Residents arriving at a public forum in South Portland this month to voice concerns about the potential of an oil spill from the Portland-Montreal Pipe Line found they had something else to worry about: Toxic smoke from two 70-foot stacks that would reduce the city’s air quality and threaten children in nearby schools.

They learned about the threat from workers with the Natural Resources Council of Maine, who handed out an information sheet with a fuzzy photo-illustration showing where “smoke stacks” at the end of the Portland Pipe Line Corp. pier would emit toxic chemicals.

What most people didn’t realize is that Portland Harbor already has three similar stacks that burn toxic vapors from petroleum pumping. Thousands are located in oil ports worldwide.

Also left unsaid is that these two stacks would increase air emissions by only a small fraction, compared to what already is allowed in Greater Portland.

The meeting was held to present the pros and cons of the heavy crude from western Canada known as tar-sands oil, and the potential of the pipeline pumping it to ships in Portland Harbor. The pipeline currently pumps oil from vessels to refineries in Montreal, but it’s possible the flow could be reversed someday.

The pipeline company canceled a plan to do that in 2010. The NRCM and other activists groups are fighting any revival of the idea.

Most of their opposition has focused on the potential of an oil spill and the difficulty of cleaning the heavy crude from sensitive waterways. Raising the specter of toxic emissions and air pollution is a new tactic.

The emissions are a byproduct of international safety requirements for loading petroleum tanks. Simply put, a “blanket” of an inert gas is introduced into the empty hold of a ship, to maintain a low-oxygen atmosphere. That prevents explosions or fires when vapors generated by loading the oil, and from the gas blanket, are released.

To reduce the amount of particles and volatile organic compounds from escaping into the atmosphere when the ship is filled, the vapors are captured and piped into combustion units that burn off most of the pollution.

The Maine Department of Environmental Protection has licensed three existing units in South Portland that burn the vapors from loading refined petroleum products, such as gasoline, jet fuel and heating oil, into delivery trucks.

One, at the Global Petroleum tank farm, involves an open flare atop a 35-foot stack. A second is at the Citgo terminal. A third is at Irving Oil’s South Portland Terminal LLC. It uses the same technology as the Portland Pipe Line Corp. had first proposed in 2008, when it applied for an air emissions permit from the DEP.

This technology is called a vapor combustion system. It features a stack that encloses pipes, a blower and a pilot light that fires the gas burner. The enclosure is designed to limit noise and heat from the flare.

Two units were permitted, because the company pier can handle two ships at a time. In the 2008 application, the twin combustion systems were permitted to emit a maximum three tons of particulates and 39 tons a year of volatile organic compounds, or VOCs.

Small particulates are associated with a greater risk of heart and lung problems. VOCs can cause eye, nose and throat irritation, and some compounds are suspected of causing cancer in people.

These maximums assume the units run all year long, around the clock, seven days a week, burning crude with the highest vapor concentrations.

“I would expect the totals to be much less than that,” said Lynn Cornfield, an assistant environmental engineer at the DEP’s air bureau.

By comparison, the Sappi paper mill in Westbrook is licensed for 321 tons a year of VOCs and 568 tons of particulate. Bath Iron Works can emit a maximum of 102 tons of VOCs and 24.9 tons of particulates.

With its current license, Portland Pipe Line Corp. can emit 220 tons of VOCs and less than one ton of particulate from its crude storage tanks. The additional emissions from vapor destruction would boost maximum VOCs by less than 20 percent.

This information wasn’t made available in presentations during the public forum, by either the NRCM or the pipeline company. The NRCM handed out tags that read: “No tar sands in South Portland. Stop the smoke stacks,” and many people put them on.

At the comment period, some residents expressed concerns about the stacks. One woman worried about going to the beach. Another woman, who said she suffers from asthma, questioned if she could continue to live in her house.

Dylan Voorhees, the NRCM’s clean-energy director, said his goal was to make people aware of the potential. The maximum permitted emissions set that potential, he added, even if it’s not reached right away.

Voorhees said he wasn’t aware of the harbor’s existing vapor units, but said that doesn’t change his group’s point.

“If you put up two more stacks, they’re going to generate more pollution,” he said.

Tux Turkel can be contacted at 791-6462 or

tturkel@mainetoday.com