Puget Sound has made Seattle a home port to generations of fishermen and recreational boaters, a highway for commuters and a gateway to...

Share story

Puget Sound has made Seattle a home port to generations of fishermen and recreational boaters, a highway for commuters and a gateway to global commerce.

But it also contributes a less savory legacy: air pollution.

Ships, along with all the trucks, trains and cranes that haul their cargo, create about a third of the region’s toxic diesel emissions, according to a study released Tuesday. Diesel soot is the biggest regional health threat from air pollution, the study says.

The findings in the Puget Sound Maritime Air Emissions Inventory, three years in the making, are the most detailed accounting yet of the air pollution from maritime sources throughout the Sound.

Unlimited Digital Access. $1 for 4 weeks.

The report doesn’t propose specific solutions to the problem. Instead, it’s meant to help industries and governments understand where the pollution is coming from, so money can be best spent to clean the air.

It comes at a time when the same groups have been working together in hope of avoiding the pollution problems that have plagued California ports, fouling the air in Los Angeles and Long Beach neighborhoods.

“Our primary concern has been with the growth of the ports,” said Dennis McLerran, executive director of the Puget Sound Clean Air Agency, which enforces federal clean-air regulations in King, Snohomish, Pierce and Kitsap counties.

“How do we have a sustainable future, so that we don’t run into the same issues that they did in Southern California?”

Soot, greenhouse gases

The report was completed by the Puget Sound Maritime Air Forum, an alliance of maritime industries, ports and environmental regulators, including McLerran’s group and the American Lung Association. It quantifies the pollution from literally thousands of engines, on everything from ferries to small personal boats to hulking freighters.

Together they produce roughly 40 percent of all the sulfur dioxide, which helps make acid rain, in the region’s air, according to a Seattle Times analysis of data in the report. And they crank out approximately 35 percent of all the region’s airborne diesel particles, which are thought to raise cancer risks, exacerbate asthma and heart problems, and shorten life spans.

The report cautions that some of those calculations may not be precise because of the way different clean-air agencies estimate pollution.

Those engines also produce nearly 1.9 million tons of greenhouse gases such as carbon dioxide per year. That’s only around 2 percent of statewide emissions.

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

The latest report finds that massive oceangoing vessels, along with state ferries and the on-shore equipment used to haul cargo, are the biggest sources of diesel soot from maritime sources.

Oceangoing freighters

For now, Puget Sound industries and government agencies have begun voluntary initiatives to clean the air, rather than tightening regulations.

“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.

For example, several shipping lines announced this year they will start burning cleaner fuel in their auxiliary engines while idling in Seattle and Tacoma. Several cruise-ship companies plug the huge ships into the electrical grid while docked in Seattle, rather than leaving engines running.

Meanwhile, the state ferry system is converting its fleet to ultra-low-sulfur diesel, which cuts down diesel soot. It also has experimented with cleaner-burning biodiesel, but it clogged the engines.

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

The biggest challenge may be oceangoing freighters, which have few controls on the fuel they use. Unlike diesel engines in trucks, trains and other land vehicles, the Environmental Protection Agency (EPA) does not regulate the big freighters, instead deferring to international treaty.

The ships account for roughly half the total diesel soot from all the maritime sources, according to the new report.

Much of that soot is belched out as the ships travel through the Strait of Juan de Fuca, past the Olympic Peninsula, using a black, syrupy “bunker fuel” in their main engines. That may actually pose less of a health threat because the diesel soot has time to disperse before it reaches heavily populated areas.

But Robin Evans-Agnew of the American Lung Association of Washington still wonders where that leaves the rural residents of places such as Clallam County.

“I’d just like some assurance that there aren’t health effects for them,” he said.

Warren Cornwall: 206-464-2311 or wcornwall@seattletimes.com

Custom-curated news highlights, delivered weekday mornings.