Some states and local pollution agencies are stepping in. California has banned ships from burning dirty kinds of fuel, and is rolling out other clean port initiatives.
Since 2001, the Ports of Los Angeles and Long Beach – the nation’s two busiest shipping ports – have offered financial incentives to shippers that voluntarily reduce their speeds to 14 mph. Baker said it has led to 90 percent compliance.
Smog-causing nitrogen oxides from the Los Angeles port’s ships declined 30 percent between 2005 and 2011, while particulate matter decreased about 70 percent. Carbon dioxide was not reported.
"I think it has been quite effective," said Sam Atwood of the South Coast Regional Air Quality Management District, the local air pollution agency that monitors the side-by-side ports of Los Angeles and Long Beach.
In August, the Port of New York and New Jersey approved several initiatives to reduce emissions, including a voluntary speed reduction program similar to the Ports of Los Angeles and Long Beach. Ocean-going vessels that reduce their speed to no more than 10 knots (11.5 mph) starting 20 nautical miles from the entrance to the New York-New Jersey harbor earn financial incentives and recognition.
Smaller ports, such as Port Miami, are considering setting new policies for cargo ship speeds to help clean the air.
Shippers might not want to slow down because “hours lost in transit can cost carriers and their shipping customers dearly," said Aaron Ellis of the American Association of Port Authorities.
An industry group, the U.S. Shippers Association, noted that there are other ways to clean up the industry.
“Speed limits are only one, and not necessarily the most effective, way to reduce greenhouse gas emissions. Vessel owners should be encouraged to implement as many options as possible to meet and exceed emission reduction standards,” said Beverly Altimore, executive director of the U.S. Shippers Association.
In Southern California, one other solution has been to supply shore-side power so that ships can plug into the electric grid while docked rather than idling their engines, Atwood said.
The authors of the new study warned that emissions reductions near ports could be negated if the ships travel faster than normal cruising speeds outside of the slow zones.
“It is important to note that vessels speeding up to make up for lost time at the slower speeds in the [vessel speed reduction] zone could have an overall increase in CO2 and other emissions,” the researchers wrote.
This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.