The EPA estimated that burning cleaner fuel would add $7 per day, on average, to individual cruise fares. In a recent briefing to the Maryland Port Commission, state transportation officials estimated that using less-polluting fuel could raise the cost of six- to 10-day cruises from Baltimore by $66 to $140 per passenger, depending on destination. Rates now being advertised run from $905 and up for two people in an interior cabin on a late-fall voyage to the Bahamas.
State officials also warned the commission that the cost increases were such that cruise routes could be changed and vessels might be relocated.
Carnival is "not ready to announce anything, but it's our understanding based on discussions we've had with them that they're inclined to leave," Winfield said. She added that "we're hoping they'll return in the future" should the EPA offer relief.
Environmentalists say they are skeptical of industry threats to abandon Baltimore, noting that the fuel regulation would apply to cruises departing from any other U.S. port.
Scher said Carnival has done good business out of Baltimore, from which it has been sailing since 2009.
"Their ships have sailed full continuously," he said. "They recognize it's a strong market."
But he said Carnival has indicated its concern about the impact of the fuel mandate. Baltimore is at a disadvantage, port officials say, because its location near the head of the Chesapeake Bay adds hundreds of miles per voyage.
O'Malley's press secretary said the EPA chief had told him the agency was reviewing Carnival's request for relief and was leaning toward granting it. After speaking with Perciasepe by phone in late May, the governor also spoke with him briefly in person at a meeting in Washington, said Alisha Johnson, Perciasepe's press secretary.
Johnson said Perciasepe told O'Malley that regulators have been talking with the shipping company but nothing has been decided.
Another EPA spokeswoman, Julia Valentine, said officials were unaware of any other governors, except Alaska's, who have expressed concerns to the federal agency about losing cruise business because of the fuel mandate. Spokesmen for government agencies overseeing cruise departures from Boston and New York said they had not heard similar warnings about ships being pulled or making less frequent voyages.
Asked how O'Malley's appeal on behalf of Carnival squared with his oft-stated advocacy for clean air and water, Winfield said the governor had been told that there was alternate technology for reducing air pollution from cruise ships, obviating the need for the EPA requirement to burn more costly ultra-low-sulfur diesel fuel. She said she believed that information came from Carnival.
"The governor is a strong advocate for the environment and protecting the bay," Winfield said, "But as we are in this economic recovery, we're always fighting for jobs. So we have to strike that balance."
Neither EPA officials nor Carnival's spokesman would discuss what the company is asking of the agency.
International maritime rules do not allow a waiver from the fuel requirement but do permit consideration of alternatives that would provide the same overall pollution reductions. Rules also allow temporary exemptions to try out new emission-control technology.
The EPA, in consultation with the Coast Guard and a Canadian shipping authority, has approved a proposal by Royal Caribbean to meet the fuel sulfur limits by averaging emissions among some of its ships, according to an agency official, who was allowed to speak only on background.
Some of Royal Caribbean's ships are powered by diesel turbines that burn a more-refined, less-polluting fuel. Their cleaner emissions, when paired with those of other ships operating in the same region, produce emissions that meet the air-quality standard on average, the EPA official said.
Royal Caribbean also has been granted a temporary exemption from the low-sulfur fuel mandate for some ships while they are being outfitted with scrubbers that remove pollution from engine exhaust. A Royal Caribbean spokeswoman said in an email that the line is seeking such permits for six ships, including Baltimore-based Grandeur of the Seas, but did not respond to further questions.
During the retrofit, the affected ships are allowed to burn fuel with up to 21/2 times the sulfur content that all other vessels are now supposed to be using, according to EPA officials. The agency would not say how long the exemptions would be, saying it varies by ship and was up to Royal Caribbean if it wants to provide that information. But the EPA did say the scrubber installation could take anywhere from six months to four years or more, depending on whether the work was done in drydock or while the vessel remained in service.
O'Donnell said the EPA appears to be softening a major pollution-control initiative under political pressure, including from cruise industry supporters in Congress.
"At least for the short run," he said, "breathers are going to get dirtier air and health damage."
He said that while the ships could clean up emissions if and when they're fitted with scrubbers, it was troubling that neither the EPA nor the industry could say how long that might take.
O'Donnell likened the industry's bid for temporary exemptions while installing pollution controls to a famous line from an old animated cartoon.
"They're saying, 'I'll gladly pay you Tuesday for the hamburger I eat today,' " he said. "But they're not saying Tuesday. That's a reason for concern."
Even after the tighter fuel limit begins in 2015, cruise ships would be able to burn fuel with 60 times the sulfur allowed in diesel used by buses and trucks in the United States, according to the EPA.