For many in New England, fresh powdered snow is a welcome sign of the season. For Maine mother Jill Callela, the flakes showcase something much darker – the dirty air her family is breathing.

“OK, we have black snow again,” Callela, 39, said, remembering recent winters when the factory directly across the river from her home in Bradley, Maine, polluted the snow in her yard with what she says was lead-laden soot spewed from its smokestack.

Tests Callela had done have shown elevated levels of lead in the snow, she said. Icy winds sweeping over the Penobscot River behind her home amplified the problem.

“It was in everyone’s house and got into the blowers in our cars,” Callela said. “When we would turn on our heaters it would come through the vents.”

The factory, Old Town Fuel & Fiber, a paper mill, has over the past five years racked up $267,000 in federal air pollution fines for releasing illegal amounts of carbon monoxide, sulfur dioxide and methanol into the air above its facility. Callela claims her complaints about the mill to state regulators have been ignored even though it is among a number of New England facilities labeled “high priority violators” by the U.S. Environmental Protection Agency.

A facility can become a high priority violator, or HPV, by exceeding emission limits, violating a local state or federal order or meeting other criteria developed by the EPA to identify polluters in need of close scrutiny. An investigation by the New England Center for Investigative Reporting shows that regulators in Maine and nearby states have taken months and even years to sanction facilities violating the Clean Air Act – even those the government itself has called HPVs, such as the Old Town paper mill.

The factory has been violating its carbon monoxide limits since December 2010 but the issue is still not resolved.

Melanie Loyzim, head of Maine’s Bureau of Air Quality, said regulators are in negotiations with the factory's owners to improve their technology and has proposed fining them $497,000. Loyzim argued the emissions are not dangerous.

“You can say we don’t act fast enough but we are talking about carbon monoxide emissions at a level that don’t have a public health impact,” she said.

Dan Bird, a spokesman for the factory’s owner, Patriarch Partners, said most of the pollution happened under previous owners and it was never proven that the soot in Bradley came from the mill. He said the plant struggles to stay within its carbon monoxide limits and is seeking a state permit to increase emissions of the gas.

“This is a huge economic engine in our relatively rural neck of the woods,” Bird said. “That doesn’t give us license to be outside of our legal requirements at all, but we’ve had a difficult time in a few areas. We’ve had some episodes but the majority of the time we are operating within our parameters.”

It took Massachusetts approximately 18 months to levy a fine against resin manufacturer Solutia Inc., for failing to properly operate required pollution control equipment on several occasions at its Indian Orchard plant in Springfield.

“It smells a lot. I can tell you that,” said Donald Carr, a Springfield postal employee who has worked across the street from the plant for 10 years. “I’m not surprised it’s a major polluter and I don’t even know the effect it will have on me.”

Massachusetts Department of Environmental Protection spokesman Edmund Coletta said that there is no set length of time for the state to find and resolve a violation.

“Every case and every facility is different,” Coletta said. “There are some (facilities) that work quickly to resolve issues while others don’t.”

Solutia is on schedule to return to compliance, he said. Messages left at Solutia’s Indian Orchard plant and its Missouri headquarters were not returned.

Being labeled a high priority violator may earn such facilities slots on a closely guarded EPA “watch list” that is updated monthly. The list was made public for the first time following federal Freedom of Information Act requests by the Center for Public Integrity and National Public Radio. The release was part of a joint CPI/NPR investigation into lax enforcement of the Clean Air Act in hundreds of communities nationwide.

Following last year’s investigation, the EPA, for the first time, made the lists of alleged Clean Air Act, Clean Water Act and Resource Conservation and Recovery Act violators available on its website.

The most recent available Clean Air Act list, from November 2011, includes nearly 250 government and industrial facilities, with the majority located in the South and Midwest. The nine New England facilities on the list include power companies, manufacturers and a hospital.

The facilities’ status, and ensuing slow state enforcement, is notable given that many of them have emitted toxics deemed so dangerous to human health they were targeted for control in amendments to the federal law more than two decades ago.

The first Bush administration promised that reductions in airborne emissions of nearly 200 chemicals would lead to sharp declines in cancer, birth defects and other serious health problems. A focus of the amendments was to reduce the chemicals’ release into the air by tighter state and federal regulation of chronic polluters.

But in New England, as in many other parts of the country, that has not always happened.

A leak in June, 2008 at CYTEC Industries in Wallingford, Conn., didn’t result in a notice of violation from state regulators until September, 2009, records show. Jaimeson Sinclair, supervising air pollution control engineer for the Connecticut Department of Energy and Environmental Protection, said the delay came about because state officials had to confirm with the EPA the failure to promptly repair the leaks was a violation of the Clean Air Act.

CYTEC has been labeled a high-priority violator and was on the EPA “watch list” as recently as September 2011 for illegal nitrogen dioxide emissions. The chemical can impair lung function and is an irritant to the nose and throat, according to the EPA.

In May 2011 Connecticut environmental officials fined the global chemical giant $52,000 for the 2008 leak as well as failing to run timely, required tests on boilers for nitrogen oxide in early 2010.

Nancy Alderman, an environmental law and public health expert who heads up the non-profit watchdog group Environmental and Human Health Inc., in Conn., has studied CYTEC’s emissions with concern.

“If you look at CYTEC, we know that they release formaldehyde into the air, which is a carcinogen and a respiratory irritant. But we also know they release butyl alcohol, which is a nervous system depressant. What we haven’t understood yet is what is in the air at what time and how the effects of these combine together,” Alderman said.

Company officials for CYTEC, headquartered in New Jersey, did not respond to several requests for comment.

Sinclair defended the state’s record on forcing CYTEC to comply with air pollution laws.

“Once we learn of a violation, we take action,” he said.

Environmental watchdogs and even some state officials claim a sharp reduction in resources is to blame for slow enforcement of the law. Congress delegated enforcement of the Clean Air Act to the states and authorized the federal government to cover up to 60 percent of the states’ compliance activities.

Lately, however, that figure has been closer to 25 percent. And over the past three years, funding for environmental enforcement has been cut in four of six New England states, budget records show.

Sean Mahoney, vice-president of the Maine office of the Conservation Law Foundation, a network of environmental advocacy groups, said he and his colleagues try to bring the most urgent air quality concerns to the states’ attention as regulators struggle with dwindling resources.

“To be honest, we’re like a finger in the dike,” Mahoney said.

State officials hope the cuts are only temporary as they shoulder bigger enforcement burdens. In Maine, about a dozen employees of the state’s Bureau of Health Quality are responsible for monitoring air quality for more than 600 facilities, said Loyzim, of the Bureau of Air Quality.

“I have every confidence that the struggle for funding at the moment is not an undermining of environmental regulation, but a reflection of the difficult economic climate nationwide,” Loyzim said.

And some state officials said the EPA’s HPV criteria can make states appear to be lagging in their enforcement duties. When a violation is reported, a facility is only returned to compliance in the eyes of EPA when the offense is redressed formally, which can take years, Sinclair said. He pointed to an uneven ratio of violations to staff.

“We can only do what we can with the people that we have,” he said. “Addressing actions are prioritized around the severity and risk to human health.”

An EPA spokesman cautioned that there can be flaws in the watch list. Allegations not yet proven against a business may land it on the list, while other companies remain on the list even after they have corrected problems because they are being watched by regulators for continuing compliance, the spokesman said. Officials say that institutions can linger on the list for years, until the EPA formally closes out enforcement actions.

Still, the EPA’s own internal watchdog has expressed concern about the level of attention being paid to high priority violators.

A 2009 report by the agency’s inspector general found that “in many instances EPA and States are not addressing high priority violations . . . in a timely manner,” thereby allowing “continued emissions from facilities (that) may result in significant environmental and public health impacts, deterrence efforts being undermined, and unfair economic benefits being created.”

Last year, another Massachusetts HPV, the Milford glass bottling factory for building materials conglomerate Saint Gobain, agreed to a $2.25 million fine for violating the Clean Air Act over a 20-year-period by improperly building or modifying its glass furnaces. As part of the enforcement agreement, the company has converted two furnaces to reduce greenhouse emission, nitrate dioxide, sulfur dioxide and particulate matter emissions at its Milford facility, according to an emailed statement provided to NECIR by company spokesman Craig Kovan.

“We don’t believe the inclusion of any Saint-Gobain Containers’ Inc. (SGCI) facility on the EPA list is appropriate,” the statement read.

Meanwhile, in Maine residents are bracing for state regulators’ decision about Old Town’s efforts to get permission to double its carbon monoxide allowance. Callela said neighborhood dogs and cats run through the “gray mucky sludge” that she claims at times has coated her backyard from the factory’s emissions and then track it inside her house.

“Imagine what is not visible,” said Callela.

Mary Dolan, who has lived in Old Town for nearly a decade, attended a public meeting last fall to protest Old Town’s permit application, pointing out that the factory has already broken federal air pollution rules.

“It just seemed ridiculous that if you can’t meet one license, you can just ask for a new one,” Dolan said.

Old Town spokesman Bird defends the move, saying the facility cannot operate economically under the current license. “You can increase emissions standards to a certain point, but eventually no technology will produce at that level,” Bird said.

The New England Center for Investigative Reporting is a non-profit newsroom based at Boston University and WGBH and a member of the Investigative News Network.