The International Maritime Organization (IMO), a United Nations agency that oversees shipping, is poised to tighten sulphur standards for marine fuels. A new cap on sulphur in marine fuels of 0.5% (5000 parts per million) will be in placed by 2020, and control areas with limits of up to 0.1% by 2015. The current cap, set in 1997, is at 4.5%.

The cap is undoubtedly good news for the world’s oceans. Pervious work, some of it in this journal, has shown that sulphur emissions cause cloud formation over shipping lanes, altering the local climate. More pressingly, sulphur particles frequently blow onshore, where people inhale them. The emissions could contribute to as many as 80,000 premature deaths by 2012 according to one recent study.

The cap doesn’t go far enough, according João Vieira, of Transport and Environment, a Brussels-based non-profit. He claims that shipping fuels will still be 500 times more polluting than road fuels. Vieira hopes that Europe will place the strictest limits in its waters.

But getting fuels much cleaner might be impractical, adds Eelco Leamons of the North Sea Foundation, a Dutch charity. He suggests other mitigation methods, such as requiring ships to use onshore power while they’re in port.

As is the way with international treaties, the final wording is being finalized at a painstakingly slow pace, but if all goes well, the new limits will be in force in another eight months or so.

Image: Alamy