State ferries, massive container ships, trains and cranes are major contributors to air pollution in the Puget Sound region, according to a new study.

The report concludes that maritime activity at area ports like the Port of Seattle and Port of Tacoma account for roughly one third of the region's diesel emissions.

The findings were released Tuesday in the Puget Sound Maritime Air Emissions Inventory, and could help guide future pollution-reducing efforts by the ports, their customers, the state ferry system and the Puget Sound Clean Air Agency.

"There's a lot of good information here, and it will help us reduce the impact of ports and make room for the economic growth that comes with the port growth," said Dave Kircher, the agency's air resources program manager.

Reducing emissions is also a concern for the International Longshore and Warehouse Union, whose members breathe the polluted air while working on the docks.

The union started the Saving Lives campaign to urge ports, shipping lines and terminal operators to reduce harmful emissions generated by their equipment.

"We look at ourselves as the canaries in the coal mine because we work around these emissions on a daily basis," said Mike Jagielski, a Tacoma longshore worker with the union.

The report was compiled by the Puget Sound Maritime Air Forum, a group representing maritime industries, ports and environmental regulators that estimated emissions based on 2005 port traffic data.

It doesn't suggest specific solutions to the problem but provides the most detailed account yet of air pollution from maritime sources throughout the sound.

Data showed that maritime activity produces about 40 percent of all sulfur dioxide, which helps make acid rain, in the region's air, according to a Seattle Times analysis. It contributed to approximately 35 percent of all the region's airborne diesel particles, which are thought to increase cancer risks, exacerbate asthma and heart problems, and shorten life spans.

A Seattle Times analysis of federal air-quality data last year found that neighborhoods near ports have some of the unhealthiest air in the state, largely thanks to diesel pollution.

Everything from ferries to personal boats to freighters together produced nearly 1.9 million tons of greenhouse gases such as carbon dioxide per year - 2 percent of statewide emissions, according to the report.

The Puget Sound region currently meets all federal, state and local air quality standards for pollutants that are regulated, including standards for particulate matter, tiny pieces of soot and dust.

Rather than tightening regulations, Puget Sound industries and government agencies already have begun voluntary initiatives to clean the air.

Some companies that unload freight at terminals in Seattle and Tacoma have switched to cleaner fuels and installed pollution-control equipment.

Earlier this year, some shipping lines announced plans to begin burning cleaner fuel in their auxiliary engines while in Tacoma and Seattle.

"We're collaborating up here right now, and we need to keep it that way," said Michael Moore of the Pacific Merchant Shipping Association, which represents major shipping companies.

Many cruise-ship companies now plug into an electrical grid while docked in Seattle, rather than leave engines running.

The state ferry system plans to reduce diesel soot by converting its fleet to ultra-low-sulfur diesel. It also has experimented with cleaner-burning biodiesel, but it clogged the engines.