346 days; by 2011, it ran for only 2,095 hours, about 87 days. Brayton Point Power Station in Somerset, Mass., ran at roughly 85 percent capacity in 2008, but only 16 percent capacity in 2012.

Age is another factor. New England’s coal fleet is old, built mostly in the 1950s and 1960s. Many needed costly upgrades.

Public Service Enterprise Group, owners of the Bridgeport plant, invested $150 million in state-of-the-art mercury and particulate emissions control technology in 2008. Dominion, the operator of Brayton Point, was in the process of completing a $1 billion upgrade that included cooling towers and an emissions-scrubbing system. The cost of complying with pollution regulations proved too great as natural gas prices plummeted. In March, Dominion agreed to sell Brayton Point and two Midwestern coal plants for a total of $650 million.

While the power being produced by coal is diminishing, the remaining plants provide reliability for the electric grid.

“During periods of system stress, plants that burn coal and oil are an important part of the mix. All resources are necessary to meet consumer demand and maintain power system reliability,” said Ellen Foley, director of communications for ISO-New England, the organization that oversees the region’s grid.

In New England, those periods of stress may be most prominent in the winter, when companies that provide gas for heating get most of the natural gas. Gas-fired power plants generally get what’s left over, which on most days is plenty. But during winter cold snaps, the availability of natural gas for electric generation becomes uncertain, so coal and oil, another infrequently used fuel, become backup supplies.

Building new pipelines to bring more natural gas into New England from the lucrative Marcellus shale region to the west may be part of the solution, according to Foley, who said that ISO-New England is talking with state and federal regulators about the need for new pipelines in the region.

However, some environmental advocates feel that building new natural gas pipelines for reliability issues that happen a few days a year would not justify the long-term expense.

“Once we overbuild the pipeline infrastructure, we are stuck burning fossil fuel for another 50 to 100 years,” said Peres, the Conservation Law Foundation lawyer.

Coal vs. natural gas

Neither gas nor coal is an ideal fuel source in terms of its environmental and human health footprints, but at least by some environmental measures, natural gas may be the better choice.

A U.S. Department of Energy life-cycle analysis found that globally, the greenhouse gas footprint of natural gas is likely to be smaller than coal’s.

Age is another factor. New England’s coal fleet was built mostly in the 1950s and 1960s, and many of the plants need costly upgrades.A shift from coal to gas also results in less soot, mercury and other air pollutants. Coal plant smoke contains tiny particles of soot that can lodge in the lungs. Numerous studies around the world have shown that when ultrafine particles increase, deaths and hospitalizations from asthma, heart attacks and other cardiovascular and respiratory ailments increase, too.

Emissions from the plants have declined substantially. Last year, the Bridgeport plant emitted about 250 tons per year of sulfur and nitrogen oxides, two pollutants linked to asthma attacks and other respiratory effects. That compares with about 4,800 tons in 2005.

Its emissions of carbon dioxide, a greenhouse gas linked to climate change, also are a fraction of what they were: 146,000 tons compared with more than 3 million tons in 2005. That’s equivalent to taking 570,000 cars off the road.

Tiffany Mellers understands she will likely never know the cause of her daughters’ asthma. But she suspects that the plant is partially to blame.On the other hand, one of the major drawbacks to natural gas is that many of the environmental and health risks to air and water, especially from fracking, simply have not been studied. While New England may benefit from an influx of natural gas, other regions, where the gas extraction is taking place, may not. Some environmentalists have raised concerns about water quality in fracking areas. In 2011, a study found evidence of methane contamination in drinking water associated with shale-gas extraction in Pennsylvania and upstate New York.

Community activists are pushing for a coal-free New England. In Bridgeport, asthma mortality for children is nearly 10 times the rest of the state. Health officials can’t link that to power plant emissions, but activists hold Harbor Station partially responsible.

Back on the beach in Bridgeport, Tiffany Mellers is one of those who blames the plant, in part, for her girls’ asthma. Her husband is a longtime Bridgeport resident, and she’s lived in Bridgeport for the past 12 years. A U.S. Army Reserve civil affairs specialist who served in the Horn of Africa, Mellers started attending meetings of the Healthy Connecticut Alliance out of concern about her children.

“I can protect my country. I can tutor my girls on how to be safe and keep them from running in the street, but I can’t protect them from the asthma. I felt helpless,” she said.

Mellers understands she will likely never know the cause of her daughters’ asthma. But she suspects that the plant is partially to blame. “These asthma attacks are about what they are breathing in. The plant is part of the problem and it needs to go,” she said.

Not everyone in the community agrees. For 19 years, Rev. Carl McCluster has been the pastor at Shiloh Baptist Church, across the street from the coal plant.

McCluster has grown wary of the message put out by the Healthy Connecticut Alliance, a coalition of environmentalists campaigning for the end of coal in Connecticut.

“They say that they have come to help the community and that the coal plant is making us sick, but there is no empirical evidence. To say something is the cause of something and not have a reasonable level of proof is more than irresponsible,” he said.

McCluster has called for a study to determine the contribution of various pollution sources in the neighborhood. Bridgeport’s South End is home to two other power-generating plants and is bordered by the perennially congested Interstate-95. The neighborhood also copes with serious sewage overflow problems.

“To say something is the cause of something and not have a reasonable level of proof is more than irresponsible.” - Rev. Carl McCluster “Who is the greatest polluter, and where can we have the greatest impact immediately?” said McCluster, who believes that improved access to health care in his community would also go a long way in improving environmental health outcomes.

While cutting coal in the region would have some benefit for public health, it’s likely the impact would be minimal given that the plants operate infrequently and some already have cut emissions substantially.

“Curbing pollution by closing plants in the Midwest will likely have a greater effect on air quality in New England than closing plants locally,” said Alberto LaMadrid, a resource economist at Lehigh University in Pennsylvania.

On certain hot summer days, even if every source of emissions in Bridgeport, including the coal plant, were shut down, the city could still exceed national ozone standards, based solely on emissions transported from upwind states, according to the Connecticut Department of Energy and Environmental Protection.

An EPA regulation that requires states to reduce power plant emissions that pollute other states, along with new standards that will reduce mercury and air toxics emissions beginning in 2015, may help. The EPA estimates that, in Connecticut alone, the new mercury and toxics standards will prevent up to 90 premature deaths and create up to $750 million in health benefits in 2016.

“As a whole, New England power is already fairly clean,” said LaMadrid.

Emerging from an industrial past

For now, old coal plants such as Bridgeport’s will continue to operate in the region on a reduced basis. In September, the state granted owner PSEG a five-year extension on its operating permit. In November the EPA followed suit.

Some believe the plant doesn’t have five more years. “It’s operating a couple days a month and paying large amounts to do so,” said Peres.

However, PSEG has not announced any plans to delist. “We remain committed to the environment and the local Connecticut community,” said PSEG spokeswoman Lee Gray.

City officials in Bridgeport, which depends on PSEG for its tax base, don’t want to see Harbor Station go. In 2010, PSEG was the city’s third highest taxpayer.

David Kooris, Bridgeport’s director of the Office of Planning and Economic Development acknowledges that with coal-fired power comes air pollution. But, “we’re in a good situation right now where the plant runs only a few days a year but pays full tax revenue,” he said.

Redevelopment plans for life after coal are in the works. “My guess would be that a large portion of the site will continue to be used for some sort of electricity generation, while the remainder is positioned for commercial or industrial use,” Kooris said.

But Mellers, who is completing her bachelor’s degree in the hopes of attending graduate school to become a physician’s assistant, doesn’t plan to stick around long enough to see if Bridgeport will get a cleaner future. If the coal plant doesn’t close in the next couple of years, she vows to relocate her family.

“I want to give my daughters the best opportunity in life,” she said. “That is all that matters to me.”