According to a recent report resulting from the 2016 Puget Sound Maritime Air Emissions Inventory, regional port-related air pollution has decreased substantially since 2005.

The report estimated the amount of greenhouse gases, diesel particulate matter, and other polluting substances, and focused particularly on emissions from harbor vessels, ships, and other heavy-duty trucks and vehicles involved in maritime activities.

The Northwest Seaport Alliance, a partnership between the Port of Tacoma and the Port of Seattle, was launched in 2015 to help manage marine cargo facilities. Therefore, the report compares 2016 measurements to measurements for both ports in 2005.

Overall carbon dioxide pollution within the airshed has dropped 36 percent, the report states. Sulfur dioxide pollution in the airshed has dropped 97 percent. The amount of nitrogen oxides in the airshed dropped 35 percent.

The Northwest Seaport Alliance credits the stricter fuel and engine standards and the voluntary investments made in cleaner energy and vehicles for the pollution improvements made in the last decade.

Also a factor in reducing emissions in the region is the Northwest Ports Clean Air Strategy, a collaborative effort between the ports of Tacoma, Seattle, and Vancouver, B.C. By 2020, the strategy aimed to achieve an 80 percent reduction per ton of cargo for diesel particulate matter and a 15 percent reduction per ton of cargo for all greenhouse gases.

The seaport alliance met both of those goals already, and continues to make further progress toward even cleaner air and even less pollution.