The fragile and increasingly ice-free waters of the Arctic are expected to benefit from tougher environmental rules likely to be passed this week when an international body holds a final vote on northern shipping regulations.

But environmental groups at the meeting of the International Maritime Organization in London say that the proposed measures for the Polar Code still leave significant gaps. 

"It's a big step forward but there's a ways to go," said Kevin Harun of Pacific Environment, a U.S.-based group that has been part of the talks.

The International Maritime Organization is a UN-sponsored body that sets shipping rules for oceans. Last fall, it gave preliminary approval to a series of environmental measures. 

It's scheduled to take a final vote on those measures this week and they are expected to pass. They include a ban on the discharge of oil, oily water or noxious chemicals.

That's stricter than the rules for other oceans, said Harun. "That's a real big first for a region."

The proposals also limit the discharge of food waste. Any such waste would have to be ground and dumped at least 20 kilometres from land or the nearest ice.

Requirements for sailors to avoid Arctic marine mammals were passed last fall.

Countries such as Canada already have regulations for territorial waters in the Arctic that are more stringent than the proposals, but national rules don't cover the central Arctic Ocean. The proposals offer added protection for that area.

What they don't do is ban the use of heavy fuel oil, Harun said. 

'Thick, viscous, dirty, persistent'

"It's thick, viscous, dirty, persistent, doesn't evaporate and would be a real disaster if there was a spill," Harun said. "They haven't dealt with that at all."

Such oil is also a major source of black carbon, which is considered a significant driver behind climate change because it darkens snow and ice and causes it to melt faster. 

Michael Byers, an Arctic law expert and University of British Columbia professor, points out that the heavy fuel burned by most of the ships plying the Arctic is already banned in the Antarctic.

"There was real hope the IMO would extend that ban," he said. 

"(The code) is a necessary first step but it doesn't address the big issue."

The ban was opposed by countries with a large number of ships under their flags. Russia, which is trying to promote the use of its Northern Sea Route, also opposed it.

Byers said reputable shippers already live up to what will be the new  requirements.

Environmentalists will continue to push for improvements, Harun said.

"They did a good job advancing some of these issues, but if they don't deal with some of these other issues it's all going to be for naught.

He also noted that enforcement will be up to individual nations in territorial waters and ambiguous everywhere else.

"Enforcement is an area that really needs to be looked at." 

The new rules are expected to take effect on Jan. 1, 2017.