Ocean-going vessels now belch out more of the major air pollutant sulfur dioxide than all of the world’s cars, trucks and buses combined, according to a study released Thursday.

The group behind the report, the International Council on Clean Transportation (ICCT), also said the shipping industry emits more of the greenhouse gas carbon dioxide than many industrialized nations.

The ICCT, comprising transport and air quality experts from around the world, called on the industry voluntarily to clean up its act and also submit to tough standards as part of efforts to combat global warming.

“International ships are one of the world’s largest, virtually uncontrolled source of air pollution,” said Alan Lloyd, the ICCT’s president and former secretary of California’s Environmental Protection Agency.

“Air pollution from diesel trucks and buses in Europe, Japan, and the US has declined steadily for over a decade. At the same time, air pollution from international ships is rising virtually unchecked,” he said.

The study said the sulfur dioxide (SO2) content of marine diesel fuel is an average of 27,000 parts per million (ppm), compared to just 10-15 ppm for road fuels in Europe, Japan and the United States.

SO2 is blamed for causing respiratory illnesses and acid rain, and for forming atmospheric particles that choke off air visibility.

The ICCT cited recent estimates as saying at least 17 percent of emissions of nitrogen oxide come from ships, which can contribute more than 25 percent of the pollutant in some port cities and coastal nations.

The group said the International Maritime Organization (IMO) had been “slow to take advantage of the best available technologies and fuels,” with its only action on ship emissions adopted in 1997 and implemented two years ago.

However, the IMO is debating whether to adopt a new round of emission standards for international ships leading up to meetings in April and June, the ICCT noted.

It called on the IMO to mandate a 90-percent reduction in marine diesel’s sulfur content, use up-to-date technologies to govern emission standards, and set new standards to address the impact of climate change.

Axel Friedrich, co-author of the report and a senior official in Germany’s Federal Environment Agency, said all that was required was an industry will to make changes.

“We’ve found that the public health and environmental consequences are clear and compelling and the technology is available now to dramatically lower air pollution from international shipping,” he said.

“It’s time for the IMO to make overdue changes that will save lives, help millions of people breathe easier, and reduce global warming.”

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