By Roger Harrabin
BBC environment correspondent
European environment ministers are facing calls to reduce the amount of air pollution from ships.
Ships use fuel with a high sulphur content
A conference on marine protection - taking place in Germany on Wednesday - is being told that ships give off as much sulphur as all the cars, lorries and factories in Europe put together.
By 2010, up to 40% of air pollution over land could come from ships.
Airborne sulphur is a major cause of acid rain that harms crops and buildings.
It also forms particles which are breathed deep into people's lungs and shown to increase the risk of heart attacks and respiratory problems.
Governments have made laws to achieve huge cuts in sulphur from cars, buses, lorries, factories and power stations.
But ships have evaded legislation, partly because they appeared to be a relatively minor source and partly because of the complexity of addressing an international industry based across many countries, some of them outside of Europe.
Ships now fill up with bunker fuel which is very cheap but high in sulphur.
"They use the waste products from the refinery, so the refineries make clean fuel for cars, for inland boats, and the rest they simply dump into the tanks of ships going to sea," says Irene Blooming, a spokeswoman for the European environmental coalition Seas at Risk.
A ship lets out around 50 times more sulphur than a lorry per metric ton of cargo carried.
Countries like the UK promised six years ago that they would cut emissions from shipping by ratifying a clause in a marine treaty but they have not done it yet.
Now the European Parliament is demanding that the EU insists that ships make emission cuts of 80% to protect people living near the coasts.
Ms Blooming welcomed the move.
"I'm very confident that we can realise this," she said.
We've been campaigning for this for more than 20 years, and if we can make a big step forward in 80% cuts then I would say, okay, we're done for the next 20 years as well."